Researchers from Spain, Switzerland, and the U.S. used ultrasound to measure the carotid artery wall thickness of 1,483 people living near freeways in the Los Angeles area. They took measurements once every six months for three years and correlated the numbers with estimates of outdoor particulate levels at each participant's home.
The artery wall thickness among those living within 100 meters (328 feet) of a highway increased by 5.5 micrometers (roughly 1/20th the thickness of a human hair) each year during the three-year study, which is more than twice the progression observed in participants who did not live within this distance of a highway.
The authors of the study report:
Atherosclerosis--or the stiffening and calcification of arteries--is the underlying cause of most cardiovascular disease and related deaths, which are the number one killer in the Western world. A few animal studies conducted in recent years have observed that the inhalation of ambient particulate matter from traffic and other sources accelerates atherosclerosis in rabbits, rats and mice.... So far, no study has ever investigated whether the slow but chronic process of the development of atherosclerosis would be affected by ambient air pollutants.
Study co-author Michael Jerrett, a University of California at Berkeley associate professor of environmental health sciences, says the team's findings could have extremely broad public health implications worldwide:
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 and to a growing proportion of deaths in the rapidly industrializing nations of Asia and Latin America. The implications are that by controlling air pollution from traffic, we may see much larger benefits to public health than we thought previously.
Jerrett co-authored the report with Nino Künzli, vice director of the Swiss Tropical and Public Health Institute in Basel, and Howard Hodis, director of the Atherosclerosis Research Unit at the Keck School of Medicine at the University of Southern California.