NEW YORK (AP) - The huge plume of smoke and grit that spread from the World Trade Center could trigger attacks of asthma, emphysema and other chronic lung disease even a day or two after people were exposed, doctors said Wednesday.

Even people away from the immediate area of the blasts might suffer respiratory attacks if they have such diseases already, lung experts said.

"If it's sort of obvious you're breathing in smoky air, that would be enough to set off somebody who has lung disease," said Dr. Mark Siegel, an assistant professor of medicine at the Yale School of Medicine.

Breathing particles from the smoke could also harm people with heart disease or who are frail because of other illness, Siegel said. That could increase the risk of heart attacks or make congestive heart failure worse.

Those at the scene - like firefighters, police and office workers who escaped after the attack - may also developg pneumonia or an asthma-like syndrome within about 24 hours, said Dr. E. Neil Schachter, medical director of respiratory care at Mount Sinai Hospital in New York. That can be fatal, but more often it leads to a chronic condition resembling asthma, he said.

Schachter said that at the scene, even protective equipment might be overwhelmed by the smoke, gas and fumes.

Siegel said people who had been at the scene and were already hospitalized for smoke-related damage to the lungs and airways - signaled by shortness of breath, coughing and sometimes chest pain - may get worse within about four days after exposure as their lungs fill with fluid and become inflamed.

"The people who are already showing signs of injury to the lung from the smoke may not have seen the worst of it yet," he said. But "the people who are OK now are probably going to stay that way."

Aside from the smoke itself, the primary environmental concern about the disaster right now is asbestos, said Environmental Protection Agency Administrator Christie Whitman.

Three preliminary samples already taken by the agency showed "minimal or no" airborne asbestos, Whitman said, but a fourth did detect significant levels of the cancer-causing material.

"We're going to take more samples as time goes on," she said. Wetting down the debris and wearing filter face masks can help protect rescuers and workers from asbestos, dust and smoke.

Most cases of asbestos-related disease are caused by repeated exposure rather than a single dose, although a single large exposure may lead to a cancer called mesothelioma, lung experts said.

In the longer term, Whitman said, the EPA has offered its assistance in properly disposing of the debris that blankets downtown Manhattan. The agency does not expect permanent environmental damage from the attacks.

At St. Vincent's Catholic Medical Center, medical director Dr. Anthony Gagliardi said Wednesday that most symptoms appeared to be caused by large-particle dust, not toxic gases. Many patients had come in with respiratory complaints, he said, and had been coughing up dark, gray and black phlegm.

Other experts said they didn't expect any risk of disease spreading from the dead bodies trapped in the rubble. The main risk would be contamination of a water supply by germs from such bodies, but that is not likely in Manhattan, which gets its water from elsewhere.

"As long as people use normal sanitary precautions in handling the corpses and normal sanitation in terms of clean water and food, there is no infectious risk related to the corpses," said Dr. Richard Forthingham of Duke University and the Veterans Affairs Medical Center in Durham, N.C.

National writer Matt Crenson in New York contributed to this report.

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