California-based researchers conducted a study to test for associations between the risk of having a child with autism spectrum disorder and prenatal exposure to pesticides.
They found that the risk of autism and other developmental abnormalities increased with exposure.
The study split the pesticides into classes and found different results depending on the chemical class of the pesticide compounds. The findings were published on Monday, June 23, in Environmental Health Perspectives, by researchers at the UC Davis MIND Institute.
The lead author of the study was Janie F. Shelton, a graduate student at UC Davis. Her research, supervised by principal investigator Irva Hertz-Picciotto, is a validation study on earlier research that also found some associations between autism and exposure to pesticides.
Conducted in multiple sites in California, which has the highest grossing revenue from agriculture in the nation, the study examined information from surveys of 1,000 women taken while they were pregnant and later, after birth. The women were participants in the Northern California-based Childhood Risk of Autism from Genetics and Environment (CHARGE) study.
Researchers first collected the study participants' addresses and information about their pregnancies. Then, using information from the California Pesticide Use Report, researchers mapped the address over geographic locations reported for pesticide application. They also split the data according to which chemicals the participants were exposed.
A third of the participants lived within 1.25 and 1.75 kilometers of pesticide application regions. There were some associations that were found to be significantly higher due to proximity.
Many of the associations seen depended on the time of exposure and the type of pesticide chemicals. Pesticides containing chemical compounds called organophosphates were linked to a higher risk of autism, especially when exposure occurred in the second trimester. Another class of pesticide chemicals, called pyrethroids, showed a moderate association in the pre-conception period and in the third trimester. A third class of chemical compounds called carbamates was associated with developmental delay, but not autism.
The study explains that fetal brains, much weaker than adult brains, are in greater danger from pesticides because such chemicals are neurotoxic, meaning they cause developmental changes in the way the neurons connect and produce signals.
Hertz-Picciotto, in a statement released Monday, stressed the importance of taking prenatal vitamins to reduce autism risks, and paying attention to risky environmental exposures.
"We need to open up a dialogue about how this can be done, at both a societal and individual level," Hertz-Picciotto says. "If it were my family, I wouldn't want to live close to where heavy pesticides are being applied."
