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Fine-Particulate Matter Linked to Heart Diseases
Three new studies released last month by the California Air Resources Board (ARB) reveal that exposure to airborne fine-particulate rnatter 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.
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," said ARB Chairman Mary D. Nichols. "These new studies underscore the need to eliminate the threat from California's air."
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 - a human hair is about 60 microns in diameter.
"It is crucial that we better understand the health threat posed by fine particulates," said South Coast Air Quality Management District's Chairman William A. Burke. "This research will help us develop strategies for further reducing particulate pollution in Southern California and across the state."
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.
In another study, 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 over 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.
These two studies demonstrate a relationship between long-term PM2. exposure and cardiovascular effects, such as heart attacks and strokes.
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.
A breakdown by air basin is available in ARB's report estimating the premature death associated with PM2.5 exposure, which can be found on ARB 's website: http://www.arb.ca.gov/research/health/pm-mort/pm-report_2010.pdf.
This article appeared in the February 2011 issue of Indoor Environment Connections, a publication of the Indoor Air Quality Association. Reprinted by permission.
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