At first, Mike Greene thought it might just be a bad allergy.
But when his sense of smell didn't come back for months, the paramedic suspected it was caused by polluted air he'd breathed at the most harrowing job site of his career: the wreckage of the World Trade Center.
Turns out he is not alone.
A significant portion of those on duty at the twin towers suffered long-term damage to their sense of smell and their ability to detect harmful irritants through the nose, Philadelphia researchers reported in a new study last week.
Far from being just an inconvenience, this chronic condition represents a breakdown in the body's defense against toxic substances, said lead author Pamela Dalton, an experimental psychologist at the Monell Chemical Senses Center.
In a sample of 102 workers in construction, emergency services, and other fields, 22 percent had an impaired sense of smell more than two years after exposure at the twin towers site, and 74 percent had a reduced ability to detect irritants. That ability is separate from the sense of smell, and is illustrated by the burning sensation you get from say, the noxious fumes in a bottle of bleach.
People caught in the initial dust cloud on Sept. 11, 2001, suffered the greatest degree of impairment, as indicated by their lack of response when taking brief sniffs of an irritant in a laboratory setting.
"These people just didn't react because their ability to sense that irritation was just literally wiped out," Dalton says.
That means in the future, they won't know to shield themselves from such irritants before they penetrate to the lungs, she says. An impaired sense of smell, meanwhile, makes it tough to detect hazards, such as spoiled food and smoke from a fire.
Previous studies have documented respiratory problems in those who were exposed to the haze of pollutants in the days and weeks after the attacks, but the workers' ability to perceive odors and irritants is a new area of research.
While other scientists have found links between air pollution and a decline in the sense of smell, the impact of dirty air on the nose's ability to detect irritants has not been widely studied. These sensations are picked up by the trigeminal nerve, which has some endings in the nose.
Though the World Trade Center was an extreme case, the new research illustrates the need for further study in other occupational settings for construction and rescue workers, says Dalton, who collaborated with researchers at the Mount Sinai School of Medicine and other institutions.
Richard L. Doty, a University of Pennsylvania scientist who was not involved with Dalton's paper, agreed. Researchers don't know the exact composition of the airborne pollution from the towers' collapse, which included smoke, dust, gases, and acid mists. But it was clearly harmful in multiple ways, he says.
"Whatever has damaged the olfactory pathway has probably also damaged the trigeminal nerve endings," says Doty, director of the Smell and Taste Center at Penn's school of medicine.
In Dalton's study, the sensory function of twin-tower workers was compared with that of control subjects of similar age and occupation. Nearly all the workers at the World Trade Center were there the first week after the attacks, and most continued working there in the weeks afterward.
They were more than three times as likely to have trouble detecting irritants than workers who were not exposed.
And they were about twice as likely to have an impaired ability to detect odor as measured on samples of an alcohol with a pleasant floral smell, though they were not any worse at identifying smells such as peanut butter and strawberry.
Doty, on the other hand, has done his own research with workers at the twin towers site, and has found they did have a harder time identifying smells. Those findings are awaiting publication.
Greene, the paramedic, was not part of either study but said he was not surprised by the findings.
The Queens resident, 53, who worked for the New York City Fire Department, was on duty for the first day and a half of the rescue effort and then came back repeatedly until December, he says.
"I couldn't even breathe through my nose," because it was clogged, Greene says.
More than eight years later, he says he has little sense of taste and smell, despite taking nasal steroids and undergoing several procedures to clean out his nasal passages. He has now retired on disability with a bad back and the lack of smell.
The participants in the Monell study were tested anywhere from 2 to 31/2 years after the towers' collapse.
The findings could not be published until now, in the online edition of Environmental Health Perspectives, because it took until last year for the Mount Sinai people to extract personal histories for the 102 subjects - from among the more than 20,000 people who were screened for other research.
Dalton says she suspects the workers with impaired sensory function continue, like Greene, to have such problems today. She is seeking funds to conduct further study.
Greene says he never fully appreciated his olfactory sense until he lost it. The treatments sometimes give him back some sense of smell - and the related sense of taste - but only for a while.
"I eat a lot of food I will enjoy," Greene says, "because I know I will lose the taste again."