Early exposure to air toxics linked to childhood autism risk

Association of National Air Toxics Assessment Exposures and the Risk of Childhood Autism Spectrum Disorder

Researchers found that children highly exposed to two specific air pollutants - styrene and chromium - during their mother's pregnancy or up to the age of 2 years were more likely to have autism.
Pitt Public Health researchers found that children highly exposed to two specific air pollutants – styrene and chromium – during their mother’s pregnancy or up to the age of 2 years were more likely to have autism.

Children with autism spectrum disorder (ASD) were more likely to have been exposed to higher levels of certain air toxics during their mothers’ pregnancies and the first two years of life compared to children without the condition, according to the preliminary findings of a University of Pittsburgh Graduate School of Public Health investigation of children in southwestern Pennsylvania.

Abstract

Background:
Autism spectrum disorders (ASD) constitute a major public health problem, affecting one in every 68 children. There is little understanding of the cause of ASD despite its serious social impact. Air pollution contains many toxicants known to have adverse effects on the developing fetus.

Methods:
We conducted a population-based case control study in six southwestern PA counties estimating the association between ASD and USEPA census tract modeled NATA levels for 30 neurotoxicants. Cases were recruited from local ASD treatment centers. There were two different control groups:

  1. Interviewed controls with complete residential histories from pre-pregnancy through age two recruited through mailings using the Pennsylvania Department of Health birth registry (2005-2009).
  2. 5,007 non-interviewed controls from a random sample of the birth records using residence at birth.

Logistic regression analysis was conducted using quartiles of exposure, adjusting for age of mother, smoking, race, and education.

Results:
There were a total of 217 cases.

  • For the first group of 224 controls, median levels of chromium, styrene, cyanide, and polycyclic aromatic hydrocarbons were higher in cases compared to controls (p<.05). Women in the highest quartile of exposure to styrene had an odds ratio of 1.78 (95% CI: 1.035-3.068) of having a child with ASD compared to the lowest quartile, after adjustment for covariates.
  • In the second control group, each increase of interquartile range exposure to cyanide resulted in a 16% higher odds (95%CI; 1.04-3.46) of ASD in the adjusted logistic model. Additionally, women with the highest quartile of exposure to chromium had 1.65 (95%CI; 1.10-2.47) times the odds of having a child with ASD compared to the women in the lowest quartile of chromium exposure.

Conclusions:
Chromium, cyanide and styrene exhibited elevated odds ratios using two different control groups. These findings need to be verified with exposure assessment at the individual level.

Sources and more information:
  • The Association of National Air Toxics Assessment Exposures and the Risk of Childhood Autism Spectrum Disorder: A Case Control Study, American Association for Aerosol Research, October 20, 2014.
  • Pitt Public Health Finds Association Between Air Toxics and Childhood Autism, UPMC/University of Pittsburgh Schools of the Health Sciences, Oct. 22, 2014.
  • Early exposure to air pollutants linked to autism risk, medicalnewstoday, Oct. 23, 2014.
  • Association between air toxics and childhood autism, eurekalert, Oct. 22, 2014.