EPA memorandum regarding asbestos reservoir, June 2002

NYC 9/11 Public Portal Document

Potential health effects related to asbestos exposure. The nature of asbestos-related diseases; routes of exposure; dose-response relationships and the lack of a safe exposure level; the synergistic effect between cigarette smoking and asbestos exposure: the latency periods for asbestos-related diseases; a discussion of the relationship of asbestos exposure to asbestosis, lung cancer, mesothelioma, and cancers of other organs, [emphasis added]

Data showing background levels of asbestos in dust inside buildings

Because it is impossible to get away from all asbestos pollution because of the widespread past use of this material in brake linings, building insulation, etc., it is not realistic to clean up asbestos contamination to zero levels, even though this would be desirable. Cleaning up to background levels is the only solution. Under the CAA, all areas around an asbestos site must be tested and cleaned up so that there is no asbestos above background levels.^'

A widely accepted guideline for asbestos dust levels in relation to background is given in Table 2. If “background level” is defined as the dust levels inside buildings where no asbestos containing materials are used, then the level is less than 200 asbestos structures per square centimeter of surface area (s/cm^). There are also levels categorized as low, above background, and high, based on measurements of a large number of surfaces inside buildings.

Estimating air concentrations and risks from settled dust levels

When air concentrations are unknown, or when available air testing is not sensitive enough to detect asbestos at the extremely low levels related to cancer, it is possible to use settled dust levels as a way of predicting air levels. Appendix A provides a chart for estimating air levels of asbestos from measured asbestos levels in settled dusts. Appendix B provides a chart relating air levels to cancer risks.

This method is widely recognized. It is used not only in the field of asbestos, but also for dusts containing other toxic substances such as lead, beryllium, uranium particles, alpha emitters, radioactive iodine, zinc sulfur powder, and microorganisms.^^ It involves using experimentally determined ratios of levels in surface dusts to air levels, depending on the amount of human activity that would stir up the dusts. These ratios are called “K-factors”.

The air test that EPA is providing, the AHERA TEM clearance test, is not sensitive enough to measure asbestos at the very low concentrations that can cause asbestos-related diseases such as lung cancer, mesothelioma, and asbestosis. The “passing” level of 70 structures per square millimeter is the same as about 0.01 PCM-equivalent fibers per milliliter (PCM f/mL).

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