Pregnant women who lived near farms and fields where chemical pesticides had a two-thirds greater risk of having a child with autism or other developmental delay, according to a new UC Davis study.
MIND Institute researchers found the link was greater when pregnant women were exposed to pesticides during the second or third trimester. The journal Environmental Health Perspectives posted the study, which was consistent with earlier research, online on Monday.
“The message is very clear: Women who are pregnant should take special care to avoid contact with agricultural chemicals whenever possible,” said lead author Janie Shelton, a UCD graduate student who now consults with the United Nations, in a news release.
Fetal brains may be more vulnerable than adult brains to insecticides, the researchers say. Exposure during development may alter the mechanisms the govern mood, learning, behavior and social interaction.
“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,” said Irva Hertz-Picciotto, a MIND Institute researcher and vice chair of the department of public health sciences, in a news release.
“The formation of these junctions is really important and may well be where these pesticides are operating and affecting neurotransmission.”
The researchers compared the California Pesticide Use Report to the addresses of about 1,000 participants in the UCD-led Childhood Risk of Autism from Genetics and the Environment Study, or CHARGE, who were surveyed about where they lived during pre-conception and pregnancy.
The UCD-led CHARGE study includes families, the majority of whom live in the Sacramento Valley, Central Valley or Bay Area, with children ages 2 to 5 who have been diagnosed either with typical development or with autism or developmental delay.
About one-third of the participants lived within three-quarters of a mile to a mile from places where commercial pesticides were used. Some links were greater when mothers lived closer to the application sites.
“In California, pesticide applicators must report what they’re applying, where they’re applying it, dates when the applications were made and how much was applied,” Hertz-Picciotto said. “What we saw were several classes of pesticides more commonly applied near residences of mothers whose children developed autism or had delayed cognitive or other skills.”
The researchers looked at organophosphates, pyrethroids and carbamates applied nearby during the study participants’ pregnancies and later diagnoses of autism and developmental delay in their offspring.
They found that organophosphates applied during pregnancy were associated with an elevated risk of autism spectrum disorder, particularly for chlorpyrifos applications in the second trimester.
Pyrethroids were moderately associated with autism spectrum disorder just prior to conception and in the third trimester, while carbamates applied during pregnancy were associated with developmental delay.
About 200 million pounds of pesticides are applied in California each year, most of it in the Central Valley.
Finding ways to reduce exposure to it is important, Hertz-Picciotto said.
“We need to open up a dialogue about how this can be done, at both a societal and individual level,” she said. “If it were my family, I wouldn’t want to live close to where heavy pesticides are being applied.”
Other study authors include Estella Geraghty, Daniel Tancredi, Lora Delwiche, Rebecca Schmidt, Beate Ritz and Robin Hansen, all of UC Davis.