Narrator:       This is Science Today. About 30 to 35 percent of our nation's urban population live about 325 feet from a major road or a freeway. According to a study co-led by the University of California, Berkeley, auto exhaust is linked to thickening of arteries, or atherosclerosis. Co-author Micahel Jerrett, an associate professor of Environmental Health Sciences at the School of Public Health, says this can increase chances of a heart attack and stroke.

Jerrett:           This study takes it a step further by looking at whether there are progression so their artery thickening over time is actually associated with air pollution. And we do find evidence that there is a significant association, particularly for people living about 325 feet of a major highway and 150 feet from a major road. We're dealing with a large population that's impacted and it's certainly significant because when we look at Western societies, heart disease is still the biggest killer.

Narrator:       For Science Today, I'm Larissa Branin.