Washington: In a new study, scientists have found that children with autism spectrum disorder (ASD) were likelier to have been exposed to high level of certain air toxics while they were in their mothers' womb and in the first 2 years of life.
Evelyn Talbott, Dr.P.H., principal investigator of the analysis and professor of epidemiology at Pitt Public Health said that despite its serious social impact, the causes of autism were poorly understood. Very few studies of autism have included environmental exposures while taking into account other personal and behavioral risk factors. Their analysis was an addition to the small but growing body of research that considers air toxics as one of the risk factors for ASD.
Dr. Talbott and her colleagues performed a population-based study of families with and without ASD living in six southwestern Pennsylvania counties. The researchers found links between increased levels of chromium and styrene and childhood autism spectrum disorder, a condition that affects one in 68 children.
Dr. Talbott and her team interviewed 217 families of children with ASD and compared these findings with information from two separate sets of comparison families of children without ASD born during the same time period within the six-county area.
For each family, the team used the National Air Toxics Assessment (NATA) to estimate the exposure to 30 pollutants known to cause endocrine disruption or neurodevelopmental issues. NATA is the Environmental Protection Agency's (EPA) ongoing comprehensive evaluation of air toxics in the U.S., most recently conducted in 2005.
Based on the child's exposure to concentrations of air toxics during the mother's pregnancy and the first two years of life, the researchers noted that children who fell into higher exposure groups to styrene and chromium were at a 1.4- to two-fold greater risk of ASD, after accounting for the age of the mother, maternal cigarette smoking, race and education. Other NATA compounds associated with increased risk included cyanide, methylene chloride, methanol and arsenic. As these compounds often are found in combination with each other, further study is needed.
Styrene is used in the production of plastics and paints, but also is one of the products of combustion when burning gasoline in vehicles. Chromium is a heavy metal, and air pollution containing it typically is the result of industrial processes and the hardening of steel, but it also can come from power plants. Cyanide, methylene chloride, methanol and arsenic are all used in a number of industries or can be found in vehicle exhaust.
Dr. Talbott said that the results added to the growing body of evidence linking environmental exposures, such as air pollution, to ASD.
The research will be presented at the American Association for Aerosol Research annual meeting in Orlando, Fla.