The evidence linking particulate air pollution to cardiovascular disease and deaths has strengthened in recent years and high levels of the pollutant should be considered a modifiable risk factor for cardiovascular disease along with such well-known factors as high blood pressure, high cholesterol, obesity and diabetes, the American Heart Assn. said Monday.
The very fine particles in the air, produced by fossil fuel combustion in industry, automobiles and power generation, among other sources, can trigger heart attacks and other problems in susceptible individuals within hours to days of exposure and can shorten lives by months to years, the statement said. In fact, health consequences to the cardiovascular system from air pollution are greater than those due to lung diseases, the statement concluded. Those who are most susceptible to its effects should take steps to minimize their exposure when pollution levels are high, such as reducing strenuous activities, avoiding commuting and staying indoors.
The association first addressed the link between air pollution and cardiovascular disease in 2004, concluding that exposure contributes to increased disease and mortality and that long-term exposure shortens lifetimes.
But "the body of evidence has grown and been strengthened substantially" since then, the statement said, and the links are now much clearer. Although all forms of air pollution are troublesome, the best evidence involves fine particulates -- those that are less than 2.5 micrometers in diameter. Such particulates can be inhaled deeply into the lungs, make their way into the bloodstream and trigger inflammation and other problems.
The increased risk is greatest among those who are susceptible to cardiovascular disease but who are not necessarily critically ill. That includes the elderly, people with preexisting cardiovascular disease and perhaps those with diabetes. Women and the obese may also be at higher risk. Short-term exposure can trigger heart attacks and similar acute problems, but long-term exposure can also produce disease and deaths. The effects on death are better documented, the committee that prepared the report concluded, because the effects of long-term exposure on disease have not been studied as thoroughly.
There does not appear to be any discernible safe threshold for exposure to such pollutants, but reductions in particulate levels can lower cardiovascular mortality in a time frame as short as a few years.
The best way for patients to protect themselves from the harmful effects of air pollution is to control their other risk factors, which will lessen their susceptibility. Physicians should also counsel patients about steps they can take to minimize their exposure during periods of high pollution. The best way is to stay indoors, especially in homes equipped with filters that will remove the particulates. If travel is necessary, keep car windows closed and set the heating/air conditioning system to recycle inside air rather than drawing in air from outside. Filters for cars are also available that will remove many of the particulates.
The statement was prepared by a multidisciplinary panel headed by Dr. Robert D. Brook of the University of Michigan. The panel considered all research on human health effects conducted in the last six years to reach its conclusions.
-- Thomas H. Maugh II
Heavy air pollution, such as in Mexico City last week, can not only trigger heart attacks but increase the long-term risk of cardiovascular disease and death. Credit: Sashenka Guierrez / EPA