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The epidemiology and environmental impact of organophosphate pesticide use in Ecuador, with emphasis on parathion
Scheutzow, Mark Howard, Ph.D.
The Ohio State University, 1992
UMI 300 N. Zeeb Rd. Ann Arbor, MI 48106 THE EPIDEMIOLOGY AND ENVIRONMENTAL IMPACT OF
ORGANOPHOSPHATE PESTICIDE USE IN ECUADOR, WITH EMPHASIS
ON PARATHION
DISSERTATION
Presented in Partial Fulfillment of the Requirements for the Degree
Doctor of Philosophy in the Graduate School of the Ohio State
U n iv ersity
By
Mark Scheutzow, B.S.
The Ohio State University
1 9 9 2
Dissertation Committee:
P. A. Colinvaux Approved by
S. W. Fisher
T. J. Logan Department of Environmental Sciences M. C. Miller To My Mother And My Wife, For Their Continual Support ACKNOWLEDGMENTS
I express my sincere appreciation to the Noyes Foundation for their financial support, also to the members of my dissertation committee for their contributions, patience, and suggestions during the course of my time at the Ohio State University. I wish to especially thank my dissertation advisor, Dr. Paul Colinvaux, who allowed me the freedom to pursue my graduate training to the "beat of a different drummer". Without his insight, enthusiasm, experience, knowledge, and tolerance, this work would not have been possible. I wish also to mention the contributions of Dr. Daniel
Couri, whose death between my oral exam and final defense was an immeasurable loss. Thanks also are extended to all the individuals in the
United States and Ecuador who gave of their time to assist me in my endeavors.
iii VITA
August 19, 1957 ...... Born - Middleburg Hts., Ohio
1979 ...... B.A., Case Western Reserve University, Cleveland, Ohio
1981 - 1982 ...... Research Associate, Department of Biololgy, Case Western Reserve University, Cleveland, Ohio
1983 - 1986 ...... Teaching Associate, The Ohio State University, Columbus, Ohio
1986 - 1988 ...... Research Associate, Department of Environmental Biology, The Ohio State University, Columbus, Ohio
1992 - present ...... Research Associate, Department of Preventive Medicine, The Ohio State University, Columbus, Ohio
FIELDS OF STUDY
Major Field: Environmental Sciences
Minor Fields: Epidemiology and Biostatistics TABLE OF CONTENTS
ACKNOWLEDGMENTS ...... ii
VITA ...... iii
LIST OF TABLES ...... v ii
LIST OF FIGURES ...... ix
INTRODUCTION ...... 1
CHAPTER PAGE
I. PESTICIDE REGULATION AND US E ...... 8
A Background to the commercial attitude of companies selling to developing nations and the FAO draft code of conduct on the distribution and use of pesticides ...... 8 The agriculture of Ecuador ...... 19 A history of pesticide legislation in Ecuador ...... 23 Pesticide importation in Ecuador 1978-1989 ...... 28 Conclusion ...... 32
II. SURVEYS ...... 45 45 Introduction ...... Methods ...... 47 A survey of retail pesticide shops in Quito ...... 50 A survey of retail pesticide shops in Otavalo ...... 60 A 1989 followup survey of retail pesticide shops in Quito ... 65 Conclusions from the surveys to assess the effectiveness of the FAO code ...... 66 Results of interviews on pesticide use and exposure in an Indian village ...... 69 Results of a survey of pesticide use in 19 Otavalan households ...... 79 Conclusions from the surveys to assess pesticide use and exposure in subsistance farming Ecuadorean Indians ...... 82
v Introduction to surveys of profit-motivated farmers in agricultural provinces ...... 84 Surveys of profit-motivated farmers in Azuay province ...... 88 Surveys of profit-motivated farmers in Tungurahua province ...... 91 Surveys of profit-motivated farmers in Manabi province ...... 93 Surveys of profit-motivated farmers in Carchi province ...... 95 Conclusions from the surveys of profit-motivated farmers in agricultural provinces ...... 98
III. PESTICIDE POISONING ...... 124
Introduction ...... 124 Results of case history interviews regarding pesticide poisoning in Checa, Ecuador ...... 126 Results of case history interviews regarding pesticide poisoning in Chimborazo, Ecuador ...... 127 Results of case history interviews regarding pesticide poisoning from malarial outbreaks ...... 128 Information on rural pesticide poisoning from discussion with rural physicians in Lago Agrio ...... 131 Information on rural pesticide poisoning from discussion with rural physicians in Otavalo, Ecuador ...... 133 Generalizations of the agricultural surveys ...... 135
IV. PARATHION IN A TROPICAL LAKE ...... 155
Introduction ...... 155 Site description ...... 159 Parathion loading ...... 162 Properties of parathion ...... 166 Degradation pathways ...... 169
V. MIXIS IN LAKE SAN PABLO ...... 182
Introduction ...... 182 Methods ...... 187 Results and discussions ...... 188 Conclusions ...... 202
v i VI. PARATHION AND THE LIMNOLOGY OF SAN PABLO...... 232
Introduction ...... 232 Methods ...... 239 Results and discussion ...... 246 Conclusions ...... 275
VIL SUMMARIES AND CLOSING STATEMENTS ...... 295
APPENDICES
A. Summary of the EAO code ...... 306
B. Individuals contacted in Ecuador regarding pesticide use ...... 3 1 1
LIST OF REFERENCES...... 3 1 3
vii LIST OF TABLES
TABLE PAGE
1. Pesticides imported into Ecuador from 1978-1990 in thousands of kilograms ...... 36
2. Costs of pesticides imported into Ecuador in thousands of US dollars ...... 37
3. 1986 gross sales of pesticides by the 8 largest importers to Ecuador ...... 39
4. Pesticides imported into Ecuador by the 3 largest suppliers to that nation ...... 40
5. Pesticide type as a percent of the total kilograms of pesticides imported into Ecuador from 1978-1986 ...... 41
6. Banned or restricted pesticides imported into Ecuador from 1978-1982 ...... 42
7. Organophosphate pesticides found in Ecuadorean pesticide shops ...... 113
8. Carbamate pesticides found in Ecuadorean pesticide shops ...... 115
9. Pyrethroid pesticides found in Ecuadorean pesticide shops ...... 1 15
10. Results of a survey of Quito pesticide retailers with and without phones in their stores ...... 116
11. Results of a survey of pesticide retailers in Otavalo ...... 117
12. Pesticide use in nineteen Otavalan households ...... 118
13. Pesticide products of nineteen Otavalan households ...... 119
14. Surveys of farmers in four agricultural provinces ...... 120
viii TABLL PACK
15. Illnesses experienced within the past year by farmers after pesticide applications ...... 122
16. Pesticides most often used by surveyed farmers ...... 123
17. Physical characteristics of Lake San Pablo ...... 229
18. Morphometric data of Lake San Pablo ...... 230
19. Oxygen saturation of Lake San Pablo at 2661 meters ...... 230
20. Change in lake oxygen with wind stress ...... 231
21. Least squares linear regression for prediction of oxygen delivery ...... 231
22. First and second order degradation constants for parathion by sediment and aufwuehs bacteria ...... 289
23. Location and number of sediment and pelagic bacteria in Lake San Pablo ...... 290
24. Bacterial numbers found in open water of Lake San Pablo compared to other aquatic ecosystems ...... 291
25. Bacterial numbers found in the sediments of Lake San Pablo compared to other aquatic ecosystems ...... 292
26. Parathion toxicity to Daphnia pulex ...... 293
27 Decreases in phytoplankton oxygen production with 0.5, 294 1.0, and 10.0 ppm parathion ......
ix LIST OF FIGURES
FIGURE PAGE
1. Vitavax and Basudin advertising on the Pan-American Highway ...... 33
2. Monitor and Difolatan advertising on the Pan-American Highway ...... 34
3. Bayleton and Furadan advertising on the Pan-American Highway ...... 35
4. Pesticides imported into Ecuador from 1978-1989 ...... 43
5. Relative costs of pesticides imported into Ecuador from 1978-1982 ...... 44
6. Pesticide type as a percent of total kilograms imported into Ecuador ...... 44
7. Pesticide label for Nogos, a diclorvos insecticide ...... 102
8. Brochure advertising Temik, an aldicarb insecticide ...... 103
9. Pesticide application near Otavalo ...... 104
10. Total number of poisonings requiring hospitalizations by year ...... 105
11. Total number of pesticide poisonings per 100,000 population ...... 105
12. Pesticide importations and poisonings from 1978-1988 ...... 106
13. Pesticide poisonings in Tunguruhua and Azuay from 1980-1988 ...... 107
14. Pesticide poisonings in Manabi and Carchi from 1980-1988 ...... 108
x i-Kii r i; p a g e
15. Frequency of illnesses experienced by fanners after applying pesticides ...... 109
16. Frequency of illnesses experienced by farmers after applying pesticides (Manabi province) ...... 1 10
17. Empty bags of pesticides discarded at the edge of a field .... Ill
18. Observations noted during the agricultural surveys barefoot Ecuadorean farmers and eggs sold in pesticide shops ...... 112
19. Perception by different groups of the cost/benefit ratio of pesticide use ...... 154
20. Degradation pathways of parathion ...... 178
21. Degradation and activation products of parathion ...... 179
22. Map of Lake San Pablo ...... 180
23. Field laboratory at Lake San Pablo ...... 181
24. Thermocline development by 0800 ...... 206
25. Thermocline development by 1400 ...... 206
26. Oxygen and temperature profiles at 0800 after 2 hrs of wind-11 ...... 207
27. Oxygen and temperature profiles at 1400 after 8 hrs of wind-U ...... 208
28. Change in oxygen distrihutionfrom 0800-1400 with 6 hours of wind-11 ...... 209
29. Oxygen and temperature profiles at 1900 hours after 3 hrs of wind-lV ...... 210
30. Change in oxygen distribution from 0800 to 1900 with 3 hours of wind-lV ...... 211
xi ik; iri<; p a c k
31. Oxygen and temperature profiles at 0800 after 2 hrs of wind-II ...... 212
32. Oxygen and temperature profiles at 1400 after 8 hrs of wind-II ...... 213
33. Oxygen and temperature profiles at 2000 after 4 hrs of wind-IV ...... 214
34. Change in oxygen distribution from 1400 to 2000 with 4 hrs of wind-IV ...... 215
35. Oxygen and temperature profiles at 1100 after 3 hrs of wind-III ...... 216
36. Oxygen and temperature profiles at 1900 after 12 hrs of wind-III ...... 217
37. Change in oxygen distribution from 1100 to 1900 with continual wind-III ...... 218
38. The effects of wind strength and duration on depth of mixing ...... 219
39. Thermal profiles formed by mild winds or no winds ...... 220
40. Thermal profiles formed by moderate winds ...... 221
41. Thermal profiles formed by 8 hrs of moderate wind with overcast skies ...... 222
42. Thermal profiles formed by 8 hrs of moderate winds with clearskies ...... 223
43. Thermal profiles formed by strong winds ...... 224
44. Oxygen depth-time for figures 26-28 ...... 225
45. Oxygen depth-time for figures 31-34 ...... 225
46. Oxygen and temperature profiles at 1100 after 3 hrs of wind-II ...... 226
xii h g i r i ;
47. Oxygen and temperature profiles at 1700 after 11 lirs of wind-II ...... 227
48. Relationship between oxygen concentration and wind speed duration ...... 228
49. Disappearance of parathion in littoral sediments ...... 280
50. Disappearance of parathion in aufwuehs ...... 281
51. Littoral pH changes on clear and overcast days ...... 282
52. Littoral temperature changes on clear and overcast days ...... 283
53. Littoral oxygen profile at 0400 hours ...... 284
54. Littoral oxygen profiles at 10 am on clear and overcast days ...... 285
55. Littoral oxygen profiles at 4 pm on clear and overcast days ...... 286
56. Ratio of macrophyte production to control values before and after parathion exposure ...... 287
57. Changes in phytoplankton productivity relative to paired controls ...... 288
xiii INTRODUCTION
We are entering a time when the ability to correct adverse environmental or human health situations will be limited more by financial considerations than by the availability of technological solutions. Medical and environmental problems will be in competition for similar resources, and the appropriate disbursement of funds will depend on a careful consideration of respective cost-benefit analyses. Given these utilitarian circumstances, it will be imperative to have for any contaminant or group of contaminants, a perspective of both the environmental effects and the ramifications on human health.
The latter will be affected by both environmental exposure and cultural patterns of use. Inaccurately estimating the effects of a contaminant in either category could reduce the effectiveness of proposed remedies. Developing countries may contain several different sub-cultures, each with their own language and belief system. Attempting to find a common denominator for all groups of people may not be possible. Western science and technologies are sometimes striking even to the educated; they can be absolutely incomprehensible to third world peoples.
1 2
The World Health Organization estimates the global death toll of pesticides to be approximately 210,000, 99% of which occur in developing nations. More disturbing is their yearly estimate of over 28 million incidences of sub lethal pesticide poisoning, again the majority occurring in third world nations. The severity of the situation is greater than first realized as developing nations use only 20-25% of the total annual world-wide pesticide production.
An additional problem has been a shift in pesticide type, perhaps first initiated by the 1962 publication of Rachel Carson's book, Silent
Spring. This led to the banning in the United States of DDT and created an awareness of the life-time of various pesticides. The increasing use of organophosphate pesticides, first developed as a nerve gas by the Germans in World War II, was fueled partially by chemical companies exploiting their more rapid environmental degradation as an alternative to persistent agricultural chemicals. In 1990, exports of organophosphates and carbamates from the United States totalled over 100 million pounds.
President Carter attempted to restrict the exportation of pesticides from American companies by signing on January 15, 1981 Executive Order
Number 12264. Slightly over one month later, the order was revoked by newly-elected Ronald Reagan on the grounds that it would generate a regulatory schema that would be so costly as to seriously disrupt the agrochemical industry. 3
In Ecuador, the consensus among government and conservation officials is that the increasing use of organophosphate pesticides has the potential to create two sets of problems: contamination of the environment and negative health effects in populations of native farmers. However, there is little information available on the relative importance of either of these concerns. Environmental and human health conditions have usually been considered independently of the other. This has been especially true in developing countries, where little emphasis has been shown for either issue. The purpose of this study was to investigate both the environmental effects of parathion contamination and the effects of organophosphate pesticides use on the health of profit motivated farmers and native Indians.
The Food and Agricultural Organization (FAO) of the United Nations had chartered a code that was to be used by the agrochemical companies of pesticide importing countries. This code was designed to minimize both environmental contamination and human intoxication by regulating the importation and merchandizing of pesticides. The character and nature of the code developed over a period of several year after sets of meetings of agrochemical producing companies. As ultimately formulated, the key elements of the code relied on the attitude and philosophy of the government of the developing country, which was held to be primarily responsible for enforcement. To the chemical companies, management plans were to be initiated and enforced by each individual country. 4
My research essentially involved three aspects of pesticide use in
Ecuador. 1 first investigated the legalities of pesticide importation: examining the effectiveness of outside regulatory laws as proposed through the FAO Code of Conduct, and the influence of internal regulations as reflected by the history of pesticide legislation. The next step involved surveys to ascertain the effectiveness of these management measures in matters of sales, application, and misuse. These variables were considered relative to both cultural and economic differences, although the two were usually synonymous. The final aspect of the study looked at the environmental handling characteristics of parathion in a small high altitude aquatic ecosystem.
Interviews with over a dozen government and conservation officials in Ecuador allowed me to develop a synopsis of the Ecuadorean government's position toward pesticide importation. Many people were concerned with the increasing incidence of pesticide related illness.
Unfortunately, however, the history of legislative action indicated that there had been little regard for either environmental or toxicologic considerations of pesticides.
Since the code was essentially written to agrochemical companies 1 conducted a survey of 38 retail pesticide shops in two Ecuadorean cities to determine if pesticide importers were voluntarily following the FAO guidelines, in spite of governmental indifference. Surveys were made in the capital city of Quito, and Otavalo, a small community in an agricultural province. I visited shops and questioned salespeople and shop managers to investigate adherence to the main provisions of the code: labelling, 5
advertising, product safety, etc. In general, I found that the FAO Code of
Conduct was essentially ineffective in regulating the distribution of pesticides. I was even able to purchase black market chemicals at major retail establishments.
I also conducted surveys among the native farmers of Ecuador to determine if cultural differences affected the epidemiology of human exposure to pesticides. I was assisted in the data collection by an
Ecuadorean medical student and an educated native Otavalan Indian.
Nineteen households were visited and over 200 farmers were interviewed.
My overall impression from the responses to survey questions was that both subsistence and plantation farmers understood very little of the effects and dangers of pesticides.
I also found evidence indicating that profit motivated farmers and subsistence farmers had very different uses for pesticides. Subsistence farmers primarily used pesticides as medicines or in food storage. Common diseases, especially skin infestations with lice, were routinely treated with pesticide preparations. Although profit motivated farmers had more conventional agricultural applications, they lacked an awareness of the appropriate means in which to apply and store pesticides.
I also spent time in the agricultural fields, observing the working conditions of both profit motivated and subsistence farmers and their preparation, application, and exposure to pesticides. Both groups experienced a characteristic set of illnesses and also suffered high rates of intoxication. My estimates of intoxication rates were compared to official estimates obtained from the Ministry of Public Health. In most instances, 6
governmental values greatly underestimated the severity of the resulting disease processes. I expanded this investigation to include specific case histories of poisonings through interviews with conservation and government officials and rural physicians.
The second half of my investigation centered on a particular concern expressed by Ecuadorean officials. Population growth in areas of
Ecuador will require the management of small lakes, both natural and man-made. Most of these lakes will have as watersheds agricultural areas that receive tremendous quantities of pesticides. However, the lakes will also be used continuously through the day for household water. There was a need to determine how these diametric situations could be mutually tolerated within the financial limitations of developing countries, and within Ecuador in particular.
To address this question a part of my research centered on the limnological characteristics of Lake San Pablo, a high altitude poiymictic aquatic ecosystem in an agricultural watershed. 1 examined characteristics of the lake that could be relevant to a model of pesticide handling. Emphasis was placed on understanding the mixing characteristics of the system. Specifically, the pattern of overturn, depth of mixing, and the relationship between production and oxygenation.
Physical changes were also measured within the near-shore littoral zone and an attempt was made to investigate this region as a potential
"trap" for pesticides adsorbed to soil particles. The final aspect of the study looked at the effects of parathion on macrophyte productivity, phytoplankton productivity, and zooplankton survival. The 7
disappearance of parathion in incubations with aufwuchs and sediment samples was also measured. Combining all aspects of the investigation allowed conclusions to he drawn about the overall fate of parathion in the ecosystem. CHAPTER I
PESTICIDE REGULATION AND USE
A BACKGROUND TO THE COMMERCIAL ATTITUDE OF COMPANIES SELLING TO DEVELOPING NATIONS AND THE FAO DRAFT CODE OF CONDUCT ON THE DISTRIBUTION AND USE OF PESTICIDES
The "green revolution" of the 1960s and 1970s introduced less developed countries (LDCs) to the techniques and methods of Western agriculture, especially the use of high yield seeds supplemented with fertilizers and pesticides. As a result, pesticide purchases by LDCs increased from 642 million to more than one billion dollars during 1974 to
1978. Shipments to developing nations now constitute over one-third of total world pesticide exports (Hill, 1988). In the United States, pesticide exportations doubled in the 1910s although pesticide production rose by only 50%.
Concomitantly, as a result of the restrictions placed on pesticides in their countries of origin and the increasing cost of testing and submitting new pesticide for registration, the number of major manufacturers declined by nearly 60% between 1970 and 1981 (Hollis, 1986). The agrochemical industry became trapped between the need for effective solutions to the agricultural problems of LDCs, especially the increasing 9
resistance of pest organisms, and the prohibitive costs of development and
registration of new products (International Group of National Associations
of Agrochemical Manufactures, 1984). Consequently, the industry chose to
initiate efforts to minimize the misuse of existing pesticides.
In 1979 the Brussels-based international branch of the National
Agricultural Chemicals Association (NACA), the International Group of
National Associations of Agrochemical Manufacturers (IGNAAM), began a
series of meetings with several Latin American governments (IGNAAM,
1983a). This culminated in formal conferences held in 1982 and 1983 in
which recommendations were made to government representatives in areas
of pesticide classification, labeling, education, and appropriate use
(Agricultural Chemicals Dialogue Group, 1983). It was the IGNAAM's
intention that individual governments would subsequently develop a
protocol unique to their country (International Group of National
Associations of Agrochemical Manufacturers, 1983b).
Before this was realized a formal set of regulations was developed by
the Food and Agricultural Organization of the United Nations (FAO) at the
FAO Consultation on the International Harmonization of Pesticide
Registration Requirements held in Rome, Italy, in 1985. The FAO Draft Code of Conduct on the Distribution and Use of Pesticides consists of 12 articles
which describe regulatory and safety practices for the handling of pesticides (FAO 1985). A translation of the version presented to the
Ecuadorean conservation organization, the Fundacion Natura (trans.
Nature Foundation) is presented in appendix A. 1 0
The FAO code was supported by the IGNAAM (International Group of
National Associations of Agrochemical Manufacturers, 1984). However, it
was their position that the code function as an interim measure only until
their original proposal could be implemented, i.e. the separate
development by each government of registration legislation unique to that
country. This was thought to be indicative of the IGNAAM's philosophy that
the importing country must bear the responsibility for protecting their health and environment (Hill 1988).
The regulations of the FAO code necessitate voluntary actions on the part of the LDCs (Agricultural Chemicals Dialogue Group, 1985). Although the burden of instituting many of the code's recommendations pragmatically falls to local distributors and importers, the overall success depends on the attitude and support of that country's government. Of
major importance is an administrative philosophy that stresses environmental concern and human safety over short term agricultural goals. It seems that this type of infrastructure, by requiring governmental actions and legislative decisions, conveniently extricates the
international agro-industries from any position of responsibility.
Agricultural companies have used 3 strategies in distributing products to LDCs: caveat emptor, informed consent, and prior consent. The attitude of caveat emptor, which appears to be most favored by the agrochemical industry, squarely assigns the responsibility of regulation to the importing country (Hollis, 1986). Prior consent maintains that the
LDC make a decision before the actual importation occurs, using the exporting company's data (Hill, 1988). Informed consent allows unlimited 11 shipments to take place without the importing country's consent, once the initial consignment has been accepted. This has been the trend since 1978, and is that strategy for which the FAO Code appears to have been written
(Hill, 1988). Agricultural importers contend that the FAO Code of Conduct gives LDCs the foundation upon which to structure their importation policies. They further maintain that the practice of informed consent is best suited to these recommendations. Consequently, their marketing strategies have been in this direction (Hill, 1988).
The FAO code suggests that the government of the importing country provide to the pesticide companies regulations that will determine the products they import. In turn, the agrochemical company will provide to government representatives all relevant information on the pesticide.
However, this information is to accompany only the first shipment, which, most commonly, has already been purchased. The United States
Environmental Protection Agency also has a notification regulation, which requires information be sent with the first shipment of the calender year.
In either case the importing company does not have to provide an estimate of the amount of pesticide to be imported, only the technical data as suggested hy the code. Obviously, not knowing the quantity of pesticide to be imported encumbers the decision making process of the LDC. There will be some pesticides, regardless as to whether they have been banned or restricted in their country of origin, that are ideally suited for a specific task at hand. However, there is no way for an LDC to ensure that only the amount necessary for that particular situation will be imported. 1 2
The government of the importing country is ultimately responsible for ensuring that the importing companies are following the code. This requires vigilance over formulation, packaging, distribution, advertising, application, and disposal. Most LDCs have neither sufficient capital nor adequately trained manpower to monitor and enforce all aspects of the regulations (Ponce, 1987). This also raises an interesting point about the
FAO code; there are no penalties for noncompliance.
There are substantial problems with informed consent which reduce the decision making capacity of the LDCs. The country is not aware of all the dangers of the pesticide until after it has been imported (usually after purchasing). Processing plants may alter the pesticide after it arrives in the country, hence the information available to the importing country may not be relevant. If the pesticide is unaltered, the developing country's technical staff may lack the expertise necessary to extrapolate from data generated in a laboratory or under different field conditions, and there are few opportunities for conducting new tests.
Given currency exchange rates it is very difficult for laboratories in
LDCs to purchase and maintain expensive equipment. The currency of most developing countries is extremely devalued relative to the dollar. In
Ecuador, at the present rate of exchange of 1:11, a piece of equipment costing $5,000.00 US dollars would sell at the Ecuadorean dollar equivalent of
$55,000.00, excluding shipping and taxes. Also, once purchased there will be problems with maintenance, technical service and the acquisition of parts. Even if equipment could be bought and maintained it will always be 1 3
difficult to obtain laboratory grade chemicals and gases required for the analyses.
The United States statute used to regulate the export of pesticides is the Federal Inseetieide, Fungicide, and Rodenticide Act (FIFRA). This legislation was amended in 1978 by the addition of labeling requirements and the stipulation for prior notification of the receiving country. Certain pesticides also require the prior receipt of an acknowledgement statement by the importing country. By submitting this document the purchaser acknowledges that they understand the registration status of the chemical: either open, restricted, or banned (Federal Register, 1980). However,
FIFRA explicitly states that banned or unregistered pesticides are legal for export. Also, American companies do not have to register with the EPA pesticides made only for export. (Weir and Schapiro, 1981).
A study conducted by the General Accounting Office of the United
States found that 10% of the pesticides exported by American companies have not been registered for use in the United States, and over 20% previously have had their registration revoked or suspended because of environmental or toxicologic problems (Hollis, 1986). An attempt was made to regulate the exportation of hazardous products from the United States by
President Carter in 1981 through his "Executive Order on Federal Policy
Regarding the Export of Banned or Significantly Restricted Substances (Hill,
1988). This document, over 2 years in the making and finally signed only 5 days before President Carter left office, modified and improved procedures to notify countries of the toxicity of the material they were receiving. The
Order was rescinded by President Reagan shortly after his inauguration on 1 4 the grounds that it would hinder American trade (Hill, 1988). However, relative to the sales of other chemical products, the agrochemical industry in the United States is quite small. It accounts for only 2% of the total gross sales of all United States chemical industries (Hollis, 1983).
There are several international organizations presently concerned with the regulation of pesticides. These include the United Nations
Environmental Program (UNEP), the European Economic Community (EEC) and the Organization for Economic Cooperation and Development (OCED).
There is also the International Registry of Potentially Toxic Chemicals
(IRPTC), which was created at the United Nations conference on the Human
Environment, held in Stockholm in 1972 (Springer, 1983). This is now supervised by the United Nations World Health Organization.
Europe is a major supplier of pesticides to third world countries. The philosophy of the EEC determines to a great extent the exporting policies of the agrochemical manufacturers. The European Industrial Commissioner of the EEC stated that, given the availability of data through the United
Nations, "...the Commission's view is that it should be for the importing country to lay down its own rule for trade in these products" (Springer,
1983). However, a major problem is a lack of support from the United
States which limits the accessibility of the UN to data on banned or restricted pesticides. The United States was the only country voting against a December 1984 United Nations resolution calling for expansion of the
IRPTC, claiming that the Registry simply duplicates the work already underway in other agencies (Hill, 1988). Obviously, the Registry's effectiveness is greatly diminished by not having access to the pesticide 1 5 data held and controlled by regulatory agencies of the United States.
Current United States policy generally falls into the category of informed consent (Hill, 1988).
A proposal for prior consent was initiated in the EEC during the tenure of the Netherlands' representatives from January to June of 1986.
However, this was not accepted by the member countries. The EEC now has a lenient policy regarding approximately 20 pesticides which have been banned in European countries; the only requirement is that the importing country be notified of a shipment (Hill, 1988). Both the United States and the countries of the EEC currently have a policy of informed consent.
This regulatory philosophy has been constantly criticized by the
Pesticide Action Network (PAN), an organization of over 200 non governmental organizations with a combined membership of one million.
PAN was founded in 1982 by the Friends of Earth (Malaysia division) and the
International Organization of Consumer Unions. The Network documents world pesticide trade and use. In 1985, as a result of the influence of PAN,
The Coalition Against Dangerous Exports was formed from 7 major environmental groups. This organization is involved with lobbying
European governments and the EEC to establish regulatory measures for pesticide exportation.
The most influential group in the regulation of pesticide exportation is the Organization for Economic Cooperation and Development (OECD).
This collective includes all 12 members of the EEC plus the United States,
New Zealand, Australia, Sweden, Norway, Switzerland, Finland, Iceland,
Austria, Turkey, and Yugoslavia. The OECD advocates supplying importing 1 6 countries with information regarding product restrictions only at the time of first exportation. This is similar to the philosophy of informed consent, with one difference. According to the OECD, this disclosure is not mandatory, it requires an initial request for the information by the government of the receiving country. Their stated philosophy is that the
"Primary responsibility is on the importing country ... because chemicals, unlike hazardous wastes, are 'wanted' by the importing country and it is not up to the exporting country to deny them" (cited in Hill, 1988).
As of 1989, pesticide regulation was still the responsibility of the importing country. Agrochemical manufacturers continue to maintain the belief that the guidelines of the FAO code both provide sufficient control over pesticides and minimize dangerous commercial practices. To examine the veracity of this contention, I conducted several surveys. The first was a survey of pesticide retailers in two Ecuadorean cities. I also conducted surveys of pesticide use in households of native farmers.
The Fundacion Natura, a privately funded conservation organization in Ecuador conducted a survey of 11 companies which control over 90% of
Ecuador's pesticide market. Four of the 11 companies are multinational industries: Bayer, Celamerck, Dupont, and Hoechst. The remaining companies are Ecuadorean corporations who buy commercial grade pesticides from international manufacturers and then dilute, mix, reformulate, and distribute relabeled insecticidal products. Multinational agrochemical companies have, in other countries, tried to circumvent regulatory control by separately shipping chemical ingredients of banned 1 7
pesticides which are then combined in the reformulating plant (Weir and
Schapiro, 1981).
Of the 11 companies investigated, representatives of 8 could produce a copy of the FAO code; all stated that the code's provisions had been adopted
(Sevilla, P., 1987b). However, when questioned further, none of the individuals could cite specific circumstances that had been changed. The interviewer noted that their responses tended to be "general and vague"
(Sevilla, P., 1987a). Even the representative from Bayer-Ecuador,the largest importer, could not name any specific measures taken by his company (Sevilla, P., 1987b). The few instances that were mentioned pertained to less important articles of the code: withholding the sale of empty containers, increasing security, informing staff members of the
Code, and enforcing the use of protective clothing among its workers
(Sevilla, P., 1987a).
Not one company had restricted the distribution of those pesticides banned under a recent resolution passed by the Ecuadorean government
(Ponce, 1987). All the interviewed managers acknowledged they were selling products which had been banned in other countries and admitted an absence of efforts to recall or substitute safer chemicals. Not one company initiated among their distributors programs to publicize the recommendations of the Code (Sevilla, P., 1987b). They justified their complacency by the absence of such directives from the mother company.
The Foundation also interviewed officials of the Ministry of
Agriculture, including the director of the Plant Protection Division and the
Director of the Institute of Norms and Measures (the division of the 1 8
government largely responsible for information consolidation, including economic and agricultural data). The former was vaguely familiar with the FAO code while the latter had no knowledge of the Code and "was not aware of any pesticide problems" (Sevilla, P., 1987a). The director of the
Plant Protection Division stated that the current administration had made no attempt to enforce the FAO code or monitor imported substances (Sevilla, P.,
1987a). Hence, the Fundacion Natura concluded that, as of August 1987, the FAO code has had little effect on the industrial practices or commercial strategies of pesticide importers (Kakabadse, 1987). 1 9
THE AGRICULTURE OF ECUADOR
Ecuador has an extensive and varied agriculture the success of which is essential to the country's development. Ecuador is roughly the size of
Colorado (283,520 square km) and is bounded by the Pacific ocean to the west, Columbia to the north, and Peru to the east and south (Brooks, 1987).
There are 3 very different geographical areas: the coastal lowlands, the
Andean highlands, and the eastern Amazon lowlands. Until the discovery in 1972 of oil reserves in the Amazon, Ecuador's main source of foreign exchange was agricultural exports. Although more revenue is generated from oil sales, Ecuador is still the largest producer of bananas, and continues to export increasing quantities of sugar, rice, coffee, and cacao, which amount to roughly 30% of all yearly export dollars (Blouet and
Blouet, 1982). In response to the world-wide growth of the fast-food industry, cattle are becoming important as a source of revenue and areas in the sierra and coastal regions are being developed for grazing (Brooks,
1987). In the last 5 years there has been a governmental emphasis on intensive cultivation of coffee, cacao, and bananas. Concomitant with this trend has been an increase in the use of pesticides, especially after 1985.
The coastal region is a low altitude strip, less than 300 m above sea level. At its northern extreme there is a 4 tiered rain forest with 2 rainy seasons. Slightly below the Columbian border the 2 seasons merge to one which lasts from December to June. Continuing south, the precipitation begins progressively later and ends progressively earlier, to become almost nonexistent as the Peruvian border is reached. Vegetation changes parallel the rainfall and the forest thins to a savanna, scrub-land, and 20
finally to a desert. In the middle of this coastal strip is the Guayas lowland, the center of Ecuador's agriculture, with the major port city of Guayaquil.
A large agricultural area is centered to the north of Guayaquil. This region currently supplies a major portion of Ecuador's banana exports.
Areas to the west are covered by alluvial plains from the Western Cordillera.
The soil, temperature, and humidity are ideal for growing coffee and cacao.
During the dry season the areas are grazed by cattle. Commonly, the animals feed on vegetation that contains extremely high levels of pesticides that remain from applications during the growing season. Much of the meat from these animals is subsequently shipped to the United States, primarily for the fast-food industry (Kakabadse, 1987).
The Andean highlands, known as the Sierra, consists of 2 mountain ranges, the Eastern and Western Cordilleras, separated by a central plateau that has an altitude of 1800 to 3000 m. The Cordilleras contain some of the world's highest peaks and more than 30 volcanoes, 8 of which are still active. Almost half of Ecuador's population live in the 10 between-ehain basins within the central plateau. The capital city of Quito, with a population of 1.2 million, occupies one of these basins. There is little seasonal variation in temperature in this region and the daily temperate ranges of 6° to 23° C, exceed the yearly averages of 8° to 18° C (Liounio,
1986). Temperature is dependent on altitude and rainfall is principally determined by the location of channels within the Cordilleras. The rainy season extends from November to May, peaks in April, and averages 1300 mm. (Brooks, 1987). 2 1
Large areas of the Sierra are grassy paramos which are now being used to graze cattle and sheep. Corn is a major crop, both as a staple in the
Indian diet and as fodder for animals. Other crops include wheat, barley, oats, fruits, and potatoes (Brooks, 1987). All are altitude dependent and only potatoes can be grown at the higher elevations, with an upper limit of
3500 m. Indigenous Indian populations are large in this region and provide almost all the agricultural manpower.
Indian-held agricultural cooperatives are increasing in number and size but most land is still held by large, family-owned haciendas (Ponce,
1987). In many areas the "huasipungo" still persists, an arrangement in which the Indians are essentially slaves to hacienda owners who supply their dwellings, food and clothes, and too meager a salary to allow them to move (Espinoza, 1987). Agricultural reforms are only slowly improving conditions as there is presently a great deal of governmental prejudice toward the Indians (Ponce, 1987). They are considered inferior, backward people who pay little or no taxes and hence deserve no administrative support, especially in comparison with the tax laden, wealthy land owners.
The Oriente or the eastern Amazon lowlands is a tropical rainforest with the headwaters of the Amazon River system. Although it consists of
36% of Ecuador's total area it harbors only 3% of the country’s population
(Brooks, 1987). The discovery in 1972 of extensive oil reserves near the
Columbian border has led to the construction, of a pipeline to the coast. Oil has recently replaced agriculture as the principal source of foreign revenue. Due to the decline in the world oil market and the 22 damage resulting from a 1985 earthquake, production has fallen slightly from the peak of 90 million barrels a year reached in 1983 (Ponce, 1987).
The development of this region has been hampered in recent years by the resurgence of malaria. In particular, the presence of a strain which shows complete resistance to most malaria drugs (Echeverria, 1987). As a result, the government has begun an extensive control program using DDT
(Vuelta, 1987). 2 3
A HISTORY OF PESTICIDE LEGISLATION IN ECUADOR
Published accounts of pesticide legislation are very rare in Ecuador.
The information for this section was collected through 14 interviews with government officials, environmentalists, and conservation organization administrators. A list of those interviewed is provided in the appendix.
Where possible I have documented the individual who presented the information. However, there were many instances in which details or descriptions that were vaguely presented in one interview were elaborated upon in another interview by a different individual. Consequently, it was sometimes impossible to ascribe specific facts to any one person as the information developed from patterns or trends which were described over several interviews by different people. There were also both general and specific discrepancies in some of the information provided. When these situations arose, I accepted the opinion of the individual who appeared to have a better understanding of the problem.
As of January 1989 there were no pesticide producing companies within Ecuadorean boundaries. Imported pesticides are sent to processing plants where the chemical is diluted, reformulated, and packaged. The
lack of internal production has led to a reliance on the policies of the parent companies whose international headquarters are in the major cities of Europe and the United States. This dependence is reflected in the decisions and actions taken by the branch office managers and is fully tolerated by the Ecuadorean government (Sevilla, P., 1987b).
Consequently, the administration does not have a strong or consistent policy 24
regarding the distribution and regulation of pesticides (Kakabadse, 1987).
This situation greatly reduces the effectiveness of the FAO Code.
In the late 1970s and early 1980s, the government began to establish agricultural and production expectations. Less priority was given to traditional farming using local varieties of plants. Emphasis was placed on the modernization of agricultural practices with the intention of developing increased productivity (Bonifaz, 1987). Short term increases were perceived to be immediately necessary to supply increased demographic requirements and supplement exportations (Viteri, 1989).
Consequently, the use of pesticides steadily increased from 1975 to 1985
(Sevilla, R. 1987). This agricultural philosophy was at least partly influenced by additional requirements placed on loans provided by the
World Bank (Viteri, 1989). This was a reflection of the declining oil market which had previously provided the required collateral.
The Ecuadorean government is organized into a cabinet and several ministries and institutes. Each ministry is then divided into both
"divisions" and "programs", the latter being the least important (Ponce,
1987) The Ecuadorean Institute of Health and the Ministry of Hydraulic
Resources originally published articles (i.e. policies) which regulated the discharge of pesticides to soil, water and air (Kakabadse, 1987). These articles were enforced by a set of fines and jail terms mandated through the penal court system. Concern for the environmental and health effects of pesticides was overshadowed by a perceived need for increased productivity.
This resulted in steadily decreasing penalties for pesticide infarctions 2 5
(Sevilla, P., 1987b). Newly invoked taxes on pesticides were used to subsidize the purchase of additional chemicals.
In addition, the government requested local industry to encourage the use of fertilizers and pesticides through extensive advertising (Sevilla,
R., 1987). Most of this advertising took the form of brightly colored signs painted on the sides of countryside buildings (figures 1-3). In 1987 there were an average of 3.5 painted walls per km within 5 km of a major town, and at least one advertisement per kilometer on open stretches of agricultural land. The signs are very conspicuous, well maintained, and painted with cool, eye-pleasing colors.
The subsequent indiscriminate use of pesticides resulted in extensive lobbying of the government by the Fundacion Natura (Kakabadse, 1987).
As a result of their efforts pesticides were redefined and classified by
Executive Decree Number 2331 of December 28, 1983, termed, "The
Regulation for the Production, Fabrication, Formulation, Importation, and
Use of Pesticides and Other Agricultural Products" (Sevilla, P., 1987b).
Unfortunately, most of the information used to categorize the pesticides was obtained from the manufacturing companies themselves. The National
Program of Vegetative Health (NPVH) of the Ministry of Agriculture was made responsible for the registration and regulation of all phases of pesticide importation, management, use, education, and labeling (Ponce,
1987). The Ministry could restrict or ban the use of any pesticide based on toxicologic data or the legislative action of other countries. The NPVH was also given complete legal control over the approval of importation permits.
However, these responsibilities became essentially titular as the 2 6 department was given neither the required financial resources nor the personnel to enforce the regulations (Ponce, 1987).
The declining environmental situation again prompted lobbying of the Ministry of Agriculture by the Fundacion Natura ((Kakabadse, 1987).
As a result, Executive Decree Number 242 was passed in July of 1985. This legislation banned the importation of 23 pesticides which were not approved for use in their country of origin (Sevilla, 1987). All remaining stocks in Ecuador were to be sold by January of 1986.
This situation was radically altered by Executive Decree Number 2260 of July 1986 which transferred the control of pesticides from the NPVH in the Ministry of Agriculture to the Banco Central, the Central Bank of
Ecuador (Sevilla, P., 1987b). Two major policy changes accompanied this transfer. The pesticide importation restrictions of Executive Decree 242 were removed and the Banco Central was given complete control over the issuance of importation permits (Sevilla, P., 1987a). The administrative justification for this action was a World Bank loan that required the removal of all restrictions on the importation of agricultural equipment, including those on pesticides.
The Banco Central is primarily concerned with financing the
Ecuadorean government and has been built up over the last several years to have almost dictatorial control over the economy. It does not stipulate provisions to determine the suitability of items being imported.
Consequently Ecuador, like many other developing countries, has the potential to became a dumping ground for compounds which had been 27
banned in other countries, overstocked by the parent companies, or were of too inferior a quality to have been sold elsewhere.
