Have There Been Multiple Studies Linking Pesticides To IQ Deficits?

Prenatal exposure to organophosphate (OP) pesticides that are widely used on fruit and vegetable crops throughout the United States has been linked to IQ deficits in school-age children, according to 3 new studies published online April 21 (2011) in Environmental Health Perspectives.

The studies add to the growing body of literature linking exposure to pesticides and insecticides to adverse neurologic and cognitive outcomes in children.

In February, a study in Pediatrics and reported by Medscape Medical News at that time showed that prenatal exposure to piperonyl butoxide, a chemical added to pyrethroid insecticides used in the home, was associated with delayed neurodevelopment in young children.

“The fact that 3 research groups reached such similar conclusions independently adds considerable support to the validity of the findings,” Hugh A. Tilson, PhD, editor-in-chief of Environmental Health Perspectives, said in a statement.

In the first study, Stephanie M. Engel, PhD, from University of North Carolina, Chapel Hill, and colleagues analyzed third trimester maternal urines for OP metabolites and prenatal maternal blood for paraoxonase 1 (PON1) activity and genotype in 360 multiethnic pregnant women living in New York City between 1998 and 2002. PON1 is a key enzyme in the metabolism of OPs.

In the second study, researchers from the University of California, Berkeley, School of Public Health found that prenatal exposure to OP pesticides was related to lower intelligence scores at the age of 7 years.

The third study, by Virginia Rauh, ScD, MSW, from Columbia University, New York City, and colleagues, showed children exposed to prenatal chlorpyrifos (CPF), a pesticide used to kill roaches and other pests, had declining IQ and memory. It is now banned for use in the home but is still commonly used to spray food crops.

“These findings are important in light of continued widespread use of CPF in agricultural settings and possible longer-term educational implications of early cognitive deficits,” the investigators write.

“Since agricultural use of CPF is still permitted in the US, it is important that we continue to monitor the levels of exposure in potentially vulnerable populations, including pregnant women in agricultural communities, and evaluate the long-term neurodevelopmental implications of exposure to CPF and other organophosphate insecticides,” they conclude.

“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,” Dr. Tilson commented.

“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 3 different groups of children.” - Emily Hanson