Association of Heat, Cold, and Ambient Pollution in the First 1000 Days of Life with Autism Spectrum Disorder Risk Indicators in Two-Year-Olds. Findings from the ELFE National Birth Cohort

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Early life is a vulnerable period to environmental exposures that may be associated with autism spectrum disorder (ASD). We investigated associations between prenatal and postnatal exposure to weekly averages of temperature and air pollutants (PM2.5, PM10, NO2) with autism screening scores (based on the Modified Checklist for Autism in Toddlers, Revised version) in 12,139 2-year-olds from the French ELFE birth cohort. Exposures were based on daily outdoor predictions at 1 km resolution (200 m in large urban areas for temperature and NO2). Relationships were modeled with confounder-adjusted distributed lag nonlinear models and generalized linear models. Autism screening scores significantly increased following exposure to night-time heat throughout the beginning of the third trimester and possibly toward the end of pregnancy, even after adjusting for PM2.5 and PM10. During the postnatal period, night-time heat (months 2–7.5) and increased PM2.5 and PM10 exposures (months 7–11.5) led to higher scores in males compared to females. Conversely, night-time heat (months 17–20) led to higher scores in females. Our findings suggest that prenatal exposure to heat, but not air pollution, may be associated with early ASD risk indicators, while sex-specific effects of heat and PM exposure were observed in the postnatal period.