The Fundacion Natura again initiated lobbying efforts and an extensive media campaign to alter the importation of pesticides. This resulted in resolution 427-87 which prohibited the importation of Aldrin,
Dieldrin, Endrin, Chlordane, Lindane, Heptachlor and Parathion (Sevilla,
P., 1987a). It gave the Ministry of Health authority in the importation and use of DDT due to the need for malaria control. Also, control over importation permits for several herbicides was returned to the Ministry of
Agriculture. Unfortunately, this regulatory act again named the NPVH as administrator. Not only was this small department again incapable of enforcing the importation restrictions but, because of the structure of the
Ecuadorean government, it was subservient to the Banco Central. The
Central Bank presently has the power to overrule any decisions made by the
NPVH (Viteri, 1989). Consequently, the resolution has had little impact on pesticide importations. 28
PESTICIDE IMPORTATION IN ECUADOR 1978-1989
Details of costs and amounts of pesticides imported were assembled using data from the Fundacion Natura, the Banco Central, interviews, the
Ministry of Agriculture, and newspaper articles. Each source had slightly different figures, usually the Banco Central listed a lower number for a particular time period than did other sources. The lack of consistent numbers attests to the difficulty of accurately assessing the amount and cost of pesticides imported into Ecuador.
From 1978 to 1989 Ecuador imported approximately 62 million kg of pesticides at an estimated total cost of 294 million dollars (tables 1 and 2).
From 1976 to 1986, approximately 50% of the pesticides were purchased from corporations based in America and 40% from manufacturers in
Germany (Kakabadse, 1987). The products and 1986 gross sales of the 8 largest pesticide importers in Ecuador are listed in table 3. There has recently been a decrease in the amount of pesticides purchased from
Germany and an increase in the amount obtained from Colombia (table 4).
Imports of herbicides from Germany decreased to only 1 and 2% of the total imported into Ecuador in 1988 and 1989, respectively. Conversely,
Colombia supplied 21% of the total herbicides imported in 1988 and 17% of the total imported in 1989. Colombia also surpassed Germany, and the
United States, by supplying 27% and 14% of the fungicides imported in 1988 and 1989, respectively.
Although cost may be a factor, a more important consideration is the lack of regulatory controls in Colombia. Agricultural products come under no export restrictions; any agrochemical produced in Colombia can be 29
shipped to any nation willing to receive the merchandise. Also, Colombia has recently begun to ship large quantities of DDT to Ecuador for use in the malaria eradication programs. However, the United States is still the largest supplier of pesticides to Ecuador, providing 22% of the fungicides and over 40% of the herbicides. The majority of insecticides are also obtained from the United States: 63% of all insecticides imported in 1988 and
68% of the those imported in 1989 originated from American manufacturers.
Attempting to control pesticide use in a developing country by regulating the source will be difficult. Many pesticides are no longer restricted by patents. Preventing or restricting the importation of a pesticide by regulating export from a developed country only opens doors for suppliers from countries that do not have as stringent regulations. The example of Colombia replacing West Germany as a provider of DDT may be an example of this situation.
From 1978 to 1988, herbicides were the largest category of imported pesticides. Imports steadily increased from 1978 and peaked in 1986 at 3.3 million kg, or 57%, by weight, of total pesticides (table 1 and 3).
Importation decreased by 1989 to 2.7 million kg or 40% of total pesticides.
This was also the first year that importation of insecticides exceeded herbicides. Fungicide importation peaked in 1980 at 1.35 million kg and gradually declined to 676,000 kg in 1986. However, approximately 1.1 million kg of fungicides were imported each year in 1988 and 1989. The nematocide imports declined to almost negligible levels by 1986. These changes are presented graphically in figures 4, 5, and 6. 3 0
In 1978, 1.03 million kg of insecticides were imported into Ecuador, or 26% of all pesticides. Imports increased approximately 15% per year from 1978 to 1988, except in 1982 when only 983,000 kg were brought into the country. By 1989 insecticide importation had increased to 2.9 million kg and insecticides constituted 43% of all imported pesticides. Expenditures on insecticides made up 17% of the total cost of pesticides imported from
1978 to 1986, hut had increased to 43% of the total cost of pesticides imported from 1988 to 1989.
Over the past decade, prices of various pesticides have decreased.
Statistics that use for comparative purposes only dollar amounts of pesticides can be deceptive. For example, Ecuador imported 3.95 million kg of pesticides in 1978, and 6.74 million kg in 1989; an increase of almost 71%.
However, the dollar amount spent on these chemicals increased only 13%, from 25.7 million dollars in 1978 to 29.0 million dollars in 1989.
The nematocide most commonly imported into Ecuador was 1,2- dibromo-3-chloropropane (DBCP). This was primarily used in the banana plantations (Ministry of Agriculture, 1987). In 1977 the State of California banned the sale of DBCP because of its suspected role in causing sterility in manufacturing plant workers. Shortly thereafter it was found to have both mutagenic and carcinogenic properties. By 1979 the United States
Environmental Protection Agency issued an emergency suspension of all uses of DBCP (except on Hawaiian pineapples). Production was cancelled by the three largest producers of DBCP: Shell, Occidental Petroleum, and
Dow Chemical (the original patent holder to whom all other companies were paying royalties). However, Amvae Chemical Corporation continued to produce the chemical for export stating, at their stockholders meeting, that they were "filling a void" (Weir and Schapiro, 1981). Amvac ultimately suspended manufacture of DBCP by 1981 and liquidated their stocks.
Importation of DBCP in Ecuador did not show significant declines until after
1982, 5 years subsequent to initial action in the country of origin.
A large percentage of the insecticides shipped to developing nations are restricted in the western world. According to a 1979 United States
Government Accounting Office study, 30% of all pesticides exported were not registered for internal use by the Environmental Protection Agency, and 20% had been previously banned (Hill, 1988). From 1978 through, and including 1982, 5.7 million kg of insecticides were imported into Ecuador.
Of these, 865,300 kg, or 15% were banned or restricted in their country of origin (table 6). Carbamates, used extensively by potato farmers, constituted 57% of the banned insecticides with the remainder evenly split between organophosphates and organoehlorines. 32
CONCLUSION
Internationally, pesticide legislation has been a series of decisions which consistently increased the autonomy of the importing companies.
The effectiveness and success of the FAO code depends on the philosophy and concerns of the developing country’s government. The administration of Ecuador does not have an effective, comprehensive set of regulations to control pesticide importation and distribution. As a result the majority of pesticide importers are free to operate in whatever manner is consistent with the marketing strategy of their corporation.
Although both the government and individual corporations are aware of the FAO code there is no indication that it has had an impact on the advertising, labeling, or the distribution of pesticides in Ecuador. If
Ecuador is indicative of other developing countries, the agrochemical industry's preference for a "caveat emptor" approach to distributing pesticides is being realized as a result of the indifference shown by the government.
The organization in Ecuador which has had the most impact on monitoring the importation of pesticides is the Fundacion Natura. Their efforts to stimulate awareness and bring about more stringent regulations have been more effective than voluntary adherence to the FAO Code.
However, these crusades have been consistently undone by the Ecuadorean government. Ecuador continues to import increasing quantities of herbicides and insecticides, many of which have been banned or restricted
in their country of origin. W INSECTICIDE ^ ASUDIN ECUAQUIHICA
FKIl'RIS 1 VITAVAX AND BASUDIN ADVKRTISINC ON TIIK PAN-AMFRICAN IIK illW A Y 3 4
EURfy DE LOf INJECTKIDAI
FOLATAN 4F LA /OIUCION A LA LANCHA
FIGURF 2 MONITOR ANI) 1)1 FOLATAN ADVERTISING ON TIIF PAN-AMFRICAN HIGHWAY EKiURE 3 BAYLETON AND KURADAN ADVERTISING ON THE PAN-AMERICA IIIOIIWAY TABLE 1 PESTICIDES IMPORTED INTO ECUADOR FROM 1978-1989 IN THOUSANDS OF KILOGRAMS
PESTICIDE 1 97 8 a 1 9 8 0 a 1 98 2 a 1 9 8 4 b 1 986 b 1988° 1 989c EST. TOTALd
HERBICIDES 1,655 1,659 2,223 2,754 3,300 3,272 2,700 30,000
FUNGICIDES 728 1,354 1,122 941 676 1,168 1,110 12,000
INSECTICIDES 1,037 1,320 983 1,350 1,750 2,373 2,934 18,000
NEMATOCIDESe 532 467 395 175 72 NA NA 3,300
TOTAL 3,952 4,8 0 0 4,723 5,220 5,798 6,813 6,744 63,300
a Modified from data supplied by the Fundacion Natura, Quito, Ecudaor. b Engineer Arturo Ponce, personal communication. c Oficina de Estadisticas Comerciales del Banco Central (Office of Commercial Statistics, Central Bank of Ecuador). Values for 1989 are pro-rated using import records of the first 3 quarters d Totals estimated using values from known years. e Records of nematocide imports were combined into general insecticides after 1986. Given their trend they would be only a small fraction of the total insecticides imported in later years. TABLE 2 COSTS OF PESTICIDES IMPORTED INTO ECUADOR IN THOUSANDS OF U.S. DOLLARS
PESTICIDE 1978 1978 1982 1982 1986 1986 1978 -8 6 1978-86 TOTAL % OF TOTAL % OF TOTAL % OF EST.TO TAL % TOTAL COST8 TOTAL COST TOTAL COST TOTAL COSTb IMPORTED HERBICIDES 8,991 35% 10,390 40% 11,736 43% 89,000 38%
FUNGICIDES 11,816 46% 12,989 50% 6,134 23% 105,000 45%
INSECTICIDES 4,881 19% 2,598 10% 8,801 33% 39,000 17%
TOTAL 25,688 1.00 25,977 1.00 26,671 1.00 233,000 1.00
Modified from data supplied by the Fundacion Natura, Quito, Ecuador a Data expressed as 1000's of US dollars, current year valuation; e.g. 1,572 = 1.572 million dollars b Total pesticide imported estimated from known years
'-j TABLE 2 (continued) COSTS OF PESTICIDES IMPORTED INTO ECl'ADOR IN THOUSANDS OF DOLLARS
PESTICIDE 1988 1988 1989 1989 1 9 8 8 -8 9 1 9 8 8 -8 9 1978 -8 9 1978 -8 9 TOTAL % OF TOTAL % OF TOTAL % OF TOTAL % TOTAL COST TOTAL COST TOTAL COST TOTAL COST IMPORTED HERBICIDES 13,382 42% 10,368 36% 23,750 39% 112,750 38%
FUNGICIDES 6,494 20% 4,873 17% 11,367 19% 116,367 40%
INSECTICIDES 12,245 38% 13,761 47% 26,006 43% 65,006 22%
TOTAL 32,121 LOO 29,002 1.00 61,123 1.00 294,123 1.00
NOTES: 1988 and 1989 data from La Oficina de Estadisticas Comerciales del Banco Central (Office of Commercial Statistics, Central Bank of Ecuador. Values for 1989 are pro-rated using import records of the first 3 quarters Totals estimated using values from known years.
oc 3 9
TABLE 3 1986 GROSS SALES OF PESTICIDES BY THE 8 LARGEST IMPORTERS IN ECUADOR
COM PAN V TOTAL SALES PRODUCTS IN DOLLARS
SIIKLL not released lindane, aldrin, endrin, in onoerotop lios CIEBY-UEIUY not released lindane, m on oe r ot op h os
UNION CARBIDE not released a 1 d i e a r li
BAY ER not released earbol'uran. I'enthion, inethyl- parathion, parathion, dimelhoate SKRVICIOS 4,000,000.00 earbol'uran, fenthion, incthyl- (division of paralhion, parathion, dimelhoate B a vcr) IIOECIIST 3,500,000.00 ea rb o I'ura 11
CELAMERCK 8 2 5 ,0 0 0 .0 0 mcthy l-parathion, parathion. BHC, aldrin, dieldrin INDIA IMPORTS 6 5 ,2 5 0 .0 0 di m eth o a te
NOTES: Source: Sevilla, P. 1987. 40
TABLE 4 PESTICIDE IMPORTED INTO ECUADOR BY THE THREE LARGEST SUPPLIERS TO THAT NATION
Uniter States Germany Colombia
1988 1989 1988 1989 1988 1989 PESTICIDE %a % % % % % TOTAL TOTAL TOTAL TOTAL TOTAL TOTAL HERBICIDES 42% 42% 1% 2% 21% 17%
FUNGICIDES 19% 22% 20% 12% 27% 14%
INSECTICIDES 63% 68% 7% 14% 8% 6%
n o t e s : a Percent of all pesticides of that type imported into Ecuador, i.e. 42% of all herbicides imported into Ecuador during 1988 originated in the United States. TABLE 5 PESTICIDE TYPE AS A PERCENT OF THE TOTAL KILOGRAMS OF PESTICIDES IMPORTED INTO ECUADOR FROM 1978-1986
PESTICIDE 1978a 1980a 1982a 1984b 1986b 1988c 1989c 11 YEAR AVERAGE HERBICIDES 43% 34% 47% 53% 57% 48% 40% 46%
FUNGICIDES 18% 28% 24% 18% 12% 17% 16% 21%
INSECTICIDES 26% 28% 10% 12% 30% 35% 43% 26%
NEMATOCIDESd 13% 10% 8% 3% 1% NA NA 7%
a Modified from data supplied by the Fundacion Natura, Quito, Ecuador. b Engineer Arturo Ponce, Ministry of Agriculture, personal communication. c Oficina de Estadisticas Comerciales del Banco Central (Office of Commercial Statistics, Central Bank of Ecuador). Values for 1989 are pro-rated using import records of the first 3 quarters d Records of nematocide imports were combined into general insecticides after 1986. Given their trend they would be only a small fraction of the total insecticides imported in later years. 4 2
TABLE 6 BANNED OR RESTRICTED PESTICIDES IMPORTED INTO ECUADOR FROM 1978 - 1982
INSECTICIDETYPE A M Ta EXPORTER AGRICULTURAL 1978 USES 82 CARBOEURAN CAR 452.0 Hoescht, Bayer potatos
ALDIC ARB CAR 38.9 Union Carbide coffee, rice, cotton
EENTIIION OP 77.2 Bayer coffee, potatoes, rice, cotton METHYL OP 34.2 Bayer, Celamerck alfalfa, rice, coffee, PARATHION sugar cane, corn, cotton PARATHION OP 27.7 Bayer, Celamerck alfalfa, rice, coffee, sugar cane, corn, cotton DIMETHOATE OP 26.6 India Imports, potatos, rice, cotton, Chevrol, Baver co ffee MONOCROTOPIIOS OP 26.2 Shell, Ciba-Geigy coffee, rice, cotton, sugar cane ENDRIN OC 60.3 Shell, Velsicol rice, cotton, sugar cane, coffee, fruit, corn, palms BHC OC 44.1 Celamerck rice, cotton
ALDRIN OC 34.7 Celamerck, Shell cotton, rice, bananas, coffee, corn, soy beans LINDANE OC 25.3 Shell, Ciba Geigy rice, cotton, coffee, corn, fruits, potatos CIILORDANE OC 8.4 Proficol corn, potatos
HEPTACHLOR OC 7.3 Proficol cotton, rice, fruit, corn, sugar cane DIELDRIN OC 2.4 Celamerck extensive use in areas of high resistance
TOTAL = 865,000 kilograms NOTES: 11 Total amount in 1,000 Kg. imported between 1978 and 1982 (last year that comprehensive data were available). Data consolidated from Sevilla and Sevilla, 1985. 3500 -
3000 “
2500 - HERBICIDES 2000 - FUNGICIDES INSECTICIDES 1500 -
1000 -
500
0 1976 1978 1980 1982 1984 1986 1988 1990
FIGURE 4 PESTICIDES IMPORTED INTO ECUADOR FROM 1978 TO 1989 44 100 n
H Z Ui o cc UJ CL □ HERBICIDES □ FUNGICIDES H INSECTICIDES
1 978 1 982 1 986 1 988 1 989
FIGURE 5 RELATIVE COSTS OF PESTICIDES IMPORTED INTO ECUADOR FROM 1978-1982
u j 40
E3 NEMATOCIDES □ HERBICIDES H FUNGICIDES ■ INSECTICIDES 0 0 O CM "St < o 0 0 a t ro 0 0 0 0 0 0 0 0 0 0 0 0 o t a t a t 0> a t a t a t T— *— T"“ T— i— y — y —
FIGURE 6 PESTICIDE TYPE AS A PERCENT OF TOTAL KILOGRAMS IMPORTED INTO ECUADOR CHAPTER II
SURVEYS
INTRODUCTION
Surveys were conducted to explore aspects of pesticide availability, use, and potential toxicity to Ecuadorean farmers. One set of surveys assessed the effectiveness of the FAO code in regulating pesticide sales at the retail level. Another set investigated the differences in pesticide use among subcultures of Ecuadorean farmers. All surveys took the form of open ended responses to a core set of questions.
The recommendations and suggestions of the FAO Code are ultimately designed to influence the use of pesticides at an individual level. To assess the effectiveness of the existing regulations 1 conducted surveys of retail pesticide shops in the capital city of Quito and in Otavalo, a small agricultural city 2 km north of Lake San Pablo. Surveys were completed in
July and August of 1987; a less extensive followup survey was made in 1989.
Surveys conducted in Otavalo and in 4 agricultural provinces investigated the differences in pesticide use between impoverished Indians who raise crops only for subsistence and profit-motivated farmers using westernized agricultural techniques. Profit motivated farmers did not use pesticides for non-agricultural purposes, as did the Otavalan Indians. To examine the latter group's use of pesticides I conducted a household survey
4 5 46 in the community of Peraguehi, near Otavalo. I was aided in the household survey by an Otavalan Indian who had received 2 years of university education in Spain and was familiar with pesticides and their problems.
An Ecuadorean medical student assisted with data acquisition in the survey of agricultural provinces. 47
METHODS
A list of all pesticide stores was made using the Quito Yellow Pages.
Fifteen stores were selected using a random number table and the last 2 digits of their phone number. In order to control for any bias that may have resulted from visiting only those stores with a telephone I divided the city into 4 areas and visited 6 additional stores; 2 stores in areas near the center of town and 2 pesticide stores each at the northern and southern limits of Quito. The companies listed in the phone book were professional merchants who sold a variety of fertilizers and application equipment. The other 6 establishments tended to be general merchants that sold an assortment of household goods.
The Otavalan survey covered 23 businesses which were visited over a period of 2 weeks in July of 1987. In addition to conventional stores, there appeared to be several transient vendors who operated out of the back of their pickup truck or car. These individuals were not included in the survey as I was not able to locate anyone actually conducting business. The shops in Otavalo were primarily poor generalmerchants who offered a greater diversity of non-pesticidal products, similar to the 6 non-phone
shops in Quito. There were no shops of similar size or specialization as the
21 stores in Quito.
The stores surveyed in Otavalo were located by randomly selecting a
location within the city. After traveling to this location I walked around
the block until I came across a pesticide store. If there were no shops on that block I moved to the adjoining block north or south, and east or west, as determined by 2 coin tosses. It is assumed that the selection of the 15 48
Quito shops with phones and the Otavalan shops satisfied the conditions for
simple random sampling. The 6 smaller shops in Quito were chosen in a non-random manner.
Store personnel were asked about the service they received from agrochemical company salesmen, primarily the timetable of their visits. A record was kept of the safety equipment on display: gloves, masks or respirators, boots, and overalls or jumpsuits. I attempted to assess the knowledge of sales people or shop keepers by asking about 5 aspects of a pesticide which was prominently displayed, although the products were not the same from store to store. I reasoned that store personnel would he more familiar with these items. Points were not awarded for vague or general responses. Although this was quite subjective, it was usually very easy to determine which sales people were truly knowledgeable. Each of the 5 categories was worth one point, for a perfect score of 5. Most questions involved yes/no responses and concerned:
1. Safety precautions.
2. Crops or uses.
3. The method and timing of applications.
4. The minimum amount of time to wait before harvesting.
5. First aid information.
In addition, I asked specifically about the FAO code :
1. Do they know of its existence.
2. What was the reason for its inception.
3. What changes have they made in their store as a result of the code. 49
I examined the displays within the store and recorded the names of pesticide products, these are listed in tables 7-9. I also tabulated the number of containers that had unreadable labels, the number that had been opened, and those that were, or had been, leaking. The sale of additional agricultural products was also noted. The types of advertisements, posters, etc. were categorized into safe or unsafe illustrations of practices. Unsafe practices usually involved illustrations of farmers without adequate protection engaging in pesticide preparation, application, etc. I questioned store personnel about the pesticidal products most commonly sold within the last month and asked if they obtain DDT, a pesticide that was strongly regulated by the Ministry of Health. 5 0
A SURVEY OF RETAIL PESTICIDE SHOPS IN QUITO
The survey results are presented in table 10. The population of stores with phones tended to be larger shops that were relatively neat and well-organized. These shops, and the 6, smaller non-phone stores, were constantly visited by company representatives who could usually provide whatever products they needed within a week. This promptness is usually not the way of business in Ecuador.
Safety equipment was also displayed and aggressively marketed.
Consumers in Quito, compared to rural farmers, are perhaps more aware of the dangers of pesticides and certainly have greater financial flexibility.
Gloves and some type of respirator were sold at every establishment 1 visited, although only the 15 stores with phones carried boots or overalls.
This was most probably due to the space necessary to maintain a suitable inventory of different sized articles. The 6 non-phone stores were stocked from floor to ceiling with pesticides or agricultural products and had no additional storage space for items as large as boots or clothing. The types of respirators varied from a simple fiber-cloth mask, similar to a craftsman's dust mask, to more expensive units with replaceable filters. Of the 6 smaller establishments, all 6 sold only the inexpensive fiber-cloth masks.
All stores sold some type of pressurized application equipment which ranged from large pump-pressure containers (hand-carried or back- carried), to small hand held sprayers. There were also motorized spreaders to scatter granules. The most common applicator was a back-carried, pressurized sprayer. Only one store had a push cart spreader. Since lawns 5 1 are so small and garden labor cheap most pesticides sold for ornamental ground use are cast by hand or sprayed. Products sold for use on flowers or garden vegetables were primarily pyrethroid powders in shake-out containers. There appeared to be more powders than liquids, but many of the former were designed to be mixed with water and sprayed.
The responses of sales personnel to the 5 questions listed in the methods section were summed and are presented in table 10 as total points.
Most of the sales people in Quito were well versed in their products, one individual was quite knowledgeable and could provide accurate information in all five categories of questions. However, the level of my fluency in
Spanish made it difficult to ascertain whether some of the people at the shops were being truthful in their answers or whether I was just being persuaded by accommodating responses.
In several instances the only available assistance was provided by general office help who were not familiar with the products. The individual to whom questions should have been directed was not in at the time. This accounted for several low scores. However, it was still possible to purchase products. The 6 non-phone shops had clerks who, overall, were not as knowledgeable as the larger shops. Their appearances were also less professional. Question 2, regarding crops or uses, and question
3, concerning application methods were answered by representatives of all but two stores. People in these 2 stores appeared to be secretaries filling in for the regular sales clerk.
Safety precaution questions were answered with specific suggestions for equipment purchase. Sales clerks in all stores recommended gloves and 5 2
most considered respirators necessary. The responses given in the 6 non phone stores seemed to down-play the toxicity of the pesticides. On several occasions the only suggestion made in these shops was to "wash your hands" after applications.
In several urban stores, question 4 in the "knowledge of staff" category was altered to "time before handling". In many cases the most prominently displayed product was a pesticide for ornamental flowers, usually roses. Questions as to the time before harvest were not as relevant as time before handling. Also, because of the availability of medical care many sales people simply suggested to call a physician if accidental contamination occurred. The most frequently mentioned symptoms of overdose were nauseousness and headaches.
Only 4 people knew of the FAO code, none of whom were working in a non-phone store. Of these 4 people only one understood that its purpose was to "control dangerous pesticides". In many instances sales clerks asked other employees in the store ahout the code, so there were more than 21 individuals questioned. Since some of these people were the store managers it is ohvious that even minimal information on the code has not reached the retail level. Those individuals who recognized the FAO code could not recall any change in operating principles that may have reflected its recommendations.
The FAO Code suggests that pesticides bear labels that contain: the name and address of the manufacturing company; information on toxicity, first aid and safety measures, and; application procedures and timing.
Labels must also list ingredient statements of weights or measures. The 5 3
Environmental Protection Agency further stipulates that pesticides exported from the United States must have a skull and crossbones displayed if the chemical is highly toxic. They must also contain, in the language of the country to which the product is being imported, the statement "Not
Registered For Use in The United States of America", if appropriate. The ingredients lists, warning statements, and toxicity must also be stated in the native language.
Two of the 21 stores in Quito had an unlabeled container for sale, one in the phone and one in the non-phone samples. I differentiated between containers that were being used for temporary storage and those which clearly contained materials offered for sale. In both instances the unlabeled containers contained a powder which was a mixture of pesticides for "general garden insects".
Labels that contained the information recommended by the FAO code were more the exception than the rule. Products distributed by Ceramack were consistently ambiguous on application instructions, suggesting the use of "conventional methods" and "adequate protective equipment".
Specifics regarding protective clothingwere ubiquitously absent as were technical data regarding batch numbers, dates of manufacture, and maximum storage times.
Open containers were noted in 11 of the 21 shops, including all 6 of the non-phone stores. Several businesses apparently sold pesticides by weight, scooping out product from master containers and packing it in tin cans. There were 5 phone-stores with open containers. In 2 of the stores this appeared to be the result of shop carelessness, only 3 appeared to sell 5 4
pesticides by measure. However, all 6 non-phone stores sold pesticides by weight. I observed this transaction and noticed that in most cases the sales person wrote the name of the pesticide and some additional details on a label which was then attached to the can. Six of the 21 stores displayed products which were, or had been, leaking. Many containers had faded or damaged
labels which could have resulted from leakage or simply have been a reflection of the age of the product. Only 2 of the phone-stores had damaged containers compared to 4 of the non-phone stores.
Figure 7 is a photostat of the only label on a product available in
several agricultural supply stores in Quito. Nogos is the Ciba-Geiga trade
name for Diclorvos, an organophosphorus insecticide. The description on
the left hand side of the label lists the crops on which the pesticide can be
used: cotton, rice, beans, corn, potatoes, soy beans, and ornamental or
horticultural plants. There is also the advice to apply the pesticide at the
rate of 375 to 500 cc per hectare during the last hours of the day. There are
no additional instructions regarding spacing of application, time before
harvest or even the recommended method of application. Neither is there
information on first aid, handling precautions nor statements to suggest
the dangerous nature of the chemical. The label itself was also damaged by
either bottle leakage or external spillage.
The description of "moderately toxic" is technically correct but the
semantics of the description are misleading to layman. Diehlorvos has an
RO LD50 of 80 mg /kg and thus is closer to the "highly toxic" classification
(1 - 50 mg/kg) than to the "slightly toxic" classification (500 - 5000 mg/kg). 5 5
The label was printed by the Ecuadorean distributor, Ecuaquimica, and does not include manufacturing information or the address for Ciba-Geigy.
Advertising is another area which is addressed by the FAO code. The
Fundacion Natura considers advertising infringements the single greatest industrial violation of the code. (Sevilla, R. 1987). Many manufacturing publications depict unsafe practices while being suggestive of greatly increased harvests of near-perfect crops. I collected brochures and pamphlets from stores offering them to customers and examined their content. Their overall message was that pesticide use is necessary to ensure a profitable harvest. An example is provided by figure 8, a descriptive brochure describing Temik 10, a pesticide containing aldicarb as the active ingredient, produced by Union Carbide. ft is advertised as the "best foundation for producing potatoes" and shows an overflowing sack of potatoes, indicative of high yield, resting on a box of pesticide.
The label precautions on Temik warn against using the product around children or animals, suggest the use of appropriate applicators and gloves, request that the worker read the enclosed instructions before use, and advises that "all agricultural products are dangerous to the health if there is unsuitable handling". Illiterate farmers who are not able to read the precautions will instead look to the illustrations for guidance. The pamphlet contains three photographs of farm workers applying the product using knap-sack sprayers. Although not clearly visible in the illustration, the workers are not wearing respirators, masks, or boots, and are applying the product in what appears to be their normal clothing. In 5 6
direct contradiction to the label precautions, none of the workers are wearing gloves.
Many fliers or pamphlets are specific for a particular agricultural product and list scores of insects that could conceivably inflict damage. The recommended dosages are listed for each group of pests; absent were suggestions for the timing of repeat applications. Several times during my questioning of sales clerks I was told to repeat an application whenever the insects reappeared. If this occurred within a few days of treatment the concentration of pesticide should be increased. This combination of published and verbal information will unquestionably lead to blatant overuse of pesticides.
An entomologist at the Natural Science Museum in Quito examined the pesticide application sheets I had collected. He told me that although the data were technically correct, they were not regionally accurate and made no mention of temporal changes in abundance. Several species of insect pests would be seen only in specific areas of the country and then only at certain times of the year. The manufacturers' sheets gave the impression that the insects were ubiquitous, extremely abundant, and required constant vigilance.
There was a paucity of advice regarding safety on the information sheets. Suggestions were made to: use gloves or a respirator; wash work clothes after application, and; thoroughly rinse the applicator when finished. There were no warnings to wash clothes separately or rinse the equipment in an area that would minimize animal or human exposure.
Those brochures that did mention safety precautions usually located them in 5 7
smaller print after describing the application procedures. The use of hold text or demonstrative graphics was reserved for those topics which pertained to the beneficial qualities of the product.
Some sheets did not provide any information on adverse health effects or symptoms of over-exposure. None listed any effects of chronic exposure. Several companies suggested that mixtures of pesticides be used to completely eradicate persistent pests. The general contents of the information sheets tended to discount the adverse health and agricultural effects and minimized safety precautions. Conversely, they indirectly overemphasized necessity and encouraged misuse.
Posters depicting beautiful flowers, healthy agricultural products, and smiling pesticide applicators were quite common; 9 out of 21 stores had such displays. Only 3 of the 9 shops had posters which presented unsafe application procedures. Two of the 6 posters which showed safe techniques in handling appeared to be primarily stressing the ease of use of the advertised product. Only 1 of the 6 non-phone stores had an advertisement, and this was an illustration of the correct procedure to fill and seal a pressurized sprayer. The other 5 shops had no available space for posters or illustrations. Seven of the larger shops had space but did not display any promotional material. The most interesting advertisement was a smiling, well dressed, matronly woman with lipstick and mascara, shaking a pesticidal powder over her vegetables. She was wearing gloves and an apron, however. In keeping with the predominant advertising practice, the woman more resembled a Western housewife than an Ecuadorean. Many 5 8
products are advertised in a manner that suggests they are popular in the
United States.
Store stocks of pesticides appeared to be evenly split into 3 categories:
products designed for fruit trees, those for agricultural and flower pests, and pesticides for insects found inside the home. The last category included
many insecticides which were recommended solely for preventive
measures. There was a tendency for the shops to sell primarily organophosphates. Phone-stores also sold organochlorines, carbamates, and pyrethroids whereas non-phone stores carried only organophosphates, organochlorines and pyrethroids. Carbamates were the most expensive pesticides, and usually consisted of Sevin or Carbofuran.
Several sales people thought that organophosphate pesticides were becoming more popular and mentioned instances where customers requested any product except organochlorines. This was thought to be due to the adverse effects of DDT which were consistently mentioned in
newspaper articles describing the malaria control program. During the first half of 1987 there was considerable media coverage of a resurgence of
malaria on the coast and in the jungle. One individual told me that the organochlorines were "very bad" when he recommended an organophosphate product.
Animal feed was sold at only 3 of the 21 stores: 2 of the phone population and 1 of the non-phone population. All but 5 shops sold either
liquid or powder fertilizers. No shops sold any type of human food. Stores
with phones also sold a greater variety of general household and farm equipm ent. 5 9
I attempted to purchase DDT at all the stores I visited. Because of the malaria situation this chemical is supposedly tightly controlled. However, several government and conservation individuals with whom I had spoken regarding the history of pesticide legislation indicated that there was an extensive black market trade and that the chemical should not he very difficult to obtain. When questioned, the majority of sales people stated that
I would not be able to purchase DDT unless I had a permit from the Ministry of Health. When I offered to pay any price the majority still refused but 3 individuals said that they could provide small amounts. It was probably the case that I aroused more suspicion in my requests than would a native
Ecuadorean and there were actually more shops capable of providing DDT than originally offered. 60
A SURVEY OF RETAIL PESTICIDE SHOPS IN OTAVALO
Otavalo is a small town approximately 1 km2, located 2 kilometers north of Lake San Pablo. Both the lake and town are surrounded by small satellite villages of 30 to 50 houses, large haciendas, and isolated farms.
The inhabitants are primarily Quetchua Indians. They have their own language, alphabet, and culture to which they adhere quite strongly.
Although Roman Catholic, they maintain vestiges of their ancestral religion. Lake San Pablo and the mountain at its eastern end are considered the homes of several Quetchua gods. Economically, the region is controlled by a plutocracy of wealthy hacienda owners, although Indian held cooperatives are beginning to increase in number and size. The Indians are essentially self-sufficient but recently several kinds of manufactured goods have become necessities; foremost among these are pesticides.
The survey conducted in Quito was duplicated in Otavalo (table 11).
The Otavalan shops were not as specialized as those in Quito and commonly stocked pesticides along with general purpose home and farm equipment.
Although they were occasionally called upon by distributors, most shop owners went to Quito to purchase their products. Evidently, some of the distributors were not factory authorized representatives and operated as self-employed middlemen. Better prices could be obtained directly from the distributors in Quito. There had also been problems in obtaining shipments from the cities. Store proprietors personally brought their pesticide purchases back to Otavalo, usually packing them on top of buses next to animals, food products, and the luggage of other passengers. The 6 1 general feeling was that commercial shipping was very expensive
compared to the cost of a bus ticket.
Gloves were available at all but 2 stores, respirators and masks at 8, boots and overalls only at the 2 largest shops. These products were generally of lesser quality and higher price than similar products in Quito.
Most stores had a greater selection of application rather than safety equipment. All but 5 stores sold some type of applicator although several carried only simple half-literhand-pump sprayers. Most of the equipment was designed for liquid formulations. Additional accessories usually
included plastic buckets, funnels, and mixing cups.
The Otavalan stores carried a larger proportion of emulsifiable concentrates than wettable powder insecticides, compared to the stores in
Quito. I would have expected dry chemicals to be preferred because of the ease in transportation and storage. I asked one storekeeper about this situation and he told me that he did not purchase dry chemicals as they were usually packed less securely, were easily damaged by humidity or water, especially during transport in the rainy season, and were difficult to dilute
in small quantities. Many of his customers preferred liquid pesticides primarily because of the convenience of mixing and dilution.
Many of the shops in Otavalo had as attendants children with little knowledge of the products. This resulted in very low scores in the
"knowledge of staff" category. Older shopkeepers were more familiar with the type of crops for which each pesticide was best suited, had rudimentary knowledge of application procedures, and could estimate application rate or dose. I was given the same advice in Otavalo as I received in Quito 6 2
regarding application frequency. If the insects reappeared shortly after
the initial application the pesticide solution was too weak. A stronger
solution was to be repeatedly applied until the insects were no longer present.
As to he expected, there was a noticeable difference between rural and urban store personnel in the awareness of the toxicity of pesticides.
Most storekeepers felt that there was no need to have a long delay period between application and harvesting, especially if water was available for
washing. Some suggested using the pesticide during storage of crops.
Several people would simply look at the label in their attempts to answer my
questions. There was also a general lack of concern over any adverse
health effects from misapplication. Not one individual had heard of the
FAO code. In general, the products were consistently treated with far less
respect than required by their toxicity.
All the shops in Otavalo had open or leaking pesticide containers.
Also, several shops had the remains of liquid and powder spillage visible on
the walls, floors, and even the counters. Several bottles had such
extensive leakage that their label was unreadable. A particularly striking
image was a bottle with fingerprint ridges clearly visible in the dried
residue. Five of the stores were selling unlabeled containers straight from
their shipping box. The box itself was marked, in one instance as
Malathion and in another as Sevin, but the individual containers were not
(the former pesticide is an organophosphate, the latter is a carbamate).
Several dry chemicals were sold by weight from a master container, being
measured out on an open scale. The chemical was then dumped into a 6 3
plastic hag and knotted, appearing much like flour sold in an identical manner at the food stores. I noticed that some customers even brought their own containers. Posters and signs were rare due to space limitations as most stores were stocked from floor to ceiling. Illustrations were usually of procedures or equipment promotions. In several, the workers were pictured without gloves or othertypes of protective clothing.
Carbamates and organophosphates were more commonly sold than organochlorines. The former was dominated by Sevin (carbaryl) or
Furadan (carbofuran). There was a greater range of different organophosphate products but an emphasis on malathion and Baytex
(fenthion). Many times the opinion of the shopkeeper was based on a single product which he preferred to sell. The selection and diversity in any one shop were, understandably, not nearly as great as shops in Quito, but the range of products offered between all the shops was quite large. It may be that the pesticide market in Otavalo has been divided into more specialized retailers to minimize competition.
There was no shop that sold only pesticides. Two shops were corner food markets with small sections devoted to pesticides; in both cases the pesticides were displayed next to, and above, raw fruits or boxes of food products. Neither of these stores sold any type of protective equipment.
The remaining 19 stores sold pesticides, fertilizers, and miscellaneous farm equipment; 2 of these also carried food products. Thirty percent of the
Otavalan shops, compared to 14% of the Quito stores said they were able to acquire DDT, although the quoted price was exorbitant. This was more likely due to my "gringo" characteristics and 1 doubt whether the price would be as high to a native. Evidently, the black market connections were more extensive in rural areas and stores showed little concern with regulations or laws. 6 5
A 1989 FOLLOWUP SURVEY OF RETAIL PESTICIDE SHOPS IN QUITO
A brief followup survey of Quito pesticide shops was made in 1989.
Few characteristics of the shops had changed. As was suggested in 1987, the general trend had been a reduction in the sales of organochlorine insecticides and an increase in organophosphates. Approximately 80% of the pesticides sold were organophosphates; pyrethroids and carbamates split the remaining 20%. Organochlorines were not carried by the 4 stores visited.
The content of advertising and the style of the application brochures had not changed. The impression gleaned from the promotions was that pesticides were needed to ensure high yields of quality products. Although stores stocked gloves, respirators, and boots, there was still a lack of published safety information. The number of opened or damaged containers had decreased appreciably. This was due more to the packaging of organophosphates in small, heavy plastic bags than to any increase in awareness. Labels did not contain significant safety precautions.
Although application rates were described, application schedules were not.
Even after two additional years, the FAO code has still to make a significant contribution to the manner in which pesticides are marketed in Ecuador. 6 6
CONCLUSIONS FROM THE SURVEYS TO ASSESS THE EFFECTIVENESS OF THE FAO CODE
There is no standardization or regulation evident within shops. Only economic solvency and a commercial location are required to operate as a pesticide distributor. It appears that few of the pesticide manufacturers required distributors to become familiar with safety requirements and risks of their products. However, if they did so in the past, there are no provisions to maintain a particular educational level. Most shops did not have adequately trained personnel and could not offer advise to customers on appropriate procedures or safety precautions. Most agrochemical companies have not published educational or instructive materials, or at least the pesticide stores do not make it readily available. Rather, their publications promote indiscriminate application through subtle promises of increased productivity and yield. Only 3 companies consistently delivered technical information: Bayer Farmaceutica, Equaquimica, and Servicios
Agricolas.
General observations of the pesticide retailers, especially the smaller stores, suggested that there was little concern for safety. There was no visible absorbant, such as sand, to treat spills. Although floors were primarily tiled, there were commonly cracks and worn grouting that could trap powders, especially during cleaning. In some cases stain marks on the floor indicated that pesticides had leached out of the store and onto the street. The custom of sweeping out wash water used on floors would also contribute to chemical laden waters entering street drainage channels, the water of which is sometimes used by beggars and street merchants. 6 7
Ventilation was poor, and the characteristic odor of pesticides was always present. Pesticides were also commonly stored near hardware, foodstuffs, clothing, and other agricultural products. Several sales clerks were observed to be eating or drinking inside the store. Many pesticides were without labels, or were difficult to identify due to faded or damaged labels and very few had any date of receipt stamped on the container. This is suggestive of poor inventory control such that products are not sold in a time-regulated manner, e. g. the oldest product first. The potential danger exists in that customers who first purchase a product whose potency had been diminished by storage past the shelf life may incorrectly assess how much pesticide is needed to perform a certain task. Purchasing a newer product of stronger potency at a later date could easily result in overuse and intoxication. Improvements in many of these areas can be had without an increase in costs. Record-keeping and inventory control can be integrated without tremendous increases in personnel.
Individuals, especially managers, were very apprehensive about questions concerning accidental poisoning of their staff; most denied any injuries. However, a survey conducted by the Tropical Development and
Research Institute in London found that of 48 pesticide stores in developing countries, 27% of store manages indicated that either they, or a member of their staff for whom they were responsible, had at one time suffered symptoms of intoxication; 14% of these cases required hospitalization
(Haines, 1985).
The FAO code has not succeeded in regulating the labeling, marketing, or advertising of pesticides. In this regard, the main 68
contentions of the agrochemical industry are invalid: importing countries cannot rely solely on the guidelines of the FAO code to effectively regulate the sale of imported products. In addition, the existence of a black market makes it possible to purchase pesticides that are supposedly regulated.
