Air Pollution and Atherosclerosis: Epidemiologic Studies
A large and growing body of epidemiologic studies has demonstrated increased cardiovascular morbidity and mortality associated with increased air pollution levels, but the pathogenesis of air pollution-related deaths remains uncertain. Although both acute elevations in particulate matter air pollution (PM) and increased long-term average PM or traffic-related pollutants more generally have been associated with overall cardiovascular mortality and events such as myocardial infarction and sudden cardiac death, it is not known whether pollutants only acutely trigger cardiovascular events or they also induce slow progression of atherosclerotic disease burden. Toxicologic studies show that inhalation of fine particles accelerates atherosclerosis in animals, but the human epidemiologic studies characterizing the role of PM in atherosclerosis have only begun to examine this hypothesis in detail. Most human epidemiologic studies have focused on outcomes (such as mortality and acute myocardial infarction) that do not distinguish the extent of atherosclerotic burden in exposed individuals, and therefore cannot assess whether long-term air pollution exposure is associated with an increase in atherosclerotic disease burden or simply triggering of acute cardiovascular events. To date, few epidemiologic studies have directly addressed the relationship between air pollution and atherosclerotic disease; however, there is growing epidemiologic evidence that chronic air pollution exposures lead to acceleration or initiation of the atherogenesis.