12 December 2010

Three new studies released by the California Air Resources Board (ARB) found that exposure to airborne fine particulate matter elevates the risk for premature deaths from heart disease in older adults and elevates incidence of strokes among post-menopausal women. The ARB commissioned the studies to further investigate the connection between fine particulate pollution and public health impacts in California.

“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 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.

Michael Jerrett 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 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 PM2.5 exposure and cardiovascular effects. The third study, by Fern Tablin and Dennis Wilson 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.

Source: California ARB