Retailers and their suppliers have done little to minimize pesticide exposure and misuse. 69
RESULTS OF INTERVIEWS ON PESTICIDE USE AND EXPOSURE IN AN INDIAN VILLAGE
Peraguchi is inhabited by impoverished self-sufficient farmers who subsist on corn, potatoes, chickens, dairy products, and pork. Their houses are usually made of cement block covered with metal or clay tile roofs; most have electricity. Some have running water piped in from a nearby river. The floors are dirt, or in rare cases, planked. Bed clothes and sleeping mattresses are spread on top of reed mats which lay on the dirt ground. This eontributes to a high level of insect infestation. The kitchen is usually a large room with access to outside storage areas where food is kept. Foodstuffs are kept in piles on the ground or in large open containers. Children and animals roam freely through the storerooms and kitchen areas. The people are, for the most part, of good health and spirits.
The individual who assisted me in conducting interviews in the village of Peraguchi was named Carlocito (diminutive form of Carlos, his father's name). He was the second oldest son and third oldest child from a family that originally had 12 children, 7 girls and 5 boys. His household, and its attitude toward pesticide use, is representative of the majority of
Quetchua families living in the small rural villages of the Andean highlands. His village is similar to a large extended family, in which households grow their own foods and tend private stocks of animals but are very willing to share if disaster befalls a neighbor. Almost all major building endeavors are community efforts. At the time of my research the community was building a water line from a mountain river to the village, a distance of 5 km. 70
Carlocito showed me his family's collection of pesticides. They were bought or bartered from a "veterinarian" who makes sporadic visits in his pickup truck. This individual has heen selling fertilizers, pesticides, and occasionally treating livestock for several years. He is of Otavalan descent and thus is more trusted than some of the non-Indian store keepers in
Otavalo. Although he is slightly more expensive, he negotiates through bartering, which is something that is not customary in city shops.
The "veterinarian" is a major source of information regarding insecticidal and pesticidal products. This involves oral descriptions or demonstrations of suggested preparations. Evidently,this individual is ahle to recognize specific insects or their signs and recommend the appropriate pesticides. Unfortunately, safety concerns are minimized and little precautions are given. For some pesticides individuals are advised to
"wash their hands" or "take a bath" after application. Questions as to the appropriate amounts are usually answered with the advice to use "as much as needed" to obtain the desired effects. Obviously, products with high toxicity but low knockdown (the time required for visual verification of insect death) are in great danger of misuse.
Carlocito's family had a small can of malathion (10% concentration in an inert liquid), Fosfemo (powdered parathion of unknown concentration), and several coffee cans and small jars marked only with the name of an insect or agricultural product, e. g. corn, beans. Carlocito explained that these were "custom" mixtures prepared by the "veterinarian. " An unknown insect, or a plant fragment with a particular type of damage, is saved for inspection and "custom-made" mixtures are purchased, at usually 7 1
a much greater cost. There is no information provided as to what these mixtures contain. Oral advice on use is given upon their purchase. The can of malathion had written in Spanish information regarding the type of plants for which the product is best used and a general warning to avoid
"direct skin and eye contact". Unfortunately, Carlocito said that there were only 2 or 3 literate people in his village.
Carlocito's father and other farmers mentioned that the types of insect pests appeared to be changing and their quantity increasing. Part of this was attributed to contamination during shipments of goods from other parts of Ecuador, especially the jungle regions. The "veterinarian", who was always mentioned in high regard, had always been able to provide a new, satisfactory insecticide. Recently, there was some feeling that he had been diluting his products as more substance was needed to obtain the desired effects. Although this may be a legitimate reason, another explanation could be the increasing resistance of the insects.
The villagers used pesticides primarily to treat lice and other body insect infestations and to control damage to stored foodstuffs. They were too poor to make extensive use on their fields of agricultural pesticides, except in threatening situations. Following the advice of the "veterinarian" they make a paste or slurry and apply this directly to the skin as a salve. The skin usually dries up and peels off. A salve is also used in the same manner to treat insect bites. Many individuals also use this method to treat rashes, unknown skin discolorations, and ulcerous sores. The pretense is that the chemical is removing unhealthy or contaminated skin. 72
This is in keeping with the general belief among the Indians that pesticides are "medicine for plants". They believe that plants were placed on the earth by benevolent gods for the benefit of man. Insect pests are representatives of evil who attack and destroy the "goodness" of plants.
Consequently, there is no reason that "medicine for plants" should not also function as "medicine for man". The lack of a sense of danger regarding the risks of these chemicals is compounded by the fact that they are trustfully purchased from one of their own kind who promotes their use for a variety of purposes.
Carlocito described, and demonstrated, how insecticides are dusted on children to help control head lice, spread in beds to control bed bugs, and used to wash clothing. Because of their living conditions,
Indians are extremely susceptible to head lice. Prior to the use of insecticides, lice were removed by mutual grooming. Carlocito recounted that 2 of his family members (out of 12) had died shortly after treatment with insecticides. However, both had been ill for several months and had previously received insecticidal treatments, so it was difficult to ascribe their deaths to the direct effects of pesticide poisoning.
Other members of the family suffer headaches and nausea following pesticide use. When I asked him why they continue such dangerous practices he replied that the discomfort of the insect bites was greater than the illness, and sometimes even the risk of death. Carlocito's father mentioned that body insect pests have never been as bad as in recent years.
He, and the other farmers visiting his house, noted that pests are increasing in both number and severity. Also, they maintained that the 7 3
younger children appear to be more prone to head lice than previous generations.
Carlocito's father and several other individuals discussed changes they had seen in health related areas. The average family in Peraguchi consists of about 6 children with a range from 3 to 13 children. Larger families usually have children separated by about 18 months of age. Of the
19 families visited, all had lost at least one, and some 2 or 3 children, before they had reached 10 years of age.
The high infant and child mortality rate has primarily been due to diarrheal disease complicated by pneumonia. When diarrheal disease persists in combination with a heavy parasite load the malabsorption of protein and food substances can add further complications through malnutrition. The resulting triad of diarrhea-pneumonia-malnutrition is a chief cause of infant mortality in developing nations.
Of interest was a new type of death that was occurring more frequently. It was mentioned that people,especially children, appeared to die more suddenly, some without any visible signs of illness. Active, healthy children are suddenly found either dead or unconscious, with death occurring within a matter of hours. Most childhood deaths in the past had followed weeks or at least days of physical illness. Overall, the consensus was that even though the general health of the Indians was relatively good, there were now unusual situations which had not occurred until the last 10 to 15 years.
There were also the general feeling that it was more difficult for a woman to conceive and that the number of still births had been increasing. 74
Townspeople believe this results from the government's attempts to control their population by placing chemicals in the water. It is felt that there are several households where the women cannot bear children as a result of this tactic. It was not possible to obtain information about mutagenicity as most families immediately destroy or bury deformed infants, due to the negative religious connotations associated with such births.
Carlocito states that the government provides few medical services; the government run health clinic was closed several years ago. The only professional health care is provided by volunteer medical students or the
Peace Corps. He maintains the government turns a deaf ear to any account of pesticide poisoning as they feel the family size of the native Indians is too large; pesticide poisoning is a convenient method of family planning. This prejudice was reinforced by his European wife who said that she has seen bottles labeled "For Indigenous Peoples' Use Only" written in English and displayed on shelves in government medical clinics; contents unknown.
When I asked about the local doctors Carlocito replied that they are only concerned about individuals with money, his family and most of Peraguchi are very poor.
Several of the families we visited tended cattle. Evidently there is an insect similar to the hot fly which the Indians claim has been introduced through cattle shipped in from the eastern rain forest region of Ecuador.
One individual obtained a treatment for this insect from the "veterinarian" and applied the chemical in the manner recommended. Unfortunately, 4 of the cattle died following treatment. The animals were immediately 7 5
butchered and eaten, and their hides were sold to the local leathersmiths.
Apparently, the chemical was kept, diluted, and used for other purposes.
We spent some time with a local builder who described how he and his workers spray pesticides to kill the mosquitoes resting on walls being constructed. He then produced a small hand-held sprayer and demonstrated. Powdered chemicals are purchased and scattered in the pools of water around building sites, as these too are breeding grounds for mosquitoes. The unidentified larvicides were purchased at a building supply store for use against insects are attracted to the water that collects during construction.
The builder, and several other individuals, purchase empty pesticide drums which they resell for household use. He recommends the containers for crop storage, water collection and bathtubs. The drums were commonly used as cisterns, as the village did not have a reliable water supply. One drum, with faint technieal-style yellow lettering barely visible, was being used by a near-by street food vendor to wash out pots and plates. When confronted with the dangers of chemical contamination the builder replied that he washes them out before selling. However, as pointed out by Carlocito, he probably employs children to wash them out for him.
Several Indians work for the large haciendas near the village. They regularly hand-apply pesticides and agricultural chemicals as is illustrated by the photograph in the top of figure 9. This photo was taken with a telephoto lens from the side of a main road. Although not clearly visible in the illustration, the workers were covered with the white powder they were 76
hand casting from bags carried over their shoulders. The men were not wearing gloves, face masks, or using respirators; one individual appeared to have a scarf wrapped around his face. When I attempted to approach the workers I was stopped by the foreman. He was not covered with white powder, as were the workers, and he prevented me from speaking with the field hands. 1 asked him if the workers were applying a fertilizer or a pesticide, he responded that it was a pesticide.
Several of the workers with whom Carlocito and I had spoken had combined funds and purchased head gear which they would use on windy days. They described times when they were completely covered with powder or spray after a days work. The hacienda foremen did not call off spraying because of high winds, he just instructed the workers to hold their wands closer to the plants. All the individuals questioned reported feeling ill at least once or twice during or after applying these chemicals.
Their chief complaints were differing degrees of headache, nausea, vomiting, dizziness, and moderate amounts of twitching. Although several large haciendas had their own clinic and physician, the workers were reluctant to report any illness for fear of losing their job. All of the workers were illiterate and could not read the information on the sides of the containers they were unloading and applying.
If severely ill, the workers were usually given the remainder of the day to recuperate. This involved returning home, taking a bath, and resting. Contaminated clothing was washed by wives and children in household tubs or in Lake San Pablo. That clothing could be heavily contaminated was made evident by the fact that several families would then 77
use the wash water as an insecticide, applying it to family members or washing infested bed clothing. However, most field hands would work regardless of how they felt as they could not afford to lose a day's wages and they did not want to risk losing their job by appearing weak.
The large haciendas use three methods for applying pesticide. The most common procedure is hand spraying from a pressurized tank strapped to the back of the field worker. The second method is the hand scattering of pesticide granules carried in shoulder bags. The granules are designed to be scattered by motorized equipment but most haciendas substitute manual labor for machinery. These treatments were thought to be in response to specific pests and were more common at certain times of the year, e. g. immediately following the rainy season. The chemicals used in the sprayers were evidently expensive as the workers were repeatedly admonished for carelessness which led to spillage or waste. A third method, used only by the wealthy land owners, was crop dusting from small airplanes. In many instances, the workers were not told that the fields in which they were working were to be sprayed. The plane simply appeared, was flagged to the appropriate field by the field foreman, dusted the area, and flew off. If the workers did not get out of the path of the plane they too, were covered with pesticides.
The bottom photo in figure 9 was taken near Otavalo, in a field which appeared to be part of a large hacienda. I observed that pesticides were delivered either as liquids in large drums or as powders packed in metal containers. The drums were unloaded by hand, again with no protective equipment, and their contents poured into buckets. The appropriate 78
amount was measured out and mixed with water within the application
equipment. Many times the workers would prepare mixtures of compounds
from different containers, apparently under the direction of a foreman.
The foreman left in midafternoon and I approached the single
individual who had not gone into the field. The individual guarding the
equipment told me that he had worked for the people who own the fields for
several years and hence was in a position of seniority. When I asked about
the foreman's background I was told that he had gained his knowledge
through experience. The guard mentioned that the majority of workers
were hired for only short periods of time. He also said that the workers who
apply the chemicals quit very frequently because they become ill. He
ascribed this to their weak constitution mentioning that he could spend the
whole day in the fields applying pesticides.
None of the workers I observed had protective clothing, the
hacienda did not even supply gloves. The only visible safety measure
involved wrapping a bandanaor handkerchief around the mouth area to
prevent inhalation of the dust or spray. Several workers were barefoot and
all wore short sleeved shirts. Working in the hot sun the workers would
sweat profusely and drink large amounts of water which was provided from
a large cistern. Unfortunately, the cistern was uncovered and in the area
used for pesticide preparation; it most certainly was contaminated by dusts
raised during the unloading. Several times I observed the field workers
splash their face and body with water from drainage ditches along the side
of the field to which they had just applied pesticides. 79
RESULTS OF A SURVEY OF PESTICIDE USE IN 19 OTAVALAN HOUSEHOLDS
In July 1987, with the assistance of Carlocito and his wife, 19 households in Peraguchi were surveyedregarding pesticide use (table 12).
A total of 67 containers of insecticidal products were found; 59 in labeled containers and 8 in unlabeled. Each household had at least one type of pesticide with an average of 3. 5 and a range from 1 to 6. With one exception organophosphates were present in all households. The common products were: Malathion, Fosfemo (parathion), and Baytex (fenthion).
Carbamates consisted of Sevin, Temik, and Furadan; pyrethroids were represented by Baytroide and Methomyl. Over 2 dozen containers of fungicides were found, the most common were Difolatan 4 (captaphol) and
Daconil (chlorotalonil). It is unusual that a larger number of fungicides was not found. It may have been the case that fungicides were used immediately upon purchase.
Only 4 organochlorines were present; 2 cans of Soydrin and 2 cans of
Panoram (dieldrin). These containers appeared more aged than other containers. Six unknown pesticides were in containers with extremely faded labels or had trade names that I could not reference. Most of these containers also appeared to be quite old. Eight containers of pyrethroids were counted. There were also 8, unlabeled household containers which contained pesticides. These included old coffee cans, a small box, plastic bags, and liquids stored in soft drink bottles. Conversely, many houses used pesticide jars and cans to store household liquids and dry goods. The products, their occurrence, and toxicity data are presented in table 13. 80
Only 6 out of the 19 households separated their insecticidal products from foodstuffs, usually in an outside equipment shed. These homes were larger than the average and contained outbuildings used for farming implements. No household made efforts to ensure that the products would be inaccessible to children. Although most of the pesticides were stored on shelves or in cupboards there were many instances in which the products were kept on the floor or ground and could be within reach to the chickens or other livestock that were allowed to roam freely. All but one household had at least one open container and 15 had 2 or more.
Most of the products were purchased from Otavalan stores. Only 4 of the 19 homes purchased goods from transient vendors. Those individuals who purchased products in the city usually did so because of an acute need.
Many households shared pesticides, traded them for other necessities, or sold small portions to their neighbors.
All the households had made use of at least one of their insecticidal compounds within the last 7 days, with an average of 2.1 days; 25% of the families used pesticides on a daily basis. Pesticides were primarily used to control body lice and insects that could damage stored crops. In most cases the products were applied to bed clothes and mattresses (18 out of 19).
Pesticides were frequently added to bath water or water used for the washing of clothes; some compounds were also dusted on the heads of children.
Pesticides, at one time or another, were used on crops by 14 of the 19 homes, but only 2 used them regularly. Corn was the major agricultural product to be protected by pesticides, and in most cases was treated after harvesting. The Indians were frugal with their pesticides and usually treated the corn only after it had been in storage for several months. By this time the remaining corn had become infested with insects. It was then
soaked in a tub filled with a dilute pestieidal solution and laid out to dry in the sun. It would be washed again before consumption. Other crops in storage would be treated if necessary, but they usually were consumed before they became heavily infested. 82
CONCLUSIONS FROM THE SURVEYS TO ASSESS PESTICIDE USE AND EXPOSURE IN SUBSISTENCE FARMING ECUADOREAN INDIANS
It is difficult to obtain statistics about pesticide toxicity in populations of indigenous Indians. The people who are exposed in agricultural settings are usually transient workers. The lack of health care facilities and trained personnel preclude medical record keeping. Likewise, the self-sufficient nature of the population and their isolation from the bureaucratic operations of the province preclude the use of official records. However, the observations noted in Otavalo, Peraguchi, and the surrounding villages suggest both direct and circumstantial evidence for increasing occurences of pesticide related health and environmental problems. There are occurrences of over-exposure and misuse in handling and application.
Perhaps not coincidentally, increases in childhood mortality, sterility, illness, death, and the resistance of the insect pests have been noticed by the Indians.
The task of increasing the awareness of the Indians is compounded by a lack of trust and confidence in anyone who does not speak Quetchua or have the physical characteristics of the Otavalans. The people are apprehensive and distrustful of any venture that has even a hint of government involvement. They also prefer business dealings with members of their own culture. This is exemplified by the faith put in the veterinarian charlatan. Educated individuals can accomplish little, regardless of their intentions or manners, unless they can identify with the cultural nuances of the indigenous people. Only natives or friends of natives are trusted. The best way to disseminate information to the Indians 8 3
would be through a community center staffed by someone originally from the village, trained in matters of health and agriculture. 84
INTRODUCTION TO SURVEYS OF PROFIT-MOTIVATED FARMERS IN AGRICULTURAL PROVINCES
Four of the most intensively farmed provinces were selected for interview surveys. The 2 primary agricultural regions of Ecuador, the coastal plain and the Interandean plateau, were represented by 1 (Manabi) and 3 provinces, (Azuay, Tungurahua, and Carchi) respectively. Each of the 3 provinces on the Interandean Plateau were at slightly different economic levels. The coastal province and one of the Interandean Plateau provinces primarily raised agricultural products that would be exported.
The 2 remaining provinces grew products primarily for internal consumption.
Surveys took the form of open-ended responses to a core set of questions. Farmers usually talked about related areas and a record was kept of these responses. In 2 of the provinces, interviews were made in agricultural fields. Fields were usually worked by 4 people, with a range of 1 to 12. In 2 provinces interviews were conducted at main agricultural supply stores. The surveys were concluded in 3 provinces after 50 individuals had been interviewed and in the fourth province, because of logistical considerations, after 20 people had been interviewed.
Survey results are presented in tables 14 and 15. Table 16 lists the frequency with which farmers of different provinces purchased specific pesticide types. Farmers were asked if they received technical assistance upon purchasing their pesticide, e. g. concentration to be used, frequency of application, safety information, etc. Farmers were also questioned about their storage and disposal of pesticide containers. Adequate storage simply meant any manner which kept the pesticide out of the reach of children. 8 5
Careless disposal usually involved leaving the pesticide container in the field, throwing it in a ditch, a ravine, etc. Adequate disposal referred to any method which minimized contamination. A separate question asked specifically about the location of water resources during disposal. In most cases, pesticides were emulsifiable concentrates or wettable powders that were mixed with water and sprayed.
The next set of questions addressed individual exposure. Frequencies are reported for the method of mixing: wooden sticks, ungloved hands, or gloved hands. Clothing worn during application was categorized into daily clothes or specific clothing used for pesticide applications. These were usually older clothes; special clothing referred to overalls or jumpsuits.
Post application hygiene activities included hand washing, hand washing with a change of clothes, and bathing with a change of clothes; many farmers did nothing. Symptoms of intoxication took the form of specific illness or suites of illness experienced after pesticides had been applied.
Their occurrence was limited to within the previous year.
The illness are self-explanatory and the frequency of occurrence in each province is listed in table 15. Although most farmers felt ill after pesticide applications they usually kept working. Severe intoxication was interpreted to imply any suite of illness which resulted in a cessation of daily activity. It did not necessarily involve medical treatment as several areas were removed from medical centers and many farmers preferred self- medication remedies. Nauseousness included a range of symptoms from general abdominal discomfort to intense vomiting. Irritations of the skin, nose, or eye involved cases of contact dermatitis, irritation of the mucous 86
membranes of the lips and nose, or burning sensations in the eyes. The incidence of diarrhea claimed to result from pesticide exposure may have been caused by chronic infection, malnutrition, alcoholism, etc.
However, in some provinces, looseness of the bowels following pesticide applications was a common complaint.
The total number and the rate per 100,000 population of pesticide intoxications that required hospitalization over the last 10 years, as determined by the Ecuadorean Ministry of Health, are presented in figures
10 and 11. Hospitalizations and the total amount of pestieides imported are presented in figure 12. The number of poisonings parallels the importation of pesticides. The large increase in pesticide importation after
1984 is matched by an increase in the number of poisonings. In 1988, 362 people were hospitalized because of pesticide intoxication. The number of poisonings per year, for the last 10 years, in each of the 4 provinees surveyed is presented in figures 13 and 14. Unfortunately, the government's data does not separate out suicides caused by pesticides. In general, administrative patterns of data collection emphasize areas of commercial interest, there is little concern with public health.
Three provinces had abrupt increases in pesticide poisoning after
1985. The province of Carchi showed a consistently high number of poisonings over the last 7 years. This may be an artifact, and does not necessarily imply that the other provinces had, in the early part of the decade, a lesser number of poisonings. Carchi is a more prosperous province and has more accessible medical care. The Ministry of Health used only hospital records to generate their estimates. Consequently, their 87
data arc very suspect. Farmers are not likely to use medical facilities: they are usually geographically isolated, unable to afford the expense, and practice self-medication. Even if they did seek medical assistance, records are not kept for treatment provided only within the emergency ward. To become registered as a hospital patient an individual must he admitted to the clinical wards. The data of figure 10-14 are actually the number of people who suffered an intoxication sufficient to warrant their admission to a hospital, which necessitates they were within traveling distance of the facility. Consequently, these numbers severely underestimate the number of pesticide poisonings. 88
SURVEYS OF PROFIT-MOTIVATED FARMERS IN AZUAY PROVINCE
A survey was conducted in Canton Santa Isabel, a small community
1600 m above sea level on the Interandean Plateau. The city is located approximately 80 km from the city of Cuenca, in the southern half of
Ecuador. Santa Isabel has a population of 8500, the majority of whom are farmers. Agricultural products include sugar cane, tomatoes, beans, potatoes, and fruits from lemon, orange, and mandarine trees.
The center of agricultural activity in this region of Ecuador is the
"CREA", the Center of Agricultural Reconversion for the provinces of
Azuay, Canar, and Morana Santiago. The CREA has the responsibility of replacing sugar cane with more profitable agricultural products, particularly tomatoes, which will be sold to foreign corporations. The government also claims that the center provides technical assistance to the farmers.
Fifty farmers were interviewed at an agricultural supply store managed by the Ministry of Agriculture in the CREA center. Pesticides were sold predominantly in small, sealed, heavy plastic packages. Unlike
some other stores, there were no large containers from whieh pesticides
were removed, weighed, and sold. Most farmers had preferences for particular pesticides, some simply asked for a product to cure whatever problem they seemed to be having in their fields; almost all were illiterate.
The majority of farmers, 76%, preferred organophosphates while 22% preferred pyrethroids. Very few used carbamates or organochlorines; the former were relatively expensive and the latter were not available. Most products were sold as formulations to be applied with a sprayer. Farmers 89 usually purchased products in sealed containers. Two individuals purchased previously opened containers from neighbors as their fields were very small and they could not use the amounts in commercial packages. Technical assistance was very limited; only 12% of the farmers stated they had received application advice upon their pesticide purchase.
The majority of farmers safely stored their pesticides in some other manner that kept them out of the reach of children. Six farmers described situations of careless storage within their house and one even kept them in his bedroom.
Half of the farmers questioned disposed of pesticide containers by simply throwing them on the ground; 32% buried the containers, 4% burned them, 8% kept them in the house, evidently for use as storage containers, and 2% threw them in the river. Most farmers used a wooden stick to mix the pesticides with water but only one or 2 wore gloves in the process. Ten percent of the farmers said they mixed pesticides with their bare hands; 6% used gloved hands. Most farmers applied pesticide in their normal clothes, only 36% had a particular set of old clothes used only for pesticide applications, or other equally messy jobs. Aside from boots, and
scarves used as a face mask, no farmer had special clothing. Forty percent of the farmers did not clean up after applying pesticides. 14% washed only their hands, usually in a drainage ditch near the field, 34% washed their hands and changed clothes, and 12% bathed and changed c lothes.
Within the previous year, 50% of the farmers experienced some type of health problem after they had applied pesticides; an additional 16% 90
suffered severe intoxication. The 34% of the farmers who did not experience any health effects were attentive during mixing, sprayed with the wind, always used gloves, and in many cases, old clothes, and practiced post application hygiene. Those who became ill developed a combination of a severe headache, nauseousness, blurred vision, and dizziness. The frequency of dermal irritations was surprisingly low. Chest pain and weakness were common, but not frequent, occurrences.
Many intoxications resulted from general carelessness during the application and handling procedures. One individual suffered burns on his back because of a malfunctioning sprayer. A woman who required medical treatmenthad lunch without washing her hands after she had used them to mix a pesticide solution. There were also two accidental poisonings of 13 year old adolescents. The exact details of their intoxication were not known but they survived without medical treatment. One farmer reported being severely intoxicated 3 times, all as a result of mixing pesticides with his bare hands. 9 1
SURVEYS OF PROFIT-MOTIVATED FARMERS IN TUNGURAHUA PROVINCE
A survey was conducted in the agricultural fields around Amhato, the capital of Tungurahua province. Amhato is on the Interandean Plateau,
2500 m above sea level, and is heavily populated with over 400,000 inhabitants. The surrounding agricultural areas produce a variety of fruits and vegetables: apples, pears, peaches, berry fruits, alfalfa, corn, potatoes, beans, and other common vegetables. Most of these products are destined for internal consumption. Interviews of 50 farmers were made at the Agricultural Center of Ambato, a large agricultural supply store.
The majority of farmers used organophosphorus pesticides, but 19 and 5% preferred pyrethroids or carbamates, respectively; organochlorines were not available. Only 10% of the farmers did not safely store their pesticides, and all of these individuals kept their pesticides in their bedroom: either farmers believed that insecticides repelled insects or they were worried about theft. Empty containers were thrown in fields or in the ravines and rivers surrounding the fields by 44 percent of the interviewed farmers. Burial, rather than incineration, was the most common safe method of container disposal. One individual resold the metal drum containers and another kept them for personal use.
Four farmers mixed pesticides with their bare hands. Although the majority used wooden sticks, only one individual wore gloves during this process. Most farmers applied pesticides in their daily clothes, only one- third used a special set of old clothes. Masks were rare and not one farmer used boots. After application, 52% washed only their hands and 32% 92
washed their hands and changed clothes. Only 6% of the farmers did nothing.
Within the past year 36% of the farmers experienced severe illness as a result of exposure to pesticides. One farmer was intoxicated after using his bare hands to mix a combination of parathion and Roxion, a dimethoate organophosphorus insecticide. Two teenagers, ages 16 and 18, were intoxicated while preparing sprayers for a hacienda field crew. The most common post-application symptoms were headaehes (64%), nauseousness
(48%), and irritations of eyes and nose (58%). General weakness, dizziness and blurred vision were experienced by approximately one- quarter to one-third of the farmers. 9 3
SURVEYS OF PROFIT-MOTIVATED FARMERS IN MANABI PROVINCE
Canton Santa Ana is 20 km south of the coastal city of Portoviejo, the capital of the province of Manabi. This area has been severely deforested over the last 20 years and, as a result, has become very impoverished.
Manabi is located in the Guayas lowland, the principal agricultural region of Ecuador. Most growing concerns are large plantations owned by wealthy individuals or multinational corporations. Coffee, peanuts, tomatoes, and sunflowers are grown, primarily for export. This region of
Ecuador is part of the coastal plain and is only 20 m above sea level. The climate is hot, humid and subject to the intense seasonal rains of El Nino.
Twenty farmers were interviewed in agricultural fields.
Farmers received no technical assistance from the 3 larger agricultural stores, which stocked over a dozen insecticides, 2 dozen fungicides, and 4 herbicides. The majority of farmers used organophosphorus pesticides; 18% preferred pyrethroids, and 7% used carbamates. All but one farmer safely stored pesticides, this individual nonchalantly left them under his house (which was built on stilts). The farmers of this region were the most careless in their disposal of unused containers; 70% left the empty containers on the ground.
Farmers were also less concerned with safety and hygiene.
Although 75% of the farmers mixed pesticides with sticks, not one used gloves. Fifteen and 10% used bare hands or gloved hands, respectively.
All of the farmers applied pesticides in their daily clothes. Being very hot and humid, they usually dressed in shorts, undershirts, or short sleeve shirts. No one used a mask or boots, in fact, many farmers applied their 94
pesticides barefoot. The heat and humidity caused farmers to sweat profusely when applying pesticides which may be the reason that 75% of the farmers bathed and changed their clothes following applications. The remainder washed only their hands and, in rare cases, changed their clothes.
Farmers of this area had the highest frequency of severe intoxications. In the past year, 50% experienced some type of problem and only 5% had not suffered any post application illness. A high rate of hospitalizations had also been recorded by the Ministry of Public Health
(figure 14). Among the 4 provinces, Manabi farmers had the highest frequencies of headaches, blurred vision, nauseousness, and irritations of the skin, nose and eyes. Diarrhea, chest pain, and dizziness were also common. There were two reports of multiple intoxications. One individual was severely intoxicated 8 times within the past year while another individual was twice intoxicated with parathion. 9 5
SURVEYS OF PROFIT-MOTIVATED FARMERS IN CARCHI PROVINCE
Interviews were conducted in the agricultural fields around the city of San Gabriel (pop. 30,000). San Gabriel is 2745 m above sea level and 40 km from Tulcan, the capital of the province. Agricultural products include potatoes, beans, corn wheat, barley, and general vegetables.
Almost all farmers (94%) preferred organophosphate insecticides, the remainder used pyrethroids. Farmers did not receive any type of technical assistance from agricultural stores. Seventy percent of the farmers stored their pesticides away from children, but many kept them within their house. Several farmers kept pesticides freely exposed in their bedrooms, because of a general belief that the products repelled insects.
Thirty percent of the farmers disposed of pesticide containers by throwing them in several of the rivers in the region. A similar proportion scattered them within the fields. Thirty percent of the farmers burned or buried containers. Most farmers mixed their pesticides with wooden sticks although 12% used their bare hands. Roughly half of the farmers interviewed had a special set of clothing for pesticide spraying and 40% wore heavy boots. Two farmers also used eyeglasses. Following applications, 48% of the farmers bathed and changed their clothes, 28% washed their hands and 24% washed their hands and changed clothes.
Carchi farmers had the lowest rate of severe intoxications: 8%.
Among all four provinces, Carchi also had the highest proprotion of farmers, 40%, who experienced no ill effects after applying pesticides.
This is remarkable as farmers of this region use extremely strong concentrations of pesticides and multiple combinations of products, 96
evidently because of heavy infestation. During the course of the surveys, many farmers mentioned the care they took in preparing pesticides, e. g. not mixing the product with their bare hands, washing their hands, not spraying into the wind, etc.
This finding is opposite to that which suggested by the hospital record data of the Ministry of Public Health (figure 14). According to the Ministry, Carchi province has had, since 1961, the highest rate of intoxication per 100,000 population. The government's estimate of 20. 4 poisonings per 100,000 is almost three times the rates reported for the other provinces (Tungurahura = 5. 14; Azuay = 8. 37, and Manabi = 6. 65)
However, this field survey found that Carchi farmers had the best safety record among the 4 provinces. The difference may be explained by either sampling error, or severe under-reporting in the other provinces.
Those people who did feel ill complained primarily of headaches, dizziness, and nauseousness. One farmer accidentally drank a pesticidal solution, thinking that it was liquor, a consequence of storage within the house. Self medication was common among the farmers of this region, the most common treatment being a mixture of milk, sugar, and raw eggs.
Most intoxications followed the spraying of several different insecticides, in some cases up to 4 different products.
The use of mixtures of pesticides run the risk of a potentiation of effects due to the combination of one insecticide with another. One of the most widely cited textbook examples is the potentiation of the toxicity of malathion by EPN (0-ethyl 0-p-nitrophenyl phenylphosphonothioate).
The physiological mechanism involves an inhibition of the 97
carboxylesterases that are used in hydrolysis reactions. In Pakistan, in
1976, severe poisoning of farmers resulted from malathion potentiation by contaminants in the technical material (Baker et al. , 1978). Cohen (1984) has shown that doses of organophosphates which produce no overt signs of intoxication can increase the toxicity of other organophosphorus pesticides.
It is very likely that the large number of intoxications seen in the
Ecuadorean field workers are partially the result of potentiation effects given the variety of chemicals commonly mixed together. 98
CONCLUSIONS FROM THE SURVEYS OF PROFIT-MOTIVATED FARMERS IN AGRICULTURAL PROVINCES
Field use of pesticides has been found to exposure workers to extreme hazards. Part of the problem may be due to the available lack of technical assistance; less than 5% of the farmers were able to obtain application information from the agricultural supply stores. Organophosphates were preferred by an average of 80% of the farmers in the 4 provinces.
Carbamates were favored by approximately 16% of farmers, pyrethroids by
3%, and organochlorines were generally not available.
The application of pesticides usually resulted in a suite of illnesses and frequently caused severe intoxication. Several farmers reported multiple Occurrences of severe intoxication, one experienced 8 episodes within the past year. The sequela consisted of headaches, nausea, blurred vision, and dizziness. Weakness, dyspnea, diarrhea, skin, eye and nose irritations, and chest pain are not as common on the average, but occurred with high frequencies in some locations.
An average of 26% of the farmers in the 4 provinces experienced severe intoxication within the past year. The rates of severe intoxication may be inflated because of an inexact quantitation of severity. Although farmers may have stopped their daily activities, individuals who were ill for several days were not differentiated from those who were ill for only a few hours. There may also have been an inability properly to conceptualize activities within the last 12 month period. However, these results are similar to the findings of a study conducted in 1984 by the Asian
Association of Occupational Health (AAOH). Their findings indicated that
15 to 20% of farmers in Thailand, Malaysia, Sri Lanka, and Indonesia 99
yearly suffer some type of pesticide poisoning (Turnbull and Sanderson,
1985). The frequency of specific post-application illnesses felt at least once by farmers within the past year, is averaged fur all 4 provinces and presented in figure 15. Figure 16 provides the same presentation of data for Manabi, the province with the worst safety record.
Field workers have little protective clothing and an average of 70% regularly apply pesticides in their daily clothes. Farmers usually wear short sleeve shirts, may work barefoot, and sometimes use a scarf or handkerchief to cover their mouth. Unlike subsistence farmers, profit- motivated farmers recognized the dangers of pesticides to children and 85% stored chemicals in inaccessible areas. Flowever, careless disposal methods could expose children and livestock to high concentrations of pesticides.
Most farmers left empty containers along the edges of fields or threw them in a small pile.
The agricultural provinces surveyed in the interandean plateau were at slightly different economic levels. Pesticide safety may be correlated to both the level of impoverishment and the climate. Farmers in the poorest province, Manabi, engaged in activities which reflected a disregard for the dangers of pesticides. All the interviewed Manabi farmers wore their daily clothes during spraying. A cavalier attitude was also indicated by the high frequency (70% ) of farmers carelessly disposing of empty containers.
This region also had the highest rates of both severe intoxication and general problems; only 5% of the farmers suffered no ill effects after applications. The over-exposure probably occurred during preparation and spraying as 75% of the farmers bathed and changed their clothes after 100
applying pesticides. The hot, humid weather may have resulted in more profuse sweating which accentuated dermal intoxications. However, farmers in other provinces worked under hot sun and tropical conditions and did not suffer as severe a frequency of illness.
The most economically prosperous area was the Interandean province of Carchi. The farmers of Carchi, the province with the lowest frequencies of illnesses, were also the most affluent, relative to the other 3 provinces. A greater proportion of Carchi farmers appeared to recognize the dangers of pestieides. Disposal methods were generally safer, older clothes were used in application, and more farmers engaged in post application hygiene activities, compared to Azuay and Manabi. The latter category was significantly different than the results found in Azuay: 48% of Carchi farmers bathed and changed clothes, all at least washed their hands. In Azuay, only 12% of the farmers bathed and changed clothes, and 40% did not even wash their hands. Carchi also had the lowest rates of severe poisoning and the largest percentage of farmers who experienced no problems.
In spite of their economic differences, the 2 provinces that had centralized agricultural centers, where farmers would come to purchase their pesticides, had lower frequencies of severe and general intoxications.
