California’s pesticide police could be missing a serious health concern for residents and farmworkers by failing to monitor what happens when pesticides get mixed together.

As a new report from UCLA highlighted today, California studies only how each individual pesticide affects human health. Often, however, workers and residents are exposed to a number of pesticides at the same time.

That can happen when pesticides get mixed together before they’re applied to fields or when different pesticides are used in the same field on the same day. A growing body of science is showing that the chemical cocktails could create greater health risks than each pesticide does on its own.

In particular, the report shows how three fumigants – a type of gaseous pesticide central to the strawberry industry and used near schools and homes – might combine to increase the risk of cancer for bystanders. Essentially, once in the human body together, the chemicals can team up to attack and mutate DNA in a way they wouldn’t on their own.

“The regulatory system that is supposed to protect people from harmful levels of pesticide exposure has been slow to deal with interactive effects when setting exposure limits for pesticides,” the report says.

The California Department of Pesticide Regulation’s mission is to protect humans and the environment from the dangers of pesticides. The report’s authors, who come from UCLA’s law and public health schools, said the department must begin studying the combined effects. And they point out that low-income and minority residents are at the greatest risk.

“DPR is required to assess this risk and protect public health, but isn’t doing so,” the authors wrote.

The department already is under fire for how it has managed fumigants, which can spread easily through the air. A Reveal investigation found that department leaders allowed growers and Dow AgroSciences to use heavy amounts of one fumigant despite strenuous objections of scientists because of its potential to cause cancer.

When Ventura County residents subsequently raised concern about the pesticide’s use in strawberry fields near Rio Mesa High School, department Director Brian Leahy responded with a series of exaggerations and contradictions.

The department has curtailed the pesticide’s use and begun drafting rules that would limit pesticide use around schools and require residents to be notified of fumigant use near their homes. However, the state continues to keep open the loophole it created at Dow’s request.

Last week, the department’s second-in-charge, Chris Reardon, left without explanation after nearly 13 years with the agency. An appointee of the governor, Reardon maintained close ties with the agricultural industry, copies of his calendars show.

The UCLA report focused on the fields around Rio Mesa High School to make its case. The school is boxed in on all four sides by conventional strawberry fields. Although pesticides aren’t applied during school hours, the gases can linger in the air for weeks after they’re applied without teachers or students knowing.

Combined, the health risk could be much greater than those of the individual pesticides.

“In fact, modeling shows that over the course of about one week people who live and work in the area around Rio Mesa High School in Ventura County were exposed to large doses of multiple fumigants,” the report says. “This level of exposure raises concerns about possible interactive effects.”



The report points out that 35 percent of all fumigants were applied on the same field on the same day as another fumigant, and 26 percent were applied as part of a pesticide mix.

The authors recommend the following changes in California’s pesticide regulation:

Pesticides sold as part of a mixture should be tested before being approved for use.

When pesticides are mixed at the field or applied near each other, regulators should require testing or create strict restrictions if there’s a reasonable chance of human harm.

The combined effects of the pesticides should be considered in the initial health research done by the Department of Pesticide Regulation and the rules it creates around the pesticides’ use.

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