A link between pesticides and attention disorders?

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Prenatal exposure to pesticides may be delaying kids’ nervous-system development, leading to attention problems later in life, a new study finds.

Researchers at the University of California at Berkeley followed more than 300 California children and their mothers over several years. When the women were pregnant, the researchers took urine samples and tested them for their level of organophosphate metabolites — that is, how much their bodies were creating waste products that come from breaking down a class of very common pesticides, called organophosphates. Those metabolite levels were thought to be the best marker of a woman’s pesticide exposure. Five years later, the children born to women with high levels of pesticide traces in their urine were far more likely to have been diagnosed with attention-deficit hyperactivity disorder.

This is not the first study to find a link between kids’ neurological development and pesticide exposure. Earlier this year, in fact, researchers from the Harvard School of Public Health found that children with high levels of pesticide metabolites in their own urine were also more likely than average to be diagnosed with attention-deficit hyperactivity disorder.

Together, studies like these raise concerns about the safety of the common pesticides used for food production. The researchers behind the new study stress that the women under review in California were mostly agricultural workers, who probably have unusually high exposure to pesticides. Still, principal investigator Brenda Eskenazi said in a statement, “I would recommend thoroughly washing fruits and vegetables before eating them, especially if you’re pregnant.”

The new study is published in the journal Environmental Health Perspectives.

In truth, it can be very difficult to know whether the pesticides are really causing the developmental problems or not. It’s always possible, of course, that some other factor is causing the problems, and that that factor just happens to be more common among people who are also exposed to pesticides a lot. The way to solve this problem — intellectually, at least — would be to run an experiment, exposing some people to the pesticide and some not. But that kind of experiment would be unethical; you can’t test something that you suspect is going to harm people.

So for now long-term studies like this one in California may be the best available. Experiments can be conducted in animals, too, and in mice organophosphates are known to cause brain damage when given in large doses.

The federal government monitors organophosphate use and has guidelines for allowable uses.