Posted by Jim Parker on October 02, 2005 at 13:09:31:
Air Pollution Can Trigger Heart Attacks, Spur Heart Disease
Air pollutants aren't just a problem for the lungs. They turn out to be just as bad - if not worse - for the heart and circulatory system, explains the August issue of the Harvard Heart Letter.
In the blame game for heart disease, the major players are smoking, poor diet, lack of exercise, and genes. But some studies suggest that bad air also belongs on the team. Pollution researchers have coined the term "environmental cardiology" for studies linking poor air quality to heart attacks and strokes. In June 2004, the American Heart Association threw its weight behind the research by officially identifying air pollution as an important cardiovascular risk factor.
Much of this research has focused on particles small enough (equal to or less than 2.5 micrometers in diameter) to be drawn deeply into the lungs. The main source is combustion: gasoline in car and truck engines, coal or oil in power plants, and wood in fireplaces. Chemically, the particles (often referred to as fine particulate matter) consist mainly of sulfates, nitrates, acids, metals, and carbon with other chemicals stuck to their surfaces.
Starting about 10 years ago, epidemiologists at Harvard and elsewhere began to look beyond the lungs and investigate how air pollution might affect cardiovascular disease. Some initial findings were questioned. Now, though, there's not much doubt about the connection between the fine particles and cardiovascular disease. The association isn't nearly as strong as it is with cigarette smoking, which doubles a person's chances of dying from a cardiovascular disease. Still, it's sizable. A review of studies published last year in Circulation found that each 10-microgram-per-cubic-meter increase in particle pollution hikes cardiovascular disease risk by 8% to 18%. Put another way, breathing the air in a polluted city increases cardiovascular risk about half as much as living with a smoker.
The leading hypothesis is that fine particles stir up the systematic inflammatory processes that underlie atherosclerosis. The supporting evidence includes research in animals and people connecting fine particles to a witch's brew of inflammatory and atherosclerotic factors. A study published in the February 2005 issue of Environmental Health Perspectives linked particulate exposure to increased thickness of the walls of carotid arteries in the neck, which is often used as a measure of early atherosclerosis. Other research suggests that particulates could cause sudden constriction of blood vessels and an irregular heartbeat.
So, what can you do about it? Cut back of physical activity during high-pollution days, for one thing. The Environmental Protection Agency has a Web site, dubbed Air Now (www.epa.gov/airnow), that lists particulate and ozone levels throughout the country. High temperatures in the days ahead increase ground-level ozone, but the seasonality of particulate pollution depends on where you live. East of the Mississippi, levels are highest starting about now throughout September because sulfates are more readily formed from sulfur dioxide emissions from power plants in warm temperatures. In the western half of the country, levels are higher from October to December because much of the particulate pollution there is in the form of nitrates, which form as temperatures cool off.
July 2005, Harvard Health Letter