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.
The research team, led by Dr. Evelyn Talbott, professor of epidemiology of the University of Pittsburgh Graduate School of Public Health, PA, recently presented their findings at the American Association for Aerosol Research annual meeting in Orlando, FL.
Prevalence of autism spectrum disorder (ASD) is on the rise in the US. In 2000, 1 in 150 children had the disorder, while current rates stand at 1 in 68. Although more and more children are being diagnosed with autism, the exact causes of the condition are unclear.
Some studies, however, have indicated that early exposure to environmental factors may contribute to its development. Earlier this year, for example, Medical News Today reported on a study claiming mothers exposed to pesticides during pregnancy are more likely to have children with autism.
Speaking of this latest study, Dr. Talbott says: "Our analysis is an addition to the small but growing body of research that considers air toxics as one of the risk factors for ASD."
Children exposed to styrene and chromium 'up to twice as likely to develop autism'
To reach their findings, the research team interviewed 217 families of children with autism. The children were born between 2005 and 2009, and the families resided in six counties in Pennsylvania: Allegheny, Armstrong, Beaver, Butler, Washington and Westmoreland.
- More than 3.5 million Americans are living with autism
- Between 2002 and 2010, autism prevalence increased by 6-15% every year
- In 10 years, the annual cost of autism in the US is estimated to be $200-400 billion.
The researchers estimated each family's exposure to 30 air pollutants known to cause neurodevelopment problems or endocrine disruption, using the National Air Toxics Assessment - an ongoing assessment of air toxics in the US conducted by the Environmental Protection Agency.
For comparison, the team also interviewed and estimated the air pollutant exposure of two sets of families of children without autism who resided in the same areas. The children were also born during the same period.
Dr. Talbott says having two control groups is a strength of this study, as it "provided a comparison of representative air toxics in neighborhoods of those children with and without ASD."
Results of the study revealed that children who were highly exposed to two specific air pollutants - styrene and chromium - during their mother's pregnancy or up to the age of 2 years were up to twice as likely to have autism, compared with children who were not exposed to these pollutants.
Styrene is a compound often used in plastics and paints, and it is also produced by burning gasoline. Chromium is a heavy metal produced by steel hardening and other industrial processes, as well as power plants.
Other air pollutants - including cyanide, methylene chloride, methanol and arsenic - were also linked to increased autism risk in children.
The team's findings remained after accounting for mothers' age, race, education and smoking during pregnancy. "Very few studies of autism have included environmental exposures while taking into account other personal and behavioral risk factors," notes Dr. Talbott.
She adds that these results "add to the growing body of evidence linking environmental exposures, such as air pollution, to ASD."
Grant Oliphant, president of The Heinz Endowments - a Pennsylvania-based organization that funded the research - says:
"This study brings us a step closer toward understanding why autism affects so many families in the Pittsburgh region and nationwide, and reinforces in sobering detail that air quality matters.
Our aspirations for truly becoming the most livable city cannot be realized if our children's health is threatened by dangerous levels of air toxics. Addressing this issue must remain one of our region's top priorities."
MNT recently reported on a study published in the Proceedings of the National Academy of Sciences (PNAS) suggesting that a chemical found in broccoli - sulforaphane - could help treat symptoms of autism.