Study Highlights Link Between Autism and Exposure of Mothers to Chemicals

A new research found a strong association between exposure of mothers to chemical pesticides and an increased risk of having children with autism spectrum disorder.

Several studies in the past have highlighted that exposure to chemicals during pregnancy leads to various birth defects. Adding evidence to this is the new study led by researchers at the University of California, Davis. The researchers suggest that mothers-to-be should be aware of exposure to chemicals during fetal development as it can harm the unborn child to a great extent.

The multisite California-based study found that pregnant women who reside close to fields and farms where the use of chemical pesticides is high, suffered a two-third risk of having a child with autism spectrum disorder or other development delays. But the risk was higher when the mother-to-be was exposed during the second and third trimesters.

In this study, the researchers looked into the link between particular classes of pesticides that include organophosphates, pyrethroids and carbamates. They examined the association during pregnancy, on later diagnosis of autism and offspring's delay in development.

"This study validates the results of earlier research that has reported associations between having a child with autism and prenatal exposure to agricultural chemicals in California," said lead study author Janie F. Shelton, a UC Davis graduate student who now consults with the United Nations. "While we still must investigate whether certain sub-groups are more vulnerable to exposures to these compounds than others, the message is very clear: Women who are pregnant should take special care to avoid contact with agricultural chemicals whenever possible."

Known as the leading agricultural producing-state of the nation, California's gross revenue from farm crops in 2010 was $38 billion. Each year nearly 200 million pounds of active pesticides are applied state-wide. Though pesticides are needed for modern agricultural industry, the commonly used pesticides are neurotoxic and pose great threat to brain development during gestation eventually causing development delay or autism.

In this study the researchers examined the application of commercial pesticides using the California Pesticide Use Report and then linked the data to the 1000 participants' residential address in Northern California-based Childhood Risk of Autism from Gentics and Environment (CHARGE) study.

The study included families with children between 2-5 years of age who were diagnosed with autism or developmental delay or with typical development.

"We mapped where our study participants' lived during pregnancy and around the time of birth. 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 risk of autism spectrum disorder was high when organophosphate was applied, specially second trimester.  Development delay was associated with carbamates.

Exposure to insecticides might be a major problem during gestation as development of fetal brain is more vulnerable to it than that of adults. This is because being neurotoxic in nature, in utero exposure to pesticides during the early development may hamper the structural development.

The study was documented in Environmental Health Perspective.