The test subjects, mothers and children living in California’s agricultural community of Salinas Valley, have likely had higher exposures to pesticides than the general population, and so it is uncertain how the findings of this study apply to women living in other areas of the country. The study serves as a warning, however, about how many kinds of unrecognized threats there are to child development in the environment.

The researchers evaluated the children at ages 3 1/2 and 5 for symptoms of attention disorders and ADHD using the reports from the mothers on the children’s behaviors, performance of the children on standardized computer tests, and ratings from examiners who spent time observing the children. While the link between pesticides and attention problems wasn’t strong in the 3 year olds, it was pronounced once the children reached age 5.

The delay in noting the effects in children may be explained, according to Bernard Weiss, a professor of environmental medicine at the University of Rochester Medical Center, by brain development which matures with age. Hyperactive behavior in children, he notes, becomes more apparent once the child enters school.

According to study senior author Brenda Eskenazi, director of the University of California at Berkeley’s Center for Children’s Environmental Health, the past five or seven years have seen a number of studies looking at low-dose organophosphate exposure in children’s neurodevelopment. Prior to this, researchers’ interest had concentrated on high-dose exposure.

A second paper by the same group of researchers that appears in the same journal reported that “children don’t have the level of an enzyme needed to metabolize these organophosphates the same as adults until they’re much older than we expected,” said Eskenazi. “Their metabolism is different, and now we have hard evidence of that.”

There’s also “suggestive evidence” that some children may harbor genetic variations that make them more susceptible to the neurocognitive effects of pesticides.

“If research consistently shows that symptoms of ADHD are related to the quantity of the organophosphate pesticide exposure, then it seems prudent for families to at least try to limit exposure,” said Dr. Nakia Scott, a clinical assistant professor of psychiatry and behavioral science at Texas A&M Health Science Center College of Medicine and a child psychiatrist with Lone Star Circle of Care.

There are several things people can do to protect themselves.

“You can wash produce thoroughly before you eat and try to invest in organic produce when you can,” suggests Brenda Eskenazi. This may also be a reason to grow your own garden. Or families can consider using less toxic alternatives when taking care of lawns.”

More information
The U.S. Centers for Disease Control and Prevention has more on organophosphates.