In addition to the association with overall IQ scores, each of the four cognitive development subcategories saw significant decreases in scores associated with higher levels of DAPs when the mothers were pregnant. The findings held even after researchers considered such factors as maternal education, family income and exposure to other environmental contaminants, including DDT, lead and flame retardants.
"There are limitations to every study; we used metabolites to assess exposure, so we cannot isolate the exposure to a specific pesticide chemical, for instance," added Eskenazi. "But the way this and the New York studies were designed starting with pregnant women and then following their children is one of the strongest methods available to study how environmental factors affect children's health."
While markers of prenatal OP pesticide exposure were significantly correlated with childhood IQ, exposure to pesticides after birth was not. This suggests that exposure during fetal brain development was more critical than childhood exposure.
Levels of maternal DAPs among the women in the UC Berkeley study were somewhat higher than average compared with the U.S. population, but they were not out of the range of measurements found among women in a national study.
"These findings are likely applicable to the general population," said Bouchard, who is currently a researcher at the University of Montreal's Department of Environmental and Occupational Health. "In addition, the other two studies being published were done in New York City, so the connection between pesticide exposure and IQ is not limited to people living in an agricultural community."
The prenatal exposures measured in this paper occurred in 1999-2000. Overall, OP pesticide use in the United States has been trending downward, declining more than 50 percent between 2001 and 2009, and about 45 percent since 2001 in California. At the
|Contact: Sarah Yang|
University of California - Berkeley