Long-term exposure to air pollution may lead to the development of atherosclerosis, a form of cardiovascular disease in which fatty deposits cause artery walls to thicken and harden, according to a study published today in the February issue of Environmental Health Perspectives. The study adds to the growing body of literature linking air pollution with cardiovascular disease and provides the first epidemiologic evidence linking atherosclerosis with exposure to fine particulate matter.
Researchers evaluated 798 healthy Los Angeles-area men and women over the age of 40 who showed some signs of increased risk of cardiovascular disease. They used data from 23 monitoring stations to estimate annual average concentrations of particulate matter in residential zip codes throughout the Los Angeles area. Beginning with data from 2000, researchers found concentrations of particulate matter ranging from 5.2 to 26.9 micrograms per cubic meter.
Overall, the more polluted the air to which subjects were exposed, the thicker the inner layers of their carotid artery, which transports blood to the head and neck. The most-exposed study participants experienced about 8% more artery thickening than the least-exposed participants, after accounting for such factors as diet, use of vitamin supplements and hormone-replacement drugs, physical activity, blood pressure, education, and income.
Women over the age of 60 experienced artery thickening at a rate almost four times higher than the overall population. In general, women were much more vulnerable than men, and nonsmokers and people taking drugs to reduce cholesterol also proved to be more vulnerable than average.
“From a biologic perspective, our results support the hypothesis that long-term exposure to ambient particulate matter contributes to systemic inflammatory pathways, which are a relevant aspect of atherogenesis,” the study authors write. “The findings indicate a biologically plausible link between the observed acute effects of ambient air pollution on systemic inflammation and the long-term consequences of sustained vascular inflammation leading to increased atherosclerosis and, ultimately, cardiovascular death.”
“We’ve known for some time that air pollution leads to lung damage, but this study also emphasizes the role air pollution plays on the arteries. Heart disease is a primary cause of death in the western world, so more research, perhaps focusing on those at highest risk, is important,” says Dr. Jim Burkhart, science editor for EHP.
The lead author of the study was Nino Künzli of the University of Southern California Keck School of Medicine. Other authors included M. Jerrett, W.J. Mack, B. Beckerman, L. LaBree, F. Gilliland, D. Thomas, J. Peters, and H.N. Hodis. The article is available free of charge at http://ehp.niehs.nih.gov/members/2004/7523/7523.html.
The study was supported in part by the National Institute on Aging, the National Institute of Environmental Health Sciences, the Wright Foundation, the Hastings Foundation, and the Health Effects Institute.