WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 43 of 56 Because cumulative asbestos exposure is believed to be the appropriate metric for assessing asbestos health effects, it is possible long-term, continuous low-level exposures could contribute to asbestosis. Recent studies of a population exposed to tremolite asbestos in Libby, Montana, do indicate increased pleural anomalies, consistent with asbestosis, for individuals who were not exposed occupationally. Individuals who lived with plant workers or those who had contact with vermiculite piles containing tremolite had increased odds ratios for these anomalies (56).

Although asbestos is present in some settled surface dust in lower Manhattan, aggressive sampling produced a maximum level of 0.003 f/cc (PCM). This level is not high enough to result in asbestosis after short exposures. Although it is theoretically possible that lower level environmental exposures could contribute to disease over extended exposures, the data from this pilot study are too limited to support that finding.

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/sampling program, 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

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