Los Angeles residents living near freeways experience a hardening of the arteries that leads to heart disease and strokes at twice the rate of those who live farther away, a study has found.
The paper is the first to link automobile and truck exhaust to the progression of atherosclerosis -- the thickening of artery walls -- in humans. The study was conducted by researchers from USC and UC Berkeley, along with colleagues in Spain and Switzerland, and published this week in the journal PloS ONE.
Researchers used ultrasound to measure the carotid artery wall thickness of 1,483 people who lived within 100 meters, or 328 feet, of Los Angeles freeways. Taking measurements every six months for three years, they correlated their findings with levels of outdoor particulates -- the toxic dust that spews from tailpipes -- at the residents' homes.
They found that artery wall thickness in study participants accelerated annually by 5.5 micrometers -- one-twentieth the thickness of a human hair -- more than twice the average progression.
According to co-author Howard N. Hodis, director of the Atherosclerosis Research Unit at USC's Keck School of Medicine, the findings show that "environmental factors may play a larger role in the risk for cardiovascular disease than previously suspected."
UC Berkeley co-author Michael Jerrett noted that "for the first time, we have shown that air pollution contributes to the early formation of heart disease, known as atherosclerosis, which is connected to nearly half the deaths in Western societies. . . . By controlling air pollution from traffic, we may see much larger benefits to public health than we previously thought."
The study comes at a time of growing alarm over the effects of freeway pollution on nearby schools and homes. In the four-county Los Angeles Basin, 1.5 million people live within 300 meters, or 984 feet, of major freeways.
The Natural Resources Defense Council is battling in federal court to overturn the caps on motor-vehicle emissions set by Southern California air quality officials, saying that they fail to account for higher pollution near freeways.
And Los Angeles and Long Beach residents are fighting expansion of the truck-clogged 710 Freeway, saying it will lead to higher rates of asthma, heart disease and cancer in densely populated areas.
In July, the U.S. Environmental Protection Agency launched a major study of traffic pollution near Detroit roadways to examine whether it leads to severe asthma attacks in children.
More than a third of Californians report that they or a family member suffer from asthma or respiratory problems, according to a survey last year. The Obama administration is proposing tighter standards for two vehicle-related pollutants: nitrogen dioxide (NO2) and ground-level ozone, the chief component of smog.