NYC-WTC_000232959

NYC 9/11 Public Portal Document

Short-term exposures to asbestos, even for a continuous year of exposure at the highest estimated air concentration, are not expected to result in any adverse health effects.

Assuming worst-case theoretical assumptions, the highest fiber levels measured cannot rule out adverse health effects from chronic exposures (i.e., 30 years), but it is unlikely levels will remain elevated for that long. For individuals who conduct frequent cleaning of their residences, as recommended in this report, or participate in the U.S. Environmental Protection Agency cleaning/samplingprogram, it is unlikely that their exposure would resemble these worst-case conditions.

b. Lung Cancer and Mesothelioma

Asbestos exposure is known to increase lung cancer incidence, particularly for high-level occupational exposures over an extended period of time (e.g., decades) (10,48,52). Additionally, some studies have indicated increased lung cancer and mesothelioma due to high naturally occurring levels of asbestos or low dose environmental exposures (57-60). Longer asbestos fibers can penetrate into the deeper portions of the lung. Because asbestos is relatively insoluble, longer fibers cannot be physically removed by the body’s immune systems and may remain in the lung and cause damage. Although the exact mechanism for lung cancer is not known, it is believed the localized immune response to the asbestos may contribute to cancer. Fibers may also migrate out of the lung and cause mesothelioma, a cancer specific to the lining around the lungs. In general, shorter fibers (less than 5 microns) are more efficiently cleared from the lung and therefore are less potent (10). Additionally, there is some indication that chrysotile asbestos is less potent than other forms of asbestos due to better clearance from the lungs.

EPA has established a cancer slope factor for asbestos to estimate risk in the general population due to chronic environmental exposures to asbestos (48).* Factors that influence excess cancer estimates are age at time of exposure, sex, and cigarette smoking (52).^ EPA’s Integrated Risk Information System (IRIS) is used to develop risk estimates for comparison, with the understanding that smokers will be at higher risk.

Air samples from several indoor areas with asbestos fibers detected in the settled surface dust did contain fibers as described by PCM analysis (0.001 f/cc to 0.003 f/cc).* Because

* This slope factor is based on epidemiologic studies and assumes a linear dose response for cancer, even at very low environmental doses (0.23 excess cancers per million people exposed for each f/cc of asbestos.) This type of cancer risk estimate may over predict risk and does not take into account any lower threshold for effect, which may exist. Additionally, the EPA slope factor was designed to apply equally to aU types of asbestos, and all fibers greater than 5 microns in length (IRIS). t Variability in these factors is not accounted for in the EPA slope factor because it does not include synergistic effects with the effects of smoking (48). t However, because asbestos as a percentage of settled surface dust was elevated, an area with significant dust may be capable of generating higher airborne levels of asbestos, especially during high activity'.

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