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Health & Pregnancy

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Pesticide Exposure in Pregnancy Tied to Autism Risk

But it doesn't prove pesticides cause autism, and didn't directly measure women's chemical exposure, expert notes


There's no known cure for the disorder and no certain cause. But, some studies have pointed to pesticides as one possible culprit. Children of farmworker parents, who are exposed to chronic low doses of pesticides before they are born and in the first years of life, when their brains are still developing, have a higher risk for neurodevelopmental problems like autism than children who are not exposed to these chemicals.

For the new study, researchers recruited nearly 1,000 families with children who were 2 to 5 years old at the time of the study. About 486 of those children had a confirmed diagnosis of autism. Another 168 had some other kind of developmental delay, and 316 were developing as expected.

Parents were asked extensive lists of questions about lifestyle and environmental exposures, and mothers listed the addresses where they lived shortly before and during their pregnancies.

Researchers then compared those addresses to a California database of pesticide applications. The database collects information about the kind of chemical that is used, how much is used, and when it is applied.

Most of the women in the study had not lived near any pesticide applications during their pregnancies. Only about a third had been within a mile of where the chemicals were sprayed.

The researchers found that children with autism were more likely to have lived within a mile of a pesticide exposure before birth than typically developing kids. The risk was 60 percent to about 200 percent higher, depending on the kind of chemicals that were sprayed, how close the family had been to the treated area, and when, during pregnancy, a woman had been exposed.

In general, exposure during the third trimester appeared to be riskiest, and odds of having a child with autism went up the closer the family had been living to the pesticide application, suggesting that doses got higher the nearer women were to the chemicals.

Despite some concerns about the study design, Grandjean says this study -- along with previous studies that were able to measure exposure more directly -- provides further support for the notion that pesticides may be a contributing factor in the autism story.

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