Perinatal Exposure to Traffic-Related Air Pollution and Autism Spectrum Disorders

BACKGROUND: Studies from the United States indicate that exposure to air pollution in early life is associated with autism spectrum disorders (ASD) in children, but the evidence is not consistent with European data. OBJECTIVE: We aimed to investigate the association between exposure to air pollution from road traffic and the risk of ASD in children, with careful adjustment for socioeconomic and other confounders. METHOD: Children born and residing in Stockholm, Sweden, during 1993-2007 with an ASD diagnosis were identified through multiple health registers and classified as cases (n = 5,136). A randomly selected sample of 18,237 children from the same study base constituted controls. Levels of nitrogen oxides (NOx) and particulate matter with diameter <= 10 mu m (PM10) from road traffic were estimated at residential addresses during mother's pregnancy and the child's first year of life by dispersion models. Odds ratios (OR) and 95% confidence intervals (CI) for ASD with or without intellectual disability (ID) were estimated using logistic regression models after conditioning on municipality and calendar year of birth as well as adjustment for potential confounders. RESULT: Air pollution exposure during the prenatal period was not associated with ASD overall (OR = 1.00; 95% CI: 0.86, 1.15 per 10-mu g/m(3) increase in PM10 and OR = 1.02; 95% CI: 0.94, 1.10 per 20-mu g/m(3) increase in NOx during mother's pregnancy). Similar results were seen for exposure during the first year of life, and for ASD in combination with ID. An inverse association between air pollution exposure and ASD risk was observed among children of mothers who moved to a new residence during pregnancy. CONCLUSION: Early-life exposure to low levels of NOx and PM10 from road traffic does not appear to increase the risk of ASD.