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Air Pollution & Cancer

By Steven Reinberg

MONDAY, Aug. 18 (HealthDay News) — Recently discovered so-called free radicals that are attached to small particles of air pollution could cause lung damage and perhaps even lung cancer, researchers report.

If confirmed through further research, the finding could help to explain why nonsmokers develop tobacco-related diseases like lung cancer, said lead researcher H. Barry Dellinger, the Patrick F. Taylor Chair of environmental chemistry at Louisiana State University.

It has been known for years that free radicals exist in the atmosphere, and these atoms, molecules and fragments of molecules can damage cells. It had been thought that these particles, which can be produced by combustion, exist for less than a second and then disappear.

"What I found out is that combustion-generated particles contain environmentally persistent free radicals," said Dellinger. "When the radicals are associated with particles, they can apparently exist indefinitely."

These free radicals are remarkably similar to the free radicals found in cigarette tar, Dellinger said. "The implication is you can have the same environmentally related diseases by exposure to airborne fine particles that you can get from cigarettes," he said.

Dellinger noted, however, that one would have to smoke about 300 cigarettes a day to be exposed to the same level of environmental free radicals found in moderately polluted air.

The findings were to be presented Monday at the American Chemical Society annual meeting, in Philadelphia.

The persistent free radicals (PFRs) discovered by Dellinger's team attach themselves to small particles of air pollution as they leave smokestacks, car exhaust pipes and household chimneys, and continue to exist as free radicals. Particles of air pollution containing metals, such as copper and iron, are more likely to remain in the atmosphere and can carry these PFRs great distances, Dellinger said.

As PFRs are inhaled, they're absorbed by the lungs and other tissues and cause cell damage that can lead to problems such as asthma, emphysema and lung cancer. However, there's still no direct evidence linking PFRs to any of these diseases, he said.

Dr. Neil Schachter, a professor of pulmonary medicine at Mount Sinai Medical Center in New York City, thinks it's premature to blame persistent free radicals for the adverse effects of air pollution.

"These airborne free radicals are of interest, but I am not sure we are at a point where our scalpel is sharp enough to dissect the individual components of air pollution that cause problems for people," he said.

It's possible that persistent free radicals are responsible for the respiratory damage caused by pollution, Schachter acknowledged. "There are studies that show that modifying free radicals can alter the course of disease," he said. "But the implications of this — what it means to clinics, what it means to doctors, what it means to regulators — I think we are a long way from pulling that together."

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