Thursday, 26 January 2017

Autism Spectrum Disorders

Autism Spectrum Disorders in Relation to Distribution of Hazardous Air
Pollutants in the some areas.

1Division of Environmental and Occupational Disease Control, California
Department of Health Services, Richmond, California, USA; 2Impact
Assessment, Inc., La Jolla, California, USA; 3Kaiser Permanente Medical
Care Program Division of Research, Oakland, California, USA

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

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 quarter 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