As many as 500 New York City firefighters may have to retire early as a result of "respiratory disability," chronic breathing problems caused by their exposure to dense clouds of dust, smoke and fumes at the World Trade Center, health officials said yesterday.
The potential departure of the firefighters comes as the department is still struggling to deal with the loss of 341 firefighters and 2 paramedics, who were among the 2,801 people killed in the collapse of the twin towers after the attack on Sept. 11.
As of Aug. 28, 358 firefighters and 5 emergency medical workers were still on medical leave or light duty because of respiratory disorders that began after they worked at the site. Symptoms include persistent cough, wheezing, shortness of breath and other asthma-like symptoms, sinus inflammation and heartburn.
David J. Prezant, deputy chief medical officer of the New York Fire Department, said doctors did not know exactly what the affected workers had been exposed to, or whether they would get better or worse. Many, he said, worried about whether they would develop more serious lung diseases or cancer.
Their current problems are thought to have been caused by the inhalation and swallowing of fine particles created by the fires and building collapse. Workers who had the heaviest exposure — those who were there when the buildings collapsed and in the first few days and weeks after — had the highest incidence of respiratory trouble. Very few firefighters used respirators or other types of breathing protection in the early days after the attack, when the air was at its worst.
In addition to the 363 firefighters and rescue workers with respiratory disability, 213 others were on leave with emotional stress resulting from their work at the site and from their grief over the deaths of so many friends and co-workers. The number of stress-related incidents observed among the workers during the 11 months after the attack was 17 times the number that occurred in 11 months before the attack.
Reports on the firefighters' injuries and illnesses are to be published tomorrow by the Centers for Disease Control and Prevention, and another, to be published on Thursday in the New England Journal of Medicine, has already been published on the journal's Web site, www.nejm.com.
Over all, the surviving firefighters have fared both better and worse than doctors expected. Considering that nearly all of the city's more than 11,000 firefighters worked at the site, and that 90 percent developed a cough, the proportion with chronic problems is relatively small.
"Some might have thought the percentage would be higher," said Dr. Prezant, who is also a professor at Albert Einstein College of Medicine and an author of both reports.
In the firefighters who do have lingering symptoms, however, the problems have been more severe and persistent than doctors would have expected, Dr. Prezant said. In the past, among firefighters who had respiratory problems from smoke inhalation, 90 percent recovered. But among the 332 firefighters who had a severe case of "World Trade Center cough," only 48 percent have fully recovered and returned to work. Severe cases were defined as those needing four or more consecutive weeks of medical leave.
Dr. Prezant said the reason that the symptoms were so severe was probably that the concentration of particles was very high, and the exposures prolonged and repeated.
"We're never going to know the full scale of what the firefighters were exposed to on that day," Dr. Prezant said. He said that air quality testing did not begin until several days after the attack. But he said everyone at the site was clearly exposed to "a massive dust cloud" full of tiny particles that could be inhaled into the airways and lungs.
"Even if that respirable airborne particulate matter does not include a single chemical, it is incredibly toxic at that level of exposure," Dr. Prezant said, adding that there was a great deal of evidence that exposure to such material can cause increased rates of chronic lung disease like emphysema and heart disease.
The very finest particles can make their way into the depths of the lung and persist there for a long time, he said. Some particles, like asbestos fibers, stay in the lung forever. Other particles can be digested and removed. But in some cases, Dr. Prezant said, "the enzymes used to digest them can lead to lung inflammation and destruction, and that's why, in some people, the healing response can be part of the illness."
Dr. Prezant said that one of the most important findings of the study was that many of the firefighters with persistent cough and other respiratory problems also had heartburn, or gastroesophageal reflux, a condition in which stomach acid backs up into the esophagus and throat. He said swallowing the particles may irritate the stomach and esophagus, and that in the firefighters, the condition may have been aggravated by stress, long hours and irregular meal times.
He said doctors had not realized before these