Although farmers stated they did not receive technical assistance from the stores themselves, it may be the case that a centralized agricultural center creates an environment for farmers to meet and discuss characteristics of pesticides. 101
Figures 17 and 18 are photographs of various observations noted during the surveys. Figure 17 shows empty plastic bags of pesticides discarded at the edges of 2 fields; one field was along the side of a road and the other along a path between farms. Figure 18 is a photo of the farmer who reported 8 episodes of severe intoxication, taken during an interruption in his spraying. He was wearing a short sleeve shirt, was barefoot, and used a scarf to cover his mouth and nose. The second photo in figure 18 shows a large agricultural supply store that sells pesticides, fungicides, and herbicides. Although not clearly visible, the arrow points to cartons of eggs that are sold inside the store. ??7.* ? Nogos II 5-
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A ^ . . . *.•••’ Or; . .' _ ' ~*rv CON UOMBA C \£ s a g s * m i • I r » /' !a mejor base" • ■^'iS.vKi^ *Xrc5*»e*r^.2U frUgyTr^a*5*! ( nara nroducir oaoa ^ FIGURE 8 BROCHURE ADVERTISING TEMIK, AN ALDICARB INSECTIDE FIGURE 9 PESTICIDE APPLICATION NEAR OTAVALO 05 z 4 0 0 o h Z 7 < □ 3 0 0 < Z7 I H Q. £ 7 g 200 X 100 - GC LU CO 2 3 Z 00 o> o *_ C\J CO LO CO 00 h*. 00 00 00 00 00 00 00 00 00 o> o> CD CD CD CD CD CD CD CD CD T— y— *— T— T— y — T— i— x — T- YEAR FIGURE 10 TOTAL NUMBER OF POISONINGS REQUIRING HOSPITALIZATION BY YEAR © o o o o Z v l cc LU Q- (/) 2 - z o I- < N Q. (/) o o K V X 00 CD o r *" OvJ CO LO CO r ^ 00 r ^ 00 00 00 00 00 00 00 00 00 CD CD CD CD CD CD CD CD CD CD CD x — T~* T- YEAR FIGURE 11 TOTAL NUMBER OF PESTICIDE POISONINGS PER 100,000 POPULATION 1000 KG PEST. IMPORTED 00 1 3000 2000 2500 1500 1000 500 1976 - - - - - 1978 HOSPITALIZATIONS 1000 KG PEST. IMPORTED 1980 PESTICIDE IMPORTATIONS AND POISONINGS POISONINGS AND IMPORTATIONS PESTICIDE 1982 FROM 1978 to 1988 to 1978 FROM FIGURE 12 FIGURE 1984 1986 1988 1990 r 400 -100 -200 -300 HOSPITALIZATIONS o O n 107 40 - 30 - NO. OF POISONINGS 20 10 x— v / — t v — 7 / 77 7 1 id Jd id o T- CM co i n to C- 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 an < n o > O) o > c d o > O) o > y — T ~ T“ T— T“ y — T“ T- T— TUNGURAHUA 50 i d Z T ! 40 30 NO. OF POISONINGS 20 - 10 - T— 77— 77— 7/—77^7 I o y — CM CO rt in (O h- 00 00 00 00 00 00 00 00 00 00 o> FIGURE 13 PESTICIDE POISONINGS IN TUNGURAHUA AND AZUAY FROM 1980-1988 50 i 108 y y 40 30 - y n y i y — 7 NO. OF POISONINGS 20 - •h 10 ■ft* y / j- r / iy y © T~ CM CO in IO r-. 00 00 00 CO 00 00 00 00 00 00 o> O) o> 0> O) o> © a* o> T— T— T— T- I- T- T- i— T— CARCHI 100 80 - 60 - NO. OF POISONINGS 40 - 20 - o CM CO in ID 0 0 0 0 0 0 0 0 00 00 0 0 00 00 00 o> o> CT1 O) a t O) O) o> o> MANABI (note scale change on ordinate) FIGURE 14 PESTICIDE POISONINGS IN MANABI AND CARCHI FROM 1980-1988 SEVERE INTOXICATION HEADACHE 3 BLURRED VISION 3 VERTIGO NAUSEOUSNESS 3 DYSPNEA DERMAL IRRITATIONS 3 DIARRHEA 3 CHEST PAIN 3 — i— 10 20 30 40 50 6 0 7 0 8 0 AVERAGE % FIGURE 15 FREQUENCY OF ILLNESSES EXPERIENCED BY FARMERS AFTER APPLYING PESTICIDES SEVERE INTOXICATION HEADACHE BLURRED VISION VERTIGO NAUSEOUSNESS DYSPNEA DERMAL IRRITATIONS DIARRHEA CHEST PAIN o 1 0 2 0 3 0 4 0 5 0 6 0 7 0 8 0 PERCENT FIGURE 16 FREQUENCY OF ILLNESSES EXPERIENCED BY FARMERS AFTER APPLYING PESTICIDES (MANABI PROVINCE) 111 FIGURE 17 EMPTY BAGS OF PESTICIDE DISCARDED AT THE EDGE OF A FIELD ^ ^ produclo/ ^ agropecuorio/ i_n i-mciEMDn n n o jin iH CHSIOBOJ^;!m curir:;? ,0 flH 03 - t .LUCHfl FIGURE 18 OBSERVATIONS NOTED DURING THE AGRICULTURAL SURVEY BAREFOOT ECUADOREAN FARMERS AND EGGS SOLD IN PESTICIDE STORES 1 1 3 TABU-: 7 ORGANOPIIOSIMIATK PESTICIDES EOCNI) IN ECUADOREAN PESTICIDE SHOPS COMMERCIAL NAME RETAIL NAME EORMl- RAT I.ATION ORAL 1,1)50 niR/kR A c e p li a t o Ort liene S P" 9*15 Azinphosinetliyl G utli ion E C h 11 Chlorpyriphos L orsban EC.EF 175 Clilorthion Celatliion EC 980 D iazinon Diazol, Basudin EC. Gd 76 D ichlorvos Divipan. N o r o s , Vapona EC 56 Diniethoate Diinepae, Sisteniin, Robiol, EC 2.5 Roxion, R o r o t , Perfekthion Dursban Dursban EC 150 Fen it rot hion Cidial EC 450 F e n t h i o n Baytex EC 200 Fonophos Dy fonate EC 8 Formotiou + A nthioinix EC 400 Fen it rot hi on M aiatliion M aiatliion W F* 1000 Monocrotofos Monocron, Nuvaeron, EC, 15 Monocrotofos super, Azodrin 1i t]ii i d Super NOTES: a soluble powder emulsifiable concentrate 0 emsulsifiable powder d granulate e wettable powder TABLE 7 (Continued) ORGANOPIIOSPIIATE PESTICIDES FOUND IN ECUADOREAN PESTICIDE SHOPS COMMERCIAL RETAIL NAME FORMU RAT NAME LATION ORAL 1,1)50" nm/kft Methamidophos Metainidofos, Pillaron, Monitor, ECh 19 Tainaron, MTD M ethidation Suprac id EC 25 Methyl Parathion P arathion EC 3.5 Omethoate Foliniat EC 50 Oxydenietoninethyl M etasistox EC 70 Phorate Thim et Granul. 3 Phosphamidon Dimecron EC 7 Profenophos + F en on EC 400 Cy permetrina Profenophos Curacron EC 400 T riazophos Larvin, Semevin Liquid 80 T richlorfon Dipterex, Danex Powder 144 a Source: Matsuinura, 1975. h Emulsifiable concentrate. TABLE 8 CARBAMATE PESTICIDES FOUND IN ECUADOREAN PESTICIDE SHOPS COMMERCIAL RETAIL NAME FORMU RAT NAME LATION ORAL LD50 mg/kg Aldicarb T emik Granul. 0.9 Carbaryl Carbaril, Sevin, Ravyon, Powder 500 Carbofuran Furadan Powder 5 Methomyl Nudrin, Methavin , Lannate Powder 18 Propoxur Bay^on, Unden Powder 100 TABLE 9 PYRETIIROID PESTICIDES FOUND IN ECUADOREAN PESTICIDE SHOPS COMMERCIAL RETAIL NAME FORMU RAT NAME LATION ORAL LD50 ms/kg Cipermetrin Cipermetrina, Ripcord, Fastac, ECa 250 Arrivo, Ambush, Campo-kill Cyhalotrin Karate EC NA Ciflutrin Baytriode EC 590 Deltametrin Decis EC 135 Fenvalerate Belm ark EC 450 Permatrin Pounce, Ambush, Tomade EC 1030 NOTES: Commercial names and LD 50S obtained from La Oficina de Estadisticas del Banco Central; Office of Commercial Statistics of the Central Bank of Ecuador. a Emulsifiable concentrate. 1 1 6 TABLK 10 RESULTS OF A SURVEY OF QUITO PFSTIC1DF RKTA1LFRS WITH AN!) WITHOUT PHONICS IN TIIKIR STORKS INSCRIPTION STORKS WITH STORKS WITH PHONICS NO PHONICS COMPANY REPRESENTATIVE VISITED: Within 6 months 100% 100% Within 12 months 100% 100% SAFETY EQUIPMENT SOLD: Gloves 100% 100% Masks or respirators 100% 100% Boots, overalls 100% 0 N one 0 0 APPLICATION EQUIPMENT SOLD 100% 100% KNOWLEDGE OF STAFF (TOTAL POINTS): 1 7% 17% 2 20% 50% 3 47% 33% 4 20% 0 5 7% 0 KNOWLEDGE OF THE FAO CODE Knew of existence 27% 0 Could state reason for code 7% 0 Could cite shop changes made as a result 0 0 AT LEAST ONE CONTAINER OF PESTICIDE WAS: Unlabeled 7% 17% Open 33% 100% L eaking 13% 67% ILLUSTRATIONS: Of safe practices 53% 17% Of unsafe practices 20% 0 No illustrations visible 47% 83% MOST COMMONLY SOLD IN PAST MONTH: Orga no chlorines 20% 17% Organophosphates 47% 67% Carbamates 13% 0 Pyrethroids 13% 17% No single product 7% 0 OTHER AGRICULTURAL PRODUCTS SOLD Animal feed 13% 17% Fertilizers 73% 83% Human food 0 0 ABLE TO OBTAIN DDT 13% 17% TABLE II RESULTS OF A SURVEY OF PESTICIDE RETAILERS IN OTAVALO DESCRIPTION % ERROR NUMBER p=.95 COMPANY REPRESENTATIVE VISITED: Within 6 months 35% ±17% 8 out of 23 Within 12 months 39% ±17% 9 out of 23 Don't know 26% ±16% 6 out of 23 SAFETY EQUIPMENT SOLD: Gloves 91% ±10% 21 out of 23 Masks or respirators 35% ±17% 8 out of 23 Boots, overalls 9% ±10% 2 out of 23 N one 9% ±10% 2 out of 23 APPLICATION EQUIPMENT SOLD 78% ±15% 18 out of 23 KNOWLEDGE OF STAFF (TOTAL POINTS): 1 22% ±15% 5 out of 23 2 61% ±17% 14 out of 23 3 17% ±13% 4 out of 23 4 0 % - 0 out of 23 5 0 % - 0 out of 23 KNOWLEDGE OF THE FAO CODE: 0 % - 0 out of 23 AT LEAST ONE CONTAINER OF PESTICIDE WAS: U n la be led 35% ±17 8 out of 23 Open 100% - 23 out of 23 L eaking 100% - 3 out of 23 ILLUSTRATIONS OF APPLICATION PROCEDURES: Of safe practices 17% ±13% 4 out of 23 Of unsafe practices 22% ±15% 5 out of 23 No illustrations visible 70% ±16% 16 out of 23 MOST COMMONLY SOLD IN PAST MONTH: Organ ochlorines 13% ±15% 3 out of 23 Organophosphates 35% ±17% 11 out of 23 Carbamates 17% ±13% 4 out of 23 Pyrethroids 17% ±13% 4 out of 23 No single product 4% ±4% 1 out of 23 OTHER AGRICULTURAL PRODUCTS SOLD: Animal feed 35% ±16% 8 out of 23 Fertilizers 83% ±13% 19 out of 23 Human food 17% ±13% 4 out of 23 ABLE TO OBTAIN DDT 30% ±16% 7 out of 23 1 1 8 TABLE 12 PESTICIDE USE IN NINETEEN OT AY ALAN HOUSEHOLDS DESCRIPTION % NUMBER AVERAGE NUMBER OF LABELED PRODUCTS 3.1 59 in 19 % Organochlorines 7% 4 out of 59 % Organophosphates 64% 38 out of 59 % Carbamates 5% 3 out of 59 % Pyrethroids 14% 8 out of 59 U n k n ow n 10% 6 out of 59 AVERAGE NUMBER OF UNLABELED PRODUCTS .42 8 in 19 IN HOUSEHOLD % HOUSEHOLDS WHERE PESTICIDES STORED 6 8 % 13 out of 19 WITH FOODSTUFFS % HOUSEHOLDS WHERE AT LEAST ONE 95% 18 out of 19 CONTAINER WAS UNCOVERED % HOUSEHOLDS WHERE AT LEAST TWO 79% 15 out of 19 CONTAINERS WERE UNCOVERED USUAL PLACE OF PURCHASE % PURCHASED FROM TRANSIENT VENDORS 2 1 % 4 out of 19 % PURCHASED FROM OTAVALAN STORE 58% 11 out of 19 % UNKNOWN 2 1 % 4 out of 19 AVERAGE NUMBER OF DAYS SINCE PESTICIDE 2.1 ± 1.5 days USED % HOUSEHOLDS WHERE PESTICIDES USED 95% 18 out of 19 REGULARLY ON BEDCLOTHES % HOUSEHOLDS WHERE PESTICIDES USED 84% 16 out of 19 REGULARLY ON PEOPLE For lice or fleas 84% 16 out of 19 For other insects 42% 8 out of 19 % HOUSEHOLDS WHERE PESTICIDES USED 74% 14 out of 19 PRIMARILY ON CROPS On com only 74% 14 out of 19 On other crops 32% 6 out of 19 TABLE 13 PESTICIDE PRODUCTS OF NINETEEN OTAVALAN HOUSEHOLDS NOa TRADE TYPEb COMMERCIAL LD50 MALE RATS NAME NAME mg/kg oral dermal 2 Soydrin OC Aldrin 39 98 2 Panorain OC Dieklrin 46 90 17 Malathion OP Malathion 1,375 >4,444 9 Fosfemo OP Parathion 13 21 6 Baytex OP Fenthion 13 21 2 Cythion OP Malathion 1,375 >4,444 3 Sistemin OP Dimethoate 215 260 1 Roxion OP Dimethoate 215 260 1 Furadan CAR Carbofuran 5 1 Sevin CAR Carbary 1 850 >4,000 1 Temik CAR Aldicarb 15 3 Baytroide PYR Ciflutrin NA 5 Methomyl PYR Nudrin 17 5,000 NOTES: 11 No. = number found in survey of 19 households. 11 OP = organophosphate; OC = organochlorine; CAR = carbamate; PYR = pyrethroid. I 20 t a b u : u SURVEY OF FARM ICRS IN FOt’R AGRICULTURAL PROVINCES AZl'AY TFNOFU M A N A It I ( A u c m AVKKAU AIll'A ii-50 n-50 n-20 n-50 TECHNICAL ASSIST. RECEIVED: No 88 % 96% 100% 100% 96% Yes 127r 4% 0 % 0 % 4% STORAGE OF PESTICIDES: 00 Adequate 88% 90% 90% 70% Unsafe 12% 10% 10% 30% 16% DISPOSAL: Careless 50% 36% 70% 34% 48% Bury containers 32% 28% 25% 16% 25% Burn containers 4% 18% 5% 20 % 12% Keep or sell 8% 4% 0 % 0 % 3% Throw in River 2 % 8% 0 % 30% 10% Adequate 4% 6 % 0 % 0 % 3% MIX PESTICIDES WITH: Wooden sticks Ungloved hands 84% 90% 75% 80% 83% Gloved hands 10% 8% 15% 12% 11% 6 % 2 % 10% 8% 7% TABLE 14 (CONTINUED) SURVEY OF FARMERS IN FOUR AGRICULTURAL PROVINCES AZUAY TUNGUR MAN ABI CARCHI AVERAG AHl'A n=50 n=50 n=20 n=50 CLOTHING WORN DURING APPLICATION: Daily clothes 64% 64% 100% 52% 70% Old "pesticide" clothes 36% 36% 0 % 48% 30% Above with masks 14% 2 % 0 % 2 % 5% or boots 36% 0 % 0 % 40% 19% HYGIENE AFTER APPLICATION: Wash hands and 34% 32% 5% 24% 24% change clothes Bathe, change clothes 12% 10% 75% 48% 36% Only wash hands 14% 52% 20% 28% 29% Nothing 40% 6 % 0 % 0 % 13% INTOXICATIONS: Severe 16% 36% 45% 8% 26% Some problems 50% 30% 50% 52% 43% No problems 34% 34% 5% 40% 28% 122 TABLE 15 ILLNESSES EXPERIENCED WITHIN THE LAST YEAR BY FARMERS AETER PESTICIDE APPLICATIONS ILLNESS AZUAY TUNGLR MAN- CARCIII AVER AULA ABI AGE N=50 N=50 N=20 \=50 SEVERE 16% 36% 45% 8% 26% INTOXICATION HEADACHE 42% 64% 70% 54% 58% BLURRED 42% 32% 65% 24% 41% VISION DIZZINESS 36% 22% 40% 46% 36% NAUSEOUSNESS 46% 48% 70% 50% 54% DYSPNEA OR 22% 28% 30% 10% 23% WEAKNESS IRRITATIONS 12% 58% 60% 16% 37% SKIN, NOSE, EYE DIARRHEA 10% 6 % 35% 4% 17% CHEST PAIN 22% 8% 40% 2 % 18% 123 TABLE 16 PESTICIDES MOST OFTEN USED BY SURVEYED FARMERS PESTICIDE AZUAY TUNGUR MANABI CARCHI AVERAGE AIWA Organophosphates 76% 75% 75% 94% 80% Organochlorines 1% 0% 0% 0% 0.25% Carbamates 2% 5% 7% 0 % 3.50% Pyrethroids 22% 19% 18% 6 % 16.25% CHAPTER HI PESTICIDE POISONING INTRODUCTION The U. S. Agency for International Development estimates that the rate of pesticide poisoning in underdeveloped countries is more than 13 times the rate in developed countries. Over 99% of acute pesticide poisonings occur in the third world. The 1% of deaths in developed countries are usually self inflicted. The World Health Organization quotes statistics that translate to a poisoning in a third world nation occurring every minute, and a pesticide related death occurring every 105 minutes (Weir and Schapiro, 1981). Unfortunately, these estimates do not include embryogenic, teratogenic or carcinogenic consequences, nor any nonspecific reductions in the quality of health. Sub lethal exposure is compounded by the general state of malnutrition and the prevalence of parasitic or low-grade infectious diseases in the indigenous peoples. As discussed in previous sections, there are cultural differences in the perceived uses of pesticides which result in frequent exposures from incorrect handling and misapplication. Because of the inherent toxicity of pesticides these exposures often result in lethal intoxications. There has not been a thorough epidemiologic study of lethal pesticide poisoning in Ecuador. Rural hospital emergency rooms rarely keep records of intakes. Incidences of lethal poisoning must be obtained from direct interviews with 1 24 1 25 practicing physicians, as tew situations warrant the attention of provincial authorities. I obtained information on three instances of pesticide poisoning during interviews with: Roque Sevilla, past president of the Fundacion Natura, and his wife, Pilar, now a chief administrator at the Fundacion Natura; Neptali Bonifaz of the Science Foundation, and; the director and staff members of the Espejo Foundation, a private health organization. I also questioned rural physicians engaged in private practice in Otavalo and Lago Agrio. 1 26 RESULTS OF CASE HISTORY INTERVIEWS REGARDING PESTICIDE POISONING IN CHECA, ECUADOR In 1983 more than 350 people in the village of Checa were hospitalized after eating harvested corn which had been made into popcorn. The corn had been treated with parathion either shortly before harvest or during storage (Sevilla, R. 1987). It is more likely that the pesticide was applied during storage as hydrolysis of parathion under tropical field conditions is very rapid. During my survey of Otavalan households I observed food products that had been stored following treatment with pesticides. The most interesting observation about this poisoning episode is that it does not appear in the records obtained from the Ministry of Public Health. According to their data, in 1983, only 23 people suffered from pesticide poisonings. A problem with the government's data is that it includes both people who died from their exposure and those who survived. However, even a 10% mortality among 350 poisonings would be greater than the yearly total, and this does not include poisonings that occurred in other parts of the country. It is also unlikely to assume that all 350 people were treated without admissions to hospitals, the records of which are the sources of the government's data. This brings into question the reliability and veracity of the governmental records. 1 27 RESULTS OF CASE HISTORY INTERVIEWS REGARDING PESTICIDE POISONING IN CHIMBORAZO, ECUADOR The province of Chimborazo is part of a large agricultural region which has a high frequency of pesticide poisoning (Echeverria, 1987). Approximately 6% of the recorded deaths are thought to be due to accidental poisoning (Sevilla, R., 1987). My experiences during the Otavalan household survey suggested that childhood mortality is likely to be under reported. This view is also held by Ecuadorean health officials (Vuelta, 1987). Consequently, 6% probably includes only adolescents or adults and is considerably helow the actual number of accidental poisonings. Respiratory problems made up an additional 33% of the registered deaths in Chimborazo; 80% of which occurred in rural areas (Sevilla, 1987). Inhalation of insecticides as dry dusts or sprays is a significant danger in rural areas. Rural farmers are also heavy smokers. This may synergistically exacerbate the effects of the insecticides. Although smoking is almost ubiquitous among males in Ecuador, epidemiologic data from the Espejo Foundation do not show as high a rate of respiratory illness in more urban provinces. The lack of protective equipment, which was also suggested by the agricultural surveys, is also a contributor to the high rate of respiratory disease. 1 28 RESULTS OF CASE HISTORY INTERVIEWS REGARDING PESTICIDE POISONING FROM MALARIAL OUTBREAKS The potential for pesticide poisoning in Ecuador may increase because of recent, severe, outbreaks of malaria. Localized outbreaks also occur because of the stagnant water that accumulates during the construction of buildings and irrigation systems. There are four subspecies of mosquitos which can carry the malaria protozoa; all are indigenous to Ecuador. Two species are resistant to most antimalarial drugs and one is strongly resistant to all presently known malarial drugs. The situation is very bad in villages of the eastern rainforest lowlands and mass spraying of DDT was initiated in March of 1987. Although the Ministry of Health directly imports the DDT used in the spraying programs the chemical does finds its way to the black market, as was suggested in my survey of retail pesticide shops. The Ministry of Health has received evidence of people being directly contaminated by improper application procedures. There are reports of unethical entrepreneurs who represent themselves as pesticide specialists. Playing on public fear, these individuals offer to eradicate malaria by supervising or conducting spraying programs. They possess no training in the appropriate application techniques and usually obtain the contracted results through massive over-treatment. Contamination of bystanders, water supplies, and perhaps the community as a whole, are potential and likely concerns. A European physician who was visiting Ecuador as part of a medical exchange program returned a sample of mother's milk to his attending hospital. The subsequent analysis showed a level of DDT two 1 29 hundred times greater than would he allowed in milk from his country (Vuelta, 1987). The daily Quito newspaper, El Comercio, has published several articles on pesticide contamination in attempts to discredit the administration that was facing re-election in December of 1987. The articles stressed such dangers of organochlorines as bioaccumulation, threats to wildlife, and the sequences which led to the eventual restriction of the compound in developed countries in the 1970s. The media also mentioned the economic problems of the Ecuadorean fishing industry which had resulted from severe DDT contamination of ocean fish and shrimp. In general, they accused the current government of a disregard for public safety. Because of the press releases, the president of the Espejo Foundation, Dr. Francesco Vuelta, expressed concerns about ramifications that may increase the incidence of pesticide poisoning. Thegreater toxicity of organophosphates increases the likelihood of acute intoxication. Organophosphate compounds were becoming more popular because of their lack of a DDT-like reputation. This was one of the findings of my survey of the pesticide retailers in Quito, which was confirmed by the follow-up survey conducted in 1989. In 1987, sales of organophosphates for household use had been increasing, concomitant with a decrease in the sales of organochlorines. By 1989, organochlorines were not available in urban stores or in provincial agricultural centers. Dr. Vuelta expressed concerns about Quito developing "malaria-phobia". The media's coverage of malaria outbreaks could increase the use of pesticides. Indiscriminate use 1 3 0 could easily contaminate a city whose water supplies and waste disposal systems were already severely strained. During my visit in July of 1987 there was a media report stating that four cases of malaria had been reported in Quito. The following day the newspaper published an additional article which suggested that one of the individuals may have contracted the disease from mosquitos that accompanied livestock shipped in from the Oriente (the eastern rain forest areas). 1 contacted an entomologist at the Natural Museum of Science and asked about the possibility of mosquitos crossing the Western Cordillera, the mountain chain that separates Quito from the lowland rain forest. He thought that although little chance would exist naturally there is now cause for concern because of the continual movement of plants, animals and people, as well as the increasing settlement along the roads. 1 3 1 INFORMATION ON RURAL PESTICIDE POISONING FROM DISCUSSIONS WITH RURAL PHYSICIANS IN LAGO AGRIO Lago Agrio is a small (own on the western edge of the rain forest. It surrounds a major Texaco Oil outpost involved in piping crude oil from the Amazon to coastal ports. I originally traveled to Lago Agrio to attempt to question the medical personnel at the Texaco compound as their employees use large amounts of herbicides and insecticides. Unfortunately, they did not grant me an interview. Insecticides are also extensively used by the towns people. Most are not native to the area and have come from different parts of Ecuador because of the opportunity for employment by Texaco. They are not from rainforest areas and apparently have a lower tolerance for jungle insects. Insecticides were sold at over a dozen small shops on the main street. In almost all cases shops that sold food products also sold some type of pesticide; quite often the products were displayed next to each other on the same shelf. A physician at one of the village clinics described an incident occurring in 1986 that involved several native families. The families came to the hospital complaining of severe stomach cramps and central nervous system disturbances (headaches, convulsions, and dizziness). The physician referred several individuals to the company hospital at the Texaco compound as he did not have any medication to treat the convulsions. He heard later that 2 of the smaller children and one adult had subsequently died. The illness resulted from the accidental ingestion of a pesticide, thought to be Nogos, which contains dichlorvos as its active ingredient. 1 32 Products containing dichlorvos arc restricted in the United States but freely available in Ecuador. Although not an actual piscicide, dichlorvos is highly toxic to aquatic fauna. The poisoning resulted from children using the pesticide to fish. During late afternoon they simply dumped the chemical in the shallows of Lake Lago Agrio. The fish which came to feed in these areas during the night were subsequently poisoned. In the morning the children scooped out enough fish to provide several days worth of meals. Evidently sufficient pesticide had been ingested or adsorbed by the fish to severely poison those who ate them. 133 INFORMATION ON RURAL PESTICIDE POISONING FROM DISCUSSIONS WITH RURAL PHYSICIANS IN OTAVALO, ECUADOR There are several medical clinics in Otavalo. I contacted an Ecuadorean trained physician who considered himself a general practitioner and a pediatrician. His office was close to the center of town and always appeared to be very busy. I explained the purpose of my study. He was initially distrustful, but later became quite helpful. His patients were primarily pregnant women, infants, and small children. He rarely treated adult men except in emergency or life threatening situations. He was aware of the health effects of pesticides, including organophosphorus insecticides, and even stocked a small supply of atropine. His treatment to suspected cases of pesticide intoxication was simply an intramuscular injection of atropine. If needed, he would administer a muscle relaxant, cardiac stimulants, or provide a sedative. He made little or no attempt to determine any details of the poisoning, primarily because they were common occurrences over which he could effect no influence. The physician felt that pesticide poisoning was widespread, and primarily involved women and children. Women tended to work the fields with their husbands and thus were more exposed following applications. He also knew of "many" deaths of agricultural workers that, in his opinion, resulted from overexposure to a pesticide during preparation and application. Several times this resulted from mishandling by intoxicated workers. He mentioned that pesticide mortality has the potential to be greatly under-reported as several of the larger haciendas in the area still 1 34 have their own physicians and clinics. Also, since Indians are the lowest social class, their deaths are usually considered insignificant by local province health officials. Although he was certain that poisoning of children occurred frequently he did not have any estimate of actual numbers. He felt that young children were somewhat protected as they tended the animals, although they could still be accidentally exposed to open pesticide containers. Pesticide intoxication of children was difficult to quantify as most were treated at home. If death occurred, the child was simply buried; officials were rarely notified. Child mortality from malnutrition and infectious diseases is still quite high consequently it is difficult to isolate the contribution of pesticide toxicity. However, it was the doctor's opinion that each family has probably lost at least one, perhaps two children to poisonings. 1 35 GENERALIZATIONS OF THE AGRICULTURAL SURVEYS The surveys conducted in this study did not accurately assess the agricultural skills of the farmers in areas such as disease or pest identification, pesticide choice, or knowledge of application concentrations and timetables. However, the responses provided data on factors that may contribute to pesticide intoxication and indicated areas that can be addressed in the future. There may have been a bias in that workers who were incapacitated by poisoning would not be purchasing pesticides or working in the fields, hence the intoxications or illness resulting from pesticide use would be underestimated. Although the surveys were made in different regions, farmers generally described analogous situations and used comparable approaches to problems. Most farmers preferred organophosphate insecticides. Farmers usually sprayed at the first sight of an insect, and if they saw their neighbor treating his field they would do the same. Ft seems that many farmers considered it more economical to overuse pesticides slightly and ensure that all pests were killed rather than be conservative and risk having to purchase and reapply additional chemicals. Some farmers mentioned they would lose their crops unless they immediately applied pesticides. Based on estimates by individuals familiar with measures, and personal observations during spraying, it seems that Ecuadorean farmers apply approximately 10 kg of pesticides per hectare per month in the growing season (range 1 to 17 kg). Application schedules in coffee plantations or multinational concerns were dictated by field managers. One 1 36 farmer said that the coffee plantation where he was employed sprayed almost a dozen times a year. Many farmers said they had a difficult time differentiating insect damage from plant disease. It may be the case that farmers cannot distinguish between destruction due to insects and damage from fungal or bacterial infections. In all situations, farmers assumed that the problem could be solved by the prompt application of different pesticides. This was one of the primary reasons behind using mixtures of 2, 3, or even 4 different insecticides and fungicides. Consequently, in some areas pesticide use may be correlated not to insect damage but to the severity of fungal or bacterial infections. Another similarity between farmers of different regions was their conceptualization of agricultural areas. During discussions on pests and diseases the field was spoken of as an entity. There was rarely a consideration of individual plants or proportions of a field (one-half, one- quarter, etc.), even if the field contained several species. Entire plots were always sprayed, no matter how restricted the initial sighting of the pest. Farmers apparently make all-or-none decisions about their fields. They do not consider separate species or individual plants; the field is, or is not, sprayed. This explains why spot treatments were so infrequent; when a problem developed the entire field was treated regardless of the initial localization of the pest. All farmers had some appreciation of the dangers of pesticides and almost all refrained from eating and drinking while working. However many would eat or drink afterwards, to wash the taste of pesticides out of 1 3 7 their mouth. Farmers apparently believed that serious consequences only followed direct ingestion of the pesticide. Some were able to understand the internalization of pesticides through breathing and used handkerchiefs to minimize the inhalation of sprays or dusts. However, there is still a general lack of concern about the extent of safety precautions. When asked about the use of a respirator, one farmer said that they were very expensive and were too difficult to breath through. The household structure of profit motivated farmers exposed all family members to pesticides. The male was directly exposed during preparation and application. Women, who are primarily responsible for maintaining the fields, are also directly exposed to pesticides on plant surfaces or adsorbed to dust particles. The extensive amount of hand lahor increases the amount of exposure. Children were kept from the fields during spraying as their parents were aware of the dangers of direct exposure. However, they commonly work the field along with their mother and are then exposed to pesticides and residues. The family as a whole is also indirectly exposed to pesticides from a variety of sources. Regular household laundry is washed with pesticide contaminated clothes. The lack of hygiene after field work results in the contamination of foodstuffs during preparation, or ingestion of pesticide deposits. Families may also be exposed to high concentrations of pesticide residues on the crops they keep for personal use as there is little regard for the timing of spraying relative to harvest. 1 3 8 Historically, these people have rarely been exposed to extremely toxic compounds. Their mortality has primarily resulted from sudden accidents involving physical objects or from agents that cause protracted deaths, e. g. dehydration, bacterial infections, etc. The idea of a sudden or quick death from less than a teaspoon of a liquid or powder is conceptually very new. Although hard to believe, this may explain the apparent disregard shown by those farmers who have reported multiple intoxications; one individual had been severely intoxicated eight times within the past year. Because of the illiteracy of farmers, there is a need for labels that use symbols or pictures to convey the toxicity of pesticides. Dermal exposure is also a foreign concept, and there is little effort to protect areas other than the hands. Barefooted farmers were seen to roll up their pants during spraying to protect their clothing from field puddles and mud. Almost all farmers removed their jackets, some removed long sleeve shirts and sprayed in undershirts. The rationale was that clothing is expensive and must be protected from stains or spillage. The containers used by the farmers were not designed to minimize contamination. The use of thick plastic bags which had to be ripped open or tins with lids that needed to be pried off resulted in considerable dermal and respiratory exposure. In addition, farmers were forced to use the entire contents, as there was no convenient way to reseal the containers, especially the plastic bags. Considerable dermal and respiratory exposure also occurred during the siphoning of pesticide containers and the filling of sprayers, as well as during spraying. Several farmers recounted instances of being burned or 1 39 intoxicated as a result of clogged sprayers. Observing native farmers prepare their sprayers suggested that considerations of spray delivery are secondary to pesticide concentrations. Farmers frequently tried to get several different insectides dissolved in one solution and combined products of different physical states, e. g. granulated powders and emulsifiable concentrates. This minimized the number of times they would have to sp ra y . I noticed that some of the powdered or granulated pesticide products had hardened or caked. The farmer had to separate these from the rest of the package and crush them, which increased his exposure to the pesticide. Clumping of pesticides is probably a factor in sprayer clogging. Servicing a clogged sprayer again exposed the farmer to highly concentrated solutions of pesticides and also contaminated areas within the field. Several farmers became intoxicated as a result of malfunctioning sprayers. Another problem is that sprayers were used even if in need of repair. Many older sprayers had damaged seals or spray wands that leaked at the junction of the trigger and the nose. One farmer tied an empty plastic pesticide bag around his hand as protection. Pesticide safety may be improved through the use of additives that can decrease the viscosity of mixtures, better solubilize pesticide particles, and reduce caking in high humidity climates. The cleaning of spray equipment, which was rather infrequent, also led to considerable contamination of skin and clothing. There was little regard as to the location of the preparation and cleaning sites. Wolfe et al. (1973) have shown that residues from the spillage of high concentrations 1 40 of insecticides can persist for long periods of time. There is the potential for additional intoxication as several of the locations were near areas where field hands and children congregated. Farmers frequently washed themselves and their equipment in irrigation canals or rivers. Children were seen playing in the larger canals, and they were also used as a source of household water. Many farmers used rivers to dispose of empty pesticide containers. Downstream, the water would he used to wash clothes, bathe children, or would be collected for household uses. Farmers were also not aware of the dangers of post application contamination of clothing or skin. In many families, the husband applied the pesticide but his wife tended the field. After working in the fields, she would return home to prepare food, tend to the children, etc. Her activities could result in contamination of clothing, household products, foodstuffs, etc. Acute human poisoning from pesticides is easier to detect than chronic effects. However, long term toxicity may be more serious. Aside from studies in delayed neuropathies, there is little epidemiologic information on the effects of chronic exposure to organophosphates. There are reports on changes in the central nervous system in both workers with long term exposures and in individuals recovering from acute poisoning (Hayes, 1982). These effects include: a reduction in the ability to concentrate, decreased attentiveness and vigilance, a measurable slowing of information processing and psychomotor speed, memory and language impairments, depression, anxiety, and personality instability. A multinational epidemiological study on the neurotoxic effects of long term, low-level exposure to organophosphorus pesticides is currently being 1 4 1 developed by the World Health Organization in conjunction with the United Nations Development Program (Maroni, et al. 1986). Farmers of all 4 provinces suffered symptoms consistent with organophosphate exposure and the effects may have been increased through potentiation. Most farmers practiced self-medication which included teas, coffees, or dairy preparations. Cases of severe intoxication were treated by sleeping or laying down until the symptoms dissipated. Many farmers would begin to smoke immediately after applying pesticides as it kept them from vomiting. Profit motivated farmers were more likely to suffer from dermal or respiratory exposure than subsistence farmers. The latter group suffered primarily from dermal exposure with acute episodes of oral poisoning. The health complaints reported by the farmers in the 4 agricultural provinces paralleled the illnesses reported by workers applying organophosphorus pesticides in California, the only state with a compulsory occupational injury reporting system (Peoples, et al. 1978). Both groups suffered nausea, vomiting, severe headaches, dizziness, and extreme weakness. Similarly, in both situations a large number of exposures occurred during the mixing, filling, and preparation stages of the application procedure. As an aside, organophosphate usage recommendations in the state of California include: specific labelling requirements, restricted use classifications, closed system mixing and loading, restrictions against powder formulations, specific protective clothing for applicators working in temperatures above 85° F., and specific field re-entry regulations. All are enforced by legal measures. 142 There appeared to he some confusion about the different functions of fertilizers and pesticides. Advertising or brochures provided by agrochemical companies indicate that increased yields result from the use of fertilizers. Similar advertising conveys the message that increased yields will also follow pesticide use. The farmers have applied to the latter the experiences they have gained from fertilizer use and believe that yields will be proportionate to pesticide use. Farmers also are attentive to the price being offered for their crops. Increases in the market price provide the incentive to use more pesticides as the anticipated increase in yield will generate a greater return and compensate for the additional costs. Farmers have been given a false sense of need about pesticide use, primarily from government representatives and the promotional material provided by agrochemical companies. Most farmers believe that pesticides are necessary and have been told that particular plants will not grow without periodic applications of pesticides. These statements are accepted without question by farmers with little familiarity with the exotic plants they may be growing. Although the crops may be the same as those farmed by their ancestors, they are now buying "special" seeds, which require different methods than the plants they had previously grown. Consequently, agricultural investments are fueled by positive feedback. The more money a farmer spends on seeds and fertilizers, the more money he will feel he must spend on insecticides to protect and "balance" his initial investments. 143 There was a general correlation between the level of impoverishment and awareness of the toxic effects of pesticides. Farmers in Manabi were almost as impoverished as the Otavalan Indians of Peraguchi. Both groups were subject to severe exposures because of a lack of hygiene and a disregard for safety precautions. Conversely, the wealthier farmers of Carchi had the lowest rates of severe intoxication, put more effort into disposing of pesticide containers, and engaged in the most thorough hygiene following application. The farms in Carchi are also neat and well-kept; larger animals were leashed or in penned areas and fields, and gardens were orderly and well maintained. Most of the farms and houses of Manabi were dilapidated, their yards were filled with trash, and animals roamed freely. The fields usually appeared unkempt and disordered, and there was a large amount of garbage scattered among the plants. Farmers of different provinces also used similar methods of pesticide disposal. Once pesticides are sold, it is unlikely that the means will exist to collect from farmers any unused containers. In the future, the options of disposal must be addressed to the individual farmer. For example, drum residues may be dispersed through spraying. If this is well managed it can be used as a method of pest control. Burying and burning, two common methods of disposal, are not very safe. Open burning is not advisable as the temperature is too low to combust all pesticide completely, and significant quantities of residues may be carried in the smoke. Burial is an option but few people would take the time to locate sites away from 144 water resources, if such sites actually exist, and most pesticide containers are not biodegradable. There are differences in pesticideuse between subsistence and profit motivated farmers. The latter consider insecticides as a measure necessary to provide a financial return greater than their initial investment in seeds, fertilizers, herbicides, etc. The former consider pesticides necessary to ensure survival. This alters the perceived use of insecticides. Farmers who are very poor would rather take their chances with insects in the field and use what pesticides they can afford to help store their harvests. Although pests or diseases destroy plants it is usually possible to get some products out of even a severely damaged plant. However, it is not possible to replace foodstuffs that have been eaten by insects or have rotted during storage. Consequently, the emphasis is shifted. Subsistence farmers also have a unique way of looking at the world. Native Indians still retain vestiges of their pantheistic or animistic religions, hence pesticides are not so much viewed as poisons for insects as they are considered medicines for plants. Pesticides are not applied with an ecological awareness of cause and effects; they are applied simply because the healthier plants that result have increased yields. This outlook also contributes to incidences of pesticide poisoning. Indians, because of their living conditions, are heavily infested with body lice. Their use of pesticides in treating this condition is partially a result of their view of pesticides as medications for plants. 