aerial view of farmlandResearchers from the University of California Davis MIND Institute recently conducted a study investigating whether agricultural pesticides are a risk factor for the development of autism spectrum disorders (ASD). The researchers evaluated the relationship between proximity to pesticide application during pregnancy and the prevalence of ASD. They found that pregnant mothers who lived close to these agricultural sites were more likely to have children with autism.

California produces more agriculture than any other state and uses 200 pounds of pesticides each year. The research team obtained information about pesticide application from the California Pesticide Use Report, which details where certain types of pesticides were used. Data for approximately 1,000 individuals came from the California-based Childhood Risk of Autism from Genetics and Environment (CHARGE) Study. The researchers asked CHARGE participants to provide their residential addresses during pre-conception and pregnancy. Then they mapped the addresses and agricultural chemical sites, analyzing dense locations for ASD and developmental disorders.

There is a two-thirds increased risk of having a child with an autism spectrum disorder or developmental delay for pregnant women living near fields and farms where chemical pesticides are used. The connection between pesticides and ASD is even stronger when the exposure occurs during the second and third trimesters. There were several classes of pesticides—organophosphates, pyrethroids, and carbamates—associated with the risk or autism or developmental delays. Approximately one-third of CHARGE participants lived within 1.25 to 1.75 kilometers of commercial pesticide application sites.

The researchers suspect that environmental factors like pesticide use are problematic for the developing brain not only because pesticides are neurotoxic, but because the fetal brain lacks the protections of an adult brain; in utero neural development is a delicate process.

It may be possible to minimize the risk of autism from environmental factors through maternal nutrition, but more research is necessary to understand how to mitigate the effects of environmental factors.

“While we still must investigate whether certain sub-groups are more vulnerable to exposures to these compounds, the message is very clear: Women who are pregnant should take special care to avoid contact with agricultural chemicals whenever possible,” stated lead study author Janie F. Shelton, United Nations Consultant and former UC Davis graduate student.

This research is published in the journal Environmental Health Perspective.

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