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Last Edited: 4/22/2009

Autism Spectrum Disorders in Relation to Distribution of Hazardous Air Pollutants in the San Francisco Bay Area
Written: 09/01/06

OBJECTIVE: To explore possible associations between autism spectrum disorders (ASD) and environmental exposures, we linked the California autism surveillance system to estimated hazardous air pollutant (HAP) concentrations compiled by the U.S. Environmental Protection Agency. METHODS: Subjects included 284 children with ASD and 657 controls, born in 1994 in the San Francisco Bay area. We assigned exposure level by census tract of birth residence for 19 chemicals we identified as potential neurotoxicants, developmental toxicants, and/or endocrine disruptors from the 1996 HAPs database. Because concentrations of many of these were highly correlated, we combined the chemicals into mechanistic and structural groups, calculating summary index scores. We calculated ASD risk in the upper quartiles of these group scores or individual chemical concentrations compared with below the median, adjusting for demographic factors. RESULTS: The adjusted odds ratios (AORs) were elevated by 50% in the top quartile of chlorinated solvents and heavy metals [95% confidence intervals (CIs) , 1.1-2.1], but not for aromatic solvents. Adjusting for these three groups simultaneously led to decreased risks for the solvents and increased risk for metals (AORs for metals: fourth quartile = 1.7 ; 95% CI, 1.0-3.0 ; third quartile = 1.95 ; 95% CI, 1.2-3.1) . The individual compounds that contributed most to these associations included mercury, cadmium, nickel, trichloroethylene, and vinyl chloride. CONCLUSIONS: Our results suggest a potential association between autism and estimated metal concentrations, and possibly solvents, in ambient air around the birth residence, requiring confirmation and more refined exposure assessment in future studies.

Division of Environmental and Occupational Disease Control, California Department of Health Services (now known as California Department of Public Health), Richmond, California, USA.

Suggested Citation

  • Publication Types: Comparative Study MeSH Terms: Air Pollutants/toxicity* Autistic Disorder/etiology* Autistic Disorder/pathology Child Continental Population Groups/statistics & numerical data Demography Endocrine Disruptors/toxicity* Environmental Exposure/adverse effects* Female Humans Hydrocarbons, Aromatic/toxicity* Male Maternal Exposure/adverse effects Metals, Heavy/toxicity Neurotoxins/toxicity* Pregnancy Risk Factors Solvents/toxicity Urban Health/statistics & numerical data Substances: Air Pollutants Endocrine Disruptors Hydrocarbons, Aromatic Metals, Heavy Neurotoxins Solvents