WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 42 of 56 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.

7. Asbestos

Asbestos refers to a group of natural fibrous silicate minerals of various structures (18). Used primarily for its fire resistant properties and as an insulation material during the 1900s, asbestos is now known to cause pulmonary damage, lung cancer, and mesothelioma. Asbestos fibers less than 2 microns in diameter and less than 5 microns in length with a 3:1 aspect ratio may enter and deposit in the alveolar and pleural regions of the lung (10). Material that is not cleared by the normal processes of the lung will remain, resulting in possible damaged tissue, fibrotic lesions, and cancer (10,52-54). Fibers may also migrate from the lung to the pleural lining, causing mesothelioma. This discussion will focus on the most studied health effects, asbestosis and cancer. It should be noted that the chrysotile asbestos found in settled surface dust during this investigation is believed to be cleared from lungs to a greater degree than other forms of asbestos (10). Therefore the following review, which considers all forms of asbestos, would be conservative for chrysotile asbestos exposures.

a. Asbestosis

Asbestosis is similar to other mineral pneumoconiosis of the lung. Fibers are deposited in the lung and remain due to their insoluble nature and the inability of lung macrophages to engulf and remove longer fibers (>5 microns in length) (10,54). These fibers can create localized tissue damage, stimulate the immune system, and create a scarring of the lung.

Asbestosis has been observed in workers exposed over several years to levels much higher than seen environmentally. It is believed the cumulative exposure to asbestos correlates to the development of asbestosis, and some cases of asbestosis have been reported with only a brief high exposure documented (55).

http://www.atsdr.cdc.gOv/asbestos/lowermanhattan/ResSamp_Sep2002_Text.html 07/18/2003 NYC-WTC_000178429