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Prenatal Exposure to Organophosphate Pesticides Associated with IQ Deficits in School-age Children

April 21, 2011

WASHINGTON -- Three independent investigations (from three NIEHS and EPA funded STAR Childrens Environmental Health Research Centers) were published online April 21 ahead of print in the peer-reviewed journal Environmental Health Perspectives (EHP).  All reached similar conclusions, associating prenatal exposure to organophosphate (OP) pesticides with IQ deficits in school-age children. All three found some evidence of an association between OP exposures in utero and negative impacts on intelligence and mental development at ~7 years, including working memory, processing speed, verbal comprehension, perceptual reasoning, and full scale IQ.

Forester spraying in field

The three studies were conducted at the University of California, Berkeley, School of Public Health; the Mailman School of Public Health at Columbia University; and Mount Sinai School of Medicine. All three involved cohorts of women enrolled during pregnancy. The Berkeley and Mount Sinai investigators measured OP pesticide metabolites in the pregnant women’s urine, while the Columbia investigators measured the OP pesticide chlorpyrifos in umbilical cord blood. Intelligence tests were administered to children of these mothers between ages 6 and 9 years at Mount Sinai and at age 7 years at Berkeley and Columbia.

Although the study findings are not directly comparable, all three investigations found evidence linking prenatal OP pesticide exposures with adverse effects on cognitive function that continued into early childhood.

"It is well known that findings from individual epidemiologic studies may be influenced by chance and other sources of error. This is why researchers often recommend their results be interpreted with caution until they are supported by similar findings in other study populations,” said EHP Editor-in-Chief Hugh A. Tilson. “As a group, these papers add substantial weight to the evidence linking OP pesticides with adverse effects on cognitive development by simultaneously reporting consistent findings for three different groups of children."

Organophosphate pesticides have been associated with brain and nervous system damage in animal and human studies. In 2010 more than 30 organophosphate pesticides were registered for use in the United States by the U.S. EPA, including several for home garden use. Chlorpyrifos, which figures prominently in two of the three EHP studies, is widely used in agriculture as well as in household ant and roach baits in child-resistant packaging, although all other home uses of this pesticide were phased out after 2000 due to concerns about neurotoxicity in humans.

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