NYC-WTC_000232959

NYC 9/11 Public Portal Document

expected from the skin, eye, or upper respiratory tract irritation related to the SVF exposure.

b. Pulmonan^ Effects

SVF less than 3 microns in diameter are respirable and available to enter and deposit in the pulmonary regions of the lung (41). Clearance of these fibers from the lung will be determined by fiber solubility and length (41,42). Fibers cleared from the lung have less potential to create long-term health effects.* Although some animal studies have demonstrated both fibrotic and carcinogenic potential for fibrous glass and mineral wools (41,42,46), more recent studies do not fully support this finding.^ Epidemiologic studies on workers exposed to fibrous glass do not provide consistent evidence of pulmonary effects, although some effects were noted (42,47). Similarly, when assessing deaths due to lung cancer in workers exposed to glass wool, studies do not provide strong evidence for increased risk of cancer deaths attributable to glass wool fiber exposures.

The carcinogenic potential of fiberglass has been reviewed by several agencies. The lARC originally classified both glass and mineral wool fibers as Group 2B carcinogens, possibly carcinogenic to humans, based on animal studies (50). Similarly these materials were classified as carcinogens by the National Toxicology program and the American Conference of Governmental Industrial Hygienists (41,49). However a review of the carcinogenic potential of these fibers by lARC in 2001, which takes into account updated human studies, animal inhalation studies, and mechanistic studies, recommends a change in this classification. The lARC has announced that the recent monograph designates both glass and mineral wool as Group 3, unclassifiable as to carcinogenicity in humans, because of inadequate evidence of carcinogenicity in humans and the relatively low biopersistence of the materials (50).

Although both glass wool and mineral wool have been found at elevated levels in the settled surface dust in lower Manhattan, airborne levels are extremely low, and well below a level associated with the worker exposures reviewed in this report. No adverse pulmonary health effects are expected from the airborne SVF levels measured in this investigation.

* Less soluble materials have a longer residence time in the lung and therefore have a greater potential to contribute to tissue damage or malignant disease. Within SVF types, glass fibers and slag wool are considered the most soluble, and therefore least toxic. Mineral wool is less soluble than glass wool. Fibers longer than approximately 15 microns, the diameter of a macrophage, are also cleared less efficiently, leading to a greater potential for adverse effects (26). t Early studies often relied upon injection and implantation studies, which may not accurately predict a pulmonary response from inhalation exposures. A review of inhalation studies indicates that glass wool did not cause pulmonary fibrosis or lung cancer in these animal studies (47). A recent study by Hesterberg indicates no increase in pulmonary fibrosis or lung cancer even at doses of 222 f/cc, although cancer incidence in control animals was considered high (51).

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