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Study Links Soot to Heart Disease

Low-Grade Inflammations
Trigger Defense Mechanisms
That Tend to Clog Arteries


WASHINGTON -- New research on the health effects of air pollution showed for the first time that tiny airborne soot particles such as those produced by power plants and diesel engines can be directly linked to certain types of heart disease.

The findings, part of the largest air-pollution study done to date, show how "low grade inflammation" caused by soot imbedded in the human lung triggers defense mechanisms that tend to clog arteries and lead to chest pain, irregular cardiac rhythms and heart attacks.

"This affects far more people than [who] die of lung cancer or even all other lung diseases," said C. Arden Pope III, an epidemiologist from Brigham Young University in Provo, Utah, and leader of a team of seven scientists who worked on the study, which was financed by the National Institute of Environmental Health.

The findings, according to Dr. Pope, "validate" regulatory efforts by the Clinton and Bush administrations to reduce fine particles of soot in the nation's air. But he added that they also raise doubts about a Bush administration regulatory change to prolong the operation of older, coal-fired power plants, called "New Source Review."

Dan Riedinger, a spokesman for the Edison Electric Institute, which represents most of the privately owned utilities in the U.S., asserted that "the most comprehensive research conducted in this area so far has found that power plants aren't the pollution source at issue here." He argued that cutting power-facility soot emissions further may not result in added health benefits. A spokesman for the American Trucking Association said it had no comment on the Pope study.

The Environmental Protection Agency says coal-fired power plants and diesel engines are the major producers of soot particles less than 2.5 microns in diameter. Similar in size to particles in cigarette smoke, fine soot can float on air currents for thousands of miles. Fine soot contains sulfates, carbon and nitrates and can include other contaminants, such as arsenic, cadmium, mercury and lead.

The Pope study, published Tuesday by Circulation, the journal of the American Heart Association, says the particles can cause inflammation of lung tissues. The inflammation, in turn, triggers a range of defense mechanisms including an increase in sticky blood platelets that can clog arteries leading to the heart.

Earlier scientific efforts had attributed the same problem to high levels of cholesterol in the blood, but inflammation from soot, Dr. Pope explained, "plays a bigger role than we ever understood before in terms of these fatty plaques."

Previous researchers also thought that soot contributed more to lung disease, rather than heart disease, which is a much bigger cause of premature deaths. The new study tracks the causes of death of more than 319,000 people in all 50 states and relates the findings to air-pollution levels in their communities. It uses a computer program to weigh the relative effects of other disease factors, such as smoking, body mass, diet and occupational exposures to pollutants.

"This is the clearest link yet between fine particle soot and the reason that tens of thousands of Americans are dying prematurely," said Frank O'Donnell, the head of Clean Air Trust. Earlier air-pollution regulations, according to the Pope study, have helped reduce the average load of fine soot in the air by as much as a third. However, Dr. Pope noted, "what is harder to know is when the air is clean enough."

In 1997, the Clinton White House proposed the first soot-emissions controls on power plants, rules scheduled to go into effect in 2005. Since then, both the Clinton and the Bush administrations have introduced regulations to reduce the soot emissions of diesel trucks and off-road construction equipment, moves that will phase in after 2007.

In other pollution-related action Monday, EPA said it is about to release final versions of two proposed regulations that would cut mercury emissions from power facilities and make deep cuts emissions of sulfur dioxide and nitrogen oxides in the Eastern U.S.

Sulfur dioxide and nitrogen oxides are major contributors to soot levels, which are carried from power plants and other sources in Southeast and Midwest to further complicate pollution problems in East Coast cities.

Write to John J. Fialka at




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