Evidence is accumulating for potential contributions to ASD risk from preconception or prenatal maternal nutrition, lifestyle, infection, medications, and exposures to environmental chemicals. No single or universal cause is likely; rather, multiple genetic variants and noninherited factors appear to combine to affect each child's development. Key concepts for future research include specificity to ASD versus causes common to other neurodevelopmental conditions, gene‐by‐environment interactions, and critical windows of vulnerability that may vary by exposure.
Background: Emerging evidence points to a possible association between perinatal exposure to hazardous air pollutants and autism.Objective: To examine the association between perinatal exposure to air pollution and risk of autism spectrum disorder by child sex in a large national cohort.
Methods:We used logistic regression to estimate odds ratios and 95% confidence intervals for the association between U.S. Environmental Protection Agency modeled levels of hazardous air pollutants at the time and place of birth and risk of autism in the children of a large prospective longitudinal cohort: the Nurses' Health Study II (cases=325; controls=22,120). Our analyses focused on pollutants associated with autism in prior research. We adjusted for possible ascertainment bias by both familylevel socioeconomic status (e.g., income, partner's education, maternal grandparents' education) and census-tract-level socioeconomic measures (e.g., tract median income and percent college educated). We also examined possible differences in the relationship between autism and pollutant exposure by child's sex.Results: Perinatal exposure to higher levels of diesel, lead, mercury, nickel, methylene chloride, and a combined measure of metals were linearly related to increased risk of autism in boys only (p<.05 for each). Odds ratios for autism in boys in the highest versus lowest quintile of exposure to these pollutants ranged from 1.74 (for combined metals measure) to 2.59 (for diesel).
Conclusions:Gestational exposure to air pollution may increase risk for autism in males. There may be sex-specific biological pathways connecting perinatal exposure to pollutants with autism.
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