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
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
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
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
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
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
"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."
U.S. Centers for Disease Control and
Prevention has more on organophosphates.