Document jerqkby6vD3ZRxOQQo15LRJO

MEMORANDUM o-- & -2 -2 ~7 DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE PUBLIC HEALTH SERVICE TO : See Belov Center for Disease Control National Institute for Occupational Safety and Health r DATE: l August 8, 1973 J&Uc^~ FROM : Chief, Toxicology Branch, DLCD Chairman, Committee on Threshold Limits, ACGXH SUBJECT: Identification of a Threshold of Response and Estimations of Safety Factors in the Present Recommended Standards for the Industrial Carcinogen, ASBESTOS Enterline et al. (Brit. J. Ind. Med. 30:162, 1973) reported that a study of the mortality from cancer and respiratory disease (asbestosls) of 1,348 retired asbestos workers, of whom approximately 1,000 were exposed to chrysotlle. the remainder to crocldolite*. resulted in the conclusion that "there appeared to be no direct relationship between asbestos dust exposure and respiratory cancer below 125 mppcf-years." This Information is of the highest importance for two reasons: 1) It establishes a threshold of response for a chemical carcinogen. 2) It permits an estimate of ther margin of safety. Incorporated in both the NIOSH and ACGIH recommended standard for asbestos. The margin of safety (SF) in these recommended standards for all forms of asbestos disease and for chrysotlle and crocldolite may be estimated as follows: The NIOSH asbestos recommended standard of 2 fibers/ml > 5 mu in length is equivalent to 0.3333+ mppcf, according to Lynch 4 Ayer (A1HAJ 27:431 (19C For 30 exposure-years Q 125 mppcf > 4.17 mppcf For 40 exposure-years @125 mppcf >3.13 mppcf For 50