A quarterly publication of the Autism Research Institute

The Autism Research Review International is quarterly publication of the Autism Research Institute

Summer, 2016 | Number 3, Volume 30

Large-scale study suggests link between PCBs, autism

Organochlorine chemicals banned decades ago may still be increasing the risk of autism, according to new research. 

Kristen Lyall and colleagues conducted a population-based case-control study involving 545 children with autism spectrum disorders (ASD), 181 children with intellectual disability (ID), and 418 controls from the general Southern California population. The researchers used blood samples taken during the mothers’ second trimester of pregnancy to analyze levels of exposure to two different classes of organochlorine chemicals: polychlorinated biphenyls (PCBs) and organochlorine pesticides. While production of organochlorine chemicals was banned in the U.S. in 1977, they can remain in the environment and can cross the placenta during pregnancy. 

The researchers say that children exposed prenatally to the highest levels of two PCBs in particular—PCB 138/158 and PCB 153—were between 79 and 82 percent more likely to have an ASD diagnosis than those exposed to the lowest levels. Children exposed to the highest levels of two other compounds, PCB 170 and PCB 180, were approximately 50 percent more likely to be diagnosed with ASD compared to children with the lowest prenatal exposure to these PCBs. None of the pesticides were associated with a higher rate of autism diagnosis. 

In children with ID but not ASD, the highest exposure to PCBs doubled the likelihood of a diagnosis compared to the lowest exposure. 

The researchers note that their study is very large and “is one of the few studies to date examining prenatal exposure to organochlorine chemicals, with exposures assessed from biospecimens collected during pregnancy, in relation to ASD and ID diagnoses.” Their findings, they say, “add to potential neurodevelopmental concerns surrounding these chemicals.”


“Polychlorinated biphenyl and organochlorine pesticide concentrations in maternal mid-pregnancy serum samples: association with autism spectrum disorder and intellectual disability,” Kristen Lyall, Lisa A. Croen, Andreas Sjödin, Cathleen K. Yoshida, Ousseny Zerbo, Martin Kharrazi, and Gayle C. Windham, Environmental Health Perspectives, August 23, 2016 (online). Address: Kristen Lyall, AJ Drexel Autism Institute, Suite 560, 3200 Market Street, Philadelphia, PA, 19104, [email protected]


“Chemicals banned decades ago linked to increased autism risk today,” news release, Drexel University, August 23, 2016.