145 Another consideration is the social and cultural climate that surrounds subsistence farmers. The native Indians are considered the lowest social class and usually are the most impoverished people of the region. Any Ecuadorean with European features is socially above the native peoples, regardless of his financial situation. There is also a certain amount of passivity in the culture of South American Indians, which may have resulted from their historical domination by militarily inclined, ruling cultures. The Indians are ostracized and are relegated to slave-like employment. Because of this social isolation, most of their contacts are with members of their own group; there is little interaction with non-Indians. Open communication among farmers is the most important method of disseminating information on pesticides. At the agricultural centers, farmers were overheard discussing various aspects of pesticides. Native Indians have limited exposure to the experiences of the profit-motivated farmers. Indians that work on the plantations or haciendas have a position subservient to the other field hands. As a result, they are often given jobs that have the greatest exposure to pesticides. Consequently, it is very difficult for the Indians to appreciate the dangers involved in pesticide use. They frequently steal some of the pesticidal product and take this home to use in whatever manner they feel is appropriate. They have a ubiquitous conception of all pesticides: they kill insects and create healthy plants. Any program designed to influence the farming methods of native peoples must work in conjunction with their balance of self-sufficiency, social passivity, and isolation. The methods taught to farmers by their 1 46 ancestors are no longer applicable. Different types of crops are being raised on much larger expanses of land and are being attacked by insects which, in previous times, had been controlled through ecological balances. The agricultural methods they are using involve considerations which are foreign to their way of perceiving the world. Farmers are in need of training and education but individuals living at a marginally subsistence level are not concerned with the long term consequences of pesticide use, for obvious reasons. Short term costs will be more tolerated when accompanied by additional health care, social, and agricultural services. There is a need to establish a local agricultural center manned by personnel trained in integrated pest management. Field agronomists would monitor pest levels and offer advice on the appropriate treatment method. If the centers cannot be adequately staffed they will at least serve as a congregating ground for farmers who can share their experiences with each other, as occurred at the agricultural centers in two of the surveyed provinces. Integrating field centers across a geographic area would improve responses to localized outbreaks. However, Ecuadorean agrochemical companies still interpret the concepts of integrated pest management as antipesticidal. There is considerable short-sightedness in their agricultural views, and the long term gains that may result from IPM are overridden by misunderstandings, biases, and dogmatisms. Another problem is the multiplicity of pesticide types and names. Reducing the number of pesticide brands would allow consistency to develop among the farmers. Since farmers gain knowledge through communication of personal experiences, reducing the number of pesticides 147 will also improve information exchange. This alternative is also not favored by agrochemical companies. In developed nations the general trend has been a shift in pesticide use from rigid calender timetables to need-based applications. The former had been a reflection of a philosophy that stressed "preventive” measures and underestimated the ramifications of indiscriminate pesticide use. In developing countries trends continue to neglect ecological considerations. Routine applications are promoted by the government and through agrochemical advertising. Unfortunately, the agricultural leaders in Ecuador are not farmers, or even agronomists. Rather, they are bankers, economists, and businessmen, who are more influenced by economy than by ecology or ethics. There is a need for plantation based programs that replace pesticides by a very cheap commodity in developing nations, manual labor. There will be situations in which pesticides are still necessary or even essential, but there are also situations in which their use can be minimized. It is surprising that herbicides are used so extensively in Ecuador, given the vast reserves of manual labor. The creation of a perceived need for this product is probably the single greatest testament to the marketing skills of the agrochemical companies. The Tolai banana farmers of Papua New Guinea use management practices which replace pesticides by manual labor (Putter, 1980). For example, since bananas are parthenocarpic, the flowers, which usually attract specific pests, can be removed. Other pests are controlled through the regular removal of damaged or old leaves which expose pseudostems 1 48 that are simply too slippery to allow the landing of several species of beetles. Vigilance also results in the manual removal of larvae which always seek particular parts of the plants, e. g. the base of newly forming leaves of flower clusters. The use of pesticides has now become an essential requirement of world agriculture and health programs. Plantation and cash farming are the link between industrialization and rural development and thus play an important role in the future of a developing nation. However, farmers, government officials, health providers, agrochemical companies, and environmentalists all differ in their assessment of the cost benefit ratio of pesticide use (figure 19). Urban administrators and agronomists, who are usually living life styles unimaginable to rural farmers, are perceived as demanding changes that benefit only their ideals. An accurate perception of the problems arising from pesticide use requires a consideration of cultural, economic, and environmental factors. Within a country there may exist groups of people whose exposure is consistent and predictable within their group or sub-culture, but is very different than other sub-cultures. In Ecuador, the farmers of four agricultural provinces did not use pesticides for any purpose other than agriculture. Conversely, the Otavalan Indians of Peraguchi primarily used pesticides within their households. This difference was ascribed to the impoverishment, social degradation, andcultural isolation of the latter group. Interviews with rural physicians indicated that accidental pesticide poisoning is more frequent than would be inferred from government records. Again, cultural nuances tended to mask the 1 49 magnitude of the problem. The inconsistencies between the data of the government and that of conservation and health organizations suggests that administrative data is either faulty or suspect. Matteson et al. (1984) have determined that small farmers have rarely benefitted from technological improvements designed to improve their well-being. Most "improvements" consider neither the social nor the ecological milieu in which farmers must function. The single greatest problem is the lack of technical assistance. The inappropriate selection of pesticides reduces their effectiveness and may even damage crops. Their misapplication and residual effects endanger the farmer and his family. Educational programs must always reflect the manner in which native people view their environment and their understanding of cause and effect. Proper use of a respirator may seem like a moot point, but an individual with no understanding of the purpose may only see an apparatus covering part of the face. The connection may not be made between covering the nose and mouth to breath only through the respirator. Labels or diagrams in the native language, using simplistic pictures or diagrams, are essential. There is also a need to reconsider various aspects of pesticides as they relate specifically to the tropical environment. For example, formulation guidelines suggested by the manufacturer may have heen determined for temperatures well below that found in the tropics. Sprayers can become clogged and increase the likelihood of accidental exposures. Emphasis must also be placed on spillage and waste. Farmers are not aware of the potential danger of such areas. The use of smaller packages of pesticides will 1 50 minimize overuse and decrease exposures during sprayer preparation. Ideally, pesticides should be available in pre-measured packages that are designed for sprayers of certain volumes. In developing countries as much as 10% of all pesticides are lost in transport, during storage, and from spillage (Haines, 1985). This is over 50 times the amount lost by similar accidents in industrialized nations. Promotions must be restricted and monitored. Illiterate people are swayed by the simplistic messages and eye-pleasing colors of advertising. Brochures use language that implies their products are "solutions to problems" and "disinfectants". The cool blues or agricultural greens used in roadside signs have connotations of growth and health. Indiscriminate advertising is unquestionably a main contributor to pesticide related health problems. Information pamphlets must become more like the advertising brochures and present their message clearly, succinctly, and in an attractive manner. Suggestions as to the necessity of the pesticide, promises or guarantees of increased yields, etc. should be prohibited. The use of pesticides in developing countries may be indirectly regulated by developed nations. The agricultural products grown in the province of Chimborozo are primarily destined for export, many to the United States. Those crops to which pesticides are most applied are not necessarily involved in increasing food supplies to the indigenous people. Rather, these products are destined for export to the developed countries of the world. As such, pesticides are a double-edged sword: not only are workers being poisoned in the production of goods they will never use, but residues on agricultural products are returning to the United States and 151 other countries. In some developing countries over 70% of the imported pesticides are used on crops which will be exported to the United States, Japan, and Europe; of these, 10 to 20% serve only to improve appearance (Weir and Schapiro, 1981). Importing countries can set residue tolerances on crops being received. In general, the allowable tolerances for most toxic pesticides are highest in United States. Europe and Japan have lower accepted residue limits, the latter country is particularly strict (Mulla, 1981). The United States purchases large quantities of bananas, coffee, and cacao from Ecuador. Many of the pesticides used on these products are banned in the United States, hence they are no longer registered with the Environmental Protection Agency. The Food and Drug Administration, which conducts random examinations for pesticide residues on imported foodstuffs, only tests for those products listed by the EPA (Russel, 1984). Consequently, dangerous levels of banned pesticides are not detected. Altering this policy could provide evidence of pesticide abuse. Reorganization at higher economic levels is another requirement. A study conducted by the World Resources Institute determined that farmers pay an average of only 44% of actual pesticide costs. This is due to pesticide subsidies from the World Bank, the Asian and Inter-American Development banks, and the United States Agency for International Development. The latter agency purchases pesticides from manufacturers and then distributes them free of charge to countries with shortages of foreign exchange. Ecuador is the sixth most heavily subsidized country in the world and receives over 14 million dollars annually. Consequently, pesticide in Ecuador are only 41% of their actual cost (Repetto, 1986). This encourages farmers to use greater quantities of pesticides and discourages the development of nonchemical means of pest control. The following is a summary of the sociological generalizations noted in the above studies: A. CULTURALLY SIMILAR BELIEFS ON PESTICIDE CHARACTERISTICS: 1. Pesticides: a. are needed in agriculture. b. will automatically increase yields. c. must be applied to the entire field as soon as possible following the initial sighting of pests. d. can be used to treat almost any problem, the primary difficulty is purchasing sufficient quantities. e. can be combined with fungicides or cither pesticides to improve their actions. B. CULTURALLY DISSIMILAR BELIEFS ON PESTICIDE CHARACTERISTICS: 1. Pesticides: a. can be used as home medications; b. do not have to be purchased in sealed containers; c. can be used in nonagrieultural situations, e. g. food storage. 1 5 3 2. Pesticides can he dangerous to children. 3. Governmental agricultural representatives can he trusted. 4. The role of pesticides as "medicines for plants" vs. their role as "killers of insects". 5. Pesticide containers can he used to store household goods. C. CHARACTERISTICS NOT APPRECIATED BY ALL GROUPS: 1. The dangers of pesticides as poisons. 2. The potential harm to natural predators. 3. The potential harm to wildlife. 4. The dangers of contamination of water supplies and non agricultural areas. 5. The concept of long lasting effects of residues. 6. The need for re-entry times and a consideration of harvest schedules. FARMERS PESTICIDE INDUSTRY GOVERNMENT □ BENEFITS □ COSTS HEALTH PLANNERS WILDLIFE MANAGERS ENVIRONMENTALISTS 0 100 FIGURE 19 PERCEPTION BY DIFFERENT GROUPS OF THE COST/BENEFIT RATIO OF PESTICIDE USE CHAPTER IV PARATHION IN A TROPICAL LAKE INTRODUCTION Conservation leaders and government officials in Ecuador were agreed that small lakes, both natural and manmade, will be important to the future development of the Interandean region. Unfortunately, these lakes will probably be located within the watersheds of agricultural areas and thus receive tremendous quantities of wastes and agricultural chemicals. They may also be the sole reservoir of household and agricultural water. A significant agricultural contaminant of these systems will be organophosphate pesticides. Future restrictions, when initiated, will primarily restrict only organochlorines. Because of their lesser cost compared to carbamates, the use of organophospate insecticides is likely to increase, as has already been suggested by the agricultural surveys of the preceding chapters. Water quality of San Pablo is important to the development of the northern part of Ecuador. The government is now beginning to consider sewage and treatment facilities for community effluents, but has considered neither the input of pesticides, agricultural wastes, nor the efficacy of treatment systems for their removal. In South America, as in 155 1 56 other developing countries, these issues are relevant to the growth and health of native populations. Terrestrial applications of parathion can contaminate lakes and ponds through surface run-off or erosion (Mulla et al., 1981). Contamination of lakes can also result from direct application when parathion is used as a mosquito larvicide. Changes in aquatic ecosystems can affect humans through alterations in species composition as well as by direct toxicity. Parathion, by design, is a poison and will have effects on organisms other than those for which it was originally intended. The consequences of these effects can be expected to alter the trophic structure of an ecosystem. The extent of this disruption will be a function of the response of members of different levels of the ecosystem to the available pesticide. The close dependence of surrounding communities on small tropical lakes, and the limited means to remove pesticides from contaminated waters also increase the possibility for adverse consequences. Although parathion may be rapidly degraded in aquatic environments, a special set of circumstances exists in Ecuador and other developing countries. Applications of excessive quantities of pesticides and frequent, brief, heavy rains create ideal conditions to translocate high concentrations of pesticide residues into lakes and ponds that are extensively used for water resources. The use of these lakes as sources of water requires an understanding of the time course and pathways of parathion degradation, 1 5 7 and potential alternatives that allow the lake to be used during times of heavy pesticide input. The climatic factors around Lake San Pablo, in combination with native agricultural practices, can affect the persistence of parathion in soil and foster the translocation of agricultural pesticides to the lake. The use of draft animals and hand labor results in little mechanical breakdown of soil and crops. As a result of inadequate tillage, large amounts of organic matter remain near the soil surface. Fields are also usually left as fodder for grazing and thus are enriched by animal wastes. The large amount of partially degraded organic material near the soil surface can adsorb significant quantities of pesticides. Part of the growing season is dry, windy, and of low humidity. The low nocturnal temperatures and cool days minimize volatilization. With little rain the surface of the soil will rapidly dry, decreasing the amount of microbial activity and preserving intact parathion until it can he translocated to lakes or streams. There is a need in Ecuador for data to supplement plans regarding the future development of small Interandean lakes. A primary consideration is an understanding of how to halance water use against the effects of pesticide contamination, specifically the effects of pesticides on the functioning of tropical lake systems. To estimate the potential effects of parathion on these types of aquatic ecosystems, a series of hypotheses were tested on various trophic levels within Lake San Pablo. Limnological data were collected on the productivity of pelagic and littoral water and on the distribution of bacteria. This was supplemented by parathion toxicity studies using phytoplankton, macrophytes, and zooplankton. Although San Pablo is very much larger than most farm ponds and lakes of the Interandean plateau, it is subject to inputs of similar types of agricultural chemicals and wastes. 1 59 SITE DESCRIPTION Lake San Pablo has a surface area of 6.2 km2, a maximum depth of 32 m, an average depth of 20 m, and is ringed by extensive shallow regions (Steinitz-Kannan et al., 1983). An approximate map of the lake is shown in figure 22. The boundaries of the littoral macrophytes are shown by the shaded area. The long axis of the lake runs northwest. It is surrounded by individual homes and farms, small communities, several villages, and the town of Otavalo. There are roughly 146 square km of active farmland within the catchment on the sides of the mountains surrounding the lake. Land is managed to approximately 4100 m elevation but cultivated only to 3200 m, the upper limit for potatoes, the most altitude tolerant crop. The higher fields are used for grazing. Two small streams enter and leave the lake from roughly opposite sides. The larger outlet stream, the Itambi River ("15" in figure 22), is at the western end of the lake. During the rainy season it has a width of approximately 3 m and a depth of 2 m. It courses through several small communities, supplying water and receiving wastes. The inlet stream ("14" in figure 22) is unnamed and flows through pasture land, agricultural fields, and farmlands. During the dry season both streams are reduced to less than 25% of their size and volume. The streams, and the lake itself, receive inputs of agricultural runoff and human and animal wastes. Villagers wash clothes in the lake, commonly using a high phosphate, nonbiodegradable detergent. As a result, the lake receives 1 60 very large inputs of phosphorus, nitrogen, agricultural chemicals, and bacteria. Because of the nature of the shallows, the shore areas marked by "9" and "11" in figure 22 are constantly used for domestic activities. At any time throughout the day no less than 25 and sometimes over 100 individuals can be seen washing clothes or bathing in the lake and stream. The areas around site "10" are the sites of several vacation cottages and homes. Two motels, the Chicopan and the Lagos de Cabanos are located at sites "12" and "9", respectively. The field station (figure 23) was located at site "9". The homes and motels discharge their sewage directly into the lake. The area around "13" is primarily flat pasture used for sheep and cattle grazing. Lake San Pablo is rimmed by an extensive littoral zone. This region generates substantial autotrophic production, produces detritus which drives bacterial and sediment metabolism, and functions to trap allochthonous and autochthonus material (Wetzel and Allen, 1972). Emergent vegetation also acts locally to enrich littoral waters (Boyd, 1970). Temporal, spatial, and environmental variation are greater in the littoral region than the open lake. Such heterogeneity provides habitats for flora and fauna and may play a role in maintaining species diversity (Colinvaux and Steinitz, 1980). This combination of ecological factors tends to maintain large and diverse communities of bacteria, fungi, protozoa, and phytoplankton (Wetzel, 1983). The most extensive macrophyte stands are in sections of the lake that receive both sewage discharges and runoff from agricultural areas. They 161 are especially prominent at the eastern end. This part of the watershed borders a large expanse of flat agricultural bottom land at the base of a ridge and has a gentle slope leading into the lake. Except for rocky areas at the summit, the entire side of the ridge is farmed or used for grazing. Dense macrophyte stands have resulted from the input of agricultural chemicals and surface erosion of organic rich agricultural remnants. Less extensive, but equally dense stands of macrophytes also exist at the western end of the lake, near the inlet of the stream that courses through farm land. The dominant macrophytes are the emergent sedge Scirpus totora. interwoven with dense growths of Ceratophvllum and Potamogeton. The phytoplankton community consists primarily of Scenedesmus quadricauda. Pediastrum horvanum. Volvox. and the blue green alga Microcystis aeruginosa and Lynghva hirgei (Steinitz-Kannan et al., 1983). Zooplanktors undergo a pronounced diurnal migration; species identified include Daphnia pulex. Metacvclops mendocinus. Microcvclops alius. and eubrachius sp. (Miller et al., 1984). The lake is also of religious significance to the Otavalans as it is at the base of Mount Imbaburo, the home of the gods of the Quetchua religion. The Quetchua name of the lake, still in use today, is "Imbacocha" which translates to "tht lake of the small black fish, " referring to the fish species of Pimelodus cvclopum. The pre-inea name of the lake is "Chieapan" and is still used by many Ecuadoreans (Steinitz-Kannan, et al., 1983). 1 62 PARATHION LOADING In Ecuador, agronomic practices increase the potential for parathion residues to accumulate in soil. The pH values of soil are usually slightly acidic and, unlike more developed countries, are not corrected by liming. Frequent applications of organophosphates are common due to the resilience of pests and the rapid chemical degradation of pesticide on plant surfaces. In Western agriculture, this has been shown to result in an accumulation of residues in both water and soil environments (Harris and Miles, 1975). There has been a recent increase in the use of slow-release formulations in which the pesticide is impregnated in a polymer pellet. The constant availability of pesticides to newly degraded organic material maximizes the amount of pesticide adsorbed by the soil. Parathion will be highly adsorbed to both clay and organic surfaces. During the rainy season, parathion may be displaced from the inorganic surfaces and resorbed by organic matter before it can be biodegraded (Barlow and Hadaway, 1956). The heavy rains can also cause sheet erosion that could potentially mobilize large quantities of pesticides. Terrestrial runoff will contain parathion adsorbed to particulate matter rather than in solution. (Mulla et al., 1966; Warnick et al., 1966; Miller et al., 1967). Limnologic effects are dependent on the amount of parathion that is bound by soil, the amount of soil that is mobile, and the amount of parathion that remains unchanged during deposition and transport. Surface erosion of parathion treated soil and organic matter has been shown to contaminate pond water (Nicholson et al., 1962). Although 1 63 parathion has a solubility of 24 ppm the amounts found dissolved in water are usually very low (Sethunathan et al. 1977). Studies indicate that once parathion is introduced into an aquatic environment it is rapidly translocated to the organic phase of sediments or to particulate organic matter (Mulla et al., 1966; Warnick et al., 1966; Miller et al., 1967). Pesticide runoff data have not been sufficiently quantified to provide generalizations that may be used in this study. Haith (1986) developed a mathematical model for runoff losses using the herbicide atrazine. Atrazine has a solubility of 33 ppm, which is close to the solubility of 24 ppm for parathion. Mean annual pesticide runoff, as a percentage of application, was found to be related to mean runoff volume during the month of application. When averaged over 10 sites in 5 different states, pesticide contained in runoff from the month of initial treatment averaged 2.1% of the total application. This estimate will be conservative when applied to parathion as atrazine has a much higher partition coefficient and a greater fraction will adsorb to organic material However, the solubility and binding characteristics of atrazine or parathion may change, depending on the form in which it is applied. This research was conducted in temperate climates using soil with a low organic content (<25% organic matter as determined by loss on ignition), and may not he valid for the watershed of Lake San Pablo. It also does not include the effects of soil erosivity. Nicholson et al. (1962) studied the contamination of a farm pond adjacent to parathion treated orchards and determined that most of the pesticide entered the lake adsorbed to soils 1 64 that were mobilized during periods of accelerated erosion in the spring rains. Observations made during the agricultural surveys suggested that farmers applied at least 10 kg (range 1 to 17 kg) of pesticides per hectare per month during the growing season. Using the estimate of Haith (1986) an Ecuadorean lake could receive, during the month of application, approximately 0.2 kg of pesticide per treated hectare. A lake with a watershed of 1000 hectares, 50% of which receive pesticides, would then receive 100 kg per month during times of heavy applications, depending on the amount of pesticide adsorbed to eroded soil. Although the above estimate is for one month, it was noticed that farmers tended to spray their fields at the same time, hence heavy rains could wash out much large quantities of pesticide. An Ecuadorean lake, 0.5 km in diameter with an average depth of 15 m, would have a volume of 1.2 X 10 7 m3. Adding 100 kg of pesticides to the lake would result in a final concentration of 0.8 mg/L, when distributed to the entire volume, assuming one month's worth of input is translocated at the same time. Lakes with extensive littoral zones of 10 to 30% of the total water volume may have localized concentrations greater than 0.8 ppm. Other studies have shown that concentrations of 1 ppm are reasonable estimates of contamination. Miller et al. (1967) reported that applications of parathion to a cranberry bog resulted in concentrations in the surrounding irrigation ditch of 0.75 ppm. Mulla et al. (1966) treated lake watersheds with parathion and recorded initial concentrations in the water of 0.4 to 0.51 ppm. Treatment amounts in the latter investigation were modeled after mosquito control programs conducted by the State of California. Both studies used 2.2 kg of parathion per acre, which is approximately half the amount that Ecuadorean farmers apply to their fields (10 kg to 1 hectare; 1 hectare = 2.47 acres). For these reasons, a parathion concentration of 1 ppm was used in the degradation, maerophyte inhibition, and productivity studies. Higher and lower concentrations, to simulate the effects of point loading and degradation, were also used in the maerophyte and productivity studies. 1 66 PROPERTIES OF PARATHION Parathion (0,0-diethyl O-p-nitrophenyl phosphorothioate) was discovered in 1944 by G. Schrader of Farbenfabriken Bayer (Matsumura, 1975). During the 1970s, the compound was one of the most widely used insecticides in North America (McEwen and Stephenson, 1979). Although its utility has been reduced through restrictions in the United States, there are still a large number of third world countries importing parathion, including Ecuador. It is now primarily used as a general insecticide or, less frequently, as a mosquito larvicide. Although organophosphorous pesticides do not bioaccumulate as do organochlorines, their higher toxicity creates more acute ecological problems. Normal application rates range from 0.5 to 3.6 kg of active compound per acre. In Ecuador and other developing countries excessive amounts of pesticides are usually applied, sometimes up to 10 times the suggested amounts. Residue concentrations are commonly in the ppm range rather than ppb range. Technical parathion of a purity of 98.5% is supplied to formulation companies within Ecuador by several manufacturers. It appears, or has appeared as: an aerosol of 10% parathion suspended in normal propellants; a dust of inert ingredients and 1 to 5% active pesticide; emulsifiable liquids of 15 to 60% active pesticide; and, as wettable powders of 15 to 30% active pesticide (Sevilla, 1987). Parathion is converted to paraoxon, an extremely effective anticholinesterase (McEwen and Stephenson, 1979). Activation results from oxidative desulfuration of the thiono sulfur to yield the more toxic paraoxon (P=S to P=0). This occurs in terrestrial and aquatic environments, in animals, and both on and in plants. Activation on plant surfaces is of particular concern to developing countries. Extended periods of hot, dry, weather promote the conversion on plant surfaces of parathion to paraoxon (Spencer, 1975). Paraoxon can adsorb to dust particles which may blow across the surface of the plant. Toxicity can then result from pesticide laden particles dislodged from plant surfaces by agricultural workers. The residues may be transferred directly to skin and clothing or may be inhaled (McEwen, 1977). Iwata et al. (1975) noted that repeated applications of microgram quantities of pesticides are magnified to milligram concentrations by adsorption to dust. An important factor noted in the farmer surveys was the use of sprays with strong mixtures of pesticides. These will leave more concentrated deposits on plant surfaces and increase the risk of exposure for those individuals who enter the field after application. Ecuadorean farmers use a considerable amount of hand labor when tending their plants, which increases the amount of exposure. The farmer's wife commonly works in the field after it has been sprayed. Since this is only one of her daily chores, there is a strong possibility of secondary contamination of clothing, foodstuffs, children, and household goods. The pesticide exerts its effects by binding to acetylcholinesterase, the enzyme responsible for the breakdown of acetylcholine. Acetylcholine is the neurotransmitter used by nerves of the both the preganglionic and postganglionic parasympathetic nervous system, and the preganglionic nerves of the sympathetic nervous system. The binding mechanism of 1 68 paraoxon to acetylcholinesterase involves two types of intermoleeular attractions (Matsamura, 1975). There is a lipophilic attraction due to 2 hydrophobic groups, each bonded to the 2 separate oxygen atoms attached to phosphorus, and an electronic attraction from the phenolic ring. Acetylcholine also has a positively charged nitrogen which is attracted to a component of the acetylcholinesterase, specifically the nucleophilic hydroxyl group of a glutamate molecule. To function as an anticholinergic, parathion must be converted to paraoxon. Conversion by a mixed function oxidase changes the P=S bond to a P=0 bond, which has a strong attraction to the serine hydroxyl group. The phosphate residue of parathion preferentially binds to acetylcholinesterase and, most importantly, cannot be displaced by the addition of water. The enzyme normally releases choline upon splitting acetylcholine, and acetic acid after the addition of water (McEwen and Stephenson, 1979). Upon binding, paraoxon is hydrolysed and p- nitrophenol diffuses from the enzyme. The remainder of the molecule, attached to the oxygen of serine, is stable and continues to block the active site. The strength of the binding of this half of the pesticide depends on the electrophilicity of phosphorus. 1 69 DEGRADATION PATHWAYS In higher animals, parathion is converted to paraoxon at approximately the same rate as its degradation to nontoxic metabolites (McEwen and Stephenson, 1979). Paraoxon is generally attacked at the P-0 nitrophenol bond by an enzyme sometimes called "paraoxonase", which may be present in mammalian systems as a soluble serum enzyme (Matsumura, 1975). In man, the primary metabolite of parathion is excreted in urine as p-nitrophenol. Parathion is altered within an ecosystem through a number of pathways which are summarized in figure 20. Parathion can undergo three initial reactions: nitro-reduction to aminoparathion, chemical or biological oxidation to paraoxon, and hydrolysis to p-nitrophenol and diethylphosphoric acid. The primary breakdown products resulting from chemical and biological degradation are aminoparathion (minor except in anoxic environments), p-nitrophenol, diethylthiophosphoric acid, and paraoxon (figure 2 1 ). Chemical degradation of parathion primarily involves alkali- catalyzed hydrolysis of ester linkages. The alkoxy ester linkages are more resistant to chemical hydrolysis than the nitrophenyl C-O-P bond (Graetz, 1970). Although chemical oxidation of parathion at the P=S bond has been shown to occur under ultraviolet light in laboratory settings, it is not common in aquatic ecosystems (Graetz et al., 1970). Parathion is more resistant to chemical degradation than other organophosphates (Sethunathan et al., 1977). However, it is rapidly hydrolysed to p- 1 70 nitrophenol and diethylthiophosphoric acid under alkaline conditions. In natural waters, degradation by chemical oxidation is insignificant (Lichtenstein and Schulz, 1964; Miyamoto et al., 1966). Microbial metabolism in soil and water is the primary mechanism by which parathion is detoxified (Sethunathan, et al. 1977). The enzymatic complements of microorganisms can degrade parathion by hydrolysis (phosphatases), nitro reduction (reductase) and de-ethylation (phosphatase and mixed function oxidases) (Mulla, 1981). Bacteria, especially Pseudomonas species, can also biologically oxidize parathion to paraoxon which then proceeds rapidly through hydrolytic pathways. Hydrolysis is thought to be the most common microbial degradative pathway (Sethunathan, 1973b). Complete degradation of parathion is effected through a concerted action of several different species of microorganisms, yeasts, and fungi. Fungi and yeasts degrade parathion metabolites through dealkylation and reduction of the nitro group, respectively (Lichtenstein and Schulz, 1964). Degradation of parathion in mixed sediment cultures involves both oxidative and reductive pathways and depends on the oxygen tension (Munnecke and Hsieh, 1976). In the presence of high oxygen concentrations, parathion can be degraded by 2 different oxidative pathways (figure 20). One pathway involves an oxidation of parathion to paraoxon, which is subsequently hydrolysed to p-nitrophenol and diethylphosphoric acid. These products also result from the second pathway, that of direct hydrolysis of parathion.The p-nitrophenol from 171 either pathway is subsequently metabolized to nitrite and hydroquinone. Hydroquinone is metabolized to carbon dioxide through ortho ring cleavage of a 1, 2, 4-benzenetriol or a 1, 3, 4-benzenetriol intermediate (Munnecke and Hsieh, 1974, 1975; Sethunathan, 1973). Past research has documented the role of various microorganisms in both the complete degradation of parathion and the sequential degradation of metabolic products: Rhizohium japonicum and IC meliloti (Mick and Dahm, 1970); Azotomonas. Pseudomonas. Xanthomonas. and Brevihacterium (Munnecke and Hsieh, 1976); Bacillus subtilis (Yasuno et al., 1965); various Pseudomonas species (Griffiths and Walker, 1970); and, undetermined Flavohacterium species (Raymond and Alexander, 1971). Munnecke and Hsieh (1976) isolated from mixed bacterial cultures an enzyme that hydrolyzed parathion to p-nitrophenol and diethylphosphoric acid. Most of the activity was found within the cell (99%) but in actively growing cultures hydrolase activity in the supernatant increased to 5% of total activity. Certain species of Pseudomonas bacteria were found to be extremely efficient in degrading parathion. Daughton and Hsieh (1977) have reported a culture of Pseudomonas stutzeri and P. aeruginosa capable of rapidly hydrolyzing parathion to diethyl thiophosphate and p-nitrophenol, even at concentrations as high as 5000 ppm. P. aeruginosa utilized the latter metabolite as its only carbon and energy source. Pseudomonas have traditionally been regarded as extremely adaptable organisms that are 1 72 known to utilize over 80 different organic compounds for growth (Zinsser, 1976). Miyamoto et al. (1966) isolated species of bacilli which, when cultured, inactivated high concentrations of parathion, malathion, and several other organophosphates. Concentrations of up to 20 ppm were degraded to trace levels in 8 days. The major degradative pathway of methyl parathion, when incubated with the bacterium Bacillus subtilis. was found to be reduction to amino methyl parathion (Miyamoto et al., 1966). Bacilli are evidently incapable of oxidizing methyl parathion to its oxygen analogue. B. subtilis is a common inhabitant of eutrophic waters and was determined to be the primary organism responsible for the rapid inactivation of parathion in polluted waters (Yasuno et al., 1965). It is active in both aerobic and anaerobic conditions although anaerobically it forms only amino parathion (Graetz, 1970). Mick and Dahm (1970) have shown that parathion is primarily metabolized through nitro-reduction by the nitrogen fixing Rhizohium species. In pure cultures, 90% of the original compound was found to be reduced to aminoparathion and 10% was hydrolyzed to O, O-diethyl phosphorothioic acid. Siddaramappa et al. (1973) have established a degradative pattern that proceeds from intact parathion to nitrite. Three species of bacteria are involved: flavohacteria. bacilli. and pseudomonas. Flavohacteria possess an enzyme that can attack the P-O-C linkage of parathion, degrading it to p-nitrophenol and diethylthiophosphoric acid. The p-nitrophenol is 1 73 released by the flavohacteria and taken up hy bacilli which then metabolize it to nitrite. Using constitutive enzymes pseudomonas species hydrolyze parathion and liberate nitrite, combining the previous process. Pseudomonas have also been shown to metabolize parathion by oxidation to paraoxon which is then hydrolyzed to p-nitrophenol or p-aminophenol. The latter 2 compounds are degraded to phenol and ultimately to C02. Parathion, at a concentration of 8.6 ppm has been shown to affect the growth of Escherichia coli and Rhizohium meliloti. but not Pseudomonas aeruginosa (Rosas and de Storani, 1987). Effects were due to both qualitative and quantitative changes in the phospholipids and proteins of the cell membrane. Metabolism of large amounts of parathion can also inhibit bacterial cell growth through the production of p- nitrophenol, which directly or indirectly inhibits the induction of monooxygenases and dioxygenases used in aromatic hydroxylation (Munnecke and Hsieh, 1974). P-nitrophenol was found to be toxic to mixed culture bacteria at concentrations above 450 mg/L and growth inhibitory above 30 mg/L (Munnecke and Hsieh, 1975). Lichtenstein and Schulz (1964) investigated the persistence in soil of degradation products of parathion and found that complete degradation of p-nitrophenol occurred between 7 and 16 days after initial application. Aminoparathion was degraded within 1 day and p-aminophenol was degraded so rapidly that it was not detectable. The most persistent compound was p-nitrophenol. They also determined that 0.1 mg of aminoparathion, p-nitrophenol, or p-aminophenol was non-toxic to 1 74 mosquito larvae. Aminoparathion is also 7800 times less inhibitory to the honey hee Apis mellifera and 11 times less toxic to the American cockroach, Periplaneta americana (cited in Mick and Dahm, 1970). While on plant surfaces, parathion can be degraded, absorbed, activated to paraoxon, or volatilized. However, pesticide residues reaching the soil surface can become relatively protected. In situations other than direct applications, the amount of parathion that is translocated to an aquatic ecosystem is primarily determined by soil conditions. The degradation of parathion in soil is affected by pH, reduction potential, soil moisture, soil type, and the proportion of organic matter (Sethunathan et al., 1977). There is little thermal influence on parathion adsorption by soils (Yaron and Saltzman, 1972). Although parathion is degraded through bacterial and chemical hydrolysis in alkaline soils, microbial degradation is more rapid in neutral or acidic soils (Adamson and Inch, 1973). In flooded soils, the degradative pathway is determined by the oxidation-reduction potential. If the environment is anoxic, and thus reducing, parathion is preferentially degraded through nitro group reduction to aminoparathion, rather than by hydrolysis (Rajaram and Sethunanthan, 1975). The stability of parathion is influenced by soil water content and is maximal in 2 extremes of soil type: moist, organic soils, and dry, clay soils. There is little correlation in dry soils between the proportion of organic matter and bioactivity (Harris, 1966). The adsorption mechanism of parathion in aqueous soil systems is different from the mechanism in dry 1 75 systems. Parathion is directly complexed to cations in dehydrated soils (Saltzman et al., 1972). Differences in the adsorptive capacity of dry soils are due to their mineral colloid content (Yaron and Saltzman, 1972). Additional retentive effects of dry soil are due to a combination of lowered volatility of parathion and reduced microhial activity (Lichtenstein and Schulz, 1964). The conversion of parathion to a vapor phase is usually more rapid when passing from a dissolved state rather than from an adsorbed state. Both microbial activity and volatilization increase in proportion to water content (Ou, 1985). Parathion does not displace adsorbed water and will bind only to water-free surfaces (Yaron and Saltzman, 1972). Saltzman and Yariv (1975) subsequently demonstrated that adsorption onto hydrated cations was an important mechanism for parathion binding to clays. Whereas increasing temperature decreases parathion adsorption in aqueous systems, changes are not affected in partially hydrated systems until the temperature reaches 50° C. At this point parathion adsorption rapidly increases due to an increased mobility of the adsorbed water, which frees up additional adsorption sites (Yaron and Saltzman, 1972). In sterile soils, the rate of chemical hydrolysis is determined by the kaolinite content and is decreased by moisture and organic matter. Kaolinite was shown to have a moisture dependent catalytic effect on parathion hydrolysis (Saltzman et al., 1976). Parathion molecules are thought to react with dissociated water hydroxyls at specific adsorption sites on the clay surface (Yaron and Saltzman, 1972). A small increase in 176 the water content was found to greatly accelerate the degradation rate, provided it did not exceed the quantity of water that could he sorbed. Water in excess of this amount caused a decrease in the degradation rate. This resulted from the evaporation of parathion molecules that could not bind to adsorption sites already occupied by water. Inorganic soil constituents determine the binding characteristics of parathion until the content of organic matter increases to above 2 % (Wahid and Sethunathan, 1978). Above this level organic matter tends to cover the mineral adsorptive surfaces. Consequently, the content of organic matter is the single most important factor determining parathion sorption by soils. Sethunathan (1973) has found that the amount of organic matter can also influence the degradative pathway of parathion. Degradation via nitro reduction to aminoparathion was enhanced by increased levels of organic matter in the soil. Parathion has been demonstrated to have a greater affinity for organic than for mineral adsorptive surfaces and, as the water content increases, may shift accordingly (Saltzman et al., 1972). Once bound, parathion is not easily desorbed (Gerstl and Helling, 1985). The concentration of organic matter is one of the most important determinants of persistence (Sethunathan et al. 1977). Parathion adsorbs to organic material through the formation of weak bonds between the hydrophobic portion of the pesticide and the adsorbent (Saltzman et al., 1972; Leenheer and Ahlrichs, 1971). This sequestering decreases its availability to microbial attack and partially ameliorates the effects of the 1 77 larger bacterial populations which are usually found in organic-rich soil (Harris, 1966). A high proportion of organic matter and a low pH result in a considerable stability of parathion in agricultural soils (Harris, 1966; Wahid and Sethunathan, 1978). The solubility of parathion also results in increased availability to deeper layers of the soil and its adsorption to sub surface organic matter. The adsorption of parathion to organic matter and its subsequent protection from bacterial degradation is thought to be responsible for the long-term persistence of parathion (Iwata et al., 1973; Stewart et al., 1971). Chisholm and MacPhee (1972) found persistence in the soil of up to 9 months following repeated applications of agricultural concentrations. Other researchers report the retention of significant amounts of residues 9 months, 1 year, 5 years, and even 16 years after application (Nicholson et al., 1962; Kasting and Woodward, 1951; Wolfe et al., 1973; Chisholm and MacPhee, 1972; respectively). 1 78 PARATHION PARATHION Chemical or biological oxidation Nitro-reduction (oxidative dearylation) S' I PARAOXON Hydrolysis AMINOPARATHION Hydrolysis Hydrolysis Hydrolysis I I p-AMINOPIIENOL PHOSPHORIC ACID Removal of nitro group followed Hydrolysis by ring hydroxylation IIYDROQl INONK IIYDROQl! INONK + + nitrite AMMONIA Oxidation via ring hydroxylation 1, 2, 4-BENZENETRIOL Ortho ring cleavage ( CARBON DIOXIDK FIGURE 20 DEGRADATION PATHWAYS OF PARATHION (From Munnecke and Hsieh, 1974, 1975; Sethunathan, 1973) 1 79 PARATHION: II5C2O-P- O- ^ -NC)2 OC2II5 \ PARAOXON: II5C2O-P- ( ) - { \ -NO2 OC2II5 \ _ / AMINOPARATHION: II5C2O-P- O- d ) -NH2 OC2II5 \ / p-MTROPHFNOL: IIO- -no 2 p-AMINOPIIFNOL: S DIFTIIYLPIIOSPHORIC ACID: II5C2O-P-OII OC2II5 OH 1, 2, 4-BKNZKNI<:TRIOL: ^ ‘° 11 FIGCRK 21 DKGRADATION AM) ACTIVATION PRODUCTS OF PARATHION I 80 1 6 NORTH 1 0 • • • • •• * • • • • • • INLET STREAM LITTORAL MACROPHYTE 1 2 REGIONS I KiURE 2 2 MAP Ol LAKE SAN PABLO FIGURE 23 FIELD LABORATORY AT LAKE SAN PABLO CHAPTER V MIXIS IN LAKE SAN PABLO INTRODUCTION Although research in tropical limnology is expanding, few data yet exist for mixing in smaller tropical lakes at high altitudes. Past research has concentrated on lakes in Panama, Peru, Venezuela, and Columbia. Studies in the limnology unique to Ecuador are rare, even though the country has a large number of closed basin lakes (e.g. Steinitz-Kannan et al., 1983). Ecuadorean lakes on the Interandean Plateau are examples of small, high altitude lakes. This type of lake is quite numerous in the Andes and Central America and was formed primarily during late-Pleistocene epirogenic movements. Similar lakes are found also throughout East Africa, Indonesia, and New Guinea (Serruya and Pollingher 1983). Ecuadorean lakes have formed from a variety of processes: glacial activity, riverine processes, and volcanic activity (Miller et al., 1984). Lake San Pablo is an oval, closed basin lake, approximately 3.5 by 2.2 km, located in the northern half of Ecuador, approximately 120 km north of Quito. Physical parameters are presented in tables 17 and 18; data are summarized from Miller et al. (1984) and Steinitz-Kannan et al. (1983). The basin of the lake occupies a depression in the Interandean Plateau and may have been further enclosed by a finger-like projection of an ancient lava flow. 1 82 1 8 3 One of the main factors affecting hydromechanical events in tropical lakes is the relative year round constancy of water temperature. Compared to temperate systems, tropical lakes have smaller seasonal variations in water temperature, usually only 2 to 3° C, and smaller annual heat budgets. Vertical temperature gradients between top and bottom layers of water are 2 to 4° C; much less than the 15 to 20 degree difference found in temperate systems. This results from the relatively constant radiation rates of 140 to 220 kcal cm‘2 year'1 normally found near the equator (Serruya and Pollingher, 1983). Lake San Pablo has a very small temperature difference between the top and bottom of the water column: approximately 1 to 2° C (Miller et al., 1984). Only the top several meters are appreciably warmed, the remainder of the lake is thermostatic at 17° C. This low temperature gradient is a particularly important factor in the stability of the colder waters of high montane equatorial lakes. Birge (1916) defined the work of the wind as the minimum energy necessary to produce density gradients by distributing a given surface heat load within an initially isothermal lake. Schmidt (1928) later related stability to the additional work required to transform density gradients into a uniform distribution without a change in heat content. The stability of a lake thus depends upon the density differences between the water at different levels of the water column (Wetzel, 1983). Water density differences increase with temperature, hence lakes at high altitudes with both a low temperature and a small thermal gradient will have a reduced resistance to mixing. Because of its altitude, Lake San Pablo is cooler than other equatorial lakes; it is generally 17° C, w'ith a range from 17.0 to 18.2° C 1 84 (Miller et al., 1984). At these temperatures, the density difference of water is less than 0.20 mg/L, hence there is very little resistance to mixing. Consequently, meteorological events which would be inconsequential to the thermal regime of temperate lakes or warm tropical lakes of lower altitudes have great influence on high altitude tropical systems like San Pahlo. Previous investigations of the mechanisms and patterns of circulation in tropical lakes have concentrated on the relative effects of daily, short-term weather changes or aperiodic phenomena. Tailing (1966) noted that in the tropics the diurnal air temperature range is greater than the yearly range and hypothesized that shallow waters sank to deeper layers in Lake Albert after having cooled at night. Lewis (1973b, 1985) reported that although the minimum heat content of Lake Lanao had small yearly variations, maximum values were greatly influenced by brief, non periodic weather changes. Beadle (1974) suggested that precipitation and wind may have a greater impact on tropical aquatic systems than net radiation or air temperature. In other research, the influence of rainfall was found to affect the thermal profiles of several tropical lake systems including lakes Moondarra (Finlayson et al., 1980), Eleiyele, and Suband (Arumugan and Furtado, 1980). Another distinctive feature of some tropical lakes, not found in temperate systems, is the presence of thick epilimnions which can often contain multiple thermoclines formed as result of a combination of convective and wind mixing. Tropical lakes may develop a deep epilimnion as a consequence of both a small annual temperature range and a slow rate of seasonal warming. Lake Lanao (z max = 112 m) has a thermocline at 40 m, 1 85 compared to 15 m for Lake Geneva (z max = 310 m, 45 N lat.) (Serruya and Pollingher 1983). Lewis (1973b) defines 3 categories of thermoclines based on the amount of mechanical energy needed to disrupt them: breeze, squall, and storm. Studies on the formation of epilimnions suggests that deepening results from entrainment of denser, deeper water into the base of the epilimnion (Imberger, 1985). The kinetic energy required for this process is derived from either convection, wind mixing, or both (Kraus and Turner, 1967; Foster 1971; Woods, 1980; Woods and Barkmann, 1986). Another factor of importance is shear production within boundary layers of the epilimnion (Pollard et al., 1973; Dillon and Powell, 1979; Price et al., 1986). Kling (1988) concludes that the basic mechanism of epilimnion construction appears to be wind induced stirring from above with shear generation at the base. Several types of thermal stratification unique to the tropics were originally predicted by Hutchinson and Loffler (1956). These were later modified by Tailing (1969) and Lewis (1973). Many tropical lakes of moderate depth have been taxonomieally classified as polymictic, i.e. mixing frequently at intervals of weeks, days, or even hours (e.g. MacIntyre and Melack, 1984). However, there is insufficient information on the thermal profiles of tropical lakes to propose a new scheme of classification or to relate mixing frequency to the biologic consequences of reduced stability, frequent overturn, atelomixis, seasonal, and nonseasonal phenomena (Serruya and Pollingher, 1983). 