NYC-WTC_000232959

NYC 9/11 Public Portal Document

4. Halite

Halite is simply sodium chloride, or rock salt (18). This crystalline form of the salt will readily dissolve in the body and is not expected to have any adverse health effects. Although large changes in salinity can disrupt tissues, the trace amounts of halite and the low frequency of detection do not indicate any potential health concern.

5. Crystalline Silica (Quartz and Cristobalite)

Silica is chemically inert for the most pail, so it is the physical form of silica that imparts its toxicity. Small crystals of silica may be deposited in lung tissue. Once deposited, the crystals remain and fibrogenic lesions may appear over time, damaging the lung tissue and reducing lung capacity (26). Silica has been demonstrated to be a pulmonary toxin hnked both to silicosis (a fibrotic lung disease) and lung cancer (27,28,29,30). These findings are supported by both human and animal studies. Chronic silica exposure may contribute to lung cancer; emphysema; obstiuctive airw ay. etiology, immune, or connective tissue disease; and lymph node fibrosis (27,30,31,32,33).

a. Silicosis

Generally silicosis is seen after years of high-level occupational exposures, although it can result from short-term acute exposure (26,30). It is not known if chronic ambient environmental exposure contributes to silicosis (26). Because the lung damage is proportional to the total amount of silica deposited in the lung, current evaluations are based on a measure of cumulative exposure of air concentration over work-years of exposure (28,34,35).

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

Assuming worst-case theoretical assumptions, the estimated quartz levels measured cannot rule out adverse health effects from chronic exposures (i.e., 30 years). 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.

Exposures of less than 1 milligram per cubic meter 1 (mg/rn^) of air work-year* of exposure are believed to not result in significant incidence of silicosis in workers (28,34,35). The peak respirable quartz level estimated in lower Manhattan of 19 ug/mil would be

* Cumulative exposure is expressed as a constant air concentration over a specified period of time. If a worker is exposed to a constant concentration of 1 mg/m’ of quartz throughout the workday, for an entire year, that is equivalent to 1 (mg/m^) work-year. (One milligram per cubic meter of air is 1 mg/m^).

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