Pesticide Residues for Food Safety and Environment Protection

PESTICIDE RESIDUES FOR FOOD SAFETY AND ENVIRONMENT PROTECTION

Byung-Youl Oh National Institute of Agricultural Science and Technology RDA, Suwon 441-707, Korea

ABSTRACT

Chemical pesticides have played a major role in crop protection for the last five to seven decades. However, concerns about pesticide residues in and on food, and about the environmental impact, has been growing. Most national governments today pay considerable attention to the data requirements for pesticide registration. In addition, even registered pesticides should follow a re-registration process which meets today’s guidelines, regulatory triggers and safety profiles. More recently, global conservation programs have arisen to protect all countries from environmental contaminants. These include persistent organic pollutants (POPs), endocrine disrupting chemicals (EDs), biocides, etc.. In order to secure food safety and preserve the environment, there needs to be a continuous exchange of information between global networks and relevant national agencies. At the same time, a nation-wide survey of pesticide residues is needed to monitor the presence of toxic substances in and on food items, livestock feeds, and the environment. Finally, scientific data on food safety should be open to the public to meet the consumers’ right-to-know.

INTRODUCTION economic development for the past 20 years or more, and deterioration of the global environment The role of agrochemicals in modern has accelerated. In June 1992, a summit meeting of agriculture is continuously evolving, and their 118 countries agreed to organize internationally for contribution to crop protection continues to increase. basic legislation regarding the environment. This Linking science and policy is a cornerstone of the agreement was called the “Rio Declaration”. The work of both the regulatory authorities and industry. goal of the declaration was to protect the environment Before a pesticide becomes available on the market, while achieving economic development, thus most countries insist that national authorities must attaining sustainable development of the global evaluate that pesticide thoroughly to ensure that it economy. Since then, various kinds of meetings will not harm health or the environment. Pesticides have been held to work out a solution for that pass this evaluation are granted a license or environmental problems related to agriculture. One registration that permits their sale and use according of these, the OECD Joint Meeting of the Agriculture/ to regulations. Environment Committee, developed 13 indicators Pesticides are widely used in producing food for assessing the effect of agricultural activity on the and feed. Their residues may remain in small environment, with a particular focus on pesticide amounts in or on agricultural produce and processed use and risk indicators. foods. To ensure the safety of food, most This paper deals with the current status of governments regulate the maximum level of each pesticides in relation to food safety and permitted pesticide residue. environmental protection, and the future outlook. Most countries have been pursuing a policy of

Keywords: Codex Alimentarius, endocrine disrupting chemicals (EDs), Maximum residue limits (MRLs), persistent organic pollutants (POPs) 1 OVERVIEW OF PESTICIDE RESIDUES that “Provisions essential for consumer protection Food safety in relation to the Codex (health, safety of food, etc) should be Alimentarius the focus of emphasis in Codex Standards...”. All over the world, an increasing number of The Agreement on the Application of Sanitary consumers and most governments are becoming and Phytosanitary Measures and the Agreement on aware of food quality and safety issues, and are Technical Barriers to Trade in 1995 formally realizing the need to be selective about the foods recognized international standards and which people eat. It is now common for consumers recommendations, including the Codex to demand that their governments take legislative Alimentarius, as reference points for facilitating action to ensure that only safe food of acceptable international trade and resolving trade disputes in quality is sold, and that the risk of food-borne health international law. The FAO World Food Summit in hazards is minimized. Since the first steps were 1996 agreed to: taken in 1961 to establish a Codex Alimentarius, the "Implement policies aimed at ... improving Codex Alimentarius Commission — the body physical and economic access by all, at charged with developing a food code — has drawn all times, to sufficient, nutritionally world attention to food quality and safety. For more adequate and safe food and its effective than three decades, all important aspects of food utilization” and to “Apply measures, in pertaining to the protection of consumer health and confirmity with the Agreement on the fair practices in the food trade have come under the Application of Sanitary and Commission’s scrutiny. Phytosanitary Measures and other In order to foster consumer protection relevant international agreements, that worldwide, there have been several Agreements ensure the quality and safety of food internationally on food safety. The United Nations supply...”. General Assembly Guidelines for Consumer Codex Alimentarius has held more than 30 Protection in 1985 stated that. meetings since 1963, and has achieved a number of “ When formulating national policies and agreements (Table 1). plans with regard to food, Governments Pesticides have a central position in Codex should take into account the need of all activities. In particular, maximum residue limits of consumers for food security and should pesticides (MRLs) in and on foods and feeds have support and, as far as possible, adopt become national food safety standards for member standards from the FAO’s ... and the countries. However, MRLs act as potential barriers WHO’s Code Alimentarius...”. in the international trade of agricultural produce. The FAO/WHO Conference on Food This is because the way in which pesticides are used Standards, Chemicals in Food and Food Trade (in varies from country to country, while levels of cooperation with GATT) in 1991 agreed that: pesticide applications depend on climatic conditions. "The process of harmonizing national food In addition, MRLs also vary according to the intake regulations to bring them into line with of different types of food in different countries. Fig. international standards and 1 shows how MRLs for pesticides are set. recommendations was an urgent one, The No Observed Effective Level (NOEL) of which needed to be accelerated...” and a pesticide is determined by the data from a series of

