WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 40 of 56 not known, it is believed cancer incidence is linked to the development of other silica-induced lung disease (34). It is possible the mechanisms involved in the development of silicosis are linked to the carcinogenic process through the production of reactive oxygen species and tissue responses to immune signals and fibrotic changes (36,37). Some researchers have developed dose cancer risk estimates from epidemiologic studies by building off risk estimates for silicosis (34,38,39). A risk assessment produced for both silicosis and lung cancer on the basis of crystalline silica exposures reviews major studies and proposes that lung cancer incidence may be expected to increase by 14% for each additional 1 (mg/m^) work-year exposure above the baseline of 1 (mg/m^) work-year exposure (36).*

The maximum estimated detection of quartz (crystalline silica) in air in lower Manhattan was 19 pg/m^J. Using the above risk estimates, the cumulative exposure for 1-year continuous exposure 0.08 (mg/m^) work-year poses negligible increased cancer risk. Although there are uncertainties in this evaluation, current scientific opinion would indicate short-term exposures to the measured quartz levels do not pose a health hazard.-

If the highest measured airborne levels are representative of long­ term conditions, the cumulative exposure for a continuous 30-year residence would exceed the 1 (mg/m^) work-year cumulative exposure which is believed to be the departure point for adverse effects for both silicosis and lung cancer. Therefore these data cannot rule out the potential for long-term risk. However, the highest airborne level measured during this study is not necessarily representative of long-term exposure. In addition, the XRD analysis for quartz in air is semiquantitative (i.e., an estimated value). This adds additional uncertainty to the risk estimation. As presented in the discussion section of this report, it is expected that the ongoing cleaning of lower Manhattan and natural dispersion should reduce these materials over time, thus reducing long-term risk. Therefore cleaning should be continued and levels of respirable crystalline silica monitored, until the data demonstrate that long-term risk of adverse health effects is minimal.

6. Synthetic Vitreous Fibers

The term synthetic vitreous fibers (SVF) refers to several types of manufactured vitreous fibers: glass wool, mineral wool, and refractory ceramic fibers (RCF) (41,42). Because RCF was not found during this investigation, its health effects are not discussed. The types of SVF found in settled surface dust, glass wool and mineral wool, are primarily skin and upper respiratory tract irritants. Although some data do indicate a potential for pulmonary effects, no adverse effects on the lung are expected from the levels measured in this investigation.

a. Irritant Effects

No iong-term heaith effects are

http://www.atsdr.cdc.gOv/asbestos/lowermanhattan/ResSamp_Sqj2002_Text.html 07/18/2003 NYC-WTC_000178427