Tolerance levels for pesticide residues -- the legal standards used to determine whether pesticides have been appropriately applied to food and animal-feed crops -- should not be viewed as indicators of food safety, says Carl K. Winter, a Cooperative Extension toxicologist and director of the UC Davis FoodSafe Program. Pesticide tolerances are set to slightly exceed the highest level of residues found under maximum-use conditions for a specific chemical on a given crop. Residues exceeding those tolerance levels, therefore, indicate that the grower either misused the chemical on the crop or that the crop was inadvertently contaminated by pesticide drift from an adjacent field or by pesticide lingering in the soil from a previous application. Although residue tolerance levels are not based on health criteria, the U.S. Environmental Protection Agency reserves the right to approve or deny tolerances based upon its own health risk data. "While pesticide tolerance levels are valuable enforcement tools for discouraging pesticide misuse and regulating international trade, they do not serve as accurate benchmarks of food safety," Winter told an audience at the recent American Chemical Society meeting. "Legislative attempts to increase the safety of the nation's food supply by lowering pesticide residue tolerance levels or strengthening enforcement capabilities may be misguided and would not likely benefit human health."