Pesticides Linked With Children’s Lower IQ Scores

Pesticide use has been linked with lower IQ test scores in children. (Image: Dušan Kostić/

A trio of new studies shows that children whose mothers are exposed to organophosphate pesticides (OP) while pregnant score lower on intelligence tests and may have memory problems at age 7 years.

The studies, published online today in Environmental Health Perspectives, followed up women in California and New York during their pregnancies and tested their children’s cognitive development at various intervals up to age 9 years.

One of the studies, at the University of California (UC), Berkeley, included 329 children whose mothers’ urine samples were analyzed while they were pregnant for a breakdown product of OPs that indicates their exposure levels.

At age 7 years, the children of mothers with the highest exposure to OPs scored 7 points lower on a standard intelligence test than the children whose mothers had the lowest exposures. Every 10-fold increase in the breakdown product—dialkyl phosphate metabolites—corresponded with a 5.5-point drop in overall intelligence test scores. Exposure to other contaminants—DDT, lead, and flame retardants—did not change the results.

Two similar studies in New York, 1 of which focused on the OP chlorpyrifos, also showed intelligence, memory, and perceptual reasoning deficits at age 7 years. A study last year linked OP exposure with attention-deficit/hyperactivity disorder in children and teens.

“These associations are substantial, especially when viewing this at a population level,” study leader Brenda Eskenazi, PhD, of UC Berkeley, said in a statement. “That difference could mean, on average, more kids being shifted into the lower end of the spectrum of learning, and more kids needing special services in school.”

The US Environmental Protection Agency banned indoor use of chlorpyrifos in 2001, but agricultural use is permitted. OP use has declined in the United States over the past decade, but exposure still may occur by eating foods from crops treated with OPs.

Categories: Attention Deficit Hyperactivity Disorder, Cognitive Disorders, Neurology, Occupational and Environmental Medicine, Pediatric Neurology