Indoor pest control products are less likely to contain organophosphates due to related health concerns.

The findings of three studies, funded by the Environmental Protection Agency and the National Institute of Environmental Health Sciences, correlate with other recent studies linking prenatal pesticide exposure with ADHD in children.

Women living in farming communities have the highest levels of pesticide exposures in the general population. Mothers with the highest levels of organophosphate by-products in their urine had children whose IQs at age 7 were seven points lower, on average, than the children whose mothers had the lowest levels of exposure.

“That’s not unlike the decreases we see in children with high lead exposure,” says the senior study author, Brenda Eskenazi, Ph.D., a professor of epidemiology and maternal and child health at the University of California, Berkeley. “It’s equivalent to performing six months behind the average.”

Two of the studies, looking at babies born in New York, suggest that women living outside farming communities may still be at risk, although to a lesser extent. While the average metabolite levels of the pregnant women in farming communities were substantially higher than the national average, as many as 25% of pregnant women in the general population have levels above the study average.

Researchers do not know the specific mechanism by which organophosphates affects brain development in the fetus. In insect populations, organophosphate-based pesticides affect the breakdown of the neurotransmitter, acetylcholine.