Exposure in womb to some chemicals found in cosmetics, personal care items linked to autistic traits in boys
Exposure in the womb to certain chemicals present in cosmetics and other common household or personal care products has been associated with autistic traits in boys, ages 3 and 4, but not in girls. The study, led by a University of Massachusetts Amherst environmental epidemiologist, refers to exposure to phthalates, a group of endocrine-disrupting chemicals.
These autistic traits are characterized by social behavior, repetitive behaviors, and restricted interests, but do not constitute an autism diagnosis, say experts.
The study, however, found a certain protective effect of folic acid supplements from phthalates. Fewer of these autistic traits were found among boys whose mothers had taken the recommended dose of supplementary folic acid during their first trimester of pregnancy, says the analysis published in the journal Environmental Health Perspectives.
"One of the most important findings is how adequate folic acid supplementation in pregnancy may offset the potential harmful effects of phthalates in regard to autistic traits,” says lead author Youssef Oulhote, assistant professor of Biostatistics and Epidemiology at UMass Amherst's School of Public Health and Health Sciences, in the analysis.
Oulhote adds that folic acid supplementation might also block the effects of other toxic chemicals, as already has been shown for pesticides and air pollutants.
What are these chemicals used for?
Phthalates are used in personal care products, certain plastics, food packaging, and medical devices. According to the US Centers for Disease Control and Prevention (CDC), phthalates are a group of chemicals used to make plastics more flexible and harder to break. They are often called plasticizers.
Some phthalates are used as solvents (dissolving agents) for other materials. They are used in hundreds of products, such as vinyl flooring, adhesives, detergents, lubricating oils, automotive plastics, plastic clothes (raincoats), and personal-care products (soaps, shampoos, hair sprays, and nail polishes), says the CDC.
“Phthalates are used widely in polyvinyl chloride plastics, which are used to make products such as plastic packaging film and sheets, garden hoses, inflatable toys, blood-storage containers, medical tubing, and some children’s toys,” adds the CDC.
The study
The research team in the US and Canada analyzed data from the Maternal-Infant Research on Environmental Chemicals (MIREC) prospective cohort study, which enrolled 2,001 women during their first trimester of pregnancy from 10 cities in Canada between 2008 and 2011.
The researchers measured 11 different phthalate metabolites in the pregnant women's urine samples taken during their first trimester and recorded the women's folic acid supplement intake.
“In a follow-up investigation, 601 3- and 4-year-old children of the women underwent neuropsychological assessments, including the Social Responsiveness Scale-II (SRS-2) as a measure of autistic traits and social impairment,” says the study.
It explains: “SRS-2 is a parent-reported questionnaire that has been found to be a valid and reliable method to assess autistic traits in the general population and clinical settings. It correlates well with the assessment tools that physicians use to diagnose autism spectrum disorder, although its validity in discriminating autism from other behavioral diagnoses deserves more attention.”
According to the researchers, an increase in urinary concentrations of phthalate chemicals was associated with increases in SRS scores —but only among children whose mothers did not take an adequate folic acid supplement, 400 mcg daily, during their first trimester.
Oulhote says that these are not the higher exposures for certain phthalates one would find in low-income communities. The reason: cosmetics and other personal care products free of phthalates tend to be the most expensive and not affordable for low-income communities. Most of the women in the study were white, employed, married or living with a partner, and well-educated.
While autism spectrum disorder has an underlying genetic basis, the study's findings strengthen the evidence that prenatal exposure to toxic chemicals contributes to the development of social impairment traits, say researchers. Autism spectrum disorder affects about four times more males than females. The study examined only one point in children's development.
“We do not know if these subtle effects associated with prenatal phthalate exposure will last after the preschool period,” says child development specialist and study co-author Gina Muckle, professor at Université Laval and Quebec-CHU Research Center in Quebec City, Canada, in the analysis.