Women exposed to workplace chemicals are more likely to have an autistic child, shows new study
The analysis shows that the three most common occupational exposures in mothers of both children with autism spectrum disorders and children with typical neurodevelopment were disinfectants/cleaners, solvents, and ethylene oxide
Children whose mothers are exposed to solvents at work are at higher risk of autism, shows new research. The study found that women who are exposed to workplace solvents are 1.5 times more likely to have a child on the autistic spectrum. Solvents can be absorbed through the skin and lungs, and many remain in the body, including in the brain, says the research team, adding that their results are consistent with earlier reports that have identified solvents as a potential risk factor for Autism Spectrum Disorders (ASD).
ASD is a neurodevelopmental disorder, which is both costly and leads to lifelong disability. It is a range of conditions with characteristics including repetitive behaviors, impairment in reciprocal social interaction, and difficulty communicating. According to the World Health Organization's (WHO) estimates, globally, 1 in 160 children has an ASD.
Recent prevalence estimates in the US indicate that about one in 68 children have ASD, and numerous studies have shown that the incidence has been steadily increasing. In its biennial update of autism's estimated prevalence among children in the US, released in 2018, the Centers for Disease Control and Prevention (CDC) said the new estimate represents a 15% increase in prevalence nationally: to 1 in 59 children, from 1 in 68 two years previous.
In the current study, the researchers say that the speed with which the number of new cases has increased suggests that factors other than genes may be involved. Several scientists have earlier suggested a link between prenatal exposure to environmental chemicals and pollutants. The researchers say since workplace exposures are often higher than environmental ones, they wanted to examine if they might be linked to the development of autism.
The research team drew on data collected for the CHildhood Autism Risks from Genetics and Environment (CHARGE) study. These included personal, health, and job history information for the parents of 537 children formally diagnosed with autism spectrum disorders and 414 children with typical neurodevelopment (TD). "Mothers were interviewed about their job histories and when possible, or if directed by the mother, the father was interviewed about his job history. Approximately 37% of the fathers responded. Otherwise, the mothers reported the fathers' job history. Occupational information included, for each job, the place of employment, the months and years of employment, which month(s) of pregnancy (or the postnatal period) the job was held, and the total hours worked per week. Information about what the company made or did, the parents' job title and their duties/responsibilities were also collected," say the researchers in their findings.
The analysis shows that the three most common occupational exposures in mothers of both children with ASD and children with TD were disinfectants/cleaners, solvents, and ethylene oxide. The least common maternal occupational exposures were perchlorates, asphalt, polychlorinated biphenyls (PCBs), and cutting/machining fluids.
Among fathers of children with ASD and TD, the three most common exposures were disinfectants/cleaners, solvents, and metals. The three least common exposures among fathers for children with both ASD and TD were perchlorates, asphalt, and PCBs.
Similarly, the three most common exposures when combining mothers' and fathers' data were disinfectants/ cleaners, solvents, and metals. The least common exposures were perchlorates, PCBs, and asphalt.
"This study indicates that maternal occupational exposure to solvents may be associated with higher rates of ASD in their children. Mothers with autistic children had been more frequently exposed to solvents than those whose children weren't on the spectrum. They were 1.5 times more likely to have a child on the autistic spectrum. And moderate intensity cumulative exposure to solvents was associated with a near doubling in risk. None of the other agents was associated with heightened risk in either parent or when the exposures of both parents were combined," state the findings.
Two experienced industrial hygienists conducted the workplace exposure assessment for the parents of 951 children. For each job, frequency and intensity of 16 agents — which have been linked to neurological and/or congenital abnormalities from three months before pregnancy through to the birth of the child — were analyzed. These included medicines, metals, pesticides, anesthetics, asphalt, brake fluid, plastics, and polymers, radiation, cleaners/disinfectants, and solvents to include paints and degreasers as well as other chemicals.
Exposure levels were classified as none; rare (a few times a year); moderate (weekly), and frequent (several times a week/daily). The intensity was categorized as low, moderate or high, the last of which was taken to mean well above background levels.
"Future research should consider maternal occupational exposures to solvents as a potential risk factor in the etiology of ASD and focus on identifying specific solvents rather than broad categories of solvents. Larger studies or different types of study designs may help to identify other risk factors in the etiology of ASD and further clarify the role solvents may have in the risk of ASD," the study recommends.
The research was published on June 27 in the journal Occupational & Environmental Medicine.