NEW YORK -- Firefighters and EMS personnel exposed to the dust and smoke at ground zero during the World Trade Center disaster had declines in lung function a year later that were equivalent to 12 years of pulmonary aging.
NEW YORK, Aug. 1 -- Firefighters and EMS personnel exposed to the dust and smoke at ground zero during the World Trade Center disaster had declines in lung function a year later that were equivalent to 12 years of pulmonary aging.
So found investigators who compared lung-function data that were available pre-9/11 on nearly 13,000 firefighters and EMS personnel with tests performed a year later. More than 300 rescue workers who were never deployed at the World Trade Center were controls.
The longer the exposure to the airborne contaminants at the World Trade Center site on Sept. 11, 2001, and days immediately afterward, the greater the degree of decline in forced expiratory volume at 1 second (FEV1), the investigators reported in the August issue of the American Journal of Respiratory and Critical Care Medicine.
The damage appeared to be greatest among those with massive repeated exposures to dust and particulate matter at ground zero, and subsequent use of protective equipment didn't offer much additional protection, found Gisela I. Banauch, M.D., M.S., of Montefiore Medical Center in New York, and colleagues.
"In contrast to the pronounced influence of arrival time and work assignment on lung function, respiratory protective equipment had no appreciable effect on spirometric reductions after 9/11," said Dr. Banauch. "Initial lack of adequate equipment and subsequent compliance problems diminished any protective impact."
The research team, including investigators at Montefiore, Albert Einstein College of Medicine, the fire department's Bureau of Health Services, and New York University, had previously reported that the high level of exposure to dust among emergency responders in the first few weeks after the tragedy were associated with persistent bronchitis and substantial impairments in respiratory functions.
They also found that many of the firefighters and EMS workers who were on site at the disaster had continued symptoms of airway hyperresponsiveness, or reactive airway dysfunction syndrome, long after they left the site.
In the current study, the investigators took advantage of FDNY health records, which include periodic exams, spirometry data, and respiratory questionnaires for all personnel.
They compared pre-9/11 records for 12,709 rescue personnel with post 9/11 records in the same cohort, and performed a similar analysis eliminating the 313 rescue workers who were never deployed at the World Trade Center site during the disaster or cleanup.
They looked at a total of nearly 32,000 spirometries for FEV1 and forced vital capacity and analyzed the results for differences according to estimated intensity of exposure to contaminants at ground zero. They also compared adjusted average FEV1 within the year following the disaster to the average of the five years before Sept. 11, 2001.
They found that the rescue workers who were exposed to the site had "a substantial reduction in adjusted average FEV1 during the year after 09/11/2001 (372 ml; 95% confidence interval, 364-381 ml, P<0.001)," they wrote. "This exposure-related FEV1 decrement equaled 12 years of aging-related FEV1 decline."
The investigators determined that exposure intensity, estimated by the time that firefighters and EMS workers first arrived on the scene, was associated in a linear fashion with decline in FEV1.
In addition, use of a protective mask didn't seem to help. Only 22% of early responders reported using them, compared with 38% of those who arrived at after the collapse of both towers on Sept. 11 or on Sept. 12, and 50% among those who first came to the site on Sept. 13 or later.
"Our analyses did not identify a protective effect of mask use frequency on adjusted average FEV1 or forced vital capacity after 09/11/2001," Dr. Banauch and colleagues wrote.
They also found that the severity and frequency of respiratory symptoms was predictive of greater declines in lung function, with each added symptom (e.g., chest pain, cough, wheezing, exertional dyspnea) associated with an additional 48 ml adjusted average decline in FEV1.
Their findings "should be extrapolated with caution to other, less exposed populations, but because even our least exposed group showed spirometric reductions after 09/11/2001, continued medical monitoring is prudent for all exposed populations," the authors wrote.
In an accompanying editorial, John R. Balmes, M.D., of the University of California San Francisco Lung Biology Center, pointed out that because the earliest responders to the World Trade Center disaster were exposed to smoke and ash as well as pulverized building debris, it's not possible to determine from the data which components posed the greatest pulmonary risk.
Nonetheless, he wrote, the study provides strong evidence for several important concepts:
"A single, massive exposure to an irritant is not the only route to irritant-induced asthma since multiple, submassive exposures to World Trade Center dust appear to have caused the syndrome in World Trade Center responders," Dr. Balmes wrote. "Such exposures now also appear to have caused accelerated decline of lung function, which suggests that this cohort is also at risk of developing chronic obstructive pulmonary disease."
He added that it will be important to continue to follow the firefighters and EMS workers to determine whether the early decline in FEV1 is an inevitable precursor to COPD, or whether they will be able to recover lung function, as has been seen in other cases of irritant exposure.