(NaturalNews) Exposure to air pollution in utero or during the first year of life may double a person's risk of developing autism, according to a study conducted by researchers from the University of Southern California (USC) and Children's Hospital Los Angeles.
"This work has broad potential public health implications," lead researcher Heather Volk said. "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 researchers estimated exposure to air pollution during each trimester of pregnancy and during the first year of life among 279 people with autism and 245 people without autism, all of whom were participants in the California-based Childhood Autism Risks from Genetics and the Environment (CHARGE) study. Exposure was calculated using addresses listed in residential histories and on the participants' birth certificates. The researchers then estimated regional air pollution levels using data from the Environmental Protection Agency's Air Quality System. The researchers then used air pollution data to calculate participants' exposure to three specific pollutants: nitrogen dioxide (NO2), particulate matter fewer than 10 microns in diameter (PM10), and particulate fewer than 2.5 microns in diameter (PM2.5).
In addition, the researchers used dispersion models to calculate how much air pollution the participants had likely been exposed to by local traffic. The study is the first to look at exposure not just to regional pollution, but also to that generated by local traffic. It follows a prior study by the same researchers that looked only at the correlation between autism risk and residence distance from 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," she 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."
All types of pollution are harmful
The researchers found that exposure to both local and regional air pollution - in any trimester of pregnancy or during the first year of life - significantly increased the risk of autism. Exposure to air pollution from local traffic more than doubled the risk of autism, while exposure to NO2, PM10 or PM2.5 from regional air pollution also increased the risk, even in the absence of local pollutants.
The finding that PM10 and PM2.5 both increased risk was particularly interesting, the researchers noted, because prior studies have established that the finer PM2.5 particles are more harmful to the body.
"From studies conducted in the lab, we know that we can breathe in tiny particles and they can produce inflammation," Volk said. "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."
The study was funded by the National Institute of Environmental Health Sciences and published in the Archives of General Psychiatry.