Longitudinal studies of firefighters, rescue workers and other personnel who responded to the collapse of the World Trade Center following the September 11, 2001 attacks have confirmed the presence of a positive relationship between the intensity and duration of their exposures to airborne pollutants and the severity of their pulmonary symptoms.

Results of the study, conducted by a consortium of researchers at Mount Sinai School of Medicine, Columbia University, New York University, Johns Hopkins University, The University of Medicine and Dentistry of New Jersey, and the University of North Carolina-Chapel Hill, show exposure-related increases in new-onset cough, wheeze, shortness of breath, and bronchial hyperreactivity more than 2½ years after the disaster.

In addition, follow-up of pregnant women who were inside or near the WTC buildings on September 11 found a two-fold increase in the incidence of small for gestational age (SGA) infants. The study results will appear in the May issue of Environmental Health Perspectives, the monthly peer-reviewed journal of the NIEHS. An electronic copy of the report is available on the online section at http://ehp.niehs.nih.gov.

The study was funded by the National Institute of Environmental Health Sciences, one of the National Institutes of Health, the U.S. Environmental Protection Agency, and grants from The New York Community Trust and United Way of New York City. Additional support was provided by the National Institute for Occupational Safety and Health and the Centers for Disease Control and Prevention.

"Our results indicate that the environmental exposures following the WTC disaster were associated with profound adverse effects on respiratory health," said Dr. Philip J. Landrigan, chair of the Department of Community and Preventive Medicine and director of Environmental and Occupational Medicine at Mount Sinai, and principal author of the study.

"The collapse of the towers generated thousands of tons of particulate matter comprised of cement dust, glass fibers, asbestos, lead, aromatic hydrocarbons, and organochlorine compounds, many of which significantly increased the subjects' susceptibility to bronchial spasms and asthma," said Landrigan. "These respiratory effects were most pronounced in subjects who were in or around the WTC buildings during the first 12 hours of the disaster."

Previous studies have documented the acute traumatic consequences of the September 11 attacks, most notably the occurrence of 2,726 deaths, including 343 firefighters and 60 police officers. Early clinical assessments noted a high prevalence of respiratory symptoms, including persistent cough, in firefighters and rescue workers exposed to the WTC dust.

The present study was designed to yield a comprehensive assessment of the health impacts of the chemical contaminants on first responders, construction workers and volunteers who worked initially in rescue and recovery, and then for several months clearing rubble and debris, and on residents who lived in the surrounding area.

For their exposure assessment, the researchers focused on five primary classes of contaminants taken from samples of settled dust following the collapse of the twin towers. These included airborne particles, dioxin and other related compounds, asbestos, which was used for fire insulation in the construction of the North Tower, aromatic hydrocarbons such as benzopyrene and benzoperylene, and lead and other trace elements.

Analysis of the data revealed that firefighters were among the most heavily exposed populations. Of the 10,116 firefighters who were evaluated, 332 displayed persistent cough accompanied by other respiratory symptoms so severe as to require at least 4 weeks leave of absence. "The prevalence of this 'World Trade Center' cough was directly related to the intensity of the exposure," said Landrigan.

Among firefighters without the cough, many were diagnosed with bronchial hyperreactivity, a chronic condition which triggers bronchial spasms in response to ambient air pollutants such as cigarette smoke and automobile exhaust. This condition was observed in 23 percent of those with a high level of smoke exposure, and in 8 percent of those with moderate exposure. "We believe the high alkalinity of the dust was a major contributing factor to the high incidence of bronchial hyperreactivity," said Landrigan.

Among ironworkers involved in clean-up and recovery, many of whom spent several months in and around the disaster site, almost one-third experienced a chronic cough that began shortly after employment at the site, 24 percent reported new onset of phlegm production, and more than 17 percent reported new onset of wheeze. About half of all workers reported at least one new symptom since they had begun working at the site.

Preliminary data from clinical evaluation of residents living within a 1.6-kilometer radius of the WTC site indicate that previously healthy subjects had a greater increase in cough, wheeze and shortness of breath than did residents living a greater distance from the site.

The primary health effect observed in pregnant women who were inside the towers or within 10 blocks of the WTC at the time of the disaster was a two-fold increase in the incidence of small for gestational age infants as compared to pregnant women from a demographically similar population not known to have been in Manhattan at the time.

"We had hypothesized that long-term exposure to air pollutants generated by the collapse of the towers might be associated with an increased risk of small for gestational age births," said Dr. Trudy Berkowitz, an epidemiologist with Mount Sinai. "Based on the results of subsequent studies, we have ruled out the potential role of post traumatic stress disorder in these adverse pregnancy outcomes."

Researchers are also concerned about long-term health consequences of asbestos exposure in the wake of the disaster. Asbestos, principally chrysotile, was used in the construction of the North Tower during the early 1970's. While some of this asbestos had been removed over the preceding 30 years, hundreds of tons remained on September 11 and were blasted free.

Ambient air samples showed that asbestos levels in the WTC area were initially elevated following the September 11 attacks, but fell to within federal standards after the first few days. "More research is needed to determine whether long-term exposure to asbestos fibers might lead to an increased risk of lung mesothelioma, a rare cancer that has been linked to asbestos exposure," said Landrigan. "Previous studies have shown the short chrysotile fibers found in the WTC dust to be the predominant fiber in lung mesothelioma tissue."

Reporters may contact Dr. Landrigan at (212) 241-4804.