1 86 Vertical mixing within Lake San Pablo will occur if wind strength of sufficient duration is able to overcome the buoyancy of the thermal gradient established by insolation. Conversely, mixing at night will occur by convection currents generated by heat loss augmented by wind stress. In summary, the depth of vertical mixing in tropical lakes, including San Pablo, results from an interplay of various factors: wind stress, heat flux, and nighttime heatloss. Heat transfer and oxygen injection are affected by turbulence due to convective movements as well as by mixing generated from strong winds. This portion of the study was undertaken to generate information as to the influence of daily weather patterns on the frequency and regularity of overturn. San Pablo is exposed to two periods of strong winds that primarily blow from east to west. Wind intensity is variable and ranges from mild breezes that barely disturb the surface to strong gusts that can produce whitecaps. During the dry season winds increase during mid afternoon and whitecaps frequently appear on the lake. Winds are also common during the night, although most subside by morning. These two events are expected to result in frequent, if not daily, mixis. Events are similar during the rainy season, but the afternoon increase in winds is not as predictable. The extent of mixing was assessed by time-series studies of changes in the shapes of oxyclines and thernioclines, and the rate of deepening of daily epilimnions. Water oxygenation resulting from wind-induced mixing was compared to that created through photosynthesis. It is hypothesized that mixing in Lake San Pablo will be random and not demonstrate any predictable pattern. 1 87 METHODS Weather conditions, temperature, and oxygen profiles were recorded in July and August of 1987. Wind strength was categorized as follows: (1) strength-one: no surface movement or small capillary waves; (2) strength-two: surface agitation; (3) strength-three: choppyness but no whitecaps, and; (4) strength-four: whitecaps. The field station was established at a small motel located at site "B" on the map in figure 22. In situ experiments were anchored to a small wooden platform, located approximately 10 m offshore. Temperature and oxygen profiles were made from a small boat roughly 300 m offshore at location "M", relocated by use of a surface buoy. A Yellowspings Instrument Company combination oxygen/temperature meter (YSI 51 A) was used to measure oxygen to the nearest 0.1 mg/L and temperature to the nearest 0.1° C at half-meter intervals for the first 2 m and 1 m intervals thereafter. Approximately 30 profiles were recorded at various times during the day within the 2 month period. Difficulties were sometimes experienced in obtaining accurate oxygen concentrations near the bottom of the lake. To minimize errors in this situation the probe was lowered until it was definitely resting on the bottom. Oxygen concentrations were recorded as the probe was slowly raised in half meter increments. The concentration differences of ascent and descent were compared with the distance to estimate oxygen levels near the sediment. Generally, this situation occurred only during windy periods with moderate surface agitation. 188 RESULTS AND DISCUSSION The depth of thermoclines and the boundaries between strata were found to undergo rapid diurnal change from daily weather patterns. The mixed layer was demarcated from deeper hypolimnetic waters by either a sharp, single boundary or a series of step-like transitions. Hypolimnetic waters were always 17° C. Conditions in the morning were calm, usually with clear skies. This lead to a heating of the first few meters of the lake. At 0800 hours thermoclines most frequently extended to 3 m, with a range of 0 to 5 m (figure 24). Insolation continued through the morning and into early afternoon, usually with accompanying winds. Thermoclines were pushed to 9 or 10 m, with a range of 4 to 14 m (figure 25). Strong winds that developed in the afternoon either deepened the epilimnion or overturned the lake. The lake was also well mixed during the night by either strong winds, convective cooling, or a combination of the two, as it was consistently isothermal at 0600 hours. During calm nights the air temperature was approximately about 13° C below lake temperature, which could result in convective cooling. Lake San Pablo was found to have three different thermal phases. Solar input during early morning resulted in a heating of the uppermost 2 to 3 m of water. These strata were then deepened by wind turbulence. Strong afternoon winds combined with nighttime conditions obliterated any thermal gradient and the lake was isothermal by either late evening or during the night; it was always found to be isothermal at sunrise. When winds were mild and heat flux into the lake was positive, as occurred during the early morning, mixing was moderate and thermoclines usually 1 89 extended to a depth of 3 m. Deepening of the thermocline was seen in mid afternoon following a positive heat flux usually in combination with moderate winds. A negative heat flux began during late afternoon, was promoted by strong winds, and continued through the night. It appears that Lake San Pablo overturns on a diurnal basis and does indeed fit the mixing model proposed by Spigel et al. (1986). This pattern of diurnal stratification is similar to the findings of MacIntyre and Melack (1988) and Imberger (1985). A typical sequence of this stratification and breakdown over 2 days is presented in figures 26 to 34. These were recorded on a clear day that had continual strength-two winds. The preceding 12 hours had strength-three and strength-four winds which completely mixed the lake; oxygen was homogeneously distributed through the water column and the lake was isothermal The profile recorded at 0800 hours in the morning showed heat accumulation in the top 3 m (figure 26). Two hours of strength-two winds had created 2 thermoclines, from 0.5 to 1 m and from 2 to 3 m. Oxygen concentrations were highest in the top 2 m and decreased from 2 to 10 m. Below 10 m oxygen concentration decreased rapidly to zero within 2 m of the bottom, with small fluctuations perhaps due to pockets of increased respiration from settling organic matter. By 1400 hours, after 8 hours of strength-two winds, stratification was further developed and the epilimnion had deepened to 5 m (figure 27). The oxygen profile showed entrapment of oxygen within the epilimnion. A rapid decrease in oxygen concentration hegan at 5 m, the upper limit of the hypolimnion, and extended to 14 m (figure 28). Below 14 meters the 1 90 oxygen profile had a very slight negative gradient with an area of increased respiration at 19 m. Comparing the profile of 0800 to that of 1400 hours shows that enrichment had occurred to 12 m (figure 26). This is approximately 2.5 times the seechi disc depth and most probably represents the lower limit to photosynthesis. The waters below 12 m showed the effects of bacterial respiration. Degradation of sinking organic matter had reduced the amount of dissolved oxygen by approximately 0.5 mg/L, relative to the morning values. The afternoon winds were of strength-four and lasted for 3 hours. By 1900 hours, the epilimnion had been obliterated (figure 29). Comparing the morning to the evening profile suggests that the lake had almost completely overturned. Mixing had increased the amount of dissolved oxygen to a depth of almost 30 m, but did not reduce the amount of anoxic water immediately above the sediments (figure 30). More thorough daily mixing is shown in figures 31 to 34. Figure 31 shows the 0800 hour thermal and oxygen profiles that had developed after 2 hours of a strength-two wind. Heat had accumulated in the upper 4 m of the lake, oxygen concentration was highest in the upper 2 m, and thermoeline development had begun. The trophogenic zone extended to approximately 12 m. By 1400 hours, after 8 hours of strength-two winds under overcast skies, 2 thermoclines had developed in the epilimnion, which had increased in depth by 1 m (figure 32). The afternoon winds were quite strong and lasted from 1500 to 1900 hours. By 2000 hours the lake was isothermal and oxygen was homogeneously distributed through the water column (figure 33). The homogeneity of the oxygen curve suggests a 191 complete mixing. A comparison of afternoon and evening profiles indicated that mixing had extended to the bottom of the lake and reduced the amount of anoxic water above the sediments (figure 34). Changes were more profound with winds of greater strength. Figure 35 shows the thermal profile built up by 1100 hours following 3 hours of strength-three winds under partly cloudy skies. The winds continued through the day. By 1900 hours, the mixing induced by these winds, in combination with photosynthesis, had created a marked oxygen gradient (figure 36). The strong oxygen profile may have resulted from the continual circulation of photosynthetic organisms within the upper waters. Comparing the morning and evening oxygen profiles suggests that oxygen enrichment had occurred to at least 24 meters (figure 37). Below this depth, sediment and bottom water respiration further decreased the amount of dissolved oxygen. The subtle changes in the oxygen curve of figure 29 may represent the effects of shear zones between water layers. Buoyancy forces that result from gravity will maintain a smooth interface between different water layers until a critical velocity difference is exceeded. At this point, laminar flow is replaced by disturbances that can grow in amplitude and break into vortices. This turbulence will mix the boundaryzones of the 2 layers (Wetzel, 1983). The strong afternoon winds of Lake San Pablo may have established movements of water layers that exceeded the critical velocities of laminar flow. Several series of profiles were recorded during the study period, from which the following patterns emerged (figure 38). Winds of 1 92 strength-one were more common in early morning or late evening. Early morning winds, because of their short duration before the development of stronger winds, had been observed to mix only the top 2 to 4 m. Figure 39 shows two instances of thermoeline development under strength-one winds. Stratification did not develop and the resulting heat and oxygen distribution was chaotic. The effects of light winds are probably masked by the movement of water masses brought about through through convective temperature changes, evaporation, and rainfall. In northern Ecuador, the nights are cool and daily temperature changes are greater than seasonal averages. Cooling results in a sinking of surface water masses as thermal and density differences are decreased. The descending water may carry entrained oxygen. At times, the lake may be warmed more by winds and convective heating from air than by sunlight. Strength-two winds had the greatest range of effects, depending on their duration and the degree of insolation. Figure 40 presents 2 thermal profiles recorded at 0800 hours after 2 hours of winds that began at around 0600 hours. They differ in having developed under overcast or clear skies. Heat accumulation had been mixed to 4 m in both instances. Oxygen was increased to greater depth on the day with direct insolation. This is probably a consequence of greater rates of photosynthesis from increased light penetrance, rather than a thermal effect on mixing. Strength-two winds that lasted for 8 hours under overcast skies had more definitive stratification boundaries and showed oxygen enrichment to depths of 14 to 16 m (figure 41). The accumulation of heat in the upper waters of the epilimnion was sharpened by wind action. Under conditions of day long, 1 9 3 direct insolation, the stratification profile changed; heat was distributed an additional 5 to 9 m below the lower boundary of the thermoclines that had developed on overcast days (figure 42). However, heat distribution in the lower depths was not well defined and multiple thermoclines resulted. Lewis (1973) has classified thermoclines based on the intensity of winds necessary to induce their formation, using his studies of Lake Lanao in the Phillipines. This lake has a maximum depth of 112 m, much deeper than Lake San Pablo. Breeze thermoclines are established within the top 20 m of water under mild conditions and are easily disrupted. Squall thermoclines result from more intense winds and can extend to 40 m. Inclement weather of long duration can cause storm thermoclines to develop at depths up to 60 m. In a similar manner, the degree of mixing of Lake San Pablo is proportional to wind strength and duration. Mild winds can thermally stratify and mix the lake to depths of 3 to 4 m, regardless of duration. Moderate winds from 3 to 11 hours duration can extend mixing to 6 or 19 m, respectively. Strong winds can mix the lake through its entire water column of 35 m in as little as 3 or 4 hours. Day long strength-two winds can mix and thermally stratify the top 6 meters of water. On clear days the additional insolation supplies energy to warm the lake to greater depths, but the thermal stratification that develops in the upper water effectively reduces the ability of the winds to mix into lower strata. The heat accumulation observed at lower depths may have resulted from convection. Water layers heated earlier in the day and carrying photosynthetic or wave-dissolved oxygen could be displaced downward by inertia from earlier wind action as upper water layers are 1 94 warmed to even higher temperatures. A comparison of the oxygen profiles suggested that enrichment had extended to a maximum of 5 m below the edge of the lowest thermoeline. This is approximately 7 m below the depth of the trophogenic zone suggested by the Secehi disc. The oxygen profiles also showed irregularities suggestive of shear zone mixing. Clear days with moderate or strong winds resulted in oxygen enrichment to the greatest depths. Strength-three winds of 3 hours duration had effects similar to those following 8 hours of strength-two winds (figure 43). Thermoeline development extended to 10 or 11 m. The degree of oxygen enrichment was dependent on the time of day and the amount of insolation. An afternoon wind on a day of clear sunshine increased oxygen concentrations to 20 m below the lower limit of the trophogenic zone, as suggested by the Secchi disc measurement. This profile also showed a deep and clearly defined thermoeline. Day long, intermittent strength-three winds under partly cloudy skies mixed the lake to an isothermal temperature, but only increased oxygen concentrations to 24 m. Winds of strength-four always homogenized the lake, sometimes in as little as 4 hours. This result was comparable to that reported by Lewis (1973) who also found that similar winds sufficient to cause white-capping on Lake Lanao were able to homogenize the water column to depths of 20 to 30 meters. The speed with which strength-four winds can homogenize the lake is thus dependent on prior conditions. 1 95 Oxygen depth-time diagrams for days of similar diurnal wind patterns show widely varying progressions. Changes for figures 26-30 and for figures 31-34 are presented in figures 43 and 44, respectively. Both days had similar weather patterns of approximately 8 hours of strength-two winds followed by strong afternoon winds; 0800 hour and 1400 hour thermoclines are of similar structure and depth. The only major difference was the amount of insolation: the oxygen patterns of figure 44 occurred under a clear sky, those of figure 45 resulted from overcast conditions. Greater insolation resulted in a more definitive oxycline; the oxygen concentration of upper waters increased during the day and oxygen was mixed to greater depths by the afternoon winds. Monismith (1983) using laboratory simulations has shown that a closed circulation develops within the epilimnion upon the initiation of surface stress. His prerequisite of a two-layered, stratified field are met in Lake San Pablo as shown by the morning development under a positive heat flux of a single thermal gradient above an isothermal hypolimnion. Although somewhat bilayered, the structure of the thermoclines in figures 26-34 shows a sufficiently small thermal gradient so as to be considered as a single gradient in Monismith's model. Thompson and Imberger (1980) had previously showed, using numerical simulation, that high winds in combination with a two-layered model would result in entrainment of deeper waters by the base of the epilimnion. Evidence of a closed circulation may also be seen in figures 35 and 36. The oxycline formed earlier was uniformly deepened by afternoon wind stress. This feature is predicted by the mathematical models described in 1 96 Kraus (1977). The primary feature of these models is the input of a large amount of turbulent kinetic energy at the surface of the lake to create a mixed layer. Only after the establishment of this mixed layer is wind energy brought to bear on the base of the mixed layer, resulting in a uniform deepening. By maintaining a closed circulation, the turbulent kinetic store in the mixed layer provides a buffer between the rate of energy input from the wind and the rate of deepening of the base of the mixed layer. This type of entrainment was also noted by Imberger (1985) in his studies of a reservoir with a similar diurnal pattern of thermal heating and winds. The concentration of oxygen within this layer is thus uniformly distributed and sharply demarcated from the non-mixed layer. The rapid deepening and uniform increase in oxygen levels (from 8 to 16 m in 8 hours) was also promoted by isothermal conditions occurring after breakdown of the thermal gradient. The turbulence available for mixing at the base of the epilimnion can also result from Langmuir circulations or convective motions (Spigel et al., 1986). Evidence of the former was often quite striking during windy evenings as visible lines of the interface zones extended down the long axis of the lake. Conditions in which insolation is not as intense show a different outcome under similar wind patterns. The analysis of Monismith (1983) requires as a condition the maintenance of a strong thermal gradient. If this gradient is disrupted the closed circulation breaks down. Apparently the thermal gradient that developed under cloudy skies was not sufficient to maintain circulation in Lake San Pablo during the afternoon winds (figures 197 31-34). Rather than a gradual deepening of the oxycline, a general increase in oxygen occurred to depths of 22 m (figure 44). The patterns in these two sets of diurnal changes indicate that the depth and amount of oxygen injection can be dependent upon the degree of insolation, wind speed, and a combination of the two relative to the formation and disruption of thermal gradients. Multiple thermoclines tended to develop at San Pablo only under strength-two winds. Figures 46 and 48 are examples of the thermal discontinuities that developed in the epilimnion of the lake under 3 and 11 hours of strength-two winds, respectively. The work of Imberger (1985) suggest this to be the result of a strongly convecting mixed layer. In this situation, the almost linear increase in thermoeline depth seen with increasing duration of strength-two winds has resulted from natural convection reducing the temperature difference across the base of the mixed layer, allowing it to be more susceptible to small, but consistent, wind stress. The term "atelomixis" has been proposed to describe situations where water masses of different chemical properties are maintained within a thermal layer that is not completely disrupted during mixing (Lewis, 1983). The formation of multiple thermoclines within an epilimnion is an example of atelomixis. The stability provided between thermoclines could maintain an uneven distribution of heat, nutrients, or suspended phytoplankton. At San Pablo, however, the difference between these regions will not be large, due to the brief amount of time between mixing. Because of their shallowness and the frequency and extent of overturn, atelomixis may he 1 98 more of a theoretical concern for Lake San Pablo and other high altitude Andean lakes, as compared with other tropical systems. The upper 1 or 2 m of Lake San Pablo are supersaturated with oxygen only when subject to intense insolation; values are presented in table 19. Maximum recorded values rarely exceeded 7 mg/ml, the upper level for saturation. Consequently, little oxygen is driven off into the atmosphere and water levels reflect the input from both mixing and photosynthesis. The primary productivity of San Pablo has been determined to be approximately 2.6 gm carbon/m2-day, which produces approximately 0.58 gm of oxygen/m2-hr (Miller et al., 1984). Productivity measurements, depth-dependent morphological volumes, and the coefficient of light extinction determined by Miller et al. (1984), were used to determine the relative contributions of mixing and photosynthesis to the total dissolved oxygen concentration for the profiles presented in figures 26-37 and in figures 45-47; results are presented in table 20. By comparing the oxygen content of lake water in one meter water layers, it was determined that with 8 hours of strength-two winds the net gain of the photic zone exceeded the potential contribution of photosynthesis by 1.136 gm oxygen/m2-hr (table 20). This suggests that approximately twice as much oxygen had been incorporated by solution at the water surface, followed by deep injection through mixing, as had resulted from photosynthetic activity. Respiration in the watersbelow the photic zone was found to have decreased oxygen concentrations by 0.429 gm oxygen/m2-hr. This condition is similar to a transient bilayered structure with a closed circulation predicted by Monismith (1983). 1 99 Mixing that had occurred from 3 hours of strength-four winds decreased the oxygen concentration of the photic zone by 0.205 gm oxygen/m2-hr while enriching the lower waters by a net gain of 1.341 gm oxygen/m2-hr. The total lake change during this time interval was 1.136 gm oxygen/m2-hr of which 0.56 gm oxygen/m2-hr had been provided by mixing. Overall, from 0800 hours to 1900 hours the lake showed a net gain of 1.218 gm oxygen/m2-hr of which mixing contributed an average of approximately 0.64 gm oxygen/m2-hr. Changes recorded in the second set of profiles indicate that during the 6 hours of wind-II from 0800 to 1400 the photic zone gained only 0.091 gm oxygen/m2-hr and the total lake gained only 0.309 gm oxygen/m2-hr. Unlike the first set of measures, oxygen concentrations increased below the photic zone, presumably from mixing and perhaps in combination with diminished respiration. Reduced respiration could have resulted from decreased levels of organic substrates as a consequence of particulate material having settled during a calm night; the ramifications of previous diurnal or nocturnal weather conditions. Over the time period from 0800 hours 2000 hours the lake lost 0.287 gm oxygen/m2-hr. The greatest decrease occurred in the photic zone as oxygenated waters were mixed to deeper levels, replacingoxygen lost to respiration. Photosynthetic and mixing induced oxygenation may also be affected by the morphology of the lake as the volume of water strata decrease linearly with depth. Consequently, less oxygen is needed to raise the levels of lower water volumes, due to the decreased volume. 200 Changes resulting from 8 hours of strength-three winds reflect a different consequence of mixing. From 1100 hours to 1900 hours the photic zone gained 1.472 gm oxygen/m2-hr of which 1.72 gm oxygen/m2-hr had resulted from mixing. Although this quantity is significant relative to photosynthetic oxygen, it may still be less than the amount of oxygen actually incorporated by mixing. The thermal and oxygen profiles show that oxygen supersaturation occurred in the upper waters. Mixing could have caused oxygen from supersaturated waters to be lost to the atmosphere, hence the calculated value may be an underestimation. This would presumably have occurred during the later morning and early afternoon when thermal stratification had increased the temperature of the upper 2 to 4 m. Later, mixing could have resulted in oxygen incorporation as thermal stratification broke down and surface waters were mixed with cooler, less oxygenated waters from greater depths. Overall, the incorporation of oxygen by either photosynthesis or mixing is able to keep pace with respiratory activities and maintain high oxygen tensions in solution and in lower waters. However, whether oxygen increases or decreases with mixing depends on photosynthetic levels, prior organic loads, temperature, and wind duration and intensity. Diurnal thermoclines are either broken down with the afternoon winds or replaced by isothermy over the night. This suggests a diel cycle by which surface phytoplankton are exposed to several hours of intense solar insolation and produce oxygen in amounts that supersaturate the upper epilimnion. The phytoplankton, and the oxygen they produced, are then mixed to variable depths, depending on wind strength and duration. This pattern is almost 201 identical to that observed in another high altitude tropical lake, the large and deep Lake Titicaca (Vincent et al., 1984). The marked changes in oxygen levels of the photic zone emphasize the importance of short term weather phenomena as well as previous lake conditions. For example, days preceded by intense mixing and nutrient rejuvenation of the photic waters could support more vigorous photosynthesis. The extent of deep mixing is indicated by the increase in oxygen noted in waters below the photic zone. Increases usually followed periods of intense mixing by strong winds. Under the condition of light winds (6 hours of strength-two wind) a bilayered stratification existed for sufficient time to allow a net loss of oxygen below the photic zone due to respiration. The randomness of the influence of weather variables is suggested by a least squares regression for dissolved oxygen, using as predictor variables: maximum wind speed category, average daily wind speed category, wind duration, maximum hours of wind, and time of day. No single factor was found to be a suitable predictor for dissolved oxygen concentrations although wind duration and category provided the two highest, but not statistically significant, p-values presented in table 21. When the rate of oxygen change is plotted against wind speed X duration (figure 48), no observable pattern can be ascertained (R2 = 0.13). The variability in thermoeline depth, especially at 1400 hours, indicates that no single factor, or combination of factors, occurs with sufficient regularity so as to be predictive of thermoeline development. 202 CONCLUSIONS As no persistent thermal stratification develops, Lake San Pablo probably falls into the category of warm polymictic lakes (Hutchinson and Loffler, 1956). The lake is strongly influenced by short term events. The influence of daily weather patterns tends to result in morning thermoeline development with oxygenation from both mixing and photosynthesis, followed by afternoon thermoeline disruption, mixing, and oxygen injection to deeper waters. Complete mixing is suggested by the maintenance of a high dissolved oxygen concentration in the deeper waters. The morning and early afternoon thermoclines can also result in density differences of sufficient magnitude to allow development within the epilimnion, of a transient bilayered structure. This strata is separated from the respiratory activities of the hypolimnion. At other times, multiple thermoclines can develop. However, the overall situation is one in which periods of stability of thermal stratification do not persist. The upper turbulent epilimnion descends by wind-stress induced entrainment of nonturbulent fluid from the hypolimnion with little weakening of density gradients, in some cases gradients were sharpened. These observations approximatethe mixing model proposed by Spigel et al. (1986). Lake San Pablo is overturned daily, or at most within 2 days, by strong winds that commonly develop in the afternoon and during the nighttime. Within 36 hours, the lake can be completely mixed and twice stratified with epilimnions and thermoclines of varying depths. The strong afternoon or evening winds override any nighttime convective losses. The 203 observation of Tailing (1966) that mixing may be aided by cooled surface waters sinking to deeper levels is relatively insignificant in this system as nighttime winds are rarely calm. Daily perturbations include both a sharpening and a diffusing of epilimnion and thermoeline boundaries, and alterations in the depth of each. This pattern is similar to several other tropical lakes (e.g. Imberger 1985; Serruya and Pollingher, 1983). Although not examined in this analysis, internal seiches may also be involved in mixing. Since the winds are directed along the long axis of the lake it is not unreasonable to expect that epilimnions, when developed, would tilt into the direction of the wind causing upwelling at the upwind side of the lake. The degree of tilt and the amount of oscillations incurred before the lake overturned would add horizontal density gradients to the mixed layer. The small changes in temperature in San Pablo may not create density differences of sufficient magnitude to allow the water masses to slide over each other in dampening oscillations. Rather, the interfaces may be eroded by the turbulence that develops, and mixing will occur by entrainment. Langmuir circulation occurs at wind speeds above 2 to 3 m per second (Wetzel, 1983). The wind primarily blows across the long axis of San Pablo and lines of Langmuir circulation are distinctly visible in the evening. Based on previous studies the penetrance of turbulence from these processes would affect the top 5 to 7 m (Lewis, 1973). Little mixing would result from traveling surface waves as the vertical movement of water is rapidly attenuated with depth. 204 Extensive mixing resulting from the small density difference between upper and lower waters and the regular occurrence of strong winds, the absence of long periods of stratification, intense insolation, and high pelagicproductivity ensure that hypolimnetic oxygen depletion occurs rarely, if ever. As a result of the mixing profiles it is assumed that suspended matter will he cycled within the oxygen mixed layer, delaying its sedimentation to anoxic bottom waters. Consequently, the initial degradation of exogenous chemicals may not involve anaerobic bacteria. One of the primary roles of wind stress in this system, relative to pesticide degradation, is the maintenance of a circulating pool of particulate matter. Lewis (1983) mentions that long periods of stratification in tropical lakes can lead to localized nutrient depletion in the euphotic zone. Clearly, this is not the case within Lake San Pablo. The continual and extensive mixing result in daily nutrient replenishment from anoxic bottom layers, ensuring ample nutrients for phytoplankton and bacterial growth. If Lake San Pahlo did not come under such intense wind stress its stratification profile would most probably resemble the diurnal changes noted in larger tropical systems under mild climatic conditions (e.g. Kling, 1988). Temperature stratification would develop during the day due to intense solar radiation. As water temperature increased a buoyant epilimnion would develop whose thickness would be dependent upon the rate at which the thermal gradient is established, the extent of advection currents, and the influence of mixing from slight surface winds (e.g. Henderson-Sellers, 1984). As air temperatures decreased during the night and early morning the gradient would be partially disrupted by convection 205 movements (e.g. Finlayson, et al., 1980). The persistence of thermoeline development would be dependent on the degree of disruption occurring during nighttime cooling. However, Lake San Pahlo is subjected to strong winds in nearly every daily cycle. The result is a well-mixed lake with oxygenated bottom water and constantly circulated detritus. °/o TOTAL OBSERVATIONS % T q t AL OBSERVATIONS 30 n 20 10 - - 4 THERMOCLINEDEVELOPMENT BY 1400HOURS THERMOCLINEDEVELOPMENT BY 0800 4 3 2 1 DEPTHOF THERMOCLINE(M) DEPTHOF THERMOCLINE(M) FIGURE25 FIGURE24 1 1 1 1 14 13 12 11 10 9 206 207 18.5 oo m 18.0 17.5 TEMP (C) OXYGEN (MG/L) OXYGEN FIGURE 26 FIGURE 2345678 17.0 AT AT 0800 AFTER 2 HRS OF WIND-II OXYGEN AND TEMPERATURE PROFILES AND TEMPERATURE OXYGEN 0 1 ------16.5 30 32 2 8 20 2 4 2 6 22 DEPTH (M) 208 18.5 oo O h 17.5 18.0 FIGURE 27 FIGURE TEMP (C) OXYGEN (MG/L) OXYGEN 17.0 AT AT 1400 AFTER 8 HRS OF WIND-II OXYGEN AND TEMPERATURE PROFILES AND TEMPERATURE OXYGEN 01 2345678 01 - - 16.5 32- 26- 28- 30- 20 22 24- DEPTH (M) 209 ♦ OXYGEN (MGA-) OXYGEN FIGURE FIGURE 28 2345678 0 1 0800 TO 1400 WITH 6 HOURS OF WIND-II CHANGE IN OXYGEN DISTRIBUTION FROM 32 26 H 26 H 28 H 30 20 H 20 H 22 24 H 24 DEPTH(M) 2 10 2 18.5 oo 18.0 TEMP (C) OXYGEN (MG/L) OXYGEN FIGURE 29 FIGURE 2345678 17.0 17.5 AT AT 1900 AFTER 3 HRS OF WIND-IV OXYGEN AND TEMPERATURE PROFILES AND TEMPERATURE OXYGEN 0 1 - - 16.5 28- 30- 20 22 32- 24- 26- DEPTH(M) 21 1 21 < » < OXYGEN (MG/L) OXYGEN FIGURE 30 FIGURE m m m CD CD CD CD O O 01 2345678 01 " - CHANGE IN OXYGEN DISTRIBUTION FROM CHANGE DISTRIBUTION IN OXYGEN 0800 TO 1900 WITH 3 HRS OF WIND-IV 24- 26- 28- 30- 32 20 22 DEPTH (M) 212 OXYGEN (MG/L) 01 2345678 a m TJ H I 1 20: 22 - 24- 26- 28- 30- 32- 16.5 17.0 18.017.5 18.5 TEMP (C) FIGURE 31 OXYGEN AND TEMPERATURE PROFILES AT 0800 AFTER 2 HRS OF WIND-II 2 1 3 OXYGEN (MG/L) 01 2345678 D m “O —I X 22 - oo S 24- ^ CD 26- oo 28- 30- 32 16.5 17.5 18.017.0 18.5 TEMP (C) FIGURE 32 OXYGEN AND TEMPERATURE PROFILES AT 1400 AFTER 8 HRS OF WIND-II 2 1 4 OXYGEN (MG/L) 01 2345678 D m "0 H X 22 - oo ^ 24- O 26- oo 28- 30- 32- 16.5 17.0 17.5 18.0 18.5 TEMP (C) FIGURE 33 OXYGEN AND TEMPERATURE PROFILES AT 2000 AFTER 4 HRS OF WIND-IV 2 1 5 OXYGEN (MG/L) 01 2345678 O O D m o o TJ m m -I X p O 20 - 22 - 24- 26- 28- 30- 32 FIGURE 34 CHANGE IN OXYGEN DISTRIBUTION FROM 1400 TO 2000 WITH 4 HRS OF WIND-IV 2 1 6 OXYGEN (MG/L) 01 2345678 a m •u H I 22 - 24- 26- 28- 30- 32- 16.5 17.0 17.5 18.0 18.5 TEMP (C) FIGURE 35 OXYGEN AND TEMPERATURE PROFILES AT 1100 AFTER 3 HRS OF WIND-III 2 1 7 OXYGEN (MG/L) 01 2345678 m2 1 6 - AM 8 (MG/L) OXYGEN 3j 18- x j? 2 0 - 22 - oo 24- 26- 28- 30- 32- 16.5 17.0 17.5 18.0 18.5 TEMP (C) FIGURE 36 OXYGEN AND TEMPERATURE PROFILES AT 1900 AFTER 12 HRS OF CONTINUAL WIND-III 2.1 8 OXYGEN (MG/L) 0 1 2 3 4 5 6 7 8 O m “0 H I CD CD 20 - ro oo 22 " ■D > 24- 26- 28- 30- 32 FIGURE 37 CHANGE IN OXYGEN DISTRIBUTION FROM 1100 TO 1900 WITH CONTINUAL WIND-III WIND-1 1 HR WIND-I 2 HRS WIND-II 2 HRS WIND-II 3 HRS WIND-II 7 HRS WIND-II 8 HRS WIND-II 11 HRS WIND-III 3 HRS WIND-III 8 HRS 0 2 4 6 8 10 12 14 16 18 20 22 24 DEPTH OF MIXING (M) FIGURE 38 THE EFFECTS OF WIND STRENGTH AND DURATION ON DEPTH OF MIXING TEMP (C) TEMP (C) 17.0 16.5 17.5 18.0 18.5 18.5 17.5 18.0 16.5 17.0 CHAOTIC THERMOCLINES RESULTING FROM LITTLE OR WIND LITTLE OR FROM RESULTING THERMOCLINES CHAOTIC 0 0 2 2 THERMALPROFILES FORMED BY MILD WINDS 4 4 THERMOCLINE FROM 2 HRS OF WIND-I OF HRS 2 FROM THERMOCLINE WN -) R NO(WIND-I)WINDS OR 6 6 FIGURE39 1 1 1 1 1 20 18 16 14 12 10 8 1 1 1 1 1 20 18 16 14 12 10 8 DEPTH (M) DEPTH DEPTH (M) DEPTH TEMP (C) 4 PM 4 (C) TEMP TEMP (C) 8 AM 8 (C) TEMP 220 TEMP (°) TEMP (C) 70 - 17.0 18.0 - 18.0 i 18.5 16.5 - 17.5 16.5 17.0 17.5 18.0 18.5 0 2 0 THERMALFORMEDPROFILES BY MODERATE 2 4 4 WINDS(WIND-II) SKIES OVERCAST WITH WIND-II OF HRS 2 2 HRS OF WIND-II WITH CLEAR SKIES CLEAR WITH WIND-II OF HRS 2 FIGURE 40 6 6 1 1 1 1 1 20 18 16 14 12 10 8 1 1 1 1 1 20 18 16 14 12 10 8 DEPTH(M) DEPTH (M) DEPTH TEMP (C) 8 AM 8 (C) TEMP TEMP (C) 8 AM 8 (C) TEMP 22 222 TEMP(C) 4 PM TEMP (C) 4 PM DEPTH (M) DEPTH (M) 8 10 12 14 16 18 20 8 10 12 14 16 18 20 6 6 FIGURE 41 8 HRS OF WIND-II WITH OVERCAST SKIES 8 HRS OF WIND-II WITH OVERCAST SKIES 4 4 2 (WIND-II) WITH OVERCASTWITH (WIND-II) SKIES 2 0 0 18.5 18.5 i 1 8 .0 - 17.0 - 16.5 17.5- THERMAL PROFILES FORMED 8 BY HRS OF MODERATE WINDS 16.5 17.0 18.0 18.5 17.5 (0) dmi (o) dl/\J31 TEMP (c ) TEMP (C) 16.5 17.0- - 17.5 0- .0 8 1 i .5 8 1 16.5 17.0- 18.5 -i18.5 0 THERMAL PROFILES FORMED BY MODERATE WINDS WINDS BYMODERATE FORMED PROFILES THERMAL 0 2 2 (WIND-II) WITH CLEAR SKIES (WIND-II) CLEAR WITH 4 4 8 HRS OF WIND-II WITH CLEAR SKIES CLEAR WITH WIND-II OF HRS 8 FIGURE 42 FIGURE 8 HRS OF WIND-II WITH CLEAR SKIES CLEAR WITH WIND-II OF HRS 8 6 6 1 1 1 1 1 20 18 16 14 12 10 8 1 1 1 1 1 20 18 16 14 12 10 8 DEPTH (M) DEPTH DEPTH (M) DEPTH TEMP (C) 4 PM 4 (C) TEMP EP() PM 4 (C) TEMP 223 TEMP (C) TEMP (C) 16.5 17.0- - 17.5 18.0- 18.5 i 18.5 16.5 17.0: 17.5 : 17.5 18.0 18.5 THERMALPROFILESFORMED BY STRONG WINDS (WIND-III) 0 0 2 2 4 4 3 HRS OF WIND-III WITH STRONG GUSTS STRONG WITH WIND-III OF HRS 3 6 6 FIGURE43 1 1 1 1 1 20 18 16 14 12 10 8 1 1 1 1 1 20 18 16 14 12 10 8 3 HRS OF WIND-III OF HRS 3 DEPTH (M) DEPTH DEPTH (M) DEPTH TEMP (C) 4 PM 4 (C) TEMP EP() PM 4 (C) TEMP 224 DEPTH(M) DEPTH(M) -32 2 - -28 - -24 -20 -32 2 - -28 -20 2 - -24 - 0 80 00 20 40 60 80 00 20 2400 2200 2000 1800 1600 1400 1200 1000 800 600 - 0 80 00 20 40 60 80 00 20 2400 2200 2000 1800 1600 1400 1200 1000 800 600 T OXYGEN DEPTH-TIME FOR FIGURES 31-34 FIGURES FOR DEPTH-TIME OXYGEN XGN ET-IE O FGRS 26-28 FIGURES FOR DEPTH-TIME OXYGEN T T r T T T T FIGURE 45 FIGURE FIGURE 44 FIGURE TIME TIME T T T T . MG4.5OX/ML 6.0MG OX /ML 5.5MG OX/ML 5.0MG OX/ML 4.5MG 6.0MG 5.5MG 5.0MG 225 226 18.518.0 r * 17.5 TEMP (C) 3 3 4 5 8 OXYGEN (MG/L) OXYGEN FIGURE 46 FIGURE 17.0 AT 1100 AFTER 3 HRS WIND-II OF 3 HRS AFTER 1100 AT OXYGEN AND TEMPERATURE PROFILES TEMPERATURE AND OXYGEN 0 - - 16.5 30- 32 ' 28- 22 26- 20 DEPTH (M) TEMP (C) 17.5 OXYGEN (MGA.) FIGURE 47 17.0 18.0 18.5 AT 1700 AFTER 11 HRS OF WIND-II OXYGEN AND TEMPERATURE PROFILES 0 1 2 3 4 5 6 7 8 - - 24- 26- 28- 30- 22 20 DEPTH(M) WIND SPEED X DURATION FIGURE 48 RELATIONSHIP BETWEEN OXYGEN CONCENTRATION AND WIND SPEED DURATION 229 TABU'; I7 PHYSICAL CHARACTERISTICS OK LAKE SAN PABLO La li hide 0" 13' N Longitude GO £ Altitude 2661 meters Area 6202 (1000 m2 ) Volum e 1.32 X 108 (m eters2) Shoreline Development 1.18 (circle = 1.0) M axim um 32 meters Depth Average 20 meters Depth Surface 18.0° Temperature Centigrade Seeehi Disk 4.5 Transparency Basin Type Volcanic land- lorm From: Steinitz-Kamian, et a I., 1983 2 30 t a b u ; is MORP1IOMLTRIC DATA 1 OR LAKL SAN PABLO DLPl’II ARLA (M2) 7c ARLA VO LI'M L (M-D 7c VOL (M) 0 6,510.000 100 3 1.500.000 - 5 6.090,000 93 29,200,000 24 10 5,620,000 86 27.000,000 22 15 5.200,000 80 24.800.000 20 20 4,740,000 73 19,600,000 19 25 3.160,000 49 32.395 15 30 448,000 7 0 0 - 100% 132.132,395 100% TABLL 19 OXYC.LN SATl'RATION OL LAKL SAN PABLO AT 2661 MLTLRS WATER TEMPERATURE 15 16 17 18 19 ( centigrade) OXYGEN SATURATION 7.30 7.15 7.01 6.84 6.70 (ppm) TABLE 20 c h a n g e in l a k e oxA CONCENTRATIONS w it h w in d s t r e s s CONDITION NET GAIN NET GAIN NET GAIN INCREASE IN PHOTIC BELOW OF LAKE IN 0 2 DUE WIND SPEED ZONE PHOTIC TO MIXING CATEGORY ZONE Kin 02/m2-hr Kin <) 2 / in 2 - li r Kin 02/tn2-lir Kin ()2/in2-lir 6 IIRS II 1.716 -0.429 1.287 1.14 2 IIRS II + -0.205 1.341 1.136 0.71 3 IIRS IV 8 IIRS II + 0.842 0.376 1.218 0.64 3 IIRS IV 6 HOURS II 0.091 0.218 0.309 - 8 HRS II + -0.477 0.190 -0.287 - 4 HRS IV 8 HRS III 1.472 0.831 2.303 1.72 TABLE 21 UNWEIGHTED LEAST SQUARES LINEAR REGRESSION FOR PREDICTION OF OXYGEN DELIVERY PREDICTOR VARIABLE P VALUE Maximum wind speed category 0.88 Average daily wind category 0.61 Hours of wind category 0.94 Maximum hours of wind 0.80 Time of day 0.52 CHAPTER VI PARATHION AND THE LIMNOLOGY OF SAN PABLO INTRODUCTION Parathion will enter Lake San Pablo by translocation. The first component of the ecosystem to be exposed to pesticides will be the littoral zone. The near-shore zone is the interface between lake and land and receives pesticides from agricultural fields through both runoff and inlet streams. Extensive macrophyte stands in the zone of emergent vegetation could conceivably function as filters, trapping particulate organic matter to which pesticides have adsorbed. In this regard, the littoral and near shore regions would act as effective parathion traps, preventing large amounts of the pesticide from reaching the pelagic waters. This region may be the primary location for pesticide degradation. Experimental procedures were designed to assess the degradation of parathion and its potential effects on the flora and fauna of the Lake San Pablo ecosystem. The investigation was organized within the five principal hypotheses that follow. 232 233 HYPOTHESIS I. PARATHION DEGRADATION IS A FUNCTION OF BACTERIAL DENSITY. Bacteria are the single most important factor in the degradation of parathion and larger numbers of bacteria should correspondingly result in more rapid degradation. The reducing environment created by the anaerobic conditions of the littoral zone also favors the rapid degradation of parathion by conversion to amino parathion. Having a suite of aerobic, anaerobic, and facultatively anaerobic bacteria, in conjunction with fungi, protozoa, and algae will maximize the concerted degradation of parathion and its metabolites. It may be the case that large, diverse populations of bacteria can compensate for the excessive inputs of pesticides and reduce the potential for serious secondary exposure to parathion. Estimates were made of total numbers of aerobic or facultatively aerobic bacteria within anaerobic and aerobic sediments. No attempt was made to characterize individual species. A previous expedition isolated species of Aero mo na s. Pseudomonas. Bacillus, and JL coli bacteria; species of all 3 are capable of rapid metabolism of pesticide molecules (M. Steinitz- Kannan, personal communication). Given the inputs of human and agricultural waste and especially detergents with high phosphate concentrations, it is expected that bacterial concentrations in San Pablo will be extremely high. Highest numbers will most likely be found in the littoral sediments near agricultural runoff, in those regions receiving direct sewage inputs, and near clothes washing areas. The lowest concentrations should he found in anaerobic pelagic sediments. 23 4 Measurements of bacterial populations were compared to numbers obtained from a literature survey of different lake ecosystems. HYPOTHESIS 2. LITTORAL ZONK PROCESSES ARK SIGNIFICANT IN THE DEGRADATION OF PARATHION. Because of the year long growing season and the influx of nutrient rich water macrophyte densities are very high in Lake San Pablo. It is expected that the littoral region of Lake San Pablo can be divided into 3 zones: an upper zone that is continuously oxygenated; a middle zone that shows large diurnal changes in both pH and temperature and alternates between anoxic and oxygenated conditions, and; a lowermost zone that is consistently anoxic. The alternating aerobic and anaerobic environment and the high concentration of degradable organic matter will maintain large microbial populations (Jones, 1977). Also present will be extensive and large populations of Aufwuchs communities of fungi, protozoa, algae, and bacteria. In addition, the daily changes involve variables known to affect pesticide breakdown. Organic material that may be refractory to bacterial degradation may be suitable for metabolism by members of the Aufwuchs, especially fungal species. The net result will be a rapid degradation of both organic material and any adsorbed pesticide residues. The most important component of parathion degradation in an aquatic ecosystem may be the Aufwuchs communities in the littoral zones. Gomaa and Faust (1972) have shown that the pH of aquatic environments can affect the chemical hydrolysis and oxidation of 23 5 parathion. Conversely, Smith et al. (1978), modeled the breakdown of parathion and concluded that pH induced hydrolysis, as well as volatilization and photolysis were insignificant transformation processes when compared to biodegradation. I tested the hypothesis that diurnal physical and chemical changes within the littoral zone would be of sufficient magnitude to influence the degradation of parathion. Changes in oxygen concentration, pH, and temperature were recorded on clear and cloudy days. As strong reducing conditions favor the degradation of parathion by anaerobic bacteria, diurnal oxygen changes were measured to determine time-depth oxyelines. HYPOTHESIS 3. MACROPHYTES ARE l \AFFECTED BY PARATHION. A second hypothesis to be tested was that parathion exposure will have little or no effect on macrophytes of the littoral zone. Reductions in oxygen production relative to controls were considered to he representative of pesticide damage. This part of the study investigated the effects of parathion on the oxygen production of the macrophyte Ceratophvllum demersum and its associated aufwuchs community. Few data have been published on the toxicity of parathion to aquatic macrophytes. Mulla (1966) found that parathion residues persisted up to 14 days in the water grass Eehinochloa crusgalli and up to 29 days in the smartweed Polygonum muhlenhergii. He also noted in both species an accumulation of pesticide following sequential applications. No adverse effects on the plants were described. 