Childhood Autism May Be Caused by Parents’ Exposure to Workplace Chemicals, Study Finds

Plastics, polymers and ethylene oxide were linked to the most severe outcomes for children of parents who had workplace exposures.

New research suggests that parents exposed to different types of chemicals and plastics at work may be increasing their unborn children’s risk of developing autism later.

According to findings published in the International Journal of Hygiene and Environmental Health late last month, children born to parents who were exposed to chemicals in the workplace not only were diagnosed with autism spectrum disorder at higher rates, but also had more severe autism symptoms, making it more difficult for them to function on a daily basis.

Autism spectrum disorder (ASD) involves a group of neurodevelopment conditions characterized by challenges with communication, social skills, sensory processing and repetitive behaviors. ASD has become more prevalent in recent years. In 2021, data indicated 1-in-44 children in the U.S. were diagnosed with autism. That rate has now jumped to 1-in-31 children.

Although the reason for this increase remains unknown, toxic heavy metal exposure has been linked to serious health effects in children, including increased risks of autism and attention deficit hyperactivity disorder (ADHD). For this reason, concerns were voiced after a report published by Healthy Babies, Bright Futures earlier this year found high levels of arsenic in rice sold in the U.S.

In addition, hundreds of families have filed lawsuits against baby food makers alleging that high levels of toxic heavy metals found in baby food may be to blame for their children developing autism.

For the new study, researchers from UC Davis and the National Institute for Occupation Safety and Health Effects Laboratory Division studied more than 500 families from the Childhood Autism’s Risks from Genetics and Environment (CHARGE) study, focusing mostly on children already diagnosed with autism.

The team, led by Erin C. McCanlies, used the Mullen Scales of Early Learning, Vineland Adaptive Behavior Scales, and Aberrant Behavior Checklist to assess ASD behaviors, comparing them to exposures from parent jobs for three months before pregnancy to birth. This included exposures to 16 chemicals or agents, including plastics, phenols, ethylene oxide, car fluids, disinfectants, medicines and other chemicals.

According to the findings, several parental workplace exposures were linked with autism behaviors, including anesthetic gases, disinfectants and pharmaceuticals. The most severe autism symptoms were linked to parental exposure to phenols, ethylene oxide and plastics/polymers. Symptoms included irritability, hyperactivity, receptive and visual language, as well as daily living disturbances.

The largest decline in cognitive functioning was linked to fathers exposed to plastics and polymers on the job. This was linked to declining fine motor skills, visual reception, receptive language and expressive language.

The data indicate exposure to plastics and polymers, like polyethylene, polypropylene and polyvinyl chloride or PVC, were linked to poor cognitive performance, reduced adaptive skills and increased behavioral issues like hyperactivity and social withdrawal.

Exposure to ethylene oxide, a chemical used for sterilizing other products, was linked to higher autism severity scores and weaker daily living skills. While exposure to phenols was linked to increased autism severity and behavioral symptoms like hyperactivity, repeated movements or vocalizations.

“While all of these chemicals are of concern, we highlight plastics/polymers and ethylene oxide as being associated with the broadest set of outcomes. Nevertheless, future research could elucidate biologic mechanisms for any and all of these workplace chemicals. Collectively, these findings highlight the need to address exposure effects not just on employees, but on their family members, specifically, warranting attention among parents, future parents, and workplace management.”

-Erin C. McCanlies, The effects of parental occupational exposures on autism spectrum disorder severity and skills in cognitive and adaptive domains in children with autism spectrum disorder

The researchers also noted that exposure during key fetal development periods may also play a role in developing autism and the severity of symptoms and functioning.

Ethylene Oxide Exposure Concerns

Ethylene oxide is a gas used in the sterilization process of some hard-to-clean medical devices, such as those made of metal or glass, or which have multiple layers and small crevices. However, inhalation of the gas can cause lung, throat, eye and nose irritation, and has been linked to increased cancer risks and may cause brain and nervous system damage.

Concerns about environmental risks associated with exposure to the gas began to emerge after a series of ethylene oxide leaks in 2019, at facilities operated in Illinois, Michigan and Georgia by Sterigenics, a medical sterilization company, resulting in multiple lawsuits. In addition, another medical device sterilization company, Steris, announced last November that it is facing hundreds of ethylene oxide exposure lawsuits nationwide.

Earlier this year, a Georgia jury awarded $20 million in damages to a man who says he developed non-Hodgkin’s lymphoma due to exposure to ethylene oxide from a C.R. Bard facility he lived near.

Sterigenics reached a $408 million settlement agreement for similar claims linked to its facility leaks in 2023. Plaintiffs indicated they developed breast cancer, non-Hodgkin’s lymphoma and other ailments.

To address growing concerns, the U.S. Environmental Protection Agency issued new ethylene oxide standards in March 2024 for the 90 commercial sterilization facilities in the U.S. The new rules are as follows:

• Establish standards for unregulated emissions and chamber exhaust vents
• Strengthen standards for sterilization chamber vents and aeration room vents
• Require continuous air emissions monitoring and quarterly reporting for commercial sterilization plants
• Ensure sterilizers are subject to emission standards during startup, shutdown and malfunction

Since there are safer alternatives available to clean medical equipment, experts have also been calling for the healthcare industry to move away from the use of ethylene oxide. However, it is still used to sterilize about half of the medical equipment made in the U.S.

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