THURSDAY, Aug. 19 (HealthDay News) -- Scientists have noted a possible increased risk for attention disorders in children who were exposed to organophosphate pesticides while in the womb.
The effect was not significant at the age of 3 but clearly showed at age 5, according to the report from California researchers that appears in the Aug. 19 issue of Environmental Health Perspectives.
Bernard Weiss, a professor of environmental medicine at the University of Rochester Medical Center, said the time delay of the effects didn't surprise him.
Monkey studies have shown the same thing, with the actual behavioral problems not manifesting until the "brain had become mature enough to support that kind of complex behavior," he explained.
In kids, "you wouldn't really see [hyperactivity] bloom until the child gets into school," he added.
Although the findings are far from establishing a causal link, Weiss said he thought "these are very significant studies and are another form of warning to us about how many kinds of unrecognized threats there are to child development in the environment."
According to study senior author Brenda Eskenazi, 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.
Now, including this study, three studies have now found effects of low-dose exposure on neurodevelopment, including one earlier this year that found that exposure to high levels of organophosphate pesticides could raise the odds for attention-deficit/hyperactivity disorder (ADHD).
The current findings were based on attention tests given to more than 300 children of Mexican American farm workers in the Salinas Valley of California. The researchers also took measures of organophosphate metabolites in the mothers' urine and collected behavioral reports from the mothers and from professional observers.
Although there was only a small link between attention problems and exposure at the younger age, the association became significantly larger at age 5, especially among boys.
"We saw that the children were making more errors on the test and that it was significantly related to the mother's prenatal metabolite levels for these pesticides," said Eskenazi, who is director of the Center for Children's Environmental Health Research at the University of California Berkeley School of Public Health.
It bears noting that these children had much higher exposure levels than the "average" kid.
And "attention problems are so multifactorial that it would be hard to say that this is a major agent if it is causal at all," she added.
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," she added. "This may [also] be a reason to grow your own garden. Or families can consider using less toxic alternatives when taking care of lawns."
The U.S. Centers for Disease Control and Prevention has more on organophosphates.