Prenatal Exposure To Pesticides May Raise Autism Risk

Pesticides are substances used in farming to ward off and destroy insects and other organisms. This is done to prevent the spoilage of large quantities of crops. Unfortunately, environmental exposure to pesticides has been linked to a number of health concerns. These include cancer, hormone disruption, memory loss and – most recently – autism spectrum disorder.

Autism spectrum disorder (ASD) is a condition that affects 1 in 59 American children (1). The disorder begins in early childhood and encompasses several conditions that include autism, Asperger’s syndrome and childhood disintegrative disorder.

It is associated with weak communications skills and difficulties with social interaction with children usually being diagnosed by the age of two after exhibiting signs such as avoiding eye contact, repetitive actions,  not responding to their name and having unusual reactions to the way things smell, look or sound.

The debate on what causes autism is still ongoing and studies linking pesticide exposure to autism are still rare. However, a recent study has attempted to uncover the link.

A study on pesticide exposure and autism

Researchers from the Fielding School of Public Health at the University of California, Los Angeles and led by associate professor Ondine von Ehrenstein set out to find a link between pesticide exposure and autism spectrum disorder.

For the study, researchers analyzed registry data of over 35 000 patients –  2,961 were diagnosed with ASD and 445 of them had ASD with an accompanying intellectual disability. The researchers then included 35,370 patients free of ASD as their control group. The participants were mostly males, born in California’s Central Valley – a heavily agricultural region – between 1998 and 2010.

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Data from California’s Pesticide Use Registry was also collected by Von Ehrenstein. Her team then selected 11 commonly used pesticides to analyze. The pesticides were selected because previous studies had linked them to detrimental brain development in both humans and animals. In a 2018 court case, the judge ruled that one of the pesticides – glyphosate – led to an individual developing non-Hodgkin’s lymphoma (2).

Ehrenstein and her team then analyzed the exposure the patients would have had before they were born and during their first year of life.

The results

The study revealed that exposure to commonly used pesticides is linked to a higher risk of autism spectrum disorder.

Specifically, the scientists found that the children of expectant mothers who were living within a 2000-meter radius of a highly sprayed area before their birth faced a 10% to 16% risk of being diagnosed with autism.  A child who had been exposed to pesticides while in utero faced a 30% higher risk of an autism spectrum disorder diagnosis that also came with intellectual disabilities. The risk of autism in their first year of life increased by up to 50% as a result of pesticide exposure.

The verdict

This was an observational study and cannot effectively establish cause and effect. However, Von Ehrenstein does hope that the findings are enough to help effectively decrease exposure to pesticides,

I would hope that these findings will make some policymakers think about effective public health policy measures to protect populations who may be vulnerable and living in areas that could put them at higher risk,she says.Raising awareness in the public may be the way to eventually change practices and agricultural policies.”

Nonetheless, the need for further research is still there. Thus experts are questioning the team’s findings with suspicion about the high number of autism diagnoses.

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“A small percentage of cases may have an environmental etiology. This is what this current case-control study attempts to address.” said University of Southampton research fellow Dr. David Menassa,Case-control studies only give us odds ratios that have no relationship to risk. There is no causation here, only a weak association.” 

Nonetheless,  Dr. Amanda Bakian and Dr. James VanDerSlice, professors in the division of public health at the University of Utah, did say that they agreed with the authors of the study on the importance of limiting pesticide exposure during pregnancy,

“Yet, reducing maternal exposure to zero for [pesticides] might be close to impossible in some populations,they wrote in an accompanying letter.

Reducing pesticide exposure

A 2017 study published in the Environmental Health Perspective journal revealed that expectant mothers who took the amount of folic acid found in prenatal vitamins were less likely to have their children diagnosed with ASD.

In addition to taking folic acid, expectant mothers can avoid produce that has been sprayed with pesticides. As for which foods are these? Well, the Environmental Working Group recently published their dirty dozen list which is an annual list looking at the most pesticide-heavy fruits and vegetables. If any of their favorite fruits and vegetables are on this list, they can always make sure to always buy organic produce.

You can read more on the study here.