Tracking Pesticides in the Tropics by F.P.Carvalho, D.D

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RESULTS OF AN INTERNATIONAL RESEARCH PROJECT TRACKING PESTICIDES IN THE TROPICS BY F.P.CARVALHO, D.D. NHAN, C. ZHONG, T.TAVARES, AND S. KLAINE

ince the 1940s, target toxicity of these PCBs and other chlorinated the use of pesticides has pesticides to confidently hydrocarbons. Nevertheless, Sgrown steadily at about assess the risk associated with the use of hundreds of old and 11% a year, reaching their use. new compounds as crop five million tonnes in 1995. Agricultural fields generally protection chemicals will Pesticides and fertilizers play a are located in coastal plains continue worldwide. It is central role in agriculture and and river valleys, so it is not urgent that we develop contribute to an enhanced surprising that these rivers strategies to facilitate the production of food. receive agriculture runoff and coexistence of productive, Modern trends are gradually carry residues into estuaries healthy, and economically influencing this picture. and coastal seas. For example, viable agriculture with the Agrochemical use, mainly in the USA’s Mississippi river may preservation of natural developed countries, is being have transported an estimated resources. reduced while biological 430 tonnes of atrazine in 1989 To accomplish this, more farming methods are being from midwestern corn and research is needed in developed. But in most soybean plantations to the Gulf ecosystems that are subject to countries agrochemicals will of Mexico. significant pesticide burden. remain an essential component The environmental impacts Most studies on environmental 24 of agriculture practices for the of pesticide residues and their cycling, fate and effects of foreseeable future. effect on human health are pesticides have been carried Pesticides, especially matters of much concern. out in temperate climates insecticides and fungicides, are Recent studies on the estrogen- (North America and Western more heavily applied for like behaviour of DDTs and Europe). Much less tropical cash crops — such as PCBs in humans suggest the information has been available banana, coffee, cotton and implication of these on the behaviour of these vegetables — than for crops in compounds in breast cancer. chemicals in tropical temperate regions. For Furthermore, the growing ecosystems. example, the application of awareness of the environmental To help fill this information pesticides in banana persistence of organic gap, the IAEA set up a plantations in Costa Rica pollutants (pesticides and coordinated research attained 45kg (active industrial organic chemicals) programme (CRP) on the ingredient) per hectare, recently led governments to “Distribution, Fate and Effects whereas the comparable internationally agree on a of Pesticides on Biota in the average application of Convention on Persistent Tropical Marine pesticides in Japan for crops Organic Pollutants, phasing Environment”, funded by the is 10.8 kg. out a number of noxious Swedish International Experts have estimated that substances, including DDT, Development Authority. This only a minor fraction of applied pesticide — less than Mr. Carvalho is Head of MEL’s Marine Environmental Studies 0.1% — reaches the target pest Laboratory, in Monaco; Mr. Nhan is a researcher at the Institute for species; excess pesticide moves Nuclear Science and Technique, Hanoi, Viet Nam; Mr. Zhong is throughout the environment Professor at the Zhongshan (Sun Yat-sen) University, Guangzhou, potentially contaminating soil, China; Ms. Tavares is Professor at the Federal University, Bahia, water, and biota. It is critical to Brazil; and Mr. Klaine is Professor at Clemson University, South IAEA BULLETIN, 40/3/1998 characterize the fate and non- Carolina, USA. Doc-06.qxd 1/1/70 12:00 AM Page 25

RADIOISOTOPES FOR PROGRESS

Eighteen laboratories in seventeen countries — Bangladesh, Brazil, China, Colombia, Costa Rica, Cuba, Ecuador, India, Jamaica, Kenya, Malaysia, Mexico, Philippines, Spain, the Netherlands, United States, and Viet Nam — took part in the IAEA’s coordinated research programme on the fate and effects of pesticides in tropical environments. Among the least expensive and best research tools that the laboratories applied were radiotracer techniques. Pesticides labelled with radioisotopes are used in in model systems that help researchers investigating, for example, the Research results have been presented at persistence of pesticides, degradation pathways, various scientific fora, including the and pesticide transfer in marine food chains. International Symposium on the Large numbers of samples can be processed Environmental Behaviour of Crop Protection rapidly and measured with standard liquid Chemicals, organized jointly by the IAEA and scintillation equipment at low cost. Several Food and Agriculture Organization in 1996. participating laboratories are applying this In Monaco, at the upcoming International technique to obtain previously unavailable data Symposium on Marine Pollution in October on pesticide behaviour in tropical marine 1998, participating scientists will present environments. fourteen scientific papers on their work. (See Research using compounds labelled with box, pages 4 & 5 for information on the carbon-14 was introduced in twelve laboratories, Symposium.) 25 and gas chromatography analytical techniques now are used in fourteen participating laboratories. Most of the laboratories have adopted quality assurance procedures, including Photos: Analytical work in the chemical laboratory regular participation in intercomparison at the University of Malaya in the Philippines. exercises and the use of certified reference The university hosted a CRP meeting of materials to ensure the quality of data. participants in June 1995.

