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Asbestos Exposure on 9/11: The North Tower

How Asbestos Exposure on 9/11 Led to a New Generation of Mesothelioma Sufferers

The attacks on the World Trade Center in 2001 created a new asbestos exposure hazard. The North Tower was constructed between 1970 and 1972 and asbestos was used as fireproofing up to the 40th floor. Asbestos was not used beyond that point, because it was recognized as a significant health hazard. Fireproofing was accomplished on the North Tower’s upper floors with other materials. Although some of the asbestos from the first 40 stories had been removed over the preceding 30 years, hundreds of tons remained on September 11, 2001. When the North Tower collapsed, it blasted an estimated 2,000 tons of asbestos fibers into the air. Those with the greatest exposure were firemen, policemen, construction workers, paramedics, and volunteers who worked at Ground Zero.

Because of its known potential as a carcinogen, asbestos immediately became a major health concern. The U.S. Environmental Protection Agency (EPA) collected thousands of samples of dust and analyzed them for asbestos content. Researchers from Mt. Sinai School of Medicine reviewed these efforts in a 2004 article in Environmental Health Perspectives. More than 10,000 ambient air samples from lower Manhattan were tested for asbestos using phase-contrast light microscopy (PCM) to identify fibers greater than 5 µm in length. More than 8,000 of these samples were also examined by transmission electronic microscopy (TEM) to identify fibers of 0.5 µm in length. These extremely short fibers cannot be filtered by the lungs when inhaled. They can become deeply embedded in lung tissue, where they have the greatest potential to cause diseases.

Most of the elevated asbestos levels in air were observed in the early days after September 11. Air samples showed that asbestos levels were initially elevated but fell to within EPA standards after the first few days. Asbestos was also found in settled dust at Ground Zero in concentrations ranging from 0.8 to three percent. Asbestos was found in dust in nearby apartments, sometimes at higher levels than in the outside environment. Because some residents had prolonged exposures to uncleaned apartments, these indoor exposures may have added significantly to ambient exposures.

Eight-hour time-weighted average asbestos exposures to workers were not above the Occupational Safety and Health Administration standard of 0.1 fiber/cm3. Nonetheless, workers at Ground Zero – most of whom did not wear respirators or other protective equipment – experienced repeated short-term peak exposures, inhaling asbestos fibers each time they disturbed asbestos-containing rubble.

Additional asbestos exposure increases the risk for mesothelioma. A higher incidence of mesothelioma will likely occur in the population who worked at Ground Zero and who lived and worked in lower Manhattan. Given the disease’s pattern of extremely slow development, it these cases of mesothelioma may not be identified for decades.