Document Ed1O718a7M8RJ9pQ51K5jNdrj

The Assistant Secretary for Health 2. Furthermore, one paper reported that an excess mortality from lung cancer was found in 65 men who had been exposed to an unmeasured concentration of amosite asbestos for less than one month thirty years previously. Tne mortality rate was determined on an age-specific basis. The present indications are that concentrations of asbestos fibers of 100,000 per cubic meter will occur rarely except in the asbestos-processing industry. Asbestos-containing fireproofing and anechoic linings of airducts and plenums, although they are possible sources of asbestos fiber, probably are not major polluters of air within buildings. Currently it is not possible to establish a safe exposure level for the carcinogenic activity of asbestos. Therefore, the exposure values now recommended by NIOSH are based on what NIOSH considers to be the lowest concentration at which asbestos fibers can be monitored reliably using phase-contrast fiber counting procedures. After a thorough review and evaluation of all available sampling and analysis methods, NIOSH believes that phase-contrast microscopy is the only generally available and practi cal technique for routine monitoring at the recommended environmental limit. The recommended TWA standard of 100,000 fibers greater than 5 pm in length per cubic meter of air is intended to (1) protect against the noncarcinogenic effects of asbestos and (2) materially reduce the risk of asbestosinduced cancer. Because it is not possible to specify a safe exposure level for a carcinogen, only a ban on the use of asbestos can ensure com plete protection against this mineral's carcinogenic effect. Therefore, emphasis should be placed on prohibiting the occupational use of asbestos in other than completely closed operations and on substituting other pro ducts whenever possible. Asbestos should be replaced, where technically feasible, by substitutes with the lowest possible chronic toxicities. John F. Fxnklea, 21.0. SPNY 003426