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quantity and health risk. One area of confusion in the public media is FDA's use of the term "trace" in its enforcement monitoring. Although the common meaning of "trace" is a small measurable quantity of a given analyte, FDA uses it to mean peaks of unconfirmed identity that show up in a chromatogram at a level just above background noise. FDA treats these traces as

nonviolative because they aren't identifiable or quantifiable without significant additional effort, and they could represent false positives. At least one lobbying group has recently published reports and has been quoted on television as claiming a much higher incidence of illegal pesticide use in this country than FDA acknowledges, based on the existence of these traces. Winter of UC-Davis argues,



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"They've stirred up the public but completely ignored the quantity data. They forget that the dose makes the poison." Those interviewed point out that the relative health risk of pesticide residues is currently much smaller than that of microbial contamination in foods. Bruce Ames of UC-Berkeley and others have also found that foods often contain much higher quantities of natural carcinogens than they do synthetic pesticide residues (C&EN, Jan. 7,1991,27-55). Instead of over- or underregulating pesticides based on their presence in foods, a better solution, says Winter, might be to restructure EPA's pesticide regulation process for foods based on a health standard and to adopt the concept of negligible risk, which can be made scientifically defensible and could be enforced more easily than zero tolerance. This would allow the agency to preserve residue tolerances for many important pesticides and to replace them with reduced-risk substitutes whenever possible. From the laboratory standpoint, adopting a safety-based standard might also make regulatory monitoring more affordable and easier to carry out. One of the greatest needs for the regulatory labs is to find inexpensive, rapid, and fieldportable testing methods such as immunoassay for screening. The development of this type of assay could solve some of the current problems with transporting some foods from the collection site to the regional laboratory, says Miller. Research is under way to adapt environmental immunoassays, originally designed for monitoring compounds such as alachlor in drinking water, for use in the complex matrices of food samples. If the regulatory paradigm were shifted even further, from regulating the individual pesticide residue levels to regulating the cumulative risk for all pesticides on the food, says Winter, testing the physiological effect of a food sample might reflect the real risk of eating it. For instance, a test for typical pesticide effects such as cholinesterase inhibition might be more meaningful as a screening assay for food safety than tests that are designed to identify specific pesticides. "You would actually be looking at a safety threshold," he says. Deborah Noble

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Analytical Chemistry, June 1, 1995