NYC-WTC_000232959

NYC 9/11 Public Portal Document

Maximum Estimated Value Mineral NIOSH REL (pg/m?) OSHA PEL (pg/m?) in Lower Manhattan (pg/rn^) 10,000 (total) 15,000 (total) 14J (PM 100) Gypsum 5,000 (resp) 5,000 (resp) 15J (PM4) 15,000 (total) 951 (PM 100) Portlandite 5,000 5,000 (resp) 84J (PM4) 10,000 (total) 15,000 (total) 14J (PM 100) Calcite 5,000 (resp) 5,000 (resp) lOJ (PM 4) NIOSH = National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention REL = recommended exposure level/limit OSHA = Occupational Safety and Health Administration PEL = permissible exposure limit. pg/rn^ = 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 ug/n? is a level at which mild pneumoconiosis was seen in some workers only after extended exposure (18 years).

The airborne levels of mica seen in lower Manhattan with an estimated maximum of 43 pg/m^J in respirable dust are well below levels of mica that are associated with the development of Mica and halite, although pneumoconiosis in workers (25). Although elevated in lower Manhattan disturbing settled surface dust might generate short­ relative to the comparison areas term exposures above the measured values, it is the above 59th Street, are not likely cumulative exposure that is believed to predict to contribute to any adverse health effects (23). Given the low airborne levels of health effects. 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.

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