A large new study published in the International Journal of Hygiene and Environmental Health provides evidence that exposure to certain workplace chemicals among parents may influence the severity of autism spectrum disorder (ASD) symptoms and contribute to behavioral, cognitive, and adaptive challenges in their children. The findings suggest that occupational exposures—especially to plastics, ethylene oxide, phenols, and pharmaceutical agents—may have broader developmental effects beyond autism diagnosis alone.
Autism spectrum disorder is typically understood as a neurodevelopmental condition involving a mix of genetic and environmental factors. While previous research has associated prenatal exposure to environmental pollutants with increased autism risk, most of that work has focused on diagnosis itself, not on the range or severity of symptoms children may later experience. This study sought to expand that understanding by examining whether parental occupational exposures to potentially harmful agents before and during pregnancy are associated with the intensity of ASD symptoms and co-occurring developmental difficulties.
The study was conducted by former researchers from the CDC’s National Institute for Occupational Safety and Health (NIOSH), in collaboration with the University of California, Davis, as part of the CHARGE (Childhood Autism Risks from Genetics and Environment) study. Their aim was to test whether parents’ workplace exposure to chemicals might contribute not just to ASD risk but to more severe impairments in communication, cognition, or adaptive functioning in children who are already diagnosed.
“My stepson was working with children with autism and we began discussing the spectrum of symptoms that children with autism experience and that little was understood about the causes of autism,” explained study author Erin C. McCanlies.
McCanlies had worked at NIOSH’s Health Effects Laboratory Division as a research epidemiologist, where she studied the impact of occupational exposures on health. That division was responsible for conducting research on workplace health and safety. She is now retired after the division was eliminated under the direction of Health and Human Services Secretary Robert F. Kennedy Jr.
“My job was considering how occupational exposures may result in illness or injury. This led to my thinking about the possible causes behind autism, particularly chemicals and other agents that parents might be exposed to while on the job that could potentially result in autism in their children. To better understand this potential risk I reached out to Dr. Irva Hertz-Picciotto at UC Davis, who was conducting a large study, the CHARGE study, which was designed to evaluate genetics and environmental factors that might be involved in the causes of autism.”
The researchers analyzed data from 532 children with confirmed ASD diagnoses and at least one parent with complete occupational history. All children were between the ages of 2 and 5 and participated in the CHARGE study, a large case-control investigation of autism and developmental delays in California. Each child’s ASD diagnosis was validated using gold-standard instruments such as the Autism Diagnostic Observation Schedule (ADOS-2) and the Autism Diagnostic Interview-Revised (ADI-R).
Parents completed extensive surveys about their work histories, including the types of jobs they held and any potential exposures to harmful substances during the “index period”—defined as the three months before conception through the end of pregnancy. Two industrial hygienists reviewed each job entry and assigned exposure ratings to a panel of 16 chemical categories, including disinfectants, solvents, metals, plastics, phenols, and others. These ratings were combined into a cumulative exposure score for each parent.
To assess ASD symptom severity, the researchers used a standardized metric called the Calibrated Severity Score (CSS), derived from ADOS-2 results. This score is intended to capture core autism features independently of age or cognitive ability.
In addition to the CSS, they evaluated cognitive function using the Mullen Scales of Early Learning (MSEL), adaptive functioning with the Vineland Adaptive Behavior Scales (VABS), and problem behaviors with the Aberrant Behavior Checklist (ABC). These instruments provided a broader picture of each child’s developmental profile, allowing the team to examine how parental exposures might be linked to different aspects of a child’s functioning.
The findings suggest that workplace exposures to several specific chemical classes were associated with worse outcomes in children with ASD. One of the strongest and most consistent patterns involved plastics and polymer chemicals. Fathers’ exposure to plastics was associated with lower scores across all cognitive and adaptive skill domains, including language, motor coordination, daily living skills, and overall functioning. When both parents were exposed, the deficits appeared to compound.
“I was surprised how strongly and consistently plastics and polymers stood out as being linked with multiple developmental and behavioral outcomes including irritability, hyperactivity, and daily living,” McCanlies told PsyPost.
Exposure to ethylene oxide—commonly used in hospital sterilization—was also linked to more severe autism symptoms, lower expressive language abilities, and poorer adaptive functioning. Similarly, parental exposure to phenol (used in construction, automotive, and some consumer products) and pharmaceuticals was associated with increased ASD severity and more pronounced behavioral challenges, especially hyperactivity and stereotyped behavior.
While the results do not imply that all children exposed to these chemicals will develop more severe symptoms, the patterns suggest that early life exposure to workplace toxicants may amplify certain developmental difficulties in children who already meet criteria for ASD. The study provides one of the most detailed looks to date at how parental occupation may relate not just to diagnosis, but to variation in how autism is expressed.
“Our findings suggest that certain parental workplace exposures may be related not just to autism, but to worse symptoms and autism behaviors,” McCanlies explained.
These findings are consistent with past research linking prenatal exposure to chemicals like BPA, phthalates, and metals to developmental delays, behavioral issues, and increased autism risk. The current study builds on that work by identifying specific occupational chemicals that may intensify these outcomes.
“These findings suggest that both men and women should follow recommended safety practices and use protective gear when working with these chemicals,” McCanlies said.
“This research shows that workplace safety isn’t just about protecting the worker — it’s also about protecting their future children,” added Hertz-Picciotto, a professor at the UC Davis MIND Institute. “We must consider how workplace chemicals might affect the next generation.”
The researchers suggest several possible biological mechanisms that could explain these associations. Many of the chemicals studied are known endocrine disruptors or immune-modulating agents, which can interfere with hormonal signaling, neural development, or inflammatory processes during pregnancy. Micro- and nano-plastics, in particular, have been shown in animal studies to cross the placenta and disrupt gene expression in the developing brain.
While the study offers strong statistical support for several associations, it is observational in nature and cannot prove causation. Exposure estimates were based on job descriptions rather than direct biological measurements, which may lead to some misclassification. In cases where mothers reported fathers’ job histories, the accuracy of those reports may have varied. Additionally, some chemicals had too few exposures to draw firm conclusions.
“More research is needed to better understand how these exposures affect brain development,” McCanlies noted. “Although we had a fairly large number of families, the number was still too small to see links with less common exposures.”
Nonetheless, the use of validated diagnostic tools, a large sample, expert-reviewed exposure ratings, and multiple outcome measures adds weight to the findings. The researchers note that misclassification errors in this study would most likely bias results toward the null, meaning the observed associations may underrepresent the true effects.
“Next steps would include longitudinal studies investigating workplace environments and specific exposures that affect both mothers and fathers that may be associated with autism and its severity,” McCanlies explained. “Research aimed at understanding the biological mechanisms underlying the link between work exposures and autism and its severity will also be important to confirm plausibility of causation and for developing effective intervention and prevention methods.”
“This study is unique; there are few studies that have evaluated parent work exposures and autism severity and behaviors,” McCanlies added.
The study, “The effects of parental occupational exposures on autism spectrum disorder severity and skills in cognitive and adaptive domains in children with autism spectrum disorder,” was authored by Erin C. McCanlies, Ja Kook Gu, Claudia C. Ma, Wayne T. Sanderson, Yunin J. Ludeña-Rodriguez, and Irva Hertz-Picciotto.