Environmental Causes of Autism: Traffic Pollution and Pesticide Case Studies

Environmental Causes of Autism

There are plenty of questions as to what causes Autism. Whether those have genetic roots or environmental ones- one thing is for sure, we would all love an answer… a definitive one, or a few. At this point, I don’t think any of us would be too picky if we were offered several proven causes. It’s not that science isn’t looking for those causes, it’s just that it is a slow process that requires much more funding and research.


There are many promising studies out there on the environmental causes of Autism; two of them that I want to mention are by CHARGE. One such study being on traffic-related air pollution, another being on pesticides.

Traffic-Related Air Pollution

The studies in question are by CHARGE (Child Hood Autism Risks from Genetics and the Environmental study). The first one I am going to mention was started in 2013 as a collaborative mission between Dr. Heather Volk, PhD, MPH: Department of Preventive Medicine and Pediatrics, Keck School of Medicine, Zilkha Neurogenetic Institute, and Children’s Hospital Los Angeles; Fred Lurmann: Sonoma Technology, Inc., Petaluma, California; Bryan Penfold: Sonoma Technology, Inc., Petaluma, California; Irva Hertz-Picciotto, Phd: University of California, Davis; and Dr. Rob McConnell, MD: Departments of Preventive Medicine and Pediatrics, and Keck School of Medicine. All sat out to prove that there was a link between traffic pollution and the raise in the prevalence numbers that we are seeing with Autism.

The group of researchers looked into 279 children with Autism, and 245 that were normally developing; as a control. All of these children were enrolled in the CHARGE environmental study out of California. In said study, researchers looked at the addresses listed on their birth certificates, along with the addresses given when enrolling in the study. The study took many more things into consideration though. It was very thorough.

Elements taken into Consideration by the Study
-Wind Speed and Direction
-Atmospheric Stability
-Roadway Geometry
-Link-based traffic volumes
-Vehicle Emissions Rates
-Mixing heights

In the end the findings were rather substantial. As Dr. Volk said herself, “This work has broad health implications, we’ve known for a long time that air pollution is bad for our lungs, especially for children. We’re now beginning to understand how air pollution may affect our brains.”

The findings were as follows:
-Regional exposure of Nitrogen Dioxide and Particulate matter is associated with Autism while the mother is pregnant
-Being exposed to Nitrogen Dioxide in the first year of life is a cause of Autism according to this study
-Being exposed to Nitrogen Dioxide, PM2.5 and PM10 during pregnancy and the first year of life is associated with Autism.


I find the correlation between traffic pollution and over half of the participants having either Autism or a developmental delay to be very telling of our need to cut back on emissions and air pollution all together. If we can link that many children in one study back to traffic pollution, imagine what multiple studies on this could find! In fact, there have been multiple studies, both domestic and international. All having the same findings.

Here are some links to said studies:
U.S.A 2015
U.S.A. 2012

The second CHARGE study I want to mention is on Pesticides. Now, keep in mind there are other ways to be exposed to pesticides aside from farming, but farming is a big one in this study. In this meticulous study, CHARGE used California data on pesticide usage from 1997-2008. The researchers involved in this one was: Dr. Janie Shelton of the Public Health Sciences, University of California, Davis; Dr. Estella Geraghty of the Division of General Medicine, School of Medicine, University of California, Davis; Dr. Daniel Tancredi of the Department of Pediatrics, School for Medicine, University of California, Davis and the Center for Healthcare Policy and Research, School of Medicine, University of California, Davis; Dr. Lora Delwiche of the Department of Public Health Sciences, University of California, Davis; Dr. Rebecca Schmidt of the Department of Public Health Sciences, University of California, Davis; Dr. Beate Ritz of the Departments of Epidemiology and the Environmental Health Sciences and Neurology, Fielding School of Public Health and School of Medicine, University of California; Dr. Robin Hansen of the Department of Pediatrics, School of Medicine, University of California, Davis, and the UC Davis Medical Investigators of Neurodevelopmental Disorders (MIND) Institute, Sacramento, California; and Dr. Irva Hertz-Picciotto of the UC Davis Medical Investigations of Neurodevelopmental Disorders (MIND) Institute, Sacramento, California, University of California Davis.

This study was bigger and had much more promising results. Disturbing, yet promising. Researchers used 970 individuals that had addresses linked to the CHARGE. They then looked at what type of pesticide was used within one mile of their homes. The active ingredients being things such as Organophophates, organochlorines, pyrethroids, and carbamates.

Of the 970 individuals looked at, 486 had confirmed cases of Autism and 168 had confirmed cases of developmental delays. 316 individuals were typically developing. When you break it down, that shows that 1/3 of mothers that lived within one mile from where pesticides were regularly used gave birth to a child with Autism. The study goes even further though.

This Study Shows That:

-Living close to organophosates raises the risk of your child being diagnosed with Autism up to 60 percent
-That 60 percent is even higher if you are in your third trimester
-2nd trimester exposure to chlorpyifos has a risk of over 60 percent diagnostic rate as well
-Children born to mother’s that lived near pyrethroid insecticide just before conception or during the 3rd trimester is at a great risk of the being diagnosed with Autism
-A raised risk of developmental delay was observed neighboring carbamate, but the state that they were unable to determine a “Vulnerable Period” of pregnancy

As like the previous abovementioned study, this one has others to back it up as well… here are some links:
U.S.A. 2012
U.S.A. 2016
U.S.A. 2014

These studies indubitably add credibility to the claims of environmental causes to Autism. They don’t definitively prove them; more research is needed. They do however bring the question to light, how much of a role do pollution and pesticides play in the diagnosis of Autism?