Residual levels pesticides

Subdivision O guidelines for residue chemistry data were originally pubHshed by the EPA in 1982. These have been supplemented to improve the rate of acceptance by EPA reviewers of the many reports submitted by registrants in support of tolerances for pesticides in foods. The residue chemistry studies most frequently rejected include metaboHsm in plants, food processing (qv) studies, and studies on storage stabHity of residues in field samples (57). AH tolerances (maximum residue levels) estabHshed under FIFRA are Hsted in 40 CFR under Sections 180 for individual pesticides in/on raw agricultural commodities, 180 for exemptions from tolerances, 185 for processed foods, and 186 for animal feeds. 

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). 

A subsequent comparison of these ionization techniques for the study of another eight pesticides, this time including three of the five of interest [28], i.e. carbendazim, thiabendazole and thiophanate methyl, showed that ESI gave enough sensitivity to allow reliable determination of the pesticides at concentrations below their respective maximum residue levels. 

Methyl parathion is approved only for use on crops. The maximum amount of methyl parathion residue allowed by the Food and Drug Administration (FDA) and EPA on crops used as food is 0.1-1 ppm. The FDA has monitored the food supply for pesticides for a number of years. FDA purchases many kinds of foods through Market Basket Surveys and analyzes them for residue levels of pesticides. These FDA studies allow scientists to estimate the daily intake of pesticides. Generally, the FDA monitoring studies conclude that the U.S. food supply contains only very small amounts of pesticides that are not a concern. However, there have been some reports of the illegal use of methyl parathion inside homes. For more information, see Section 1.7 and Chapter 6. 

The solubility of methyl parathion is not sufficient to pose a problem in runoff water as determined by an empirical model of Wauchope and Leonard (1980). Some recent monitoring data, however, indicate that methyl parathion has been detected in surface waters (Senseman et al. 1997). In a study to determine the residue levels of pesticides in shallow groundwater of the United States, water samples from 1,012 wells and 22 springs were analyzed for methyl parathion. No methyl parathion was detected in any of the water samples (Kolpin et al. 1998). In a study of water from near-surface aquifers in the Midwest, no methyl parathion was detected in any of the water samples from 94 wells that were analyzed for pesticide levels (Kolpin et al. 1995). Leaching to groundwater does not appear to be a significant fate process. 

Carey AE, Gowen JA, Tai H, et al. 1979. Pesticide residue levels in soils and crops from 37 states, 1972—national soils monitoring program (IV). Pestic Monit J 12 209-229. 

Duggan RE, Lipscomb GQ, Cox EL, et al. 1971. Pesticide residue levels in foods in the United States from July 1, 1963 to June 30, 1969. Pestic Monit J 5 73-212. 

Pesticide residue levels in foodstuffs are generally regulated in order to ... 

However, there is no general requirement that enforcement methods need to monitor all metabolites of an active ingredient. The primary purpose of enforcement methods is to detect violations of good agricultural practice. For this purpose, residue levels found in samples from the market (so-called Market Basket Surveys) have to be compared with MRLs, which are derived from residue concentrations found in supervised trials. It is not necessary for this comparison to be based on the total pesticide residue. Most often the choice of a single compound (e.g., parent or primary metabolite) as a marker of the total pesticide residue is more feasible. Method development and the later method application are much easier in that case. Only for intake calculation purposes, e.g., when the daily intake of pesticide residues (calculated from the results... 

The residue levels of 46 pesticides, including oxyfluorfen in soil, were determined using GC/ITDMS as described in S ection 3.2.1. The conditions for GC/ITDMS were as follows column, fused-silica capillary (30 m x 0.25-mm-i.d.) with a0.25- am bonded phase ofDB-5 column temperature, 50 °C (1 min), 30 °Cmin to 130 °C, 5 °C min to 270 °C inlet and transfer temperature, 270 and 220 °C, respectively He gas with column head pressure, 12psi injection method, splitless mode. The retention time and quantitation ion of oxyfluorfen were 23.9 min and mjz 252, respectively. ... 