Table 1.Results achieved from Codex Alimentarius activities

2 toxicological studies using test animals. The intake pesticides in order to ensure product quantity as considered a safe amount is ingested by the test well as quality. However, no proper pesticides are animals over their whole life span with no observable available on the market for these crops, because ill effect. ADIs are established by the WHO/FAO pesticide companies do not bother to register Expert Committee, but are basically the NOEL with promising pesticides for crops with a relatively a 1/100 safety level. MRLs are determined by small cropping area. Furthermore, if a pesticide is taking into account the food intake, the average not registered for a particular crop, the Korean Food body weight of human beings, and pesticide residue and Drug Administration (KFDA) adopts the lowest levels under good agricultural practices. A problem registered MRL for that crop. As a result, when in establishing international MRLs is that daily KFDA is monitoring residue levels on minor crops, intake of particular food commodities is quite permitted levels are based on the lowest value. This different from one country to another depending on means that residues in harvested produce may exceed dietary customs. the MRL, so that the crop is not accepted for For this reason, MRLs set by the Codex marketing. Alimentarius Commission are a reference, not a In the United States, trials of reasonable directive, for individual countries. As an example, pesticide levels for minor crops are handled by a the MRL for carbaryl for several foods in selected Federal-State Project known as the “Inter-regional countries is shown in Table 2. Research Project No. 4”, or IR-4. For the past In general, pesticide manufacturers are three decades, its task has been to conduct field trials concerned mainly with their profits. For this reason, and collect data needed for EPA approval of so- they pay special attention to pesticides for major called “minor-use” pesticides. crops which are grown by many farmers, such as The Korean government has been rice, apple and Chinese cabbage. In recent years, implementing since 1998 a national project called Korean farmers have began to grow minor crops or “Pesticide registration trials for minor crops”. wild herbs such as leopard plant or parsley in Biological activity and residues were tested for a greenhouses all year round. Farmers usually apply total of 65 combinations of pesticides and crops. As

Fig. 1. Schematic flow to establish the MRLs of pesticides used for food commodities

