Many workers who cleared debris from the site of the World Trade Center attack of last September 11 reported acute respiratory symptoms, according to a health assessment conducted by the Johns Hopkins Bloomberg School of Public Health.

Investigators believe the respiratory problems may be associated with exposure to dust and airborne contaminants at Ground Zero. More research is needed to determine if there is any long-term health risk to the workers.

The assessment was conducted in collaboration with the International Brotherhood of Teamsters.

"Many of the workers we assessed reported coughing, wheezing and sore throats while working at Ground Zero. These symptoms seemed to increase the longer they worked at the site. The good news is that we did not find unhealthy levels of asbestos, but we don't know what the long-term health risks may be regarding exposure to other airborne contaminants at the site," explains Alison S. Geyh, Ph.D., chief investigator and assistant professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health.

The exposure and health assessment was conducted between October 2001 and April 2002. Investigators examined the workers' airborne exposures to asbestos, particulate matter and volatile organic compounds. In October, airborne contaminants were measured at numerous locations at Ground Zero and on truck drivers who hauled wreckage away from the site. The respiratory health of the truck drivers and other debris-removal workers was assessed two months later, when a respiratory health questionnaire was administered to the workers. In addition, lung function was measured using spirometry. Additional airborne-contaminant measurements were collected in April and compared to the data gathered in October.

The air monitoring effort detected small amounts of asbestos. Investigators say exposures were generally low and did not exceed health exposure guidelines. "Low level exposures to asbestos, occurring for a short period of time relative to a working lifetime, suggest that these truck drivers are unlikely to be at a significant increased risk of asbestos-related disease," said Patrick Breysse, Ph.D., MHS, an investigator on the project and professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health.

Airborne particulate matter measured at Ground Zero was highly variable in both composition and size and depended on conditions at the site, such as how aggressively the fires were burning, how actively the debris was being removed, and how thoroughly dust suppression measures were being carried out.