The study, published in the journal Environmental Health Perspectives, and led by researchers from the University of California-Berkeley School of Public Health, tracked prenatal exposure to organophosphate pesticides for over 300 children of agricultural workers in Salinas, CA, and correlated it with ADHD diagnostic tests at age 3.5 and age 5. The researchers found that a 1,000% increase in measured prenatal exposure to organophosphates was associated with a 500% increased risk of ADHD diagnosis at age 5, the association being stronger for boys. The correlation was not significant at age 3.5, a finding explained by the study authors because ADHD is harder to diagnose at a very young age.
The study authors measured the presence of 6 organophosphate metabolites in the mothers' urine before birth, then in the children's urine between birth and age 5. At age 3.5 and age 5, the children were evaluated using mothers' reports and standardized psychological tests (respectively NEPSY-II visual attention subtest, Conners' Kiddie Continuous Performance Test [K-CPT]).
Organophosphate pesticides work by disrupting acetylcholine and other neurotransmitters. The study authors stated that young children are more vulnerable to organophosphate exposure than adults because of lower levels of acetylcholinesterase, which detoxifies these pesticides. Says lead study author Amy Marks:
"Given that these compounds are designed to attack the nervous system of organisms, there is reason to be cautious, especially in situations where exposure may coincide with critical periods of fetal and child development."
The American Council on Science and Health, a NGO partially funded by industry organizations, criticized Environmental Health Perspectives, which published this study, for publishing too many studies which link exposure to manufactured chemicals with health risks. It also disagreed with the logic of the suggestion made by the study authors to wash produce to be given to children, stating that the link between ADHD and organophosphates had not been proven for lower exposures than those of the agricultural workers' children.
While we agree that causality is not yet proven between lower exposure levels to organophosphates and increased risk of ADHD, the Berkeley study, when added to the conclusions of the previous Harvard study last May, shows a worrisome pattern of evidence that organophosphates may have strong negative effects on cognitive development. We believe that great caution is warranted for parents monitoring their children's exposure to organophosphates.
What can you do to minimize your children's exposure to organophosphates? We list generally accepted recommendations here.
Want to read more about it? Try Medscape, WebMD, Discovery News, Food Consumer, International federation of Gynecology and Obstetrics, or eMaxHealth.
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