Some new studies have added evidence in support of a growing belief in a link between exposure to air pollution and the development of autism, researchers say.
One study by researchers from the University of Pittsburgh Graduate School of Public Health examining associations between autism and air pollution in southwestern Pennsylvania suggests children suffering from autism spectrum disorder were more likely to have been exposed to high levels of air pollutants during their mothers' pregnancies and during the first two years of their life compared to children who do not display ASD.
"Very few studies of autism have included environmental exposures while taking into account other personal and behavioral risk factors," principle investigator Evelyn Talbonn 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."
In a study of families with and without children diagnosed with ASD in six Pennsylvania counties, the researchers reported finding associations linking increased levels of two pollutants, styrene and chromium, with the development of childhood autism spectrum disorder.
Chromium is a heavy metal that can become an air pollutant as the result of industrial processes, while styrene is used in the production of paints and plastics but is also a byproduct of gasoline combustion in vehicles.
Such traffic-related air pollution is a particular concern, say researchers from the University of Wisconsin-Milwaukee who conducted their own study of links between air pollution and autism in North Carolina.
"The evidence is suggesting that some component of vehicle emissions may be associated with autism spectrum disorders," says study first author Amy Kalkbrenner.
While the study is not definite proof of a link between air pollutants and development of autistic disorders, she noted, it adds to a growing body of evidence pointing to that possibility.
Some previous studies in California yielded similar evidence, even though California and North Carolina have different weather patterns and climates, researchers say.
"There is now a wealth of studies showing that systemic inflammation in the body may be responsible for the early brain damage that results in autism," Kalkbrenner says. "We also know that exposure to air pollution can cause this body-wide inflammatory response. This could very well change the way the brain is developing."
She notes that an estimated 80,000 man-made chemicals are found in the environment and have been detected in drinking water, the air we breathe and the food we eat.
"There are no requirements that these chemicals be tested for neurodevelopmental toxicity before they're put on the market," she says.
"There is a great deal that we don't know. Not to increase fear, but there are sound reasons to be concerned about some of these chemicals."
