Long term exposure of postmenopausal women to fine particulates in polluted air may increase the risk of cardiovascular disease including heart attack and stroke, a new study suggests. The finding indicates that the fine particulate matter pollution may be more harmful than ever thought.

Researchers at the University of Washington in Seattle found that postmenopausal women exposed to fine particulate matter pollution PM 2.5 were at significantly higher risk of developing cardiovascular disease and dying of a cardiovascular event.

Particulate matter is comprised of a mixture of tiny particles of soot or dust carried in the air, which can come from power plants, coal burning and motor vehicle exhaust, especially diesel exhaust. The particles considered in the study are less than 2.5 microns in diameter — about 30 to 40 of them would equal the diameter of a human hair.

What is revealed in the study is not a cause-and-effect relationship, meaning that the particulate pollution may cause, but not definitely cause the increased risk of cardiovascular events in older women. The study results are scheduled to appear in the Feb 1 2007 issue of the New England Journal of Medicine

Earlier studies have found that particulate pollution causes a series of health problems including cardiovascular disease and deaths from the disease. For instance, Deminici F and colleagues reported in the March 2006 issue of Journal of American Medical Association that elderly people exposed to fine particle matter pollution PM2.5 for a short-term were at a higher risk for cardiovascular and respiratory disease.

The current study is believed to be the largest study of its kind and the first to examine the effects of fine particulate matter pollution on new cases of cardiovascular disease in healthy women. Also, the results were deemed to be more accurate than others as the study examined air pollution at different locations in the same city rather than between different cities.

Dr. Joel Kaufman, lead author of the study, a professor of environmental health and medicine at the UWS and colleagues followed 66,000 women ages 50 to 79 without prior diagnosed cardiovascular problems in 36 U.S. cities between 1994 and 1998.

The health data on the study subjects came from the Women’s Health Initiative Observational Study. During the period of follow-up, 1,816 women had at least one fatal or non-fatal cardiovascular event such as coronary heart disease, heart attack and stroke.

The data on air pollution at a particular location came from a pollution monitor closest to a participant’s ZIP code. The metropolitan areas considered in the study had a particulate matter pollution ranging from 4 to 20 micrograms per cubic meter.

The researchers then analyzed the association between the two sets of data to see if there is any correlation between exposure to air particles and increased risk of cardiovascular disease.

They found that after taking into account known risk factors such as blood pressure, cholesterol, and smoking, each increase of 10 mcg per cubic meter was associated with a 24 percent increased risk of a cardiovascular event among the study subjects and a 76 percent increased risk of death.

They also found exposure to higher levels of fine particulate matter was linked to a higher overall risk of cardiovascular disease events, including stroke and heart attack. And the risk of cardiovascular events varies with the particulate concentration at a particular location in a city.

The researchers cautioned that the results suggested a possibility that exposure to particulate matter increased risk of cardiovascular events in the women, but did not mean that such exposure would definitely be the cause of the increased risk.

In addition, the measurements of air pollution were not free of errors. The exact exposure of a woman to particulate matter pollution was unknown as the researchers did not know how long a woman would stay indoor or outdoor or nearly an industrial hotspot where fine particulate matter pollution is originated.

Researchers don’t know how fine particulate matter would affect cardiovascular disease. Some believe that the fine particulate matter may accelerate atherosclerosis, or hardening of the arteries. But a few other mechanisms have already been proposed to explain the possible effect of fine particulate matter pollution on cardiovascular health.

The U.S. Environmental Protection Agency has been taking regulatory action to control the fine particulates with diameter less than 10 microns, which is believed most damaging the heart and the lungs. The EPA on September 21, 2006 issued the strongest national air quality standards for particle pollution in the country’s history as evidence is steadily growing to indicate that fine particulate matter pollution is more harmful than thought.

“People with heart or lung diseases, children and older adults are the most likely to be affected by particle pollution exposure. However, even if you are healthy, you may experience temporary symptoms from exposure to elevated levels of particle pollution,” the EPA states on its website.

According to the American Heart Association, particulate matter pollution implicates heart disease and pulmonary conditions, killing 60,000 men and women each year in the U.S. – a prediction based on the combined long-term effect of studies in several large cities.

By Ben Wasserman – Courtesy of foodconsumer.org
Released: Jan 31, 2007