GAO Exposes Flaws in Pesticide Testing of Food

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Report finds deficient testing and potentially misleading reporting by government agencies.

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Pesticides are commonly used to protect fruits and vegetables from diseases, insects, and weeds, but the pesticide residues remaining on these foods may threaten consumers’ health. Although several government agencies try to protect consumers from unsafe pesticide residues, a recent audit report raises serious concerns about the adequacy of their efforts, finding deficiencies in the methods agencies use to test food for pesticide residues.

The report, issued by the U.S. Government Accountability Office (GAO), noted that although few violations of pesticide tolerance levels set by the U.S. Environmental Protection Agency (EPA) have been found, existing government data cannot be used to reliably estimate rates of violations in the United States food supply. The GAO identified limitations in government agencies’ testing methods, including small sample sizes, inconsistent testing techniques, and failure to test for the most commonly used pesticides. Further, the GAO found that agencies’ failure to disclose these limitations in their reports could be misleading.

The GAO primarily focused on testing methods used by the U.S. Food and Drug Administration (FDA), which is the agency responsible for ensuring most types of food do not exceed tolerance levels for pesticide residue. According to the GAO, the FDA’s testing methods were not statistically valid, and the agency is failing “to meet its objective to determine the incidence and level of pesticide residues in domestic and imported foods.”

Although the FDA found relatively few violations, the GAO points out that it did not test very many samples and likely detected only a small fraction of violations. Further, the FDA’s targeted monitoring method hindered its ability to accurately estimate national violation rates. Because the FDA’s data are not representative of overall violations in the food supply, the GAO claims the “FDA cannot reliably evaluate the extent to which its monitoring program detects and intercepts violations at a rate greater than random chance.”

In response to the GAO’s concerns, the FDA explained that it does not use statistical sampling because of budget constraints. Although FDA officials stated that obtaining the data required to produce accurate estimates on a national basis would be “very expensive,” they did not provide the GAO with cost estimates for representative sampling methods.

The GAO also took issue with the FDA’s failure to disclose that it does not test for six of the most widely used pesticides in the United States, including glyphosate and 2,4-D. While it might not be feasible to undertake the more expensive testing methods needed to monitor these common pesticides, the GAO found that the FDA’s failure to disclose which pesticides it does not test for, or the potential effects of not testing for these, could lead users to misinterpret the data on the extent of violations.

The U.S. Department of Agriculture (USDA) Food Safety and Inspection Service (FSIS), which samples for pesticide residue in animal products, also does not test for all pesticides with an EPA-established tolerance, and is therefore not representative of the full range of pesticides that might be contained in meat, poultry, and egg products, the GAO notes. Additionally, the FSIS’s reports disclosed neither the pesticides for which it did not test, nor the potential effects of not testing for these pesticides. The GAO found this nondisclosure could result in users of the agency’s reports misinterpreting the data or misinterpreting the effect of FSIS’s programs.

The GAO also found limitations in the methods used by the USDA Agricultural Marketing Service (AMS), which conducts annual surveys of pesticide residues on a variety of foods to assist the EPA in risk assessment. The GAO noted the AMS’s failure to demonstrate representative sampling of the food types or the distribution centers selected. According to the GAO, the AMS’s nondisclosure of limitations in its survey methods “reduces transparency regarding the survey methods used, and as a result, users may not have accurate information and may misinterpret the program’s test results.” Thus, the AMS’s data may be unreliable as a basis for estimating pesticide residues in the food supply.

The GAO recommended that the FDA and the FSIS include the pesticides for which they do not test and the potential consequences of not testing for those pesticides in their reports. Additionally, the GAO suggested that the FDA create a statistically significant method to gather data, report a reliable estimate of national pesticide residue violations, and disclose any limitations in its methodology. Furthermore, the FDA should use statistically significant data to assess its effectiveness in discovering violations and to identify high risk foods. The AMS should also strive to improve descriptions of its survey methods in its reports, in part by identifying limitations of those methods and by providing more guidance for users of its reports.

Responding to the report on behalf of the FDA, the U.S. Department of Health and Human Services (HHS) took issue with the GAO’s recommendations. The HHS disagreed with the recommendation that the FDA should disclose the pesticides for which the FDA does not test, explaining that it “would enable users to more easily circumvent the pesticide monitoring program.” In response, the GAO rejected the HHS’s concern as unlikely, because the FDA’s reports currently list pesticides for which the FDA tests.

Meanwhile, the USDA generally agreed with the GAO’s recommendations and stated that the FSIS will disclose the pesticides for which it does not test in future reports.