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article highlights results of this assessment; training workshops project, including those A WIDE REACH on pesticide analyses (one achieved through national case Crop protection chemicals organized in Costa Rica and studies. are used in agriculture another in Malaysia) for the worldwide. The largest analytical training of CRP RESEARCH AIMS & amounts of herbicides are participants; and PARTICIPATION used in North America, intercomparison exercises to The CRP’s technical objectives Western Europe, and Asia, test the accuracy of laboratory were to measure the current whereas insecticides are results and encourage progress levels of pesticide residues in mostly used in East Asia, with data quality assurance in coastal environments; to North America, and Latin the analyses of organochlorine characterize the cycling and America. About 50% of the pesticides and radiolabelled fate of pesticides using world’s use of insecticides is compounds. In these exercises, radiolabelled compounds and in developing countries, in homogenates of marine nuclear techniques; to evaluate particular in tropical regions, samples of adequate matrix the effects of residues on mainly to control pests (sediments, seaweed, and marine biota; to assess the risk feeding off cash crops and mussels) were used as test associated with pesticide household insects. In samples. residues in coastal tropical coming years, a general ecosystems; and to advise on increase in pesticide use is RESULTS OF measures to protect the tropical expected in Asia, whereas use CASE STUDIES marine environment. is expected to keep declining Each CRP participating A large number of requests in Western Europe. institute planned to carry out for participation and field investigations to monitor information were received at Photo: Spraying herbicides in pesticide residues in coastal the IAEA, which attested to the Viet Nam’s rice paddy fields. ecosystems in their respective 26 project’s relevance among (Credit: Carvalho/MEL) countries. Study areas covered countries and their interest to diverse ecosystems, such as act on associated environmental Manila Bay in Philippines, the problems. Eighteen delta of the Zhujiang (Pearl) laboratories in seventeen IAEA River in China, the Bay of Member States agreed to Cartagena in Colombia, several participate in the project, which watersheds at Kingston was led by the IAEA’s Marine Harbour in Jamaica, the All Environment Laboratory in Saints Bay in Brazil, the Red Monaco. (See box, page 25.) River Valley and delta in north The first Research Viet Nam, and the Indian Coordination Meeting was Coast of Kenya. held at MEL in June 1994. It annual coordination meetings Pesticide residues identified reviewed pesticide usage and have been organized to present in coastal environments in data on contamination by and discuss the project results these regions follow, as pesticide residues in the achieved in every country. expected, the trends in local participating countries, and Between the meetings, ongoing pesticide usage. Nevertheless, identified the compounds to be liaison and data exchange volatile compounds that are targeted in research and among participants was transported by atmospheric applicable methodologies for maintained through periodic processes and re-deposited meeting project objectives. circular notes. worldwide could also be Furthermore, the equipment Major joint activities were measured in regions far from and training needs of the implemented to meet common their original application area. participating laboratories were needs or objectives. These Examples of the results defined to organize IAEA included courses (lectures) on obtained are presented below: technical support to the pesticide chemistry, aquatic ■ Research in Brazil. Analyses IAEA BULLETIN, 40/3/1998 laboratories. Since then, toxicology, and ecological risk of sediments and molluscs Doc-06.qxd 1/1/70 12:00 AM Page 27

collected in a number of one-third of world use), and Since DDT’s use is banned stations of the All Saints Bay, officially DDT and BHC were in Viet Nam, these findings Brazil, found DDT residues in discontinued for use in may require the competent mollusc tissues ranging from agriculture. authorities to enhance controls 0.24 to 44 nanograms per The Zhujiang river drains a on pesticide use. Furthermore, gram (wet weight). Regular wide fertile area, potentially the dense population of the consumption of these edible carrying these pesticide Red River Valley and multiple molluscs, as done in the fishing residues into the South China re-use of the water along the community, leads to an Sea. Research under this CRP river endorses a careful ingestion of DDTs of between found low current transport of assessment of pollution 75 and 589 nanograms per residues by the Zhujiang river problems. They should be day. These levels, although not water, which is in agreement controlled through integrated alarming, were considered with the ban of these pesticides watershed management to high. Furthermore, in today. enhance water quality and comparison with Nevertheless, in the bottom conservation. measurements carried out ten sediments and marine food ■ Research in Mexico. A field years before in the same areas, chains, from phytoplankton to survey on pesticide residues on these levels indicate an increase mussels and seabirds, DDT coastal lagoons of Mexico, state of DDT concentrations in the concentrations were high, of Sinaloa, indicated the Bay, despite Brazil’s 1976 ban attaining 1.3 and 2.1 presence of residues of DDTs, on DDT. The increase micrograms per gram (wet aldrin, dieldrin, and the suggests use of DDT by weight) in the tissues of organophosphorus compounds farmers in the region. mussels and seabirds chlorpyrifos and parathion. DDT was not the only respectively. These high The finding of organochlorine pesticide concentrations are due to the organophosphorus compounds found. Analyses of HCB, past use of the compounds in in the lagoon system was aldrin, dieldrin and endrin in the region and confirm the somewhat surprising. They are 27 the same samples have shown very long persistence of DDT generally believed to be rapidly that these compounds were in the environment. degradable and thus non- present in several sites, ■ Research in Viet Nam. persistent in the environment. although at levels generally Studies carried out on the Red The presence of these residues, below one nanogram per gram. River delta in Viet Nam originating from sugar cane Through the CRP, the concluded that cyclodien and horticulture plantations in capacity of laboratories to pesticide compounds such as the Culiacan river valley, was measure pesticide residues in aldrin, dieldrin and endrin are considered a potential threat to marine samples, such as DDT practically absent in the the development of shrimp residues in mussels, was aquatic environment there. farming activities in Sinaloa. improved significantly. This suggests that these Caution with the agriculture ■ Research in China. The persistent compounds, once runoff and waste-water environmental survey carried very popular in America and discharges was recommended out on benzene hexachloride Europe and now totally to the regional authorities and (BHC) and DDT in the forbidden, were probably never farmers. Zhujiang (Pearl) river delta was used in Viet Nam. On the ■ Research in Jamaica. The considered of much interest. other hand, DDT was investigation on pesticide This is because China, a major measurable in all samples. residues in Jamaica focused on world producer of rice and Furthermore, in freshwater contamination of mountain wheat, mainly used DDT, carp fish collected near rice streams receiving drainage HCH, and BHC in the 1950s fields, DDT concentration (13 from coffee plantations. and 1960s to control insect micrograms per gram lipid Endosulfan, as well as several pests. In 1990 the total weight) were much above the organophosphorus pesticides, consumption of pesticides in maximum permissible levels in are worrysome contaminants 6 China reached 2 x 10 tonnes food covered by European of drinking water resources and of active ingredient (about standards. freshwater biota. The stream IAEA BULLETIN, 40/3/1998 Doc-06.qxd 1/1/70 12:00 AM Page 28

conservation areas (natural awaited approval of the reserves) in both coastal Pesticide National Law. Sound regions. Residues of integrated management and edifenphos, chlorpyrifos, measures to reduce the diazinon, ametryn, carbofuran contamination of the coastal and ethoprofos were detected area can now be implemented either in the water or in clams by the Nicaraguan authorities. collected on the coast. The ■ Other surveys. Similar effects of these residues on the surveys to assess the ecosystems, however, have yet environmental contaminants discharges into the coastal to be assessed. by pesticide residues are being environment causes ■ Research in Nicaragua. In done of other tropical coastal contamination of the marine Nicaragua a collaborative study areas in Kenya, India, ecosystems, although at low was carried out by the Bangladesh, and Ecuador. level. Neverthless, strict University of Nicaragua and From the results obtained so control on pesticide use in the MEL to monitor far, the persistent mountain slopes seems to be contamination by pesticides in organochlorine pesticides are urgently required to protect the main coastal lagoons of the present everywhere, although aquifers from contamination. Pacific Coast. Most of the in some areas only in trace ■ Research in Costa Rica. In country’s agriculture and amounts fortunately. When Costa Rica, a monitoring pesticide use has been taking detected, organophosphorus programme was carried out on place for decades in this region. pesticides generally seem to be contamination by pesticide Results for a wide range of present in concentrations lower residues from banana persistent chlorinated than organochlorine plantations in two watersheds, pesticides showed levels that compounds. one on the Caribbean coast were low in several lagoons. 28 (Tortuguero-Parismina) and But levels were extremely high, RADIOTRACER another on the Pacific Coast particularly for toxaphene and TECHNIQUES (Tempisque river estuary). DDTs, in the coastal lagoons Experimental work was done Costa Rica imports about 5000 of the cotton districts using carbon-14-labelled tonnes of pesticide (active Chinandega and Leon. There, compounds and liquid ingredient) per year — of concentrations of toxaphene scintillation detection to which 56% are fungicides, attained 6.9 microgram per investigate the behaviour of 30% herbicides, and 12% gram (dry weight) in sediments pesticides in the aquatic insecticides/nematicides — and 1.6 microgram per gram environment. The research almost totally applied in (dry weight) in soft tissues of focused on a selection of banana plantations. The high clams. compounds — namely DDT, rainfall and frequent Toxaphene and DDT were endosulfan, lindane, application of agrochemicals used in cotton growing for chlorpyrifos and parathion — causes the seepage of residues several decades in this region. which have been found in to the major rivers of the Although their use was tropical coastal environments. country, which flow through discontinued in the early Experiments were designed 1990s, the cumulative reservoir to obtain information on of these compounds in the soils several aspects related to the and in the lagoon sediments is fate, persistence, and very high and their environmental persistence is Photo: Above, a liquid very long. scintillation counter is part of Results of this investigation the laboratory equipment were presented at a National pesticide researchers are using in Conference on Pesticides held Viet Nam. Left, a banana in Managua, November 1997, harvest in Costa Rica. IAEA BULLETIN, 40/3/1998 which preceded the long- (Credit: ISTN/VINATOM) Doc-06.qxd 1/1/70 12:00 AM Page 29

bioaccumulation of these in the sediments of lagoons may survive long enough to pesticides in marine waters. which receive runoff from disperse into estuarine and Studies were carried out in adjacent fields. coastal environments and laboratory microcosms and Several CRP participating impact aquatic biota. model ecosystems according to institutes in Bangladesh, Nevertheless, these compounds common methodologies China, India, Philippines,Viet will generally degrade much adopted by the CRP Nam, Malaysia, Jamaica and faster than organochlorine participating institutes. Mexico carried out similar compounds in the marine The transport, dispersion, experiments. They examined environment. and ultimately the biological the fate of DDT and effects of pesticides in lagoon chlorpyrifos in aquaria EFFECTS ON systems depend upon the simulating the conditions of MARINE SPECIES persistence of these chemicals the tropical marine Toxicity assays on marine under tropical conditions and environment and using the species under tropical their bioaccumulation and local species of marine biota. conditions are being carried biodegradation. It is generally Results show that the out by several institutes in the believed that sunlight and the accumulation of those Philippines, Jamaica, Costa elevated temperatures in the pesticides from water by Rica, and Mexico. The aim is tropics would contribute to a mussels, clams, shrimp, and to assess the sensitivity of rapid breakdown of these fish is very rapid and occurs on common tropical species likely compounds. However, time scales of minutes to to be exposed to residues (e.g., preliminary experimental hours. Furthermore, the Tilapia and farmed shrimp) results indicate that photolysis biological concentration factor under the conditions of plays a minor role in the of lipophilic compounds, such tropical ecosystems. breakdown of these as DDT and DDT One common feature of compounds in comparison metabolites, generally are very tropical coastal lagoons which with chemical hydrolysis. high. are surrounded by mangrove 29 Results of experimental Considerable progress has forests is the elevated studies indicate that persistence been achieved by the concentration of humic half-lives of dissolved pesticides laboratories using radiotracer substances. Humic substances at 32o C are in the range of 1.4 techniques in pesticide are formed by the gradual to 10 days for chlorpyrifos, 9 research. (See box, page 25.) It decomposition of the leaf litter to 46 days for parathion and includes the development of from mangrove trees. Due to 130 to 155 days for DDT, miniaturized experimental the hydrophobicity of depending upon the water’s systems to investigate organochlorine and salinity. compound degradation and organophosphorus Experiments involving volatilization. It also includes compounds, a possible sediment-water systems have the attainment of results association of these pesticides demonstrated that the showing that persistence and with particulate and dissolved persistence half-lives of bioaccumulation of pesticides humics may modify the overall pesticides sorbed onto lagoon in the marine environment are fate of these pesticide residues sediments are 10 to 100 times related with molecule and their bioavailability. longer than the half-lives for configuration and chlorine This hypothesis was tested the same compounds in the content. using marine mussels exposed overlying waters, despite the On the basis of to pesticides dissolved in sea larger microbial biomass in the experimental results obtained water either without humic sediment compared to the with radiolabelled compounds, substances or with particulate water. Therefore, the rapid it seems clear that humics already containing sorption of pesticides onto organochlorine compounds, bound pesticides. Results sediment particles may increase such as DDT, will degrade very showed that the accumulation their persistence. It is likely slowly in the environment. On by the mussels of pesticides that the largest reservoirs of the other hand, some of the dissolved in the water increased these compounds will be found organophosphorus compounds rapidly in the first 12 hours IAEA BULLETIN, 40/3/1998 Doc-06.qxd 1/1/70 12:00 AM Page 30

followed by a slower increase these areas. This instability tropical regions. Overall, the thereafter. Pesticides bound by could arise through the loss of project has enhanced awareness the humic substances were also a critical species or trophic of the need to reduce accumulated in the mussel level or through the environmental contamination tissues, although to a lesser deterioration of general water traced to persistent organic extent than directly from water. quality (e.g. dissolved oxygen) compounds. Therefore, it seems that caused by the microbial A more comprehensive previous binding of pesticides degradation of these watershed-based ecological risk by humics may act to reduce contaminants. The assessment is planned. It the bioaccumulation of those preservation of these systems would incorporate existing compounds by lagoon fauna. and associated resources would pesticide residue and toxicity However, further research is require the implementation of data, along with land-use data needed to elucidate the exact integrated management plans in the watershed, to develop mechanisms that govern the cause-and-effect distribution, fate and, thus, relationships for various the effects of pesticide activities. The study residues in tropical lagoons. would provide the foundation for ASSESSING developing land and RISKS & water resource STRATEGIES management strategies to One overall goal of the CRP ensure ecosystem is to characterize the existing stability, and provide risk to both humans and resources for agriculture, coastal marine ecosystems and aquaculture, industrial suggest strategies to reduce development, recreation, 30 that risk ( if it is presently and domestic dwellings. unacceptable) in the future. Practical solutions to Several case studies within the for coastal zones in order to treat contaminated waste CRP have generated sufficient harmonize the interests of waters and surface runoff from pesticide residue data and agriculturalists, agriculture fields still must be toxicity data to begin to assess aquaculturalists, and the investigated and tested. ecological risk in particular fishing community. Tentative solutions have been ecosystems. In some The CRP’s development suggested in a few cases, such ecosystems, particularly facilitated the assessment of as the use of natural or estuarine/coastal lagoon systems pesticide contamination in key constructed wetlands around receiving agricultural drainage, coastal areas. Furthermore, agriculture fields to remove pesticide residues in sediments experimental data on the residues from water. and biota approach the acutely cycling of pesticides was Eventually this and other toxic level. More often, obtained to provide a more suggestions could be tested on however, residues are below complete understanding of the a pilot scale in the tropics, for lethal values and represent impact and fate of residues in example around banana potential food chain problems. tropical coastal environments plantations. This move Coincidentally, these and about the implementation forward would be a logical step ecosystems are ideal habitat for of environmental management stemming from the work fish, shrimp, and oyster strategies. already performed by the farming. Hence, these residues Other immediate benefits of world’s laboratories through may find their way into the the CRP to participating this IAEA-sponsored research general population through the countries include the improved project. ❑ aquaculture industry. In capability to measure pesticide addition, these residues present residues in environmental a measureable risk to the samples, and to conduct Photo: Fishing in the IAEA BULLETIN, 40/3/1998 stability of the ecosystem in research on pesticide cycling in Philippines’ Manila Bay.