The researchers found that every 10-fold increase in organophosphates detected during a mother's pregnancy corresponded to a 5.5-point drop in overall IQ scores in her children by age 7.
In fact, the 20 percent of the children whose mothers appeared to have been exposed to the least pesticides had about a 7-point higher IQ level, on average, than those in the 20 percent born to mothers with the highest exposure, the researchers reported.
The difference is equivalent to about six months of brain development in a typical child, Eskenazi said. And the differences remained even when the researchers adjusted their statistics so they wouldn't be thrown off by factors such as the education levels of the mothers and exposure to other toxins such as lead, she noted.
Eskenazi pointed out that the association was "substantial" in terms of whole populations, and might result in more children in need of special education and other services.
The studies show more of an effect in Salinas Valley than New York City, possibly suggesting that the California kids were exposed to more pesticides because they live near farms where these chemicals are used.
"If our findings are real, what you're seeing is that there's a number of mechanisms involved" in the brain of a child as it's exposed to pesticides, Eskenazi said.
How can parents lower their family's exposure to pesticides? "Reducing exposure during pregnancy will be important for parents to think about. For example, taking steps to prevent pests getting into the home, rather than trying to manage them with pesticides," said Mary A. Fox, assistant professor at the department of health policy and management at Johns Hopkins Bloomberg School of Public Health.
"Similarly, communities can pursue integrated pest management strategies that use a combination of methods and aim to reduce use of chemical pesticides," Fox advised.
Eskenazi suggests that parents buy organic p
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