Crop-pesticide data pairs Residue level (ppm) EPA tolerance (ppm) Ratio of residue found to 5% of EPA tolerance Mean residue level (all samples) Ratio of residue found in organic samples to mean of all samples... 

Carey, A.E., J.A. Gowen, H. Tai, W.G. Mitchell, and G.B. Wiersma. 1978. Pesticide residue levels in soils and crops, 1971 — National Soils Monitoring Program (III). Pestic. Monitor. Jour. 12 117-136. 

Stehr-Green PA. 1989. Demographic and seasonal influences on human serum pesticide residue levels. J Toxicol Environ Health 27(4) 405-421. 

Pestieide tolerances are not based solely on safety, but rather are set to represent the maximum expected residue levels of a pesticide on a commodity as a result of the legal application of the pesticide. The maximum expected levels are derived from the results of controlled field studies conducted by the pesticide manufacturer, in which application conditions are chosen to provide the highest level of residue. Conditions include applying the pesticide at the maximum allowable rate, making the maximum number of applications per growing season, and harvesting the food after the minimum anticipated interval between application and harvest. 

Analysis of PDP data from 1994 to 1999 showed that 73% of approximately 27,000 food samples that had no market claim (conventional or organic) showed detectable residues, while 23% of 127 fresh food samples designated as organic had detectable residue levels (Baker et al., 2002). Unavoidable contamination of some of the organic samples was due to the presence of persistent chlorinated hydrocarbon insecticides, which had been banned several years earlier, but 13% of the organic samples showed residues of pesticides other than the chlorinated hydrocarbon insecticides. 

It is critical to realize that pesticide tolerances themselves are not safety standards but rather enforcement tools for indicating whether pesticides have been applied according to directions. Violative residues result when residue levels exceed the tolerance due to the misapplication of a pesticide, or when residues at any level are found on a commodity for which a tolerance was not established (which could result from product misuse). While a few isolated cases of violative residues have resulted in human harm, the vast majority of violative residues are of little or no toxicological consequence. 

Contemporary risk assessment practices for pesticides in foods require far more data than simply the residue levels evaluated in government monitoring programs. Exposure to pesticides is determined by multiplying the residue levels on food by the amount of the food item consumed once determined, exposure is compared with standard toxicological criteria derived from animal toxicology studies to determine the acceptability of the exposure. 

The determination of the estimated levels of exposure is obviously a critical component of the risk assessment process. Both pesticide residue levels and food consumption estimates must be considered. Methods for determining exposure are frequently classified as deterministic and probabilistic methods (Winter, 2003). 

Measurement of dietary exposure to pesticides has historically relied upon deterministic methods that assign finite values to both the pesticide residue level and the food consumption estimates to yield a point estimate of exposure. The calculations are relatively simple, but consideration needs to be given to the accuracy of the assumptions concerning residue level and food consumption. 

Such estimates yield an exaggerated level of exposure, but for many pesticides, exposure at the TMRC is far below the RfD and does not result in cancer risks greater than 1 x 10 . In some cases, where the exaggerated levels of exposure for the TMRC exceed the RfD or cause the cancer risk to exceed 1 X 10 , the exposure calculations may require refinements, such as using more realistic residue levels or adjusting pesticide use estimations. If these or other more comprehensive adjustments still do not result in acceptable levels of exposure, the EPA will not approve tolerances for the pesticide. 

Until 1994 the EPA regulated pesticides proposed for use on food crops under certain sections of the Food, Drug, and Cosmetics Act. Carcinogenic pesticides were subject to the Delaney clause, and were thus prohibited. The use of a non-carcinogenic pesticide was allowed if its manufacturer provided data sufficient to establish an RfD, and information on expected food residue levels sufficient to document that the RfD would not be exceeded when people consumed food containing residues of the pesticide. The tool for determining compliance with this criterion is called a tolerance, and it is expressed as the maximum amount of a pesticide that can be present in a given amount of food, if the RfD is not to be exceeded. 

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