Table 2.Comparison of the MRL for carbaryl for selected foods in some countries

3 an output of the trials, 20 pesticides for eight crops FOOD QUALITY PROTECTION ACT, USA were registered in 1999, and 39 pesticides for 13 crops were registered in 2000. Reasonable MRLs The 1996 Food Quality Protection Act (FQPA) for registered pesticides in or on minor crops were of the United States established a new standard of also set by the Joint Committee on Pesticide Residues. safety for pesticide residues in food, with an emphasis In addition, KFDA recognized that a wide variety of on protecting the health of infants and children. different vegetables are available in Korea. It decided There must be “reasonable certainty” that “no harm” to group vegetable foods into leaf, fruit, and root will come to infants and children or other sensitive vegetables. For example, the MRL of Procymidone individuals exposed to pesticides. All exposure to in perilla leaves was changed from 0.2 mg/kg to 5 pesticides in food, drinking water, and home and mg/kg, based on the MRL for lettuce. The MRL in garden use must be considered in determining perilla leaves has now been further increased, to 10 permissible levels of pesticides in food. mg/kg. (Note: Perilla is an ornamental plant with EPA has met an important deadline in the new edible purple or green leaves). law by issuing a schedule showing how the Agency The safety of exported agricultural produce is will reassess more than 9,700 existing “tolerances” a major issue in international trade. Basically, — or MRLs in foods — by August 2006. Pesticides residue levels for exported agricultural produce that appear to pose the greatest risks will be should be compatible with the MRLs of the importing considered first. country. However, some countries, including United Many pesticides, even when they are properly States, operate zero tolerance for residues of applied in accordance with label directions, may pesticides which have not been registered by their leave residues in or on treated fruits, vegetables, own government. Thus, trace amounts of residues grains, and other commodities. Though pesticide in imports may cause the shipment to be rejected. residues often decrease over time as food crops are Some examples of Korean exports rejected in this washed, stored, processed, and prepared, some way are: chlorthalonil in pear in 1989, procymidone residues may remain in both fresh produce (such as in ginseng in 1995, dichlorvos in cucumber in 1995, apples or tomatoes) and processed foods (such as and monocrotophos in citrus in 1996. applesauce or tomato ketchup). EPA has classified If a certain pesticide is essential to prevent into three groups the 469 pesticides which are to be damage from specific pests in specific export crops, evaluated. and if it is not registered in the importing country, an alternative pesticide must be developed, or a Group 1 tolerance level for imports must be established. Pesticides which often cause residue problems in Group 1 contains the 228 pesticides that appear internationally traded agricultural produce are those to pose the greatest risk to public health. These have used for post-harvest treatments, low (chlorpyrifos) top priority, and will be examined first. They or no Codex MRLs, and pesticides which are not include organophos-phates, carbamates and registered in major world markets. They include organochlorine classes of chemicals; probable and chlorthalonil, vinclozolin, iprodion, captan/folpet, possible human carcinogens; high-hazard inert thiabendazole, dithiocarbamate, carbendazim, ingredients; and any pesticides for which normal imazalil, procymidone, methamidophos, omethoate, usage exceeds their reference dose (RfD) (i.e.the diazinon, pyrimiphos-methyl, azinphos-methyl, amount believed not to cause adverse effects if permethrin, monocrotophos, parathion-methyl, consumed daily over a 70-year lifetime). Protection mevinphos, phosmet, esfenvalerate, malathion, and of infants and children is given high priority. Of the methidathion. approximately 1,800 organophosphate tolerances Results from monitoring pesticide residues in receiving priority review, over 300 are for residues fruits and vegetables by EU member countries on crops that are among the top 20 foods consumed showed that regardless of the country concerned or by children. the sample size, the proportion of agricultural produce with residues over the MRL was around 1% Group 2 of the monitored samples (Table 3). The pesticide residue monitoring data for This group contains 93 pesticides that are Korean domestic produce show that the percentage possible human carcinogens but which are not of samples with residues over the Korean MRL has included in Group 1, and all remaining pesticides been falling in recent years (Table 4). subject to re-registration. These have the second- 4 Table 3.Number of fruit and vegetable samples analyzed for pesticide residues in Europe (EU, 1996) showing the sample numbers analyzed per head of population

Table 4.Percentage of Korean agricultural produce with residues over the MRL, 1998-2000

