Better assay for pesticides tainting food.

Because the Food and Drug Administration relies on outdated technology to test food for dangerous pesticide residues, its routine screening assays can detect only 40 percent of all U.S. pesticides in use today. But a new test may one day help increase FDA's odds of catching foods harboring some of the most toxic residues. The experimental assay already picks up most pesticides suspected of causing cancer.

Twenty-eight of the more than 300 pesticides currently approved for use on U.S. crops have been formally designated as suspected carcinogens. Gregory C. Mattern and colleagues at Rutgers University in New Brunswick, N.J., now report that an "ion trap" mass spectrometer can simultaneously detect minute amounts of up to 17 of these (in any of the nine common crops they tested) -- and a host of other pesticides as well.

Because the pesticides Mattern's team focused on are so varied in their chemical composition, the FDA now needs more than seven different chromatographic tests to accurately identify them, the researchers note.

Ion-trap technology is the "best currently available method to detect as many pesticides as possible," Mattern says. In fact, he suspects ion-trap detectors can disclose trace residues of "just about all" U.S.-approved pesticides.

Mattern's team paired a gas chromatograph with an ion-trap mass spectrometer to create their pesticide residue detector. The gas chromatograph breaks down a sample of the food being tested into its chemical constituents. Then the ion-trap detector displays the spectra of any pesticides present. The combination is so sensitive that it can detect pesticide traces as low as 50 parts per billion of any of the 17 suspected carcinogens they studied, the researchers report in the April JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY.

Three more of the 28 suspected carcinogens could be measured just as accurately by a liquid chromatograph paired with a standard mass spectrometer, the researchers report. The gas chromatograph misses these three because heat in its chamber breaks the pesticides apart, explains Mattern, a chemist now at Mobay Corp. in Stilwell, Kan.

A 1988 report by the congressional Office of Technology Assessment (OTA) identified a widening gap between the number of pesticides that farmers use and the number of pesticides the FDA can monitor. OTA also leveled strong criticism at FDA for ignoring new technologies that could narrow that gap.

Several regional FDA laboratories are evaluating ion-trap detectors, says Marion G. Clower Jr. at FDA's Center for Food Safety and Applied Nutrition in Washington, D.C. Whether FDA will ultimately adopt this new method depends on how well ion-trap detectors function in the field and how broad a range of pesticides they can detect, he says.