Pesticide residue tolerances

The long-term treatment studies also include hydroponic studies (Hilton et al, 1974, 1976), as well as preemergence studies (Robinson et al, 1970 Gronberg et al, 1971 Church and Flint, 1973 Morgan, 1974 Fenz et al, 1987) and postemergence studies (Morgan, 1972,1973 Stanley and Flint, 1974 Maun and McLoed, 1978 Schocken et al, 1987) involving analysis of mature plants. The duration of these studies was usually measured in terms of weeks or months, and their purpose was to determine the nature of the terminal residues in crops in order to set pesticide residue tolerances. 

FAO/WHO. 1975. Food and Agricultural Organization of the United Nations/World Health Organization. Pesticides residue tolerances for foodgrains. Pesticides 9 33-34. 

When illegal residues have been found in monitoring studies conducted by the FDA or USD A, the reason has often been that no U.S. tolerance had been requested for that particular pesticide in that specific crop. For example, an imported crop would be deemed to be adulterated and would be seized at the port of entry into the United States if found to contain a pesticide residue in the absence of a tolerance in that crop. This is so even if tolerances have been set for the same pesticide in several crops grown in the United States and the pesticide had been used to control a pest that does not exist in the United States. Furthermore, an international maximum residue level (MRL) might already have been estabUshed for that pesticide—crop combination under the Codex system of standards for food of importance in international trade. The U.S. GAO issued two reports on food safety and pesticides in 1991 (89,90). 

The U.S. FDA monitors foods for half of the approximately 300 pesticides having official EPA tolerances as weU as a number of other pesticides that have no official tolerances. Multiresidue methods, most of which are based on chromatography protocols, are employed (7). Not aU pesticides are monitored on aU foods and sampling (qv) is purposely biased to catch possible problems. The overaU iacidence of iUegal pesticide residue is, however, quite smaU 1% for domestic surveiUance samples and 3% for imported foods. The methods employed can usuaUy quantify residues present at 0.01 ppm. Quantitation limits range from 0.005 to 1 ppm. 

Several aspects of the problem of herbicides being contaminated with nitrosamines, and the resulting inadvertent introduction of nitrosamines into the environment, will be discussed in other papers in this symposium. Unrecognized until less than five years ago, the situation has inspired intense debate and prompted several of the environmental chemistry studies mentioned in this paper. Like the presumed threat from the in vivo nitros-ation of pesticide residues, discussions sometimes lack the type of anticipated dose and effect calculations just mentioned. Unlike the active ingredients, whose benefits can justify residue tolerances and acceptable daily intakes, nitrosamine contaminents afford no known benefits, and the desirability of minimizing their levels is undisputed. 

W.G. Fong, Regulatory aspects pesticide registration, risk assessment and tolerance, residue analysis, and monitoring, in Pesticide Residues in Foods Methods, Techniques, and Regulations, ed. W.G. Fong, H.A. Moye, J.N. Seiber, and J.R Toth, WUey, New York, Chapt. 7 (1999). 

FFDCA, among other things, assured the safety of processed foods by establishing safe tolerance limits for pesticide residues in processed foods. The mles and interpretation of the mles were not always consistent between these two government offices. 

The FFDCA governs the establishment of pesticide tolerance for food and feed products. A tolerance is the maximum level of pesticide residues allowed in or on human food and animal feed. ... 

Pesticide residues consist of chemicals that might occur in a commodity as a result of application of a pesticide. Such chemicals typically correspond to compounds for which a regulatory agency has or will set a tolerance, i.e., a maximum residue limit, specific to the commodity. In either a field study or a market basket survey, residues to be determined will be those which result from application of the specific pesticide that the study is intended to support. A market basket survey, however, might be intended to support not just one but several different pesticides of the same or different chemical classes. In addition, a market basket survey might include pesticides not used in the USA but for which import tolerances exist. For example, some uses of the parathion family of pesticides on food products have been abandoned in the USA but remain in other countries that export the products to the USA. A market basket survey offers a means to evaluate actual dietary exposures to residues of such pesticides. In addition, tolerance expressions frequently include multiple compounds, all of which must typically be determined in residue field trials. The sponsor of the market basket survey must decide whether to analyze for all compounds in the applicable tolerance expression or to restrict the program to selected analytes, such as the active ingredient. 

Tolerances for pesticide residue and/or standard withholding registration of neonicotinoids in Japan are shown in Table 1. 

Pesticide chemical residues are not considered food additives . Therefore they must adhere to different requirements. Section 408 of the FDCA authorizes the Environmental Protection Agency (EPA) to establish a tolerance for the maximum amount of a pesticide residue that may be legally present in or on a raw agricultural commodity. This section also authorizes the EPA to exempt a pesticide residue in a raw agricultural commodity from the requirement of a tolerance. The requirements for pesticide chemical residues depend on whether they are present on raw agricultural commodities or processed foods. Pesticide residue limits for specific foods are provided by the EPA and can be accessed at http //www.epa.gov/pesticides/food/viewtols.htm. 

Processed foods may not contain more than the published tolerance allowed for the raw commodity. Tolerances and exemptions from tolerances established by the EPA for pesticide residues in raw agricultural commodities are listed in 40 CFR Part 180. Food additive regulations issued by the EPA for pesticide residues in processed food and feed appear in 21 CFR Part 193 and in 21 CFR Part 561, respectively. 

When the normal use of a pesticide on a food crop may pose the potential to leave a food residue, the EPA establishes a tolerance. The tolerance represents the maximum level of a pesticide residue allowed on the food crop. Tolerances are pesticide and crop specific different crops may have different tolerance levels for a particular pesticide, while a particular crop may have different tolerance levels for the different pesticides that may be used on it. 

Pesticide residues will be considered illegal when pesticides are detected at levels that exceed the tolerance level, or when residues of a pesticide are detected, at any level, on a commodity for which a tolerance has not been established. Illegal residues should not be confused with unsafe residues, however, since pesticide tolerances are most appropriately viewed as enforcement tools rather than as safety standards. 

While all nations of the world possess the sovereign right to establish their own acceptable levels for pesticide residues in foods, many lack the resources to develop their own regulatory programs and instead rely upon a set of international standards developed by the Codex Alimentarius Commission, frequently referred to as Codex. The Codex international standards are termed maximum residue limits (MRLs) and, like U.S. tolerances, are established primarily as enforcement tools for determining whether pesticide applications are made according to established directions. While many countries have adopted Codex MRLs, others, such as the U.S. and several Asian countries, rely on their own standards. Thus, there is no uniformity among the world with respect to allowable levels of pesticides on foods. A pesticide-commodity... 

Pesticide residues are deemed violative if the residues encountered exceed the established tolerances or when residues for which no tolerance has been established are detected on the sampled commodity. In the case of imported food sample, the FDA noted that 92.9% of the violations occurred when pesticides were detected on commodities for which no tolerance was established, with the remaining 7.1% of violations occurring when residues exceeded tolerances. Violative residues from domestic food samples presented a different pattern, with 50% of the violations stemming from levels exceeding tolerance and the other 50% resulting from pesticides being detected on commodities for which no tolerance was established. 

Reference doses for pesticides are used in just this way to establish standards (called tolerances) for pesticide residues in food. Similarly, ADIs, derived for food additives, are used to establish allowable limits on amounts that can be added to foods. Data on rates of food intake are necessary for pesticides and food additives, in the way that water intake rates were used in the example given above. 

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