highest priority for review. is closely related to the physico-chemical parameters of the chemical itself and surrounding environmental Group 3 conditions. The latter factors include application time and dose, land use patterns and target crops. The 148 pesticides in this group include most Factors related to climate and weather include of the biological pesticides, inert ingredients, and temperature, rainfall, evapo-transpiration rates and recently registered pesticides with tolerances that wind velocity. Parameters related to soil are run-off are not subject to re-registration pesticides with characteristics, organic carbon content, texture, active ingredients registered since 1984. hydraulic characteristics and pH. Several schemes have been proposed for the ENVIRONMENTAL PROTECTION assessment of the degradability of pesticides in soil. The IUPAC commission on agrochemicals proposed Process of pesticide dissipation that the half-life in soil be used for assessing the degradability of pesticides (Table 5). Half-lives, Various parameters are involved in the DT-50 and DT-90 values have also been introduced environmental fate of pesticides applied to the target. by some regulatory authorities (United States, EPA In principle, all chemicals, including pesticides, 1982; Denmark, AEP 1988; Germany, BBA 1990) which are introduced into the environment are as triggers in tiered persistence testing systems gradually recycled within and between the bio-, (Table 6). In addition to DT-50 and DT-90 values, geo-, atmo-, and hydro-spheric systems (Fig. 2). the evaluation criteria used by BBA of Germany The rate at which pesticides are moved and dissipated include the percentage of active ingredients or 5 metabolites left in the soil before the next application, Protection of water sources is one of the most the percentage of bound residues formed, and the effective ways of reducing the entry of toxic normal rate of application. substances into the water supply. Among the many Since the 1980s, a large number of chemicals encountered in drinking water, pesticides mathematical models have been developed which occupy a unique position, since they are deliberately attempt to simulate the fate of pesticides in the soil. manufactured and used. WHO (World Health Research into the interplay of factors affecting the Organization) has formulated drinking water fate and mobility of pesticides in soils has developed guidelines for some 40 pesticides. rapidly over the past 15 years. The development of Tolerable daily intake (TDI) was derived in simulation models has proved useful, both in guiding the traditional manner by dividing the no-observed- experimentation and in integrating, testing and adverse-effect level (NOAEL) or the lowest- improving our understanding of the dynamic and observed-effect level (LOAEL) for the critical effect complex nature of the soil-plant-pesticide system. by an uncertainty factor accounting for interspecies Pesticide leaching models are also now being used and intraspecies variation. The guideline value for management purposes by both industry and (GV) was derived from the TDI by multiplying it by public authorities as part of the registration process. body weight (bw; 60 kg for adults, 10 kg for children, The use of models implies a different set of 5 kg for children, 5 kg for infants) and the proportion needs and priorities. The two most important are of total intake accounted for by drinking water (P; ease of setting parameters and the reliability of 10% by default if no data exist), and divided by the predictions. To some extent, these requirements are daily drinking water consumption (C; 2 liters for conflicting, since reliability implies the need for adults, 1 liter for children, 0.75 liter for infants). mechanistic models. These minimize “model error”, This gives the formula: but at the cost of increasing the demand for data. GV = TDI x bw x Guidelines P/C for the TDI Despite many differences in detail, the most of common pesticides in drinking water are commonly used models of pesticide mobility have summarized in Table 8. much in common in their general approach, since One of the biggest problems in water supplies they are all attempting to represent the same is the short-term presence of a high concentration of phenomena. Table 7 summarizes some models a pesticide in drinking water. If, for example, a used for pesticide leaching in the unsaturated soil particular pesticide is found in drinking water at a zone. level higher than the standard, a decision has to be

