Autism spectrum disorders in relation to distribution of hazardous air pollutants in the san francisco bay area.
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.
Windham
Gayle C
GC
Division of Environmental and Occupational Disease Control, California Department of Health Services, Richmond, California, USA. gwindham@dhs.ca.gov
Zhang
Lixia
L
Gunier
Robert
R
Croen
Lisa A
LA
Grether
Judith K
JK
D000393:Air Pollutants / Q000633:toxicity*; D001321:Autistic Disorder / Q000209:etiology* / Q000473:pathology; D002648:Child; D003710:Demography; D052244:Endocrine Disruptors / Q000633:toxicity*; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D006841:Hydrocarbons, Aromatic / Q000633:toxicity*; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects; D019216:Metals, Heavy / Q000633:toxicity; D009498:Neurotoxins / Q000633:toxicity*; D011247:Pregnancy; D044469:Racial Groups / Q000706:statistics & numerical data; D012307:Risk Factors; D012997:Solvents / Q000633:toxicity; D014504:Urban Health / Q000706:statistics & numerical data
D000393:Air Pollutants; D052244:Endocrine Disruptors; D006841:Hydrocarbons, Aromatic; D019216:Metals, Heavy; D009498:Neurotoxins; D012997:Solvents