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We car-driving members of America's industrial society often forget one price we pay for modernity: breathing particulate matter (PM) from dirty air deep into our lungs. Anyone needing a reminder should drop by the pathology lab at Drexel University's College of Medicine in Philadelphia and cough up a sputum specimen for Herbert Patrick, MD.
"We say, 'Give us a good cough, and we'll tell you if you were in a dirty area today,'" Patrick said. "No one else we know of checks patients' individual sputum for signs of air pollution's effects on the airways and lungs. We're photographing PM in the sputum of people in the Delaware Valley, and it's spooky; it's scary."
Patrick and others like him can cite well-documented epidemiological research blaming PM for contributing to everything from asthma and allergies to lung cancer, heart disease and premature death.
They feel slightly encouraged these days because, for the first time in a decade, the U.S. Environmental Protection Agency is considering decreasing the amount of one form of air pollution -ground-level ozone - currently allowable under federal law.
Seizing the moment, the American Thoracic Society, the American Lung Association and other health groups are pushing EPA officials to decrease allowable ozone levels to an even lower level than what EPA is mulling over.
On the other side, however, lobbyists for industry and state governments are decrying the economic pain of further reducing ozone pollution. They are pressing EPA for a more modest lowering of federally mandated ozone levels or none at all.
One of Six Pollutants
Factories, electric utility plants, car exhausts, gasoline vapors and chemical solvents all emit nitrogen oxides (NOx) and volatile organic compounds (VOCs).
When NOx and VOCs react with sunlight, the result is ground-level ozone, a very irritating gas and a precursor to smog.
"We call it 'baked by sunlight,'" Patrick said. "When inner-city populations breathe in ground-level ozone, it's double trouble. They are getting another burden in their lungs."
Ground-level ozone triggers a variety of health problems even at very low levels and may cause permanent lung damage after long-term exposure, the EPA acknowledges. It is one of six common pollutants for which the Clean Air Act requires EPA to set National Ambient Air Quality Standards (NAAQS).
In 1997, EPA officials adopted the current federal ozone standard of 0.08 ppm/eight hours; although, implementation was delayed 4 years by court challenges. The U.S. Supreme Court finally upheld the standard in 2001.
Now, 7 years later, EPA officials are holding public hearings about dropping the allowable standard down to a range of 0.075 ppm/8 hours to 0.070 ppm/8 hours.
Advocates of public health, however, feel the standard should drop considerably more, to 0.060 ppm/8 hours. Ozone pollution "is causing unnecessary illnesses and death in America," ATS President David Ingbar, MD, declared at last year's ATS conference in San Francisco. "The proposed EPA standards fall short of providing the protection needed to keep Americans safe from ozone air pollution."
Past Progress
Medical societies such as ATS have long tangoed with EPA officials over reducing levels of particulate matter in the air. Sometimes the EPA satisfies them, most times not.
"Years ago, the EPA had a standard for PM 10 microns in size, but physicians and researchers realized it was the smaller particles getting deeper into the lungs and causing inflammation in the airways and alveoli," Patrick said. "Now the standard is based on the 2.5 micron standard. That was a good step and a necessary step in the right direction because PM in small sizes entering the airways can later result in bronchitis, asthma and inflammation in the alveoli."
More improvement came with the decision to measure the amount of pollution in 8-hour increments. "It used to be a 24-hour rule, which could allow a lot of deviations that wouldn't be violations," Patrick noted. "You can imagine if you had 4 hours of the worst pollution imaginable, then 15 good hours, the government would say, 'You're fine.' So they went to a much smaller window of time, which was very good."
EPA's most recent review of PM standards came in September 2006, after holding three public hearings and digesting more than 120,000 written comments, according to Alison Davis, senior advisor for public affairs for the EPA's Office of Air Quality Planning and Standards.
"At that time, the agency significantly strengthened EPA's previous daily fine particle standard - by nearly 50% - from 65 micrograms of particles per cubic meter of air to 35 micrograms of particles per cubic meter of air," Davis explained. But the EPA retained two other standards: annual long-term exposure to fine particles at 15 mcg per cubic meter and the daily inhalable coarse particles standard of 150 mcg per cubic meter.
The ATS and other public health advocates wanted much more. They pushed, unsuccessfully, for a daily fine particle standard of 25 mcg per cubic meter of air, not 35; and an average annual standard of 12 mcg per cubic meter of air, not 15.
Heart Disease, Sarcoidosis
When encountering particulate matter and ozone "you first get burning and tearing in the eyes as they try to wash out the material," Patrick explained.
A little eye irritation we can live with. But cardiac involvement is another matter. The science is clear: When PM is up, more heart attacks result.
"At first, that correlation was hard to explain, but the data is accurate and is supported by validation studies," he said. "The theory is that when PM enters the body, it sets up a systemic inflammatory response which can get to the coronary arteries. As they get inflamed, they can induce a coronary syndrome and a myocardial infarction that is actually immediately life-threatening."
Patrick wants to add another, far less-publicized condition to the growing pantheon of pollution-related problems.
"We have a temporary hypothesis that these particles are maybe also causing sarcoidosis," he said. "We had 54 sarcoid patients, and all of them had these particles in their lung biopsies. It's scary that air pollution might cause sarcoidosis. That's not even on the EPA's radar screen. We're saying you may want to add sarcoidosis as a potential disease triggered by PM."
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