23 6 HYPOTHESIS 4. PRIMARY PRODUCTIVITY IN THE OPEN WATER IS REDUCED BY PARATHION. Although the retentive effects of the littoral zone will minimize contamination of the pelagic region, material that bypasses littoral growth or directly enters the pelagic zone will be diluted throughout the water column by the daily mixis. Pelagic degradation mechanisms within the water column will primarily be aerobic. Because of the aerobic environment, pesticides adsorbed to organic matter may not degrade as quickly in this region, as compared to the primarily anoxic littoral zone. Also, degradation could result in the production of the more toxic oxidized metabolite paraoxon, rather than nitro-reduced compounds. Lakes with less extensive littoral regions are more likely to result in a higher concentration of metabolites toxic to phytoplankton. Lake San Pablo has been determined to fix approximately 2.6 gm carbon/m2-day (Miller et al., 1984). The most productive lakes of Ecuador daily fix an average of 6.1 gm carbon/m2, with a range of 1.5-12.1 gm carbon/m2 (Steinitz-Kannan, et al., 1983). Comparative values from other studies are: 2.3-2.7 in Lake Izabal, Guatamala; 1.7 in Lake Lanao, the Phillipines; 2.2 in Lake George, Uganda; and 4.6 and 21.4 in two Ethiopian Soda Lakes (Serruya and Pollinger, 1983). Few references exist in the literature regarding the effects of parathion on phytoplankton photosynthesis. The hypothesis tested in this portion of the study was that depression of photosynthesis would occur following exposure to parathion. Previous studies have concentrated on the effects of organochlorine 23 7 pesticides to phytoplankton growth and photosynthesis (e. g., IJkeles, 1962; Menzel et al., 1970; Stadnyk and Campbell, 1971; Butler, 1977). Gregory et al. (1969) have shown that in a solution of 1 ppm, parathion was taken up and concentrated 50 to 70 times by the bluegreen alga Anacvstis nidulans. the green alga Scenedesmus obliquus. the flagellate Euglena gracilis. and the ciliates Paramecium bursaria and P. multimicronucleatum However, changes in productivity were not investigated. Moore (1970), using Euglena gracilis Z, found a 14% decrease in photosynthesis upon exposure to a parathion concentration of 1.2 ppm. Butler (1977) reported a 9.9% reduction in photosynthesis by marine phytoplankton after a 4 hour exposure of 1 ppm parathion. Cole and Plapp (1974) found 30 to 70% reductions in the growth of Chlorella after 7 days of exposure to 1 ppm parathion. The fixation of carbon is a major determinant in driving the productivity of an aquatic ecosystem (Wetzel, 1983). Significant decreases in phytoplankton couldadversely affect higher trophic levels. Results from Lake San Pablo will be compared to the ranges suggested by these studies. Due to their more rapid growth rate, it is expected that phytoplankton will show similar or greater decreases in productivity, compared to literature values. HYPOTHESIS 5. ZOOPLANKTON MORTALITY WILL BE DEPENDENT ON ENVIRONMENTAL CONDITIONS. The final part of this study investigated the effects of a 24 hour exposure of parathion to Daphnia pulex taken from Lake San Pablo. As a 238 generalization, it has been found that these organisms are extremely susceptible to low concentrations of organophosphates. Published information on the toxicity of parathion to freshwater Daphnia include the following: 48 hour LC50 of Daphnia magna. 0.8 pph; 64 hour LC50 of Daphnia carinata. 0.5 pph, and; 48 hour LC50 of Daphnia pulex. 0.6 pph (cited in Mulla, et al., 1981). Daphnia were exposed to 3 different environments: lake water that had been sterilized by boiling and filtration, untreated lake water from the pelagic zone, and untreated littoral lake water with 10 gm wet weight of the macrophyte Ceratophvllum demersum and its associated aufwuchs. The hypothesis to be tested was that zooplankton mortality would be reduced in conditions that both increase the absorption of parathion to plant matter or increase the rate of degradation. 2 39 METHODS All measurements of oxygen concentrations and temperature were made with a Yellowsprings Instrument Company combination temperature/oxygen meter, Model 54. A Horizon pH meter, calibrated daily with stock buffers, was used to record pH changes. Oxygen, pH, and temperature changes were measured in 2 near shore regions of dense macrophyte stands, roughly 20 m into the vegetation at the north-western edge of the lake near region two on the map of figure 22. Sites were relocated with the use of anchored buoys. Oxygen concentrations were recorded at 0800 and 1600 hours. Values for temperature and pH were recorded in the littoral zone at 2 hour intervals from 400 to 2400 hours at a depth of 0.5 m, measurements from the 2 sites were averaged. The perimeter of the littoral zone was also surveyed with a small motorized boat. This was complemented by a foot survey of the immediate watershed. The number of bacteria per gram of fresh sediment was determined for locations 1 through 7 in figure 22. Sediment was obtained with an Ekman dredge which collected approximately the top 10 cm of sediment. The sample was passed through a fine screen and allowed to drain until it had the consistency of thick mud. A sample of sediment from location 7 consisted of 61% organic matter, as determined by loss on ignition at 450° C. Serial dilutions and plate counts were used to quantify bacteria populations. Non-seleetive agar plates were maintained in an aerobic environment at approximately 30° C. Plates usually spotted 10 to 20 organisms and 2 plates were used for each sample dilution. 240 Triplicate degradation experiments were conducted in 2 liter Erlenmeyer flasks filled with 1 liter of lake water collected from the same area as the sediment or aufwuchs sample. Lake water used in the Aufwuchs study was filtered, the lake water used in the sediment study was not treated. The sediment degradation experiment used one gram of the sample from location 7, with a concentration of 1.2 X 109 bacteria per gm, collected using the procedures described for the bacteria determination experiments. Approximately 5 gm wet weight of aufwuchs were collected from the littoral zone by gently removing gelatinous material adhering to macrophyte fronds. Parathion, dissolved in acetone, was added to flasks to obtain a final concentration of 1 ppm in the sediment/water mixture. The parathion- mud-water mixture was kept in the dark and continuously stirred during the length of the experiment, except during occasional power shortages. The pH of the mixture was daily checked and adjusted to the original value of 7.2. The Aufwuchs sample was blended with a small amount of lake water in a tissue homogenizer. One ml was removed for bacterial counting and one ml was added to a flask containing 1 liter of filtered, sterilized lake water and exposed to diurnal temperature and light changes. Because of oxygen production by photosynthetic algae, the pH was not artificially maintained. Approximately 5 minutes after dosing the time zero samples were taken. Duplicate samples were removed at 12, 24, 48, 96, 192, and 288 hours. As a control, parathion was added to a sample of lake water that had been filtered and sterilized by boiling. This sample was sealed and placed in the dark. All 3 samples were maintained at ambient temperature. 241 Aliquots of the sediment and water suspension were removed from each flask with a pasteur pipette and transferred to a small beaker from which exactly 5 ml were removed. One ml of 1 M NaHAc acid was added before each sample was extracted 3 times with 10 ml of hexane. Approximately 5 gm of anhydrous NaS04 were added to the combined extracts. After 30 minutes the NaS04 was removed by filtering and washed with 5 ml of hexane. The combined extracts were poured into a 50 ml glass vial that previously had been cleaned with acetone, and dried under a stream of air to a final volume of approximately 5 ml of hexane. The vial was capped with foil and stored in a refrigerator until shipment to the United States. Samples were maintained at ambient temperature during a single day of transport, although half the time was spent in cold aircraft cargo bays. Upon return to Ohio, the samples were stored at -10° C until analysis. Because of difficulties in equipment, samples were analyzed 9 months after collection. Upon analysis, it was found that parathion recoveries were very low (1 to 2%) for one particular set of the 96 hour samples from both the sediment and aufwuchs degradation. This was assumed to reflect an error in processing and these data were excluded from the analysis. The extraction procedure was developed with the assistance of R. Detra. Extraction efficiencies of solvents in parathion/lake-mud mixtures were determined by adding a known concentration of nikethamide before and after the extraction. Mud was obtained from a highly eutrophic farm lake in central Ohio. Samples were acidified by the addition of NaHAc acid and extracted with hexane; the average extraction efficiency was 81%. 242 The following column characteristics were used: injection temperature, 230° C; initial column temperature, 120° C; temperature program 10° C min final temperature, 240° C; one minute initial hold at 120° C Nitrogen carrier gas was delivered at the rate of 30 ml/min. Amounts were quantified using external standardization and peak height measurement; no adjustment was made for extraction efficiency. Immediately prior to analysis, the hexane was evaporated and the dried residue reconstituted in 50 microliters of ethyl acetate. Two microliters of ethyl acetate were injected into a gas chromatograph. Data were plotted as remaining parathion against time. Least square regression was used to determine the first order degradation constant and coefficients of determination (R2) in conformity with the model: In C = -k(t) + a, where In C is the concentration of parathion at time (t). Near surface Ceratophvllum was carefully collected to preserve as much of the aufwuchs as possible. Approximately 10 gm of wet weight macrophytes and aufwuchs were added to glass jars containing oneliter of lake water. The jars were paired and maintained at ambient temperature and exposed to normal daily insolation. Any water that evaporated was replaced at 1800 hours with filtered, fresh, lake water. On day 2 parathion, dissolved in acetone, was added to one jar of each pair to achieve a concentration of either 1, 10, or 20 ppm. As a control, the other jar received only the amount of acetone necessary to inject the pesticide. Earlier studies had shown that plants could be maintained for 5 days without any noticeable deterioration in oxygen production. 243 Oxygen concentrations were measured at 0800 and 1800 hours and the difference between the morning and evening concentrations of the treated jar was divided by the difference between morning and evening concentrations of the control jar to calculate a ratio of production. The ratio of production of the pretreatment day was compared to the ratio of production for the post-treatment day by a paired-sample t-test. If parathion had an effect on photosynthesis the ratio between the two jars before treatment would be different than the ratio after treatment. Comparing ratios compensated for variations in oxygen production due to both slight differences in photosynthetic material and differences in environmental conditions between the 2 days. Three pairs of macrophytes were compared for each concentration of parathion. Mixed species assemblages of phytoplankton larger than 64 microns were collected from lake San Pablo. Numbers or volumes of individual cells were not quantified. A microscopic examination showed species of Scenedesmus. Pediastrum. Vo 1 vox and the blue green algae Microcystis. The light and dark bottle method was used to measure changes in phytoplankton oxygen production resulting from parathion exposure. Controls and pesticide-treated samples were incubated for 12 hours from 700 to 1900 hours at a depth of 1 m. Oxygen concentrations were measured before and after incubation and production was converted to mg carbon using a photosynthetic quotient of 1.3. Parathion, dissolved in acetone, was added to the treatment bottles to achieve a final concentration of 0.5, 1.0, and 10.0 ppm. Data for the 0.5 ppm pesticide concentration were averaged from two separate experiments, each run with 3 treatment bottles 244 and 3 control bottles. Data for the remaining concentrations were averaged from two separate experiments; one with 2 controls and 3 treatments and the other with 3 controls and 2 treatments. Control and experimental production estimates were compared using a two-sample t-test. Daphnia Pulex were collected by towing a 64 micron plankton net through the upper waters of Lake San Pablo. Organisms were collected around 2400 hours and kept in fresh, unfiltered lake water. The following morning the organisms to be used in the toxicity tests were separated from other species of zooplankters. Damaged daphnids or those with eggs were not used; all zooplankton were active and swimming at the initiation of each experiment. Fifteen Daphnia were transferred to 200 ml of lake water; zooplankton exposed with macrophytes were added to 500 ml of water. Parathion was dissolved in acetone and added 30 minutes before the initiation of each test. Exposure concentrations were 0.5, 1.0, 2.0, 5.0, and 10.0 pph of parathion; a control of acetone alone was also used with each series of tests. The tests were usually set up by 1000 hours and ran 24 hours. Test jars were kept in natural light (but not sunshine) and at ambient temperatures. Duplicate experiments were made using the above suite of pesticide concentrations and 3 types of exposure conditions. One series used littoral lake water that had been filtered to remove bacteria and particulate organic materials and was then sterilized by boiling. A second condition used untreated pelagic lake water which contained phytoplankton, dissolved and particulate organic material, and suspended bacteria. A third condition used untreated littoral lake water to which had been added 10 gm of the 245 macrophyte Ceratophvllum demersum and the associated aufwuchs comm unity. At the end of each experiment Daphnia lying on the bottom of the jar were gently grazed with a metal needle. Those that began swimming upward into the water of the jar were considered mobile. Organisms that did not respond to mechanical stimulation were removed and examined microscopically. Organisms observed to have minor movements of the thoracic appendages were considered immobilized. The classification of mobilized versus immobilized involved a considerable amount of subjectivity. Errors were perhaps made in the direction of the latter. Toxicity data (EC50's) were determined with a probit analysis; 95% confidence intervals for the EC50 were calculated using the method of Litchfield and Wilcoxon (1949). 246 RESULTS AND DISCUSSION PARATHION DISAPPEARANCE Mean, and range of recoveries of parathion are presented in figures 49 and 50. Recoveries from samples ranged from 1 to 73%. Parathion concentrations rapidly decreased in the first 24 hours. A biphasic degradation is suggested by the means of the duplicate samples, but recovery variations within sample times were very high. The greatest variability in sediment samples occurred at 24 hours when recoveries ranged from 13 to 50%. The greatest variability within Aufwuchs samples occurred at 12 hours when recoveries were 34 and 72%. Recoveries from the control sample increased slightly at 24 hours and then decreased by 17% over the following 7 days. The test systems utilized 4 types of bacteria found in aquatic ecosystems: sediment bacteria, bacteria adsorbed to particulate organic matter, aufwuchs bacteria, and free-floating planktonic bacteria. The latter were present only in the lake water used in the sediment study. Since suspended materials were not separated from lake water, the measured recoveries of parathion include both dissolved and adsorbed pesticide, assuming of course, that the latter was extractable. The Aufwuchs sample also included littoral algae, which has been shown to adsorb and degrade parathion (Gregory et al., 1969). As the flask was incubated in light alga may have contributed to the degradation of parathion. The procedure used in this study extracted both sediment and water and the constant stirring obscured any relationships between sorption and sedimentation. The use of non-radiolabeled pesticide, and the analytical 247 quantitation of only parathion make it difficult to separate the causes of the observed disappearance. The decreasing amounts of parathion over time extracted from the sediment/water mixture may be due to adsorption, degradation, or a combination of the 2 processes. Degradation is obviously occurring, but since adsorption can alter the exposure of pesticide to degradative mechanisms, the rate of degradation may not he constant over time. Leenheer and Ahlrichs (1971) using muck soil with an organic matter content of 58%, investigated the adsorption of parathion to soil organic matter. They determined that equilibrium was reached in 2 hours or less. Although the water to soil ratio is different in terrestrial systems, the results of this work may be applicable in this situation. The presentation of parathion to the surface of the organic matter was determined to be diffusion limited. Upon contact, the pesticide was rapidly adsorbed to the exterior surface and, over a longer time period, diffused to the interior of the adsorbate. The large amount of organic material in the sediment sample, the continual mixing, and the rapidity of adsorptive equilibrium would suggest that in these experimental situations, most parathion did not remain in solution. Leenheer and Ahlrichs (1971) also reported that adsorption was completely reversible. Wahid and Sethunathan (1978) found that soils with a high organic content desorbed very little of their content of parathion unless treated with an organic solvent. Using water extractions, over 48% of the initially sorbed parathion was liberated from mineral soils while only 2.7% was liberated from a soil with an organic content of 24.6%. However, 248 between 29 and 39% of the initially sorbed parathion was removed from this soil by one extraction with chloroform-diethyl ether. A greater amount of sorbed parathion would be expected to have been removed by the three extractions used in this procedure. Likewise, Felsot and Dahm (1979) have also reported that adsorption generally is reversible, but mentioned that desorption is not always complete. If these findings are applicable to this study, it may be the case that the solvent extracted all, most, or a constant amount of the available parathion from the organic material sampled. As the experiment proceeded, sediment organic material would have been rapidly degraded by the high concentration of bacteria in solution, the high water to sediment ratio, and the continual mixing. Sediment particles would constantly be broken down, exposing internal surfaces and releasing interstitial water. The parathion contained in this interstitial water would be adsorbed by remaining organic material. With time, parathion that had initially been internalized would be made more accessible to the solvent. If adsorption was reversible, the disappearance of parathion represents the degradation rate of the organic material used as a carrier as bacteria would breakdown parathion in the process of degrading organic material. Parathion in refractory organic material however, would not be degraded. Based on this reasoning, the extraction procedure would have been least efficient in the beginning of the study. As degradative processes continued, the proportion of organic matter that had been degraded would increase relative to the total amount of organic matter originally in the sample. As organic matter is broken down, a greater amount of the 249 internalized parathion would be exposed and become more accessible to extraction by the solvent. Thus, it may be the case that the degradation of parathion in sediments with large amounts of organic material is dictated by the rate at which the organic matter is degraded by bacteria. The recoveries of figures 49 and 50 may represent the rate at which such organic carriers are degraded. Conversely, Graetz et al. (1970), in their study of parathion degradation in lake sediments, assumed that adsorption to sediments was irreversible and the amount of bound parathion remained constant over time, notwithstanding degradation of both parathion and the sediment. As the authors point out, this would lead to an underestimation of the degradation rates, which they feel is preferable to the overestimation that would follow from assuming reversibility of the adsorption reaction. The degree of reversibility may also affect the fate of pesticides following a disturbance of the sediments. If partitioning of the pesticide is reversible its concentration in water may increase following an alteration of the sediments, e.g. perhaps as a result of surface erosion or an input of terrestrial water from heavy rains. In this study, continually mixing the sediment water solution would have duplicated any natural disturbance that could have the potential to alter the location of parathion. Regardless of the balance between degradation and adsorption, very little pesticide was recovered by the end of 12 days. Given the high concentrations of bacteria in the sediment sample and the lake water, it was very likely that most of the organic matter, and the parathion it contained, had been degraded by this time. Studies in less eutrophic temperate lakes 250 have found that the organic carbon of dead algal cells declines about 55% in 5 days under aerobic conditions (Wetzel, 1983). Aerobic degradation of other types of limnological material resulted in losses that ranged from 8 to 68% per day. Although it may not be appropriate to quantitate a rate based on the data presented, I think it is possible to conclude that the added parathion was mostly likely degraded completely by the end of the 12 days. However, since paraoxon wasnot measured, it is not known whether the environmental hazard has been alleviated. Graetz et al. (1970), investigated the time course of the disappearance of parathion from water that was incubated with sterilized lake sediment. They observed a rapid decrease in the amount of parathion during the first 12 hours after exposure and attributed this to adsorption. A slower rate of decrease was noted from 12 to 72 hours which was thought to reflect both adsorption and degradation. After 72 hours the loss of parathion was thought to be due only to degradation. This overall pattern of inflection points, representing adsorption, adsorption-degradation, and finally, degradation appears in both figures 49 and 50. In littoral sediments a rapid decrease occurred in the first 24 hours. This was followed by a less rapid decrease from 24 to 96 hours and an even slower rate of decrease after 192 hours. Although only one data point exists for the 96 hour sample this time appears to mark the inflection point for the shift from adsorption- degradation to degradation. A similar pattern is noted in the Aufwuchs study, but the inflection points appear to be more defined, especially the transition from 24 to 96 hours. The major assumptions of first-order degradation kinetics were considered to be satisfied by the test systems. Specifically: the parathion concentration was always at subsaturation levels relative to the degrading enzymes and the degradative unit, either an enzyme or an enzyme series, was constant over time. First and second-order degradation rates, and coefficients of determination are presented in table 22. The second-order degradation constant for the aufwuchs community was determined from bacterial plate counts that indicated 1.6 X 10‘7 colony forming units per ml The second order rate constant for the sediment sample was calculated by adding the bacterial concentration determined for the sediment sample, 1.2 X 109, to the approximate concentration of bacteria in 1000 ml, 3.9 X 109, for a total population of 5.1 X 109 cells. The concentration of bacteria in 1 liter of lake water was calculated by averaging values from site numbers 1, 5, and 6, of the bacteria study of the subsequent section (table 23). Spain et al. (1980) have postulated that the degradation of parathion is analogous to that of methyl parathion. In this regard, literature values for t 1/2 constants for the degradation of methyl parathion in lake sediments ranged from 21 to 7000 hours (Van Veld and Spain, 1983; Pritchard et al., 1987). The large range is assumed to be due to differences in microbial biomass and activities (Pritchard et al., 1987). This suggests that the measured time course of degradation can be strongly influenced by the design of the test system. For example, in this analysis, the contribution of anaerobic bacteria was not considered. 25 2 A second-order degradation rate of 4.5 X 10 " L cell'1 hour1 has been reported for the degradation by aufwuchs microorganisms of methyl parathion (Lewis and Holm 1981). The rate determined in Lake San Pablo was almost 7 times faster. This difference could he explained by a more rapid first order degradation rate due to relatively higher concentrations in Lake San Pablo of bacteria that rapidly degrade parathion. Even though second-order rate expressions theoretically correct for bacterial concentrations, they do not account for differences in the ratios of degradative to non-degradative bacteria. Alternatively, it could represent the rapid adsorption of parathion by the organic matter in the Aufwuchs sample. The application of these data to different lakes within a geographical area assumes that degradation will be a linear function of the populations of either aufwuchs bacteria or sediment bacteria. More specifically, the ratio of transforming bacteria to nontransforming bacteria will be constant. Bacterial populations are primarily determined by the amount of detrital material. Pritchard et al. (1987) have shown that biodegradation rates are linearly related to detritus concentrations over a range of 500 to 5000 mg of detrital sediment per liter. Most small, high altitude tropical lakes in farming regions receive similar environmental contaminants as Lake San Pablo: raw sewage, animal wastes, detergents and household waters, and agricultural inputs of fertilizers, pesticides, and organic matter. However, the relative contribution of each factor may vary so that the main difference between systems is in the actual concentration of bacteria. Within a geographical 25 3 area, degradation rates for pesticides could he determined for several known concentrations of bacteria, which can then be correlated to the amount of detrital material. Future field studies could easily estimate the degradation rate for other lakes within the region by simply estimating the amount of organic material by loss on ignition. This assumes that seasonal variations in bacterial populations will not be substantial; given the intensity of the wet season, this may not be a valid assumption. An increase in nutrient input in eutrophic lakes increases bacterial populations in eutrophic lakes from 2 to 7 fold (Coveney et al., 1977; Jones, 1977; Rai, 1979). Small lakes may be heavily contaminated with pesticides, whose effects on the microbiota may be stimulatory or inhibitory. In some environments, the pesticides may cause an adaptation of the bacterial community through an increase in the number of bacteria specifically able to degrade the contaminant. This has been shown to occur with pollutant concentrations of 4 X 107 M. (Spain et al., 1980). Conversely, the use of different agrochemicals may result in suppression of the breakdown of one or more of the pesticides by interference with reproduction or growth of degradative species (Rosas and Carranza de Storani, 1987). In conclusion, within an aquatic ecosystem, any parathion not initially adsorbed to organic material will be taken up by suspended organic matter within the first 24 hours. However, unless pesticide is applied directly to the lake surface, most parathion will have already been adsorbed during the process of translocation and erosion. Degradation will be affected by the volume and geometry of the organic material to which the 254 parathion has adsorbed; larger organic clusters offering refuge from bacterial or chemical processes. As organic material is degraded so will any parathion residues contained within. Although it is not possible to exactly quantify the degradation rates from the results of these experiments, it appears that parathion is degraded past ppm amounts in 12 days or less. This is also consistent with time periods of the degradation of organic material reported in the literature. HYPOTHESIS 1. PARATHION DEGRADATION IS A FUNCTION OF BACTERIAL DENSITY. Sediment samples were collected at various locations within the lake (figure 22). Locations 1, 4, 5, and 7 were in areas of shallow water (less than 1 m) where macrophyte stands were not very thick. The overlying water was oxygenated to just above the sediments. Locations 2 and 3 were located between the shore and the outer limits of the littoral region and had at least 1 m of anoxic water above the sediments. Location 6 was located approximately 50 m off shore in 23 m of water; the sediment sample from this location was also anaerobic. Anaerobic samples were gelatinous, grey- black, had a faint smell of hydrogen sulfide. Surface water samples were collected at locations 1, 5, and 6, for a determination of the number of bacteria suspended in the water column. A considerable amount of suspended particulate material was observed in the water from these areas. The bacterial concentrations from region 7 were used to generate second order degradation rates. 255 Table 23 lists the number of bacteria counted at each location. Tables 24 and 25 rank water and sediment samples from Lake San Pablo in relation to data obtained from published research. Some of the referenced studies quantified bacteria with direct counting methods, rather than plating. This procedure produces measurements that are 1 to 2 orders of magnitude higher than the colony plating method used in this study (Hayes and Anthony, 1959). Population estimates from this study are likely to be underestimates as some bacteria are not able to grow on plain agar. Since the counting plates were maintained in an aerobic environment only aerobic or facultative anaerobic organisms were cultured and reported concentrations refer only to oxygen-tolerant bacteria. In addition, selection pressures, such as vitamin or nutrient deficiencies, could also result in an underestimation of population numbers. The aerobic sediments of the near shore waters produced the highest number of bacteria: 1.2 X 10y and 1.5 X I0V bacteria per gm of wet sediment. The highest counts came from a section of the lake that receives a variety of allochthonous inputs: phosphorus from the detergent the Indians use for clothes washing, untreated sewage from a motel and 2 restaurants, and agricultural runoff. The second highest counts were recorded from a location that also receives sewage and runoff. Anaerobic pelagic sediments under 23 m of water had the lowest concentrations of bacteria, 1.2 X 107, but this value was only 14% below the lowest littoral sediment concentration. The pelagic sample was taken from an area that receives inputs from the agricultural stream. Estimates of bacterial numbers from deeper, more isolated areas of the basin may not be as large. 256 Discharges of sewage and human wastes may be more important than agricultural inputs in the maintenance of high bacterial populations. The anaerobic sediment samples from locations 2 and 3 had concentrations of 1.4 X 107 and 8.0 X 107 bacteria per ml, approximately 1 to 2 orders of magnitude less than the aerobic sediments. This difference may be a consequence of the culturing methods and not reflect actual differences within the lake. However, although these areas are surrounded by agricultural land, they do not receive sewage inputs. Aerobic sediment samples from locations 2 and 4 were also from areas with agricultural, but not sewage, inputs. Likewise, they had bacterial numbers that were about one order of magnitude lower than areas receiving both. Larger populations of bacteria are maintained in localized areas that receive both agricultural inputs and sewage discharges. The density of the macrophyte stands would inhibit the spread of organic or waste material. This situation may change during the rainy season when there is an increase allochthonous inputs from agricultural areas. The sample from the open waters of the pelagic region had the lowest concentration of bacteria, 1.4 X 106 bacteria per ml, 3 orders of magnitude lower than the highest littoral sediment sample. The two samples from littoral water had approximately 106 and 107 bacteria per ml; 2 orders of magnitude less than the numbers found in the underlying sediments. The larger densities were found above location 5, the region with the highest sediment population of bacteria. The littoral waters contained concentrations of bacteria that were only 2 orders of magnitude 25 7 less than the sediments. This small difference may have resulted from being unable to quantitate the contribution of anaerobic bacteria. Concentrations of suspended bacteria would be more accurately estimated since only aerobic or facultatively anaerobic bacteria would be expected to inhabit the water column (Wetzel, 1983). If the number of bacteria in the sediments were underestimated by 1 order of magnitude the surfieial sediment concentrations would still be only 3 orders of magnitude larger than the suspended concentrations. This implies a considerable amount of bacterial activity within the littoral waters. Compared to the littoral zone, the pelagic region had a smaller ratio of suspended to sediment bacteria. Bacteria suspended in pelagic waters were only 1 order of magnitude less than the surfieial sediments. Since the bacterial composition from the pelagic sediments is predominantly anaerobic the aerobic plate counting method would severely underestimate their numbers. However, the frequent mixing of Lake San Pablo can be expected to maintain large populations of aerobic bacteria in both the suspended waters and the top few centimeters of the bottom sediments. In temperate systems, higher populations of bacteria are noted during the spring and fall overturns. Since mixing extends to the sediments, both nutrients and surfieial bacteria could be entrained to the upper waters. High rates of respiration were also noted in the hypolimnion and immediately below thermal gradients. Together, these data imply that a significant amount of degradation occurs in the water column. Frequent mixing may continually recirculate particulate organic matter within the oxygenated pelagic waters. Consequently, the majority of the decomposable 25 8 material will already have been degraded before the particles settle to bottom.This is relevant to pesticide degradation as adsorbed compounds in the open waters would be exposed to aerobic mineralization. Possible mechanisms maintaining the large bacterial populations include: retention of particulate organic matter of both autochthonous and allochthonous origin; minimal dissipation of dissolved organic matter; high inputs of wastes and terrestrial run-off, and; large, shallow areas of extensive plant growth that result in large quantities of detritus and high rates of carbon cycling. Lake San Pablo is in a valley surrounded on 3 sides by lands used for agriculture and grazing. There is the potential for large amounts of organic matter to be carried into the lake by intense seasonal rains as fields are not thoroughly plowed. Hand worked fields, or those tilled by draft animals, do not turn crop remnants deep into the soil and organic matter remains near the surface. Human and animal waste, nitrates from fertilization, and large inputs of phosphorus from detergents are also translocated to the lake. Large amounts of decomposing organic material support bacterial populations richer both in numbers and species (Wetzel, 1983). Interandean lakes and ponds will have high concentrations of bacteria from human waste, animal excrement, and agricultural runoff, similar to Lake San Pablo. Other lakes, with a smaller volume of water and extensive agricultural and human contamination could have larger concentrations of bacteria. In conclusion, aerobic or facultatively bacterial concentrations are some of the highest values reported in the limnologieal literature. Heterotrophic aerobic bacteria concentrations showed variations over 3 259 orders of magnitude. The highest numbers were found in the aerobic sediments of the littoral zone, particularly in regions adjacent to sewage discharges. These were 2 orders of magnitude greater than numbers counted in anaerobic littoral sediments. The lowest concentration was found in anaerobic pelagic sediments, also 2 orders of magnitude less than the largest value recorded from the littoral region. The number of aerobic bacteria suspended in pelagic waters was approximately 1 order of magnitude less than the concentrations found in the underlying sediments. Littoral water had bacterial concentrations 2 orders of magnitude less than the numbers found in the sediments. Again, the small difference may have resulted from underestimating the total number of bacteria in the sediments. These differences in bacterial density are expected to result in different rates of parathion disappearance. However, populations of bacteria may not affect degradation if parathion is sequestered within organic compounds. Different densities of bacteria can affect parathion metabolism provided the adsorbent materials are not refractory to bacterial degradation. Hypothesis 4 may then be acceptable provided that parathion is made available by either desorption or breakdown of the the organic "carrier" compounds. 260 HYPOTHESIS 2. LITTORAL ZONK PROCESSES ARE SIGNIFICANT IN THE DEGRADATION OF PARATHION. Changes in pH reflect the photosynthetic activity of the macrophytes, their associated aufwuchs, and phytoplankton. During both sunny and overcast days, the greatest changes in pH occurred from 1000 to 1200 hours; the highest pH values of approximately 9.5 were recorded at approximately 1600 hours (figure 51). The rate of increase in pH was slightly greater on the clear day, but the daily maximal values reached under both types of weather conditions differed by only 0.5 pH units. Regardless of buildup conditions, the pH began to decrease after 1800 hours. As in the morning increase, the largest afternoon decrease occurred within 2 hours. Changes were confined to upper waters, as the pH measured immediately above the sediments remained relatively constant at pH 7.0. The extreme PH values differed by 2.8 units on the clear day and 2.3 on the overcast day; from a low in both cases of 7.0 to highs, respectively, of 9.8 and 9.3. The change in pH is indicative of high productivity although, surprisingly, it is not as extreme as changes reported in some hypereutrophic lakes (Wetzel, 1983). Lake San Pablo is known to have occasional phytoplankton blooms which may create even greater ranges of pH. Measurements indicated that afternoon oxygen production exceeded morning production. The ratio of oxygen production to respiration, as reflected by changes in pH, decreased rapidly after sunset suggesting continually high rates of respiration. 261 Temperature variations were much higher in the littoral than in the pelagic region. The temperature of the top meter of water increased to 19.45" C and 18.7" C under clear and overcast skies, respectively (figure 52). Temperature increases were more gradual under overcast skies, although the cooling effects of the winds were not taken into consideration. The lack of correlation between littoral events and lake mixing is evident as the temperature profiles were not changed by afternoon mixing. Convection cooling began in the early evening and extended through the night; at Lake San Pahlo daily fluctuations in ambient temperature are greater than seasonal averages. This reduced the littoral temperature to the open water value of 17° C. Oxygen profiles were recorded at 0400, 1000, and 1600 hours. Early morning profiles showed near surface oxygen concentrations of 5.1 mg/L but a rapid decrease to anoxic levels at one meter (figure 53). The near surface concentrations are probably a result of diffusion.Mid-morning littoral oxygen concentrations of 5.8 mg/L were less than those of the open water by approximately one mg oxygen per liter (figure 54 ). The amount of dissolved oxygen was relatively constant in the top half meter of water. The greatest changes occurred between 0.5 and 1.5 m; the meter of water above the sediments was anoxic. Afternoon oxygen concentrations in surface waters of 11.95 and 10.9 mg/L for sunny and clear days, respectively, were higher than morning values by approximately 4 m. of oxygen per liter (figure 55). On both overcast and clear days, photosynthesis increased dissolved oxygen concentrations to a depth of 2 m, while the final half meter of water 262 remained anoxic. Dissolved oxygen concentrations gradually decreased with depth from the surface to 0.5 m above the sediments, and then fell off rapidly. This could reflect both increased amounts of respiration, perhaps from settling organic material, and a decrease in production due to shading by the overlying macrophytes. Photosynthesis may also have been inhibited by carbon. A localized reduction in bicarbonate levels near leaf surfaces can occur in very still water (Westlake, 1967). Rapid photosynthesis in water stagnated by dense macrophyte stands could develop pockets of bicarbonate depletion. Overall, the respiration that took place overnight from 1600 to 0800 hours utilized approximately 5 mg of oxygen L 1 nr1. At times, the littoral zones were agitated on days of extremely strong winds and some interchange with the water of pelagic zone may have occurred. This was especially true along the western edge as these near shore areas receive the full force of winds blowing across the long axis of the lake. Water may also build up at this end of the lake; its rebound at the cessation of wind action may "wash-out" parts of the near shore regions. These events may periodically move water, and material, through the littoral zone to the open waters. The data suggest that the littoral region of Lake San Pablo can be divided into 3 vertical zones. The uppermost half meter of water contains, for the majority of a 24 hour period, at least 5 mg/L of dissolved oxygen. Water of the middle zone shows large diurnal changes in pH and temperature and alternates between anoxic and oxygenated conditions. The composition of bacterial communities from this region will favor a large 263 diversity of anaerobic, aerobic, and facultatively anaerobic microorganisms. The lowest zone is always anoxic, hence bacterial communities and sediment metabolism are anaerobic. The upper zone is primarily influenced by photosynthesis, the lower zone responds to degradative or respiratory activities, and the middle zone to both. The extensive stands of macrophytes prevent oxygenation of the waters immediately above the littoral sediments, unlike pelagic sediments which frequently showed evidence of oxygen rejuvenation through daily mixing. The daily cycling between oxic and anoxic conditions will result in a diverse population of bacteria and aufwuchs, i.e. fungi, yeasts, and protozoa, that can degrade parathion by a variety of degradative and co-metabolic pathways (Jones, 1977; Mulla, 1981). Macrophytes and associated aufwuchs communities of Lake San Pablo can also influence the degradation of parathion through their oxygen consumption. Sediments of the littoral zone were continuously anaerobic over the 24 hour measurement period. Although high levels of oxygen were attained in upper waters, most of the water column was anaerobic for some part of a 24 hour period. Under low oxygen tensions aminoparathion can be rapidly formed by reduction of the nitro group. The aminoparathion can then be hydrolysed to diethylphosphoric acid and p-aminophenol; the latter subsequently hydrolysed to hydroxyquinone and ammonia. Munnecke (1976) measured half lives of less than one hour for methyl parathion exposed to anaerobic reducing conditions in soils and sediments. Wolfe et al. (1986) have described the disappearance of methyl parathion and formation of amino methyl parathion in anaerobic sediments using 264 first order kinetics; half-lives were only a few minutes. However individual ecosystem variations could be quite large, depending on initial conditions, bacterial or aufwuchs populations, etc. An abiotic pathway of degradation has been suggested to involve sediment adsorption followed by chemical hydrolysis of the phenyl C-O-P ester linkage, with the formation of p-nitrophenol and diethylthiophosphoric acid (Graetz et al., 1970). As these metabolites are more soluble than parathion they have a greater likelihood of desorbing from organic matter, subsequently serving as substrates for bacterial hydrolysis. Gomma and Faust (1972) have determined pH dependent rate constants for the hydrolysisof parathion in solution. Using their values, the t 1/2 constants for the hydrolysis of parathion will be approximately 2566 hours for a pH between 7.4 and 9.0, and 565 hours for a pH between 9 and 10.1. During a 24 hour period these constants will apply for 17 and 7 hours, respectively, using the data from figure 51. However, hydrolysis can occur only for dissolved parathion. It is unlikely that parathion will remain non-adsorbed, given the high littoral concentrations of particulate organic matter. Consequently, the brief amount of time parathion would remain in solution would permit only limited physical degradation. Nonbaeterial destruction of parathion is concluded to be insignificant relative to bacterial degradation, and models for physical degradation half times (e.g. Smith et al. 1978) will not be useful. Given the extensive macrophyte stands around the entire perimeter of Lake San Pablo it is unlikely that adsorb J pesticide would be translocated to the open water. Because of the density of macrophytes, parathion 2 65 adsorbed to particulate organic matter will tend to settle upon the surface of the macrophyte-aufwuchs community, rather than sink to the sediments. Aufwuchs degradation in the littoral zone, especially in the upper water regions, may be quantitatively more important than degradation from either physical changes in the littoral zone or microbial breakdown by pelagic sediment bacteria. In conclusion, the physical and chemical processes of the littoral zone appear to be relatively isolated from those of the pelagic waters. The dense macrophyte stands both dictate the aquatic physico-chemical characteristics and conceivably function as a filter that prevents suspended organic material from reaching the open water. Substantial interchanges between waters of the littoral and pelagic zone are dependent on more severe weather conditions, and perhaps diffusion limited at all other times. Physical changes in the littoral waters are not expected to greatly affect the degradation of parathion adsorbed to organic materials. The hypothesis, littoral zone processes are significant in parathion degradation, is not acceptable in regard to physio-chemical changes. However, littoral processes indirectly contribute to increased degradation by maintaining a substantially more diverse flora and fauna through alterations in oxygen concentrations; and in this regard the hypothesis may be acceptable. HYPOTHESIS 3. MACROPHYTES ARE UNAFFECTED BY PARATHION. Pesticides have the potential to substantially alter lake functioning through toxic effects on macrophytes. Destruction of macrophyte stands would increase detritus, increase dissolved and particulate organic carbon, 266 and could lead to localized oxygen depletion from respiration. Reductions in photosynthesis would further decrease the oxygen concentration of littoral waters. These situations could alter sediment and aufwuchs metabolism by affecting bacterial and faunal composition. The ratio of production between paired macrophyte samples before and after parathion treatment is shown in figure 56. Three paired samples were exposed to 1, 10, and 20 ppm concentrations of parathion. No correlation was found between parathion exposure and changes in production. A one sample paired t-test indicated no difference in the oxygen production ratio before and after exposure for any concentration of parathion (p > 0.4). Plants treated at 20 ppm were maintained for 3 additional days after exposure. No apparent changes in the color or texture of the macrophyte fronds or the aufwuchs were noted at the end of the test period. The water did