More Evidence Links Agricultural Pesticides to Autism
Drive through California's agricultural heartland, and the smell of pesticides is pervasive. Now a first-of-its-kind study has found that exposure to agricultural chemicals has an effect that can't be seen or smelled. Pregnant women who live within one mile of where common pesticides are sprayed have a 60 percent greater risk of giving birth to children who develop autism and learning disabilities, according to researchers at the University of California, Davis.
Their peer-reviewed report, published Monday in the journal Environmental Health Perspectives, is not the first to make such a linkage between pesticides and learning disabilities. But it breaks new ground in tapping a database of California children with confirmed cases of autism spectrum disorder or delayed development.
The ongoing Childhood Autism Risks From Genetics and Environment project, run by the UC Davis MIND Institute, tracks where families with autistic children have lived during the mother’s pregnancy. The researchers correlated the residential addresses of 1,043 CHARGE families with another database that maps where California's $38 billion agricultural industry has sprayed pesticides. The scientists focused on pesticides that have been associated with impaired development, such as organophosphates and pyrethroids.
"Approximately one-third of CHARGE study mothers lived, during pregnancy, within 1.5 km [just under one mile] of an agricultural pesticide application," the researchers wrote in the report. "Proximity to organophosphates at some point during gestation was associated with a 60 percent increased risk for ASD."
Women who were exposed to pyrethroid insecticides just prior to conception or in their third trimester faced a greater risk for delivering babies who developed autism, according to the study.
The biggest population of the women in the study lived in the Sacramento Valley, which is part of California's food basket, but others lived in the San Francisco Bay Area and Los Angeles.
Correlation is not the same as causation, and the researchers acknowledged that the mothers could have also been exposed to nonagricultural chemicals outside the home or in their diet. The researchers also had no data on how many hours an expectant mother spent outside the home when pesticides were being sprayed. For instance, she might have spent eight hours a day at a workplace where pesticides were not present.
Still, the UC Davis study adds to a growing body of scientific evidence linking agricultural pesticides to a host of environmental health problems, from a die-off of bees that pollinate a third of the world's food supply to the impairment of babies' brain development.
"In that early developmental gestational period, the brain is developing synapses, the spaces between neurons, where electrical impulses are turned into neurotransmitting chemicals that leap from one neuron to another to pass messages along," Irva Hertz-Picciotto, a researcher at the MIND Institute, said in a statement. "The formation of these junctions is really important and may well be where these pesticides are operating and affecting neurotransmission."
Or as Janie Shelton, the report's lead author, put it in a statement, "The message is very clear: Women who are pregnant should take special care to avoid contact with agricultural chemicals whenever possible."