• Autism is a heterogeneous disorder with genetic and environmental factors likely contributing to its origins. Examination of hazardous pollutants has suggested the importance of air toxics in the etiology of autism, yet little research has examined its association with local levels of air pollution using residence-specific exposure assignments. This study examines the relationship between traffic-related air pollution, air quality, and autism.
• This population-based case-control study includes data obtained from 279 children with autism and 245 control children with typical development who were enrolled in the Childhood Autism Risks from Genetics and the Environment study in California.
• The mother's address from the birth certificate and addresses reported from a residential history questionnaire were used to estimate exposure for each trimester of pregnancy and first year of life. Traffic-related air pollution was assigned to each location using a line-source air-quality dispersion model. Regional air pollutant measures were based on the Environmental Protection Agency's Air Quality System data. Logistic regression models compared estimated and measured pollutant levels for children with autism and for control children with typical development. The main outcome measures were crude and multivariable adjusted odds ratios (AORs) for autism.
• Children with autism were more likely to live at residences that had the highest quartile of exposure to traffic-related air pollution, during gestation and during the first year of life, compared with control children. All regional pollutant estimates were scaled to twice the standard deviation of the distribution for all pregnancy estimates.
• Exposure to traffic-related air pollution, nitrogen dioxide, PM2.5, and PM10 during pregnancy and during the first year of life was associated with autism. Further epidemiological and toxicological examinations of likely biological pathways will help determine whether these associations are causal.

Volk H.E., Lurmann, F., Penfold, B., Hertz-Picciotto, I., McConnell, R.  (2012). Traffic-Related Air Pollution, Particulate Matter, and Autism. Archives of General Psychiatry 1-7.