not become discolored and had no unusual odor. Diatom growth was minimal and there occurred no unusual blooms of phytoplankton. Several immobilized zooplankton were found at the bottom of each jar. These animals were within the macrophyte/aufwuehs community at the time of collection and succumbed to the effects of the parathion. Oxygen may have escaped through bubble formation, especially during the intense photosynthesis of midday. This additional production could not be quantified and may not have been constant between days. If parathion only slightly inhibited photosynthesis its effects may have been masked by losses through bubble formation. A relatively greater amount of oxygen would have been lost by pre-treated compared to the post-treated 267 plants which would underestimate the degree of inhibition. Goulder (1969) had found that bubble formation by macrophytes tended to be 3 to 7% of total production, hence errors would be of this magnitude. These are insignificant considering the sensitivity of the light-dark method. Parathion had no effect on the oxygen production of macrophytes from Lake San Pablo, even at concentrations as high as 20 ppm It is unlikely that concentrations of this magnitude would be attained, except during periods of peak erosion. It is concluded that macrophytes will be little affected by parathion contamination of the littoral zone, and hypothesis 2 is upheld. IIYPO'THESIS 4. PRIMARY PRODUCTIVITY IN THE OPHN VVATKR IS REDUCED BY PARATHION. Few algae are capable of degrading parathion (Ahmed and Casida, 1958; Moore and Dorward, 1968). Results of the effects of parathion on phytoplankton productivity are presented in figure 57 and table 27. Large variations were noted in the productivity values of both treatments and controls. Part of the variation was due to the low sensitivity of the light/dark method when using as the measured variable oxygen production rather than fixation of 14C. Sampling errors that resulted from having used a heterogeneous population of phytoplankton would also have contributed to experimental variances. Phytoplankton gross and net production in a solution of 0.5 ppm were similar to control values (.1 < p < .375). Although the results were not statistically significant, exposure to 0.5 ppm parathion increased gross and 268 net productivity and respiration, relative to control values. Butler (1963) also found an increase in productivity rates of phytoplankton when exposed to insecticide concentrations below 1 ppm. It may be the case that a larger sample size would have indicated statistically significant results. Compared to control values, phytoplankton net production was reduced 47% (table 27) by parathion concentrations of 1.00 ppm (.05 < p < .1). Exposure to 10 ppm of parathion reduced gross productivity by 32% (.025 < p < .05) and net productivity by 64% (.025 < p < .05). Although phytoplankton respiration was increased in all 3 concentrations of parathion the differences were not statistically significant (.1 < p < .375). again perhaps due to sample size limitations. The ratio of net primary productivity to respiration was significantly decreased with exposures to 1.0 and 10.0 ppm parathion. The results from Lake San Pablo are within the ranges suggested by previous studies (Moore, 1970; Cole and Plapp, 1974; Butler, 1977) Cole and Plapp (1974) reported that parathion at 1 ppm inhibited the growth of Chorella pvrenoidosa: contradictory to the results of Loosanoff et al. (1957). The reason for this discrepancy can be explained by their observation that the degree of inhibition was dependent more on the concentration of alga than on the concentration of parathion. Inhibition was suggested to be a function of pesticide solubility and was found to be inversely related to alga cell concentration. They reasoned that at high cell concentrations dissolved pesticide will not affect a significant proportion of alga. Exposure is increased at lower concentrations of cells as the amount of pesticide available per cell is greater. The greatest effects were noted at 269 alga concentrations of 1 microgram of algae per ml, minimal effects occurred with 1 mg of algae per ml. Since concentrations of natural populations are closer to the former than to the latter, pesticides which have not been shown to cause inhibition in laboratory settings may have toxic effects in natural environments. As phytoplankton have been shown not to have measurable changes in growth or photosynthesis at pesticide concentrations that are toxic to zooplankton, algal blooms commonly follow the zooplankton mortality caused by organophosphorus pesticides (Mulla, 1981). The composition of the bloom depends on the particular circumstances at the time of the exposure to the pesticide and may consist of either single or mixed species assemblages. Reported algal blooms from organophosphate contamination of natural lakes or ponds include mixed planktonic species (Papst and Boyer, 1980), filamentous species (Butcher et al., 1977), and blue green algae (Hurlbert et al., 1972). In regard to mechanisms: Saroja-Subbaraj and Bose (1983) have investigated the binding characteristics of parathion to chlorella and determined that the pesticide is bound by a proteinaceous component of the external photosynthetic membrane. The cell wall was shown to act as a permeability barrier and may be the physiologic mechanism responsible for species-specific differences in photosynthetic inhibition. Lohmann and Hagedorn (1985) concluded that the algae Chlorococcales removes parathion from solution through adsorption by the lipid-containing trilaminar sheath, rather than by passive or active permeation. The physiologic alteration resulting in inhibition of photosynthesis and growth 270 may involve the photosynthetic membranes as Anbudurai et al. (1981) have shown that methyl parathion inhibits photosynthetic electron transport in isolated thylakoids of higher plants. Although there was evidence for trends of decreased net and gross productivity sample size limitations reduced statistical validity. Given the consistent trends within the range of tested concentrations, it is concluded that parathion can reduce the productivity of open water phytoplanton and hypothesis 3 is accepted. However, the availability of parathion to pelagic phytoplankton will be limited, and potential effects ameliorated, by organic sequestration and sedimentation in the littoral filter. HYPOTIIKSIS 5. ZOOPLANKTON MORTALITY WILL BE DEPENDENT ON ENVIRONMENTAL CONDITIONS. Parathion was found to be extremely toxic to the Daphnia Pulex of Lake San Pablo. The 24 hour EC50s as a function of incubation media are presented in table 26. Parathion was most toxic to zooplankton exposed in filtered and sterilized lake water. The use of untreated pelagic lake water only slightly increased the EC50, relative to treated lake water, but this was not statistically significant. The EC50 was doubled when zooplankton were exposed in untreated littoral lake water containing 10 gm of Ceratophvllum demersum and its associated aufwuchs community. Errors may have resulted from my subjective assessment of the post-exposure status of zooplankton. The EC50's could also have heen underestimated because of the use of a heterogeneous population of zooplankton which included daphnids 271 that would have died regardless of parathion exposure, or organisms that were not as healthy as laboratory raised zooplankton. Scenedesmus has been shown to have adsorptive characteristics similar to that of soil that containsapproximately 2% organic matter (Lohmann and Hagedorn, 1985). Other species of phytoplankton have also been shown to absorb parathion (Sethunathan, 1977; Cole and Plapp, 1974). Grazing activity could expose zooplankton to concentrations of pesticides adsorbed to detrital material or phytoplankton that are greater than dissolved concentrations. This bioaccumulation could have the potential to expose the herbivorous zooplankton to extremely high, localized concentrations of parathion, providing the pesticide can be made available to the zooplanktor by digestive processes. McCarthy (1983) has shown that particulate organic matter can retain polynuclear aromatic hydrocarbons and decrease their accumulation by Daphnia Magna. In this study, the phytoplankton and particulate matter of raw lake water were not able to effect a change in the EC50, compared to sterilized and filtered water. If it is assumed that organic matter adsorbed parathion, the fact that no difference was noted in this study between the EC50s of filtered and sterilized water may be due to the increased availability of parathion upon digestion of contaminated algae. This could be differentiated in a future study by removing algae but not particulate matter, and increasing the exposure times. Again, studies involving larger numbers of organisms would perhaps provide evidence of statistically significant changes not seen with small sample sizes. 272 Zooplankton have been shown to be highly selective feeders with an upper and lower size limit to ingested particles (Gliwicz, 1980). The degree of protection afforded by organic material through the adsorption of pesticides may be size dependent. Organic material above specific species limitations can adsorb and thus remove pesticides from lake water. Conversely, zooplankton selectively feed on smaller particles, which absorb relatively greater amounts of parathion. The fact that the EC50 of zooplankton was increased in the presence of Aufwuchs could imply that components of the Aufwuchs were able to sequester parathion in a manner that made it unavailable to zooplanktors. In the degradation study, Aufwuchs removed within 12 hours approximately 30% of the added parathion. Whether the parathion was degraded or adsorbed could not be determined, but in either case less of the active pesticide was apparently available to the zooplankton. Sampling the natural, heterogeneous population of zooplankton in Lake San Pablo collected organisms that differed as to age, sexual status, and nutritional state. This variability could have been controlled by culturing Daphnia. However, the zooplankton used in the experiments appeared active and healthy and control populations exposed only to acetone did not experience greater mortality. The low EC50S may have resulted from the fact that Daphnids are highly susceptible to pesticides during molting (Anderson, 1944). The presence within the sampled population of molting Daphnids may have resulted in artificially low EC50s, when compared to values determined using laboratory raised animals. 273 Zooplankton populations of high altitude tropical lakes may not he as susceptible to the effects of organophosphate insecticides, compared to their temperate counterparts. Zooplankton reproduction is essentially continuous, although deinfante (1982) found seasonal abundances in the zooplankton of Lake Valencia (Venezuela). These corresponded to the breakdown of stratification and the beginning of the rainy season. Lake San Pablo, and most other high altitude Interandean lakes will not have a seasonal breakdown of stratification. However, the rainy season could increase the nutrient levels, as well as introduce high concentrations of pesticides. The increase in zooplankton populations following nutrient loading during the rainy season may be ameliorated by the introduction of pesticide containing organic matter. Zooplankton of the pelagic waters will be relatively protected if the littoral regions are effective at preventing the translocation of pesticides to open waters. However, if the littoral zones are refugia for zooplankton species the effects of pesticides could be more serious. The recovery of surviving zooplankton may alter competitive or predator-prey relationships, introducing changes in species abundances and composition. Also at greater risk are zooplankton that feed in locations that increase their exposure to organic matter with adsorbed pesticide, e.g. benthic dwellers or organisms that interact within the Aufwuchs. Given the lack of statistical significance hypothesis 4 cannot be conclusively accepted. However, the observed trends of zooplankton mortality, the effects noted in the degradation studies of aufwuchs and 274 organic matter in decreasing the extractable parathion, and data presented in the literature, strongly suggest that zooplankton mortality can he affected by environmental conditions. 275 CONCLUSIONS Parathion will enter the Lake San Pablo ecosystem adsorbed to organic-soil materials translocated by heavy rains during the wet season. Upon entry, some pesticide may desorb from the organic-soil complex and dissolve. If not rapidly degraded, parathion can then affect macrophytes, phytoplankton, and zooplankton populations. Based on conclusions from the five tested hypotheses it seems likely that either parathion will not be present in amounts shown to be damaging, or will be so rapidly degraded as to not adversely affect the flora and fauna. Those tropical lakes likely to be considered for water resources will most probably be located in watersheds that generate substantial amounts of both human and agricultural wastes. These materials will serve as the substrate for large and diverse bacterial populations which can rapidly hydrolyze translocated pesticides. Heterotrophic aerobic bacteria populations in Lake San Pablo were found to be among the largest reported in the literature. The largest populations were found in the aerobic sediments of that part of the littoral zone that received both agricultural and sewage discharges; over 100 times greater than concentrations determined for anaerobic littoral and pelagic sediments. Littoral water also had large bacterial concentrations, in some cases only 2 orders of magnitude less than the numbers found in the underlying sediments. Such large populations of bacteria will contribute to the rapid degradation of exogenous pesticides. 276 Extremely large populations of suspended bacteria were found in the Pelagic waters; only 1/10 the concentrations found in the sediments. These populations are partially maintained by high nutrient turnover resulting from the large populations of open water algae secondary to the daily mixis of the water column. As previously described, mixing events in Lake San Pablo result from the interaction of short term weather perturbations that induce regular overturns. The disappearance studies indicate that very little parathion will be present in the San Pablo Lake ecosystem after 10 to 12 days. The amount of parathion extracted from sediment/water samples showed a biphasie decrease with an overall half-life of 71 and 143 hours for sediment and aufwuchs, respectively. Although photosynthetieally induced pH increases may not be sufficiently large to affect hydrolysis of parathion, the combination of oxygenation and temperature changes in the littoral zone will create a favorable degradation environment. Both aerobic and anaerobic regions will be consistently maintained within the emergent vegetation of the littoral zone, promoting the development of abundant populations of fungi, protozoa and bacteria in the dense populations of littoral plants. The biotic components of the aquatic ecosystem of Lake San Pablo respond differently to similar dosages of pesticides. Macrophytes were exposed to 1, 10, and 20 ppm concentrations of parathion. No correlation was found between parathion exposure and changes in oxygen production as determined by a one sample paired t-test (p > 0.4). No apparent changes were noted in the color or texture of the macrophyte fronds or the 277 aufwuchs after 3 day incubations in 20 ppm parathion. Macrophytes and their associated aufwuchs show no inhibition of photosynthesis in exposures to parathion at concentrations of up to 20 ppm. In addition, they apparently removed parathion from the waters, either by degradation or adsorption, as suggested by the EC50 studies with Daphnia pulex. In spite of tremendous loading, it is unlikely that parathion will cause significant destructive changes to the littoral macrophyte community. Phytoplankton gross and net production in a solution of 0.5 ppm parathion were higher than control values but not significantly different. Compared to control values, phytoplankton net production was reduced 47% by parathion concentrations of 1.00 ppm while exposure to 10 ppm of parathion reduced gross and net productivity by 32% and 64% respectively. Phytoplankton respiration was increased in all 3 concentrations of parathion but, again, the differences were not statistically significant. Larger sample sizes may have result in more statistically sound results. These results suggest that parathion will have insignificant direct effects on phytoplankton productivity. Zooplankton EC50s were lowest when exposed in filtered, sterilized lake water (0.32 ppb) and highest when exposed with raw littoral water and Aufwuchs (0.65 ppb). Exposures in only raw pelagic water had an EC50 of 0.32 ppb. These values are lower than previous literature estimates and may be due to the use of a heterogeneous population of zooplankton or greater susceptibility due to life-history characteristics. 278 The effects of parathion on zooplankton will depend on the timing of exposure, the unique habitat and food preferences of the individual species, stages of growth and development, and the ramifications of sublethal effects on predatory-prey or competitive interactions. As the littoral zone can serve as the refuge for different zooplankton species, extensive pesticide may reduce the species diversity of the ecosystem (Colinvaux and Steinitz, 1980). Recovery of zooplankton numbers will result in more rapidly reproducing or adaptive species attaining dominance. If the replacing species are unsuitable as food there may be effects on the fish population. This may be more of a consideration if small lakes without extensive littoral regions are also used extensively as fish farms. It may be important to maintain a rim of littoral macrophytes in smaller lakes, balancing oxygen depletion against pesticide entrapment. Direct comparisons to prior studies are hindered by the general paucity of published data and the heterogeneity of the current experimental conditions. However, conclusions parallel those presented in the literature. In general, the extensive macrophyte regions of a tropical lake will serve to hinder, or even prevent, the entry of pesticides into the open water. Phytoplankton, while susceptible to reductions in photosynthesis, have such a rapid generation time that recovery will be almost immediate, even from severe contamination. Zooplankton, although susceptible, will most likely be exposed to insufficient concentrations of pesticides. 279 Based on the adsorption of parathion by organic matter, lakes that are in agricultural watersheds can be continuously used for daily water if the water is removed from the pelagic zone and passed through a filter to remove particulate organic matter. The environmental effects of pesticides and any ramifications on human health can be minimized by grooming the littoral zone of tropical lakes to create an area that favors pesticide degradation. Macrophyte growth, rather than being removed, could be allowed to develop around the edge of the lake. One consideration to the extent of littoral growth will be the potential for nighttime fish kills from oxygen depletion, which may compromise the use of the lake as a protein supplement. 100 CONTROL SEDIMENT 80 °/o REMAIN 60 40 20 0 0 48 96 144 192 240 288 HOURS FIGURE 49 DISAPPEARANCE OF PARATHION IN LITTORAL SEDIMENTS (MEAN AND RANGE) 0 8 2 100 CONTROL 80 SEDIMENT % 60 REMAIN 40 20 0 4 8 1 44 1 92 240 288 HOURS FIGURE 50 DISAPPEARANCE OF PARATHION IN AUFWUCHS (MEAN AND RANGE) 282 10 i pH CLEAR pH 2 4 6 8 1 0 1 2 1 4 1 6 1 8 20 22 24 TIME 10 pH OVERCAST 9 PH 8 - 7 - — i— i— i— |— i— i— i— i— i — •— r -i 1 r- 2 4 6 8 10 1 2 1 4 1 6 1 8 20 22 24 TIME FIGURE 51 LITTORAL pH CHANGES ON CLEAR AND OVERCAST DAYS TEMP (C) TEMP (C) 20i 17- 18- 19- 0 n 20 19- 17 - 18- 2 6 2 4 8 0 2 4 6 8 0 2 244 22 20 18 16 14 12 10 8 6 EP() CLEAR (C) TEMP EP() OVERCAST (C) TEMP 1 1 1 16 2 2 24 22 20 1 8 1 6 14 12 10 8 LITTORAL TEMPERATURECHANGES ON CLEARAND OVERCAST DAYS TIME TIME FIGURE52 283 OXYGEN (MG/L) 14i 10 12 - - 0.0 0.5 LITTORALOXYGEN PROFILE ATHOURS 0400 1.0 FIGURE 53 DEPTH (M) DEPTH 1.5 XGN(GL 4AM (MG/L) OXYGEN 2.0 . 3.0 2.5 284 OXYGEN (MG/L) OXYGEN (MG/L) 12 10 12 10 i 6 - - - - 0.0 0.0 0.5 0.5 LITTORAL OXYGENPROFILESAT 10AM ON CLEARAND OVERCAST DAYS 1.0 1.0 OXYGEN (MG/L) 10 AM OVERCAST AM 10 (MG/L) OXYGEN FIGURE54 DEPTH(M) DEPTH(M) OXYGEN (MG/L) 10 AM CLEAR AM 10 (MG/L) OXYGEN . 2.5 1.5 2.0 2.0 2.5 3.0 3.01.5 285 OXYGEN (MG/L) OXYGEN (MGA.) 12 10 14 - 0.0 0.0 1 i 0.5 0.5 LITTORALOXYGEN PROFILES AT PM4 ON CLEARAND OVERCAST DAYS 1.0 1.0 FIGURE55 OXYGEN (MG/L) 4 PM OVERCAST PM 4 (MG/L) OXYGEN DEPTH (M) DEPTH DEPTH (M) DEPTH 1.5 1.5 OXYGEN (MG/L) 4 PM CLEAR PM 4 (MG/L) OXYGEN 2.0 2.0 2.5 2.5 3.0 3.0 286 1 PPM 1 PPM 1 PPM 10 PPM 10 PPM 10 PPM □ AFTER TREATMENT □ BEFORE TREATMENT 20 PPM 20 PPM 20 PPM “i 2 FIGURE 56 RATIO OF MACROPHYTE PRODUCTION TO CONTROL VALUES BEFORE AND AFTER PARATHION EXPOSURE 287 GROSS PROD. V/////7777777//7//////A □ 0.5 PPM □ 1.0 PPM NET PROD. 7Z77777777ZZZZZ El 10.0 PPM RESPIRATION NET PROD/RESPIR i i i i i r i" ■ i i 1 t~' ~i~ l i l t T i i I i i 2 0 40 60 80 100 1 20 1 40 PERCENT OF PAIRED CONTROL FIGURE 57 CHANGES IN PHYTOPLANKTON PRODUCTIVITY RELATIVE TO PAIRED CONTROLS 288 TABLE 22 FIRS! AM) SECOND ORDER DEGRADATION CONSTANTS FOR PARATIIION BY SEDIMENT AND AUFWUCHS BACTERIA t 1/2 2nd ORDER hours R2 DEGRAD. CONSTANT L cell-1 h r 1 SEDIMENT 60.8 0.85 2.24 X 1 0 12 AUFWUCHS 142.6 0.66 3.04 X 10 >0 TABLE 23 LOCATION AND NUMBER OF SEDIMENT AND PELAGIC BACTERIA IN LAKE SAN PABLO SITE DESCRIPTION CFII/GM CEU/ML FRESH WATER SEDIMENT 1 Near shore, < 2 m. in depth, low concentration of macrophytes, no 1.04 X 108 1.1 X 106 sewage inlets nearby, aerobic water 2 15 m. from shore, straight out from mouth of stream, moderate 1.4 X 107 not maerophyte growth, 8 m. in depth, collected swampy smell to sediments, anaerobic water 3 20 m. from shore, 3 m. in from edge of macrophytes, 4 m. in depth, 8.0 X 107 not swampy smell to sediments, collected anaerobic water 4 Near shore, < 2 m in depth, apparently cleared or harvested area 1.9 X 108 not with regrowth beginning, adjacent to collected field with grazing cattle, water aerobic but sediments dark 5 Near shore, <1.5 m, cleared for boats?, sewage discharge from 1.5 X 109 9.2 X 106 house/bar and motel visible, edge of agricultural field, aerobic water 6 Pelagic sample, 50 m off shore in front of inlet stream, 23 m. of water, 1.2 X 107 1.4 X 106 sediment sample smelled like H2S, water anaerobic 7 Near shore, 1.5 m. in depth, clothes- washing areas and sewage discharges 1.2 X 109 not from homes visible, small collected agricultural fields to lake's edge, aerobic water 29 1 TABLE 24 BACTERIAL NUMBERS FOUND IN THE OPEN WATER OF LAKE SAN PABLO COMPARED TO OTHER AQUATIC ECOSYSTEMS HACTKUIA TYPE of ECOSYSTEM r e i e r e n c e M l/1 5.5 X I05 Approximate number of bacteria in Wetzel, 1983 an oligotrophie lake 1.0 X I06 Approximate number of bacteria in a Wetzel, 1983 mesulrophie lake 1.1 X I0fi Near slime region with low LAKE SAN PAULO densities of inacrophvtes 1.7 X I06 Eutrophic Lako do Castanbo Schmidt, 1969 3.7 X I06 Approximate number of bacteria in a Wetzel, 1983 eutrophic lake 9.2 X l()f' Netir shore region near LAKE SAN PAU 1.0 a g r i c n 11. fields and sen age discharge 1.4 X 107 Pelagic open outers LAKE SAN PAULO 1.6 X I07 Highest value recorded in Rio Negro Rai, 1979 varzea lakes 1.8 X 107 Maxima for highly eutrophic Lake Coveney, et al. 1977 Belso in agrie land of Sweden 2.1 X 108 Low water value recorded of Rio Rai. 1979 Negro varzea lakes Highly productive alkaline, saline Kilham, 1981 3.6 X I08 lakes in Kenya 5.8 X 108 Hypereutrophie reservoir in Russia Kuznetsov, cited in Wetzel. 1983 292 TABU; 25 BACTERIAL N EMBERS 1 ()t Nil IN THE SEDIMENTS OK LAKE SAN PABIA) COMPARED TO OTHER AQCATIC ECOSYSTEMS BACTERIA TYl’Ii or ECOSYSTEM REFERENCE c r a m -1 FRESH SEDIMENT 2.3 X 103 Approximate value for oligotrophie Wetzel, 1983 lake 2.6 X 104 Approximate value for mesotrophic Wetzel, 1983 lake 3.8 X 10s Approximate value for eutrophic Wetzel, 1983 lake 7.1 X 105 Eutrophic lake, Prince Edward Hayes and Anthony, island. Nova Scotia 1959 1.6 X 106 Lake Mendota, Wisconsin Hayes and Anthony, 1959 1.2 X 107 Pelagic sediment LAKIC SAN PABLO 1.4 X 107 Littoral sample near LAKE SAN PABLO agricultural stream 8.0 X I07 Littoral sample near pelagic LAKE SAN PABLO border 1.0 X 108 Near shore littoral sample LAKE SAN PABLO 1.9 X 108 Near shore sample near LAKE SAN PABLO agricult, fields, cattle grazing 1.2 X It)9 Near shore sample near sewage LAKE SAN PABLO discharges and agricult, fields 1.3 X I09 Hypereuthrophie Russian lakes Kuznetsov, 1958 1.5 XIO9 Near shore sample near sewage LAKE SAN PABLO discharges and agricult, fields 2.33 X 109 Hypereutrophic Russian lake Wetzel, 1983 293 TABLK26 PARATIIION TOXICITY TO DAPIIN1A PULKX EXPERIMENTAL EC50 PROBIT SLOPE CONDITIONS (95% confidence (standard limits) error) Filtered, sicrili/.ed lake water 0.30 ppb 4.34 (0.18 - 0.51) (1.014) Raw pelajtic lake water 0.32 ppb 3.83 <0.21 - 0.49) (0.396) Raw littoral lake water with 10 0.65 ppb 3.31 grants of macrophytes (0.45 - 0.96) (0.589) TABLE 27 DECREASES IN PHYTOPLANKTON OXYGEN PRODUCTION WITH 0.5, 1.0, AND 10.0 PPM PARATHION COXTRL 0.5 % CONTRL 1.0 % CONTRL 10.0 % PPM CHANGE PPM CHANGE PPM CHANGE PARA PARA PARA THION THION THION GROSS 7.97 8.25 +4 % 12.53 9.75 -22 % 9.51 * 6.42 -32 % PRODUCT. NET 5.32 5.45 +2 % 8.20 * 4.36 -47 % 5.34 * 1.92 -64 % PRODUCT. RESPIRAT. 2.65 2.80 +6 % 4.33 5.40 +25 % 4.17 4.5 +8 % NET 2.01 1.95 -3 % 1.89 0.80 -58 % 1.28 0.43 -66 % PRODUCT RESPIRAT. NOTES: * Statistically significant difference between control and exposure (.05 < p < 0.1). 294 CHAPTER VII SUMMARIES AND CLOSING STATEMENTS I have attempted in this study to gain, for the pesticide parathion, a perspective of both its environmental effects and ramifications on human health. The results of this study suggest that pesticide laden organic-soil complexes will be effectively trapped and degraded within the littoral zone of an aquatic ecosystem, and will have only minimal effects on flora and fauna. Alternatively, the greatest dangers of parathion appear to result from human exposure during transport, handling, and especially application. Cultural differences exist such that all native Ecuadoreans do not have the same exposure risks. The dangers of pesticides can be minimized by measures designed to reduce human exposure. This is clearly the direction in which developing countries must proceed, paying particular attention to cultural and socio-economic patterns of use. Another aspect of this study involved one of the first investigations of the mixing characteristics of a small, high altitude tropical lake. Lake San Pablo was found to overturn within 24 hours. Daily perturbations include sharpening and subsequent diffusion of epilimnion and thermocline boundaries. Mild winds are able to thermally stratify and mix the lake to depths of 3 to 4 m, regardless of duration. Moderate winds from 3 295 296 to 11 hours duration can extend mixing to 6 or 19 m, respectively. Strong winds can mix the lake through its entire water column in as little as 3 or 4 hours. The lake is consistently mixed throughout its depth so that the near sediment bottom waters are frequently re-oxygenated. The overall impression from interviews with government officials and the surveys of pesticide stores, Otavalan households, and subsistence and profit motivated farmers is that the FAO Code of Conduct has done little to minimize the abuse and excessive use of pesticides. Agrochemical companies do not follow the guidelines and commonly present information contrary to the recommended suggestions. Although the FAO code is of proper intention, it has been written by individuals who have been trained, and most likely reside, in developed countries. Their conceptions of perceived needs and abilities are much different than the actual cultural, economic, and ecological environment of native farmers. As an example, most of the label information required by the FAO code is of no interest to farmers. The address of the company of origin, toxicologic data, chemical formulations, etc. are essentially meaningless to the pragmatic concern of how much, and when, to apply pesticides. Since a large proportion of the people who make agricultural decisions regarding pesticide use are illiterate, any written information may be useless. Efforts at educating native people must use visual symbols that are clearly understood. However, individuals of different cultures may differ in their understanding of pictures and symbols hence the only reliable methods of communicating correct procedures of pesticide use are field demonstrations or the spoken word in native languages. 297 The government may not be overly concerned with the plight of agricultural workers because they are such a small percentage of the voting public. The population that must be politically appeased live in urban areas. If voting citizens are made more aware of the problems their country is facing the administration will most certainly feel an increased pressure to find solutions. Stressing the contamination of food by pesticide residues, or other issues that directly affect the health of urban dwellers will certainly stimulate actions. Because of the large concentrations of people within large cities effective media campaigns will be very cost- effective. There are 3 types of agricultural activity in Ecuador: plantations, cash cropping, and subsistence farming. Large amounts of pesticides are used by plantations which, because of their extensive monoculture, are subject to intense outbreaks of pests. Subsistence farmers rarely apply pesticides to their fields, they are instead used in food storage and for personal hygiene. The major problems of organophosphate pesticides follow from acute exposure, the severity of illness being related to the absorbed dose. Farmers in areas of high temperature and humidity receive greater exposure because of increased sweating and a tendency to work in shorts, undershirts and without shoes. The effects of pesticide intoxication are exacerbated in subsistent farmers because of their poor nutritional status, parasite load, and the simultaneous presence of additional diseases. Unlike developed nations, medical facilities and antidotes to poisoning are not readily available. 298 The most efficient mechanisms for promoting change, at least in Ecuador, appear to reside in non-governmental conservation organizations. International industrial regulations will tend to favor the business aspects of pesticides, which in most cases, result in practices that can be detrimental to human health without appropriate safety equipment. Administrative policies or the actions of government conservation agencies, both national and international, are ineffective in promoting change at the level of individual use, as evidenced by the failure of the FAO Code of Conduct. Emphasis on agricultural production is necessary to the development of third world economies but this must proceed in directions which consider human safety. Future studies could examine the epidemiology of pesticide poisoning with more detail through stratification by age and sex, as there appear to be gender differences in agricultural jobs, e.g. the men apply pesticides to fields that are subsequently worked by women. There is also a need to establish medical studies to quantitate exposure variables and assess the health effects of long term, sub-lethal exposures to insecticides. Developed nations have realized the importance of vigilance in protecting their ecosystems and population from the deleterious effects of man-made toxicants. However, a state of technological advancement does not necessarily imply an equivalent degree of ethical development especially when developing nations are sold pesticides deemed inappropriate for common use in their country of origin. 299 It is necessary to consider a global perspective that includes the people of these countries, and realize that they too, are a resource worthy of protection. The application of science and technology to the needs of developing nations will succeed only if focused on ecological perspectives that are integrated within the unique social and cultural values of the native peoples. Observations and summaries regarding specific sections of the dissertation follow: PESTICIDE REGULATION AND USE: 1. Originally, the intention of the International Group of National Associations of Agrochemical Manufacturers (IGNAAM) was to have individual countries regulate pesticide importations. This was superseded through introduction of the FAO Code of Conduct on the Distribution and Use of Pesticides. 2. The FAO Code consists of 12 articles which describe marketing, handling and safety regulations designed to minimize the dangers of pesticides. 3. The commercial attitude of international agrochemical companies is that individual governments are responsible for establishing importation regulations, using as guidelines the FAO Code of Conduct. 4. The IGNAAM currently supports and practices the policy of informed consent, where unlimited shipments of pesticides can take place without notification, once an initial shipment has been accepted. 3 00 5. Ecuadorean pesticide legislation has been characterized by government indifference and actions that have promoted indiscriminate importation and increased the autonomy of the importing companies. 6. Contrary to the intentions of the FAO Code, the most effective agency for pesticide regulation has been a non-governmental conservation organization, the Fundacion Natura, not the administration. 7. Approximately 300 million dollars of pesticides were imported between 1978 and 1989. 8. Herbicides were the largest category of imported pesticides from 1978 to 1989. Importation peaked at 3.3 million kilograms in 1986. 9. Insecticide importation has steadily increased since 1982 and exceeded herbicide importation in 1989 by approximately 10 percent. SURVEYS TO ASSESS TIIE EFFECTIVENESS OF THE EAO CODE: 1. Retailers in Quito and Otavalo sell at least 37 different types of insecticides. The most common products stocked were organophosphates. 2. There was a general lack of concern for safety in that: a. Containers were open, leaking, or had evidence of past damage; b. Several stores sold pesticides piecemeal from larger master containers; c. Illustrations and brochures, provided by agrochemical companies, showed unsafe practices and promoted excessive and indiscriminate use of pesticides. d. Stores had evidence of prior spills in customer areas. 301 3. Retail stores in Quito and Otavalo differed in 5 areas: a. Otavalan store owners traveled to Quito to purchase their products, although they were visited by sales representatives. b. Sales personnel in Quito were more knowledgeable. c. Quito stores had a greater selection of safety equipment. d. Otavalan pesticide stores were less specialized and carried a greater selection of general purpose home and farm equipment, several stocked food items. e. Otavalan merchants had much less regard for the toxicity of pesticides in matters of hygiene, application schedules, and timing before harvest. 4. A 1989 follow-up survey suggested that types of illustrations, and brochures had not changed since 1987. Fewer containers were open or leaking, primarily due to a change in packaging that made use of heavy plastic bags. Organochlorines had virtually disappeared from the market. SURVEYS TO ASSESS PESTICIDE USE AM) EXPOSURE AMONG FARMERS: 1. Impoverished farmers generally had at least 3 containers of pesticides. Pesticides were commonly stored in unlabeled containers, kept with food products, or uncovered. 2. Although the evidence is circumstantial, pesticide use among subsistence farmers has appeared to result in increases in childhood mortality, sterility, and increased pest resistance. 3. Indians who worked as transient agricultural labor were exposed by their employers to large concentrations of pesticides with little regard to their safety. Many reported suffering classical symptoms of organophosphate overexposure but would not, or could not, obtain medical treatm ent. 4. There are differences in pesticide use between subsistence and profit motivated farmers. The latter use pesticides to increase financial returns on their agricultural investments. They feel that pesticides can be used to treat almost any problem; the primary difficulty was the ability to afford sufficient quantities. Pesticide use by subsistence farmers was primarily nonagricultural. Pesticides were used on bedclothes, as treatments for body insects, or for protecting stored food. 5. The government's estimate of the number of 3.5 poisonings per 100,000 total population appears to severely underestimate the number of poisonings experienced by farmers. During the year prior to the survey, approximately 26% of the interviewed farmers experienced at least one episode of intoxication sufficient to cause them to stop their daily activities. 6. The most common suite of illness reported by farmers after applying pesticides were headaches, nauseousness, blurred vision, and vertigo; common symptoms of organophosphate intoxication. 7. Pesticide safety may be correlated to the level of impoverishment and the climate. Farmers in Manabi, the poorest and most humid province, had the highest incidences of post application illnesses. Carchi, the most affluent of the four provinces had the best safety record. The opposite conclusion would have been drawn from the government's data. 8. Few profit motivated farmers and almost no subsistence farmers have a conception of pesticides as toxic poisons or as substances to be used as 3 03 sparingly as possible. On the contrary, literature supplied by agrochemical companies tends to increase the perceived need for pesticides. Farmers also have no awareness of the dangers of contamination of water supplies, the lasting effects of residues, and the need for delayed field re-entry times. 9. Interviews with conservation officials and physicians indicated that pesticide poisonings may be more common than indicated by government health data as many cases are not reported to officials. There is also reason to believe that not all reported incidences are ultimately reflected in administrative health statistics. SUMMARY LIMNOLOGY OF LARK SAN PABLO: 1. Lake San Pablo undergoes regular overturns which may occur daily or at most, every two days. The lake is frequently mixed throughout its depth so that the above-sediment bottom waters are oxygenated. Daily perturbations include a sharpening and diffusing of epilimnion and thermocline boundaries. 2. Mild winds can thermally stratify and mix the lake to depths of 3 to 4 m, regardless of duration. Moderate winds from 3 to 11 hours duration can extend mixing to 6 or 19 m, respectively. Strong winds can mix the lake through its entire water column in as little as 3 or 4 hours. 3. The littoral region of Lake San Pablo can be divided into an upper zone that is continuously oxygenated, a middle zone that shows large diurnal changes in pH and temperature and alternates between anoxic and oxygenated conditions, and a lowermost zone that is always anoxic. The dense macrophyte stands will act as a filter, trapping particulate organic 304 matter to which pesticides may be adsorbed. The alteration of oxic and anoxic conditions and the input of sewage and organic matter will maintain diverse and large populations of bacteria which will positively affect the degradation of parathion. 4. Heterotrophie aerobic bacteria concentrations showed variations over 3 orders of magnitude. The largest populations were found in the aerobic sediments of that part of the littoral zone that received sewage discharges. These were 2 orders of magnitude greater than concentrations determined for anaerobic littoral and pelagic sediments. The number of aerobic bacteria suspended in pelagic waters was approximately 1 order of magnitude less than the concentrations found in the underlying sediments. Littoral water had bacterial concentrations 2 orders of magnitude less than the numbers found in the sediments. The small differences may have resulted from underestimating the total number of bacteria in the sediments. 5. Macrophytes were exposed to 1, 10, and 20 ppm concentrations of parathion. There was no correlation between parathion exposure and changes in oxygen production as determined by a one sample paired t-test (p > 0.4). Plants treated at 20 ppm were maintained for 3 additional days after exposure. At the end of the test period there were no apparent changes in the color or texture of the macrophyte fronds or the aufwuchs. 6. Phytoplankton gross and net production in a solution of 0.5 ppm were higher than control values but not significantly different (0.1 < p < 0.375). Compared to control values, phytoplankton net production was reduced 47% by parathion concentrations of 1.00 ppm (.05 < p < 0.1). Exposure to 10 ppm 3 05 of parathion reduced gross productivity by 32% (.025 < p < 0.05) and net productivity by 64% (0.025 < p < 0.05). Phytoplankton respiration was increased in all 3 concentrations of parathion hut the differences were not statistically significant (0.1 < p < 0.375). 7. Zooplankton EC50s were lowest when exposed in filtered, sterilized lake water (0.32 ppb) and highest when exposed with raw littoral water and Aufwuchs (0.65 ppb). Exposures in only raw pelagic water had an EC50 of 0.32 ppb. These values are lower than past literature estimates and may be due to the use of a heterogeneous population of zooplankton. APPENDIX A SUMMARY OF THE FAO CODE The following is a translation of the document prepared by the United Nations at the request of the Fundacion Natura, Quito. This is a summary in Spanish of the more lengthy FAO Draft Code of Conduct on the Distribution and Use of Pesticides and details the highlights of the twelve articles. ARTICLE 1: OBJECTIVES OF THE CODE. 1. Initiate acceptable and responsible commercial practices. 2. Create a suitable set of regulations for those countries that have no established controls for pesticide importation. 3. Promote safe practices in the use of pesticides. 4. Promote efficient utilization of products. ARTICLE 2: DEFINITIONS. This section contains thirty-three definitions and legal descriptions used in the remainder of the document, e.g.: corporation descriptors, fabrication and processing methods, levels of authority within corporations, environmental and public sector categories. ARTICLE 3: HANDLING OF PESTICIDES. The responsibility of the government in controlling the distribution 306 3 07 and utilization of pesticides requires the necessity of working in conjunction with industry. The government is expected to provide direction and regulations to the industry to ensure that "good practices" in importation are being followed. They are also to provide technical assistance and monitor the formulations being sold to merchants. The government is also responsible for working with international and multinational organizations to insure the dissemination of information on handling and instructions for safe use. ARTICLE 4: THE TESTING OF PESTICIDES. The fabrication companies are responsible for conducting the necessary tests to determine the safety, use and effects of each of their products. These tests must also be specific to the environment in which the pesticide is to be used. Full documentation must be kept and be made available to the government if requested. ARTICLE 5: REDUCING THE HEALTH DANGERS OF PESTICIDES. The government is responsible for maintaining a system of registration and control. The system is to be continually monitored and amended when necessary. Information is also to be distributed to physicians, health clinics and hospitals regarding the symptomology and consequences of pesticide exposure. The government should also engage in efforts to educate the public about handling, preparation, application and general dangers of pesticides. Their involvement should also extend to occupational hazards. 308 ARTICLE 6: GOVERNMENTAL REGULATIONS AND TECHNICAL DATA. The government is recommended to maintain a registration list of pesticides it considers in need of regulation. This list should he specific as to the weights or measures of active ingredients and methods of formulation. ARTICLE 7: UTILIZATION AND DISPOSAL. The government is given responsibility to ensure that pesticides are properly distributed and disposed. Extremely toxic compounds will require additional governmental vigilance to ensure their appropriate management. ARTICLE 8: COMMERCIAL DISTRIBUTION. This article considers the obligations of the importing companies in regard to the sale and distribution of pesticides. The companies are advised to: a. Test compounds before sale to evaluate their effects on human health. b. Submit the test results to the authorities of the region in which the pesticides are to be used. c. Insure that the compounds meet specific FAO guidelines for classification, packing, handling and documentation. d. Contact the parent companies to obtain application information. e. Recall the pesticide when there is evidence of human health effects resulting from its use. f. Verify that the shops selling the product are certified to handle pesticides. g. Ensure that the individuals selling the product are knowledgeable in all aspects of the pesticide use, method of application and dangers. 3 09 ARTICLE 9. THE EXCHANGE OF INFORMATION. If the compound has been banned or restricted in the country of origin, the government of the exporting country must directly or indirectly notify the appropriate authorities of the receiving country. The importing company must also provide, at the time of the first shipment, all relevant and necessary information to the receiving country to allow that country to make a decision regarding the suitability of the pesticide, including the exact address of an individual in the importing company who could be contacted for additional information. In turn, the government of the importing country must make available the channels for this information to reach the appropriate administration officials. ARTICLE 10: HANDLING, PACKING, STORAGE AND DISPOSAL. The importing company must include their recommendations on the above for each pesticide, preferably in the form of pictures or diagrams. The disposal of shipping containers and the cleaning of application equipment must also be addressed. ARTICLE 11: PUBLICITY. Pesticide companies are not allowed to publish information that results in unsafe handling, misapplication or over-use. They cannot deceive the public by renaming dangerous pesticides or engaging in any activities that do not respect the toxic nature of the pesticide. Also prohibited are advertising practices that promise or imply guarantees or benefits. The government of the importing country is advised to work with the pesticide companies to guarantee that these requirements arebeing met. 3 1 0 ARTICLE 12: FULFILLMENT OF THE CODE. The government of the importing country, the government of the exporting country and the pesticide company must all work together to ensure that all aspects of the manufacture, sale and use are handled i n a responsible and safe manner. APPENDIX B INDIVIDUALS CONTACTED IN ECUADOR REGARDING PESTICIDE USE Ing. Neptali Bonifaz A. Director Fundacion Ciencia, Quito, Ecuador. 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