As they push their investigation into the health risks to workers in the recovery and cleanup operations at ground zero, medical detectives are focusing on a group of lung diseases that can lead to long-term disabilities and, in some cases, death.
After nearly five years, it is still too early for these doctors, scientists and forensic pathologists to say with certainty whether any long-term cancer threat came with exposure to the toxic cloud unleashed by the trade center collapse. But there are already clear signs that the dust, smoke and ash that responders breathed in have led to an increase in diseases that scar the lungs and reduce their capacity to take in and let out air.
The Fire Department tracked a startling increase in cases of a particular lung scarring disease, known as sarcoidosis, among firefighters, which rose to five times the expected rate in the two years after Sept. 11. Though that rate has declined, doctors worry that the disease may be lurking in other firefighters. Experts who regularly see workers who were at ground zero in the 48 hours after the towers' collapse expect monitoring to show many more cases of lung- scarring disorders among that group.
New evidence also suggests that workers who arrived later or worked on the periphery may also be susceptible to debilitating lung ailments.
"We have thousands of people who were down there with unprotected exposures," said Dr. Stephen M. Levin, a director of the World Trade Center Worker and Volunteer Medical Screening Program. "Many will develop asthma and a few will develop this terrible lung scarring that leads to disability or death."
But even in diseases closely related to dust, making a binding connection to ground zero exposure is hard. For instance, the Fire Department has linked sarcoidosis to working at the trade center site, while the Police Department has not.
The clues that led to this new area of medical investigation were stark reminders of what was lost on Sept. 11. They are drawn from cases of statistically unexpected respiratory disease among young responders.
The ailments now seen are far more serious than the general hacking and congestion known as "World Trade Center cough" that initially hit most responders. Rather, these are a set of diseases and disorders that typically take a few years to develop, and in some cases get progressively worse.
The most worrisome to medical experts are granulomatous pulmonary diseases, which show a particular type of swirling marks left on the lungs by foreign matter like dust. Doctors say the severity of the disease is often dictated by a patient's genetic makeup. The diseases include pulmonary fibrosis and sarcoidosis, a sometimes fatal disorder that can be set off when exposure to dust causes the body's immune system to attack itself.
Some people can live with the scarring if they limit their activities, but in others the exposure to foreign material sets off a cascade of ailments that can lead to more debilitating conditions and, eventually, death. Detective James Zadroga, 34, died in January when his badly scarred lungs weakened and his heart gave out. The coroner's report gave the cause of death as "granulomatous pneumonitis," and the autopsy found swirls throughout his lungs caused by foreign material consistent with dust.
Detective Zadroga's death was the first to be officially linked by an autopsy report to exposure to the ground zero dust, although the electronmicroscope comparisons that could have proved the match beyond a reasonable doubt were not done by the coroner's office.
The Uniformed Firefighters Association earlier this year linked the deaths of two firefighters and a battalion chief — from lung disease and respiratory ailments — to the air at ground zero, although the Fire Department itself has not formally acknowledged that those deaths were connected to ground zero work. And three young emergency medical technicians who worked in the dust and smoke at ground zero have died from pulmonary diseases and coronary problems aggravated by their battered lungs, according to the union that represented them.
The use of respirators and dust masks might have reduced the incidence of respiratory ailments, but the most effective ones issued to firefighters are meant to last only 20 minutes. Other responders and volunteers who arrived after the first two days did not use dust masks at all or were only given paper masks, an issue raised in a pending class-action suit against the city and private companies involved in the cleanup.
Although the reported cases of lung disease affect a tiny portion of the 40,000 people who responded to the trade center collapse, they have already caused widespread concern among the survivors, lending urgency to medical efforts to understand the risks and illnesses involved.
"When these cases come to public attention, every individual down there who has some problem breathing thinks, 'I'm next,' " said Dr. Levin, a professor at Mount Sinai School of Medicine.