NEW YORK-The death toll associated with the World Trade Center disaster of September 11 may rise 20 or 30 years from now, according to experts who spoke at a media briefing on malignant pleural mesothelioma. Many thousands of people at or near the disaster site had some exposure to asbestos, a causative agent of mesothelioma, said Stephen M. Levin, MD, medical director, Mount Sinai-Irving J. Selikoff Center for Occupational and Environmental Medicine.
NEW YORKThe death toll associated with the World Trade Center disaster of September 11 may rise 20 or 30 years from now, according to experts who spoke at a media briefing on malignant pleural mesothelioma. Many thousands of people at or near the disaster site had some exposure to asbestos, a causative agent of mesothelioma, said Stephen M. Levin, MD, medical director, Mount Sinai-Irving J. Selikoff Center for Occupational and Environmental Medicine.
Well over 20,000 persons involved in the rescue and recovery effort, he estimated, were exposed. Others fleeing or visiting the area were more fleetingly exposed. "The risk for most is relatively low," Dr. Levin said, "but not zero."
In one study, rats exposed to asbestos for as little as 1 day developed malignant mesothelioma. With longer exposure, the incidence rose, said Arthur L. Frank, MD, PhD, professor of occupational and environmental medicine, University of Texas Health Center at Tyler.
Human data, he added, corroborates that the disease can be induced by short workplace exposures. "When it comes to the cancer-causing effect, there’s no threshold," Dr. Frank said. "There is a risk at any dose level, but the likelihood of developing disease will obviously go up as the dose goes up."
Almost all Americans have some asbestos in their lungs, but the chance of developing asbestos-related malignant mesothelioma is 1 in 1 million for the general population, Dr. Levin said. For those with heavy exposure, such as construction workers, the risk rises to 1 in 10. "We know that it takes less exposure to asbestos to cause an asbestos-related cancer than it takes to cause scarring lung disease," he pointed out.
Predicting who will develop malignant mesothelioma is difficult, Dr. Frank said, because a variety of factors, including genetics, are probably involved. The consequences are dire because the disease is rarely detected at an early stage and is difficult to treat. "It’s almost uniformly fatal," Dr. Levin said.
Asbestos in the Towers
Asbestos was sprayed onto some steel girders of the first tower of the World Trade Center during its construction in 1970, Dr. Frank said. The spray application was banned in New York City in 1971, and the EPA banned it nationwide in 1972. Even after the ban on spraying, asbestos continued to be used to insulate pipes and boilers, he noted. At the World Trade Center, Dr. Frank said, it was used in mechanical rooms and elevator shafts.
"The collapse of the towers and the other buildings nearby pulverized this material," Dr. Levin emphasized. The impact forces were so great, he noted, that much of the asbestos was fragmented into short fibers, the size usually found in the lung tissue of mesothelioma patients. In the debris pile, he reported, levels as high as 4% to 5% were detected.
Asbestos will remain suspended in air under still conditions for up to 8 hours, he said. When disturbed, it rises again to present a potential inhalation hazard. The fine dust littered a large area and drifted into nearby residences and offices.
High Exposure for Workers
The workers who came to do rescue and recovery at Ground Zero in the first days had "very high exposure," Dr. Levin said, and so did persons involved in restoration of telephone, transit and electrical services. Most of these people worked without respiratory protection, particularly in the early period. [Editors’ note: A CDC study of air samples taken between September 18 and October 4 showed "no occupational exposure to asbestos, at least after September 18, in excess of NIOSH or OSHA occupational exposure limits."]
In a group of about a dozen workers observed within a day of the disaster, Dr. Levin noted, "only one person has a respirator, and it’s around his neck." Three weeks after the disaster, only 60% of the workers at Ground Zero were wearing appropriate filters.
"We have good respiratory protection," Dr. Levin stressed, "and when it is used, it really will reduce the inhalation of this fibrous material." He acknowledged that the heat of the debris pile, the emotional drive to save lives, and interference with being able to talk to coworkers when wearing the respirators contributed to their abandonment even when they were issued.
The people cleaning buildings surrounding Ground Zero "faced a greater risk than many others," Dr. Levin said, because the commercial and residential spaces in which they worked were enclosed and afforded little opportunity for dispersal of airborne materials. "They were not provided with respiratory protection or given training, They often used dry methods rather than wet methods to clean up this material. It’s a public health outrage that they were permitted to be exposed in this way." Some residents and office workers returned to the area within a week or two after the disaster. FEMA (Federal Emergency Management Agency) funds, he stressed, "should have been provided so that professional cleanups could be done throughout the downtown area." Advisories issued to residents by the city’s health department did not recommend respiratory protection, he noted, although they did advise using high efficiency particulate (HEPA) filters.
The potential for exposure due to the way residential cleanup was handled may extend far afield, Dr. Frank said in an interview. The rugs, he noted, might be sent to a cleaning service where workers could be exposed to asbestos from thousands of asbestos-contaminated items.
Cleanups at Stuyvesant High School and at an elementary school near Ground Zero were well done, Dr. Levin said. In those schools, the asbestos risk should not concern parents, he indicated.
In general, children are at higher risk of asbestos exposure than adults, Dr. Levin commented. Because their breathing rates are faster than adults, "the dose of exposure per unit of body weight is greater," he said. "Children live close to the floor. They play on the floor. If there is settled dust on the floor or on other surfaces, children are the ones whose breathing zone is closer to that source."
The risk of developing mesothelioma increases over time, he noted. Because children have longer lifetimes ahead of them, he said, their likelihood of developing mesothelioma if exposed to asbestos is greater than that of adults.
Long-term follow-up studies of individuals exposed to asbestos contamination at the World Trade Center have not yet been launched, Dr. Levin said in an interview. "I think we are likely to get to examine some of the people who really worked at Ground Zero, maybe to establish baseline for subsequent follow-up," he said. Congress may appropriate funds to the Centers for Disease Control and Prevention for such research.