NYC-WTC_000232959

NYC 9/11 Public Portal Document

none of these air samples were analyzed by TEM, it is not known if they were asbestos fibers. For this analysis of a worst-case exposure, it will be assumed they are asbestos. Four of these samples were taken in common areas during normal daily activity. All other air samples, including the highest, 0.003 f/cc, were taken in residences that were aggressively sampled. Using the IRIS slope factor, no appreciable increase in cancer risk is seen when considering a 1-year continuous exposure at the highest fiber level cited (1x10'^ excess cancer risk).

If the highest measured PCM levels are assumed to be all asbestos fibers (a worst-case assumption) and were representative of long-term conditions (another worst-case assumption), the cumulative exposure for a continuous 30-year residence would result in a greater risk estimate for lung cancer and mesothelioma. Therefore these data cannot rule out the potential for long-term risk. However, the highest airborne level measured during this study is not necessarily representative of long-term exposure nor is the highest level necessarily all asbestos fibers. As presented in the discussion section of this report, it is expected that the ongoing cleaning of lower Manhattan should reduce levels of these materials over time, thus reducing long-term risk. Therefore cleaning should be continued and levels of asbestos monitored, until the data demonstrate long-term risk of lung cancer and mesothelioma are minimal.

8. Multiple Material Exposures

Each of the materials discussed previously may exist singly or in combination with other materials found in lower Manhattan. The combinations of materials found in this investigation are described in the discussion of results. When exposures to multiple materials occur together, there is some potential that the agents may interact with respect to their adverse effects. Agents may be additive if they impact an organ system similarly. Synergistic and antagonistic effects may also be seen if the agents either potentiate or disrupt the effects of other agents.

a. Irritant Effects

The effects of the alkaline minerals are most likely additive, although it should be noted that not all of the materials are equally caustic. Therefore, cumulative effects on pH would be the best measure of irritant effects based on the caustic nature of the dust. There may also be potentially additive or synergistic effects with the irritant effects of the SVF. The ability of either caustic action or the mechanical action of the fibers or minerals to degrade the protective properties of skin and mucus membranes may make tissue more susceptible to irritant effects. Additionally, because both types of actions may trigger localized immune responses, these irritants may potentiate each other.

b. Noncancer Pulmonary Effects

Several of the minerals detected contribute to fibrotic lung damage and may result in several diseases that reduce lung function including silicosis, asbestosis, other mineral fibroses, emphysema, and other respiratory disorders. The mechanisms and pathology of

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