Autism & Pesticides: Is There a Correlation?


by James Yang, MD

At MIPC, I have the good fortune of being the one who delivers the official news that a woman is pregnant.  As women wait for their first OB appointment at 6 weeks, they often ask for advice during the initial period when a newborn’s vital organs are developing.  Like most physicians, basic advice including taking a prenatal, avoiding alcohol and tobacco, avoiding common OTC medications, and recognizing high mercury fish are often discussed.  However, a new study published has made me consider discussing the emerging data that pesticides may have on the risk of autism and pervasive developmental disorders.

The leading theories of autism have recognized both a genetic as well as environmental contribution to autism; however, no clear environmental cause has been recognized.  The new 2014 CDC’s estimates find that a striking 1 out of 68 children are autistic, disproportionately affecting 1 out of 42 boys in the US; in New Jersey 1 out of 45 children are affected, including 1 out of 28 boys!  These new estimates are 30% higher than the 2012 CDC data showing 1 out of 88 children are affected and hundreds times higher than the prevalence in the 1990’s showing only 1 in 2500.  There is significant controversy about the meaning of this increase, with some of the increase certainly due to increased recognition and diagnosis; but many researchers believe that at least some of this increase is real.

The new study by researchers with the UC Davis MIND Institute found that pregnant women who lived closer to commercial pesticide applications sites were 60% more likely to have children who were autistic.  Researcher Dr. Hertz-Picciotto states, “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.”

There are limitations in the study, including the fact that the women were not tested for pesticide exposure by urine or blood tests.  Such testing is needed to prove that proximity to these pesticide sites lead to increased pesticides accumulation in their body.

While environmental research is costly, slow, poorly funded, and rarely definitive, the rise in autism rates is skyrocketing.  As we wait for more research to be conducted, the question of decreasing toxic exposure from pesticides is a controversial one.  In medicine, drugs are categorized by the FDA based on scientific evidence of safety.  However, my general approach is to suggest that even “safe” drugs, such as Tylenol (Category B), should be used be used sparingly or with caution.  Recent studies tying acetaminophen to ADHD and asthma have further supported my view that we should be cautious of all medications we take during pregnancy.  For chemicals designed to work as neurotoxins in insect brains, and which have been shown- at least in higher doses- to have negative neurodevelopmental effects in animal studies, perhaps some reasonable precautions should be considered.