Mixing pesticides can boost toxic effects and health risks

Regulators set exposure limits for pesticides based on comprehensive studies of the individual product. Scientists from UCLA say in a new report that this approach should be reconsidered because growers often apply pesticides as a mixture.

“That’s a serious problem, the authors argue, because pesticide interactions can ratchet up toxic effects, greatly enhancing the risk of cancer and other serious health conditions,” says The Nation in a story produced in partnership with FERN. The study has implications for regulation of pesticides on the national level as well as in California. Says John Froines, a co-author of the report, “You can’t simply look chemical by chemical to adequately address the toxicity of these compounds.”

In their study, Froines and his colleagues gathered information on the chemical and biological properties of the three most heavily used fumigants in California. Fumigants are among the most toxic of agricultural chemicals and are used on crops such as tomatoes and strawberries. “Individual fumigants are highly reactive chemicals that damage DNA and interfere with proteins that perform critical cell functions,” writes Liza Gross for The Nation. “Acting together, these effects multiply.”

A spokesman for the the California Department of Pesticide Regulation said the agency is aware of the report but says studies often lack the extensive and rigorous work that is employed in setting regulations.

FERN and The Nation reported last year about acutely disproportionate exposure to pesticides of pupils at schools in Oxnard, CA, where most residents are Latino. “Rio Mesa High School students were twice as likely as white kids to go to schools near heavy fumigant use,” writes Gross, and regulators did little to restrict use of fumigants near the schools. “The UCLA report shows that going to school at Rio Mesa still poses a health risk.”