WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 38 of 56

pg/m^ = microgram of mineral per cubic meter of air

total = all airborne particles (could include particles >100 micrometers)

resp = respirable fraction (PM4)

3. Mica

Mica is a group of water-insoluble silicate minerals (18). The mica detected in these dust and air samples of lower Manhattan was muscovite. Mica has been shown to cause pneumoconiosis in workers exposed to high levels during mining and processing operations (19,20). Although workers may have also been exposed to quartz in some of these studies, pneumoconiosis in workers with only mica exposures has been documented. (21,22)

Respirable mica particles that deposit in the deep lung may be cleared slowly due to the relative insolubility of the mineral. Over time, the presence of the mineral will irritate the lung tissue, generate immune response, and result in scarring or fibrosis (23,24). The magnitude of this response is believed to be a function of both the dose and duration of exposure. The current worker standard set at 3,000 pg/m^ is a level at which mild

pneumoconiosis was seen in some workers only after extended exposure (18 years).

Mica and halite, although elevated in lower Manhattan relative to the comparison areas above 59th Street, are not likely to contribute to any adverse health effects.

The airborne levels of mica seen in lower Manhattan with an estimated maximum of 43 gg/m^ J in respirable dust are well below levels of mica that are associated with the development of pneumoconiosis in workers (25). Although disturbing settled surface dust might generate short-term exposures above the measured values, it is the cumulative exposure that is believed to predict health effects (23). Given the low airborne levels of mica seen in lower Manhattan and the low frequency of detection in both air and settled surface dust samples, no health effects are expected from mica exposure alone.

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.

S. Crystalline Silica (Quartz and Cristobalite)

http://www.atsdr.cdc.gOv/asbestos/lowermanhattan/ResSamp_Sep2002_Text.html 07/18/2003 NYC-WTC_000178425