Fig. 2. Environmental fate and dissipation processes of applied pesticides

6 Table 5.Ranking of pesticide persistence in soil

Table 6 . Regulatory triggers for soil degradation testing

Table 7.List of current leaching models for pesticides in unsaturated soils

7 made as to whether the pesticide is a greater risk Halogenated carbons are a major group of than turning off the water supply. And despite POPs. Of these, the organochlorines are by far the current concerns about endocrine disrupting most important group. Included in this class of chemicals (EDs), it is not clear that drinking water organohalogens are dioxins and furans, PCBs, aldrin, is a major source. Many EDs are hydrophobic. If endrin, dieldrin, hexachlorobenzene, mirex, they are present in raw water, they can be easily toxaphene, heptachlor, chlordane, and DDT. The removed by treatment. use of halogenated, and particularly chlorinated organic compounds has become entrenched in Persistent organic pollutants (POPs) contemporary society. They are used by the chemical industry in the production of a broad array of Persistent organic pollutants (POPs) are products, ranging from polyvinyl chloride (millions organic compounds that, to a varying degree, resist of tons per year) to solvents (several hundreds of photolytic, biological and chemical degradation. thousands of tons), to pesticides (tens of thousands POPs are often halogenated. Characteristically, of tons) and specialty chemicals and phamaceuticals they are not very soluble in water but are highly (from thousands of tons to kilogram quantities). In soluble in fat, so they accumulate in fatty tissues. addition, human and natural processes add to the They are also semi-volatile, and can move long production of undesirable by-products and emissions distances in the atmosphere before deposition occurs. (such as chlorinated dioxins) often characterized by These properties of unusual persistence and semi- their persistence and resistance to breakdown. volatility, coupled with other characteristics, have Immunotoxicity in association with exposure resulted in the presence of compounds such as PCB to different POPs has been reported by several all over the world, even in regions where they have authors. Investigators have demonstrated immune never been used. They have been measured on dysfunction as a plausible cause for increased every continent, including sites such as the open mortality among marine mammals. They have also ocean, deserts, the Arctic and the Antarctic where demonstrated that the persistent consumption by no significant local sources exist. The only seals of a diet contaminated by organic pollutants reasonable explanation for their presence in such may lead to vitamin and thyroid deficiencies, and areas is long-range transport from other parts of the make the animals susceptible to microbial infections globe. and reproductive disorders. Exposure to POPs has

Table 8.Risk assessment of some selected pesticides in food and drinking water

8 been correlated with population declines in a number Sweden, Switzerland, the United Kingdom, the of marine mammals, including common seals, harbor United States, and the International POPs porpoises, bottle-nosed dolphins and beluga whales. Elimination Network. The scientific literature has demonstrated a direct Fig. 3 shows the procedure for identifying cause and effect relationship in mink and ferrets POPs by assessing the physico-chemical parameters between PCB exposure and immune dysfunction, and global survey data of the candidate chemicals. reproductive failure, increased kit mortality, deformation and adult mortality. Endocrine disrupting chemicals (EDs) It is difficult to establish whether human exposure to POPs has a direct effect on disease During the 1990s, there has been increasing incidence. As with wildlife species, humans concern about reproductive abnormalities in wildlife, encounter a broad range of environmental exposures, the increase of breast cancer in women, and the frequently to a mixture of chemicals at any one time. falling sperm counts in men. Many scientists have Studies of the incidence of cancer associated with suggested that the underlying cause is the pesticides occupational exposure to 2,3,8-TCDD seems to and other chemicals that disrupt the endocrine indicate that extremely high-level exposures of system. The endocrine system plays a critical role human populations do elevate overall cancer in normal growth and development and in incidence. More recently, research has been reproduction. Even small disturbances in endocrine accumulating which suggests a possible relationship function can have a profound and lasting effects. between exposure to some POPs and human disease Meanwhile, at present, scientific knowledge is and reproductive dysfunction. inadequate to inform public policy. US/EPA For a chemical to be identified as a POPs, it estimates that there are approximately 87,000 must have the following features: chemicals to be screened for possible endocine • Persistence: The ability to resist disrupting activity. These include about 900 active degradation in various media such as ingredients of pesticides; 2,500 other ingredients soil, water or sediments, measured as used to formulate pesticide products; 75,500 the half-life of the substance in the industrial chemicals; and 8,000 cosmetics, food medium; additives and nutritional supplements. The initial • Bioaccumulation: The ability of a sorting stage will separate chemicals into four chemical to accumulate in living tissues categories based upon a review of all existing relevant to levels higher than those in the scientific information as shown in Fig. 4. surrounding environment; • Toxicity: The ability of a chemical to Category 1: No testing necessary now — Hold. cause injury to humans or the Category One includes chemicals such as strong environment; mineral acids and bases, amino acids, sugars, certain • Volatility: The ability of a chemical to polymers (approximately 3,000 polymers), etc., that vaporize into air; are unlikely to exhibit endocrine activity and need • Measurements of the chemical in not be screened. For example, polymers with an remote regions: Considered by some to average molecular weight of more than 1,000 daltons be critical for identifying a chemical as are unlikely to be able to cross biological membranes a persistent organic pollutant of global and barriers, and would therefore not be biologically concern; available to influence the endocrine system. • Bioavailability: Based on field data or expert judgment, this has also been Category 2: Insufficient data for Tier 1 screening. proposed as a criterion for identifying Category Two consists of chemicals for which there POPs. are insufficient data to determine their potential for Funding global negotiations to establish a endocrine activity. Chemicals with insufficient global treaty on POPs is a challenging task. The data will undergo priority setting for Tier 1 Screwing, international community is responding to the need which may include High Throughput Pre-screening for resources by contributing through an innovative (HTPS). HPTS is presently being examined by EPA financial mechanism known as the POP’s Club. to determine if suitable technologies can be Donations and pledges have been received from developed for routine application in Tier 1 Screening. Australia, Austria, Canada, Denmark, Finland, Prescreening is necessary, because it is estimated Germany, Madagascar, the Netherlands, Norway, that up to 62,000 chemicals may belong to this 9 Fig. 3. Flow chart of POPs identification procedure

category. market. However, their production has been falling in recent years (Table 9). Category 3: Direct move to Tier 2 testing. Multi-disciplinary studies have mainly Category Three includes those chemicals that have focused on monitoring the chemicals from an sufficient data to bypass screening, but need testing. agricultural and environmental point of view. Chemicals with sufficient data to bypass Tier 1 Korea’s National Environmental Research Institute Screening will go directly to Tier 2 Testing. EPA is responsible for monitoring water, sediments, air, estimates that there are more than 1000 chemicals in and dioxins from waste incinerators. The Korean this category, and a similar number in the next FDA is responsible for monitoring disposable bowls (Hazard Assessment) for instant noodles, tin cans, etc. The National Institute for Agricultural Science and Technology Category 4: Direct move to hazard assessment. (NIAST) is responsible for monitoring agricultural The final category contains substances for which produce, arable soil and irrigation water. there is adequate data, which will be referred to the appropriate agency for hazard assessment. CONCLUSION At present, no chemicals are designated as endocrine disrupting substances on a global basis, Regulations governing pesticides have been although there are several candidates. However, the characterized by a number of trends in recent years. list of candidates is quite different in different There is a demand for more data on food and organizations. The National Environment Research environmental safety, coupled with increased Institute, the national agency responsible for international efforts to achieve global accords. The monitoring endocrine disrupting chemicals in Korea, big challenge now is the costly re-registration follows the list announced by the World Wildlife program, designed to ensure that older, but still Fund, which involves 67 chemicals. This include widely used, products meet today’s environmental 44 pesticides, 17 of which are still available on the and safety standards. The social, political and 10 Fig. 4. Screening program in United States, endocrine disrupters for organized by US/EPA

regulatory situation surrounding the crop protection be a constant exchange of information between industry has become much more complex during international bodies and national regulatory the last decade. People living in modern society agencies. Similarly, each country must regularly play the role of active and involved consumers. monitor pesticide residues on a national basis to They are concerned about the safety, price, determine trends in the levels of toxic substances in availability, and quality of their food. These demands and on food, feeds and the environment. Finally, must be reconciled by farmers, regulators, policy scientific data on residues and other aspects of makers, and farm input industry, pesticide chemical use must be open to the public, to satisfy manufacturers. In spite of a new interest in biological the right-to-know of citizens. pest control, chemical control is likely to remain the backbone of crop protection over the next decade. Future pesticides must meet the following REFERENCES criteria. They must be effective and active with low doses of less than 5 g/ha. They must degrade rapidly BBA. 1990. Guidelines for the Official and completely after their job is done. They must Testing of Plant Protection Products. not leave toxic residues in or on food, or damage the Biological Research Center for Agriculture environment. They must not be transferred away and Forestry, Germany. from the target location. They must be produced by Brooks, G.T. and T.R. Roberts. 1999. methods of manufacturing, formulation and Pesticide Chemistry and Bioscience. The packaging, and applied in ways that minimize waste Food - Environment Challenge. The and exposure. They must not disturb the treated Royal Society of Chemistry, London, ecosystem in any undesirable way. United Kingdom. In order to ensure the safety of our food and DK AEP. 988. Application Concerning keep our environment healthy and clean, there must 11 Table 9.Annual production of 17 pesticides suspected of having endocrine disrupting activities, Korea

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