Living close to highways has built-in health hazards. According to the Centers for Disease Control and Prevention, asthma and carbon monoxide poisoning are two major public health problems caused by air pollution. Now, autism could be added to the list.

Exposure to high levels of air pollution from traffic may raise the risk of autism, says Heather Volk, PhD, MPH, assistant professor of research at the University of Southern California Keck School of Medicine. USC researchers published a study in the Archives of General Psychiatry that found that children exposed to higher level of traffic-related pollutants during pregnancy or the first year of life were at increased risk of autism compared to children exposed to the lowest level. The risk of autism was two times higher during pregnancy and three times higher during the child's first year for the children close to highways compared to those living in areas with the lowest-level exposure.

The study looked at data from 279 children with autism and a comparison group of 245 children without it. Volk used the mothers' addresses to estimate exposure to air pollution during each trimester of pregnancy and during the child's first year of life. The researchers also used information from the Environmental Protection Agency and did traffic modeling to analyze how much air pollution was at each location. Exposure to particulate matter and nitrogen oxide were also factored in.

Autism may not be as easily diagnosed as other conditions, but there are a lot of parents out there learning how to have their child treated and cared for – about one in 88 children in the US have autism. As children get older, the problems can become more obvious in school, where they experience problems communicating and interacting socially.

It's only been about three years now that researchers have been looking at the potential role of air pollution in autism, Volk said. Air pollution has already been linked to other health issues, including babies being born small for their gestational age, she said. In 2011, Volk's research team reported a higher risk of autism for children living within about 1,000 feet of a freeway.

The EPA has made preventing public health hazards, along with environmental impact, one of its priorities in recent years while enacting air pollution and CO2 emissions regulations. The EPA says that enforcing the federal Clean Air Act is saving lives, preventing an estimated loss of 160,000 American lives per year in 2010 and potentially saving 230,000 in 2020.

The USC researcher acknowledges that it's too soon to claim a clear cause and effect relationship between air pollution and autism. Even if it gets dispelled, there is enough evidence to confirm that air pollution from vehicle emissions is harmful to health for humans and the planet.

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