California ARB releases three studies showing fine particle pollution a threat to cardiovascular health
|ARB regulates two size classes of particles: up to 10 microns (PM10) and up to 2.5 microns in size (PM2.5). PM2.5 particles are a subset of PM10. Source: ARB. Click to enlarge.|
Three new studies released by the California Air Resources Board (ARB) show that exposure to airborne fine-particulate matter significantly elevates the risk for premature deaths from heart disease in older adults and elevates incidence of strokes among post-menopausal women. Heart disease is the number one killer in California and is responsible for approximately 35% of annual deaths.
Particulate matter is a complex blend of substances ranging from dry solid fragments, solid-core fragments with liquid coatings, and small droplets of liquid. These particles vary in shape, size and chemical composition, and can contain metals, soot, nitrates, sulfates and very fine dust. One source of particulate matter, including PM2.5 or fine-particulate matter, is exhaust from vehicles, especially from diesel engines. PM2.5 is particulate matter smaller than 2.5 microns in diameter.
The California Air Resources Board commissioned the studies to further investigate the connection between fine particulate pollution and public health impacts in California. The two population studies were co-sponsored by the South Coast Air Quality Management District.
We’ve long known particulate matter is a major component of California’s air pollution problem. These new studies underscore the need to eliminate the threat from California’s air.—ARB Chairman Mary D. Nichols
ARB’s proposed Advanced Clean Cars rules package would further crack down on particulate matter emissions from light-duty vehicles. (Earlier post.)
It is crucial that we better understand the health threat posed by fine particulates. This research will help us develop strategies for further reducing particulate pollution in Southern California and across the state.—South Coast Air Quality Management District’s Chairman William A. Burke, Ed.D.
Two of the studies demonstrate a relationship between long-term PM2.5 exposure and cardiovascular effects, such as heart attacks and strokes.
Michael Jerrett, Ph.D., of the University of California, Berkeley, found that exposure to fine particulate matter significantly elevated the risks for premature death from heart disease. The most frequent cause of death associated with PM2.5 in this study was ischemic heart disease, which can lead to heart attacks and heart failure. The findings of this study are based on the California participants in a large study sponsored by the American Cancer Society, which tracked 76,000 adults from 1982 to 2000.
Michael Lipsett, M.D., of the California Department of Public Health, led a team that examined the effects of chronic air pollution exposure on heart disease in women. The project tracked more than 100,000 current and former female public school teachers and administrators in California. Like the University of California, Berkeley study, Dr. Lipsett found that exposure to PM2.5 elevated the risks for premature mortality from ischemic heart disease. In addition, this study found an increased risk of stroke among women who had never had one before, particularly among those who were post-menopausal.
The third study, by Fern Tablin, V.M.D., Ph.D., and Dennis Wilson, D.V.M., Ph.D., of the University of California, Davis, investigated how inhaled PM2.5 could contribute to heart attacks and strokes. A common cause of heart attacks and strokes is development of clots in the blood stream. One suggested explanation is that PM2.5 exposure activates platelets, the key cells involved in blood clotting, so that they form clots and then trigger heart attacks and strokes.
Drs. Tablin and Wilson examined the platelets of mice exposed to PM2.5 from the San Joaquin Valley Air Basin, and found that mice exposed to fine particulate matter showed platelet activation in both winter and summer, which could promote clotting and lead to stroke and heart attacks.
These new studies add to the existing scientific literature indicating that microscopic airborne particles pose a threat to public health. California Air Resources Board calculations of combined cardiovascular and respiratory (i.e., cardiopulmonary) deaths associated with PM2.5 exposure are based on the results of the national American Cancer Society study. Annually, 7,300 to 11,000 premature cardiopulmonary deaths in California are estimated to be associated with exposures to fine particulate matter.
Michael Jerrett, Ph.D. (2011) Spatiotemporal analysis of air pollution and mortality in California based on the American Cancer Society cohort
Michael Lipsett, M.D. (2011) Extended analyses of air pollution and cardiovascular disease in the California Teachers Study cohort
Tablin, Fern (2011) Systemic platelet activation in mice exposed to fine particulate matter