November 27, 2012
Study Finds Link Between Autism And Pollution
Lee Rannals for redOrbit.com — Your Universe Online
The study shows that exposure to traffic-related air pollution during pregnancy and the first year of life is associated with more than a two-fold risk of autism.
The team from the University of Southern California and Children's Hospital Los Angeles also found that exposure to regional pollution consisting of nitrogen dioxide (NO2) and small particles is also associated with autism, even if the mother did not live near a busy road.
"This work has broad potential public health implications," the study's principal investigator, Heather Volk, Ph.D., said in a statement. "We've known for a long time that air pollution is bad for our lungs, and especially for children. We're now beginning to understand how air pollution may affect the brain."
The study builds on previous research by the team that examined how close subjects lived to a freeway.
"We took into account how far away people lived from roads, meteorology such as which way the wind was blowing, how busy the road was, and other factors to study traffic-related pollution," Volk said. "We also examined data from air quality monitors, which measure pollution over a larger region that could come from traffic, industry, rail yards, or many other sources."
In the latest study, the team examined data on 279 autism cases and 245 control subjects enrolled in the California-based Childhood Autism Risks from Genetics and the Environment (CHARGE) study.
The team took into consideration the mothers' addresses from birth certificates and addresses reported from a residential history to estimate exposure during each trimester of pregnancy and the first year of life.
The researchers used air pollution levels derived from the Environmental Protection Agency's (EPA) Air Quality System to determine exposure to NO2, PM2.5, and PM10. They also applied dispersion models to figure out the amount of traffic the mothers and children were exposed to.
They said that exposures to traffic-related air pollution, PM and nitrogen dioxide were associated with an increased risk of autism.
"These effects were observed using measures of air pollution with variation on both local and regional levels, suggesting the need for further study to understand both individual pollutant contributions and the effects of pollutant mixtures on disease," the authors wrote in the journal.
Volk said that with studies conducted in the lab, the team was able to determine that breathing tiny particles can produce inflammation.
"Particles have varied composition, and there are many chemicals that can bind to them. The components of these particles could be hazardous to the brain," Volk wrote in the statement.
The authors said that research on the effects of exposure to pollutants and their interaction with susceptibility factors may lead to the identification of the biologic pathways that are activated in the autistic and to improve prevention and therapeutic strategies.
"Although additional research to replicate these findings is needed, the public health implications of these findings are large because air pollution exposure is common and may have lasting neurological effects," the authors conclude in the journal.
Geraldine Dawson, Ph.D., of the University of North Carolina at Chapel Hill, wrote in an editorial that the study points to an urgent need for more research on prenatal and early postnatal brain development in autism, with a focus on how genes and environmental risk factors combine to increase the risk for autism.
"Despite a substantial increase in autism research publications and funding during the past decade, we have not yet fully described the causes of ASD or developed effective medical treatments for it," Dawson wrote in an editorial in the journal.
He said that more research is needed in order to develop strategies to prevent or reduce the disabling symptoms associated with the neuro-developmental disorder.