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Science & Policy Update June 2014: Pesticides

New Study Strengthens Link Between Pesticides and Autism
By: Martha Dina Arguello, Executive Director

This month we have more research solidifying the links between agricultural pesticide and autism, this time from the University of California, Davis.

In January 1999, I read a report by the National Resources Defense Council titled “Trouble on the Farm: Growing Up with Pesticides in Agricultural Communities” that documented the impacts of pesticides on the heath of farmer workers and their families. To this day, a personal account from that report sticks with me. A mother living and working in McFarland, CA sees a group of neighborhood children playing with their Barbies, picking flowers and crying. When she asks the children what they are doing, they tell her that they are burying Barbie, because she had died of cancer. The mother, Marta Salinas, also recounts the numerous funerals that had recently occurred in her neighborhood, for children that had died of cancer.

For many years we have known about the carcinogenicity of many agricultural pesticides and have called for a greater understanding of the reproductive and developmental impacts of these chemicals. The UC Davis study released this week is a new addition to the ever-growing body of literature that shows a relationship between pesticides and brain development. For many years we have also known that pesticides – especially fumigant pesticides – do not stay confined to the areas where they are applied, but drift into nearby schools, homes, and communities.

In the report, researchers at UC Davis’s MIND Institute look at whether residential proximity to agricultural pesticides during pregnancy is associated with autism spectrum disorders (ASD) or developmental delays (DD), using results from the ongoing Childhood Autism Risks From Genetics and Environment Project (CHARGE). The report explores the relationship between pesticide application and neurodevelopmental outcomes by “ 1) assessing the gestational exposure during pregnancy to CHARGE study mothers, 2) testing the hypothesis that children with ASD or DD had higher risk of exposure in utero than typically developing children, and 3) evaluating specific windows of vulnerability during gestation.”

The study authors found that living near agricultural fields where organophosphates and pyrethroids are applied may increase the prevalence of Autism Spectrum Disorder. The study also found associations between living in close proximity to pesticide applications, gestational age and ASD. For organophosphates, they found that prenatal residential proximity during the second trimester was positively associated with ASD. For the commonly used chlorpyrifos, the association was found with third trimester exposure. And for pyrethroids, the association was linked to exposure during the three months prior to conception, as well as in the third trimester.

For many years PSR-LA has emphasized the link between pesticides and the health of women and children, and has called for safer alternatives to dangerous agricultural pesticides. It is important to note, however, that for many pesticides there are gaps in the health data, and these chemicals are often on the market and in use for years before we have comprehensive data on the full range of their health impacts. This lack of understanding is one of the fundamental flaws in our current regulatory system, as it puts people at risk for the negative health impacts of certain chemicals without taking the time and precaution to fully understand their effects. This study supports current thinking in the scientific community that the timing of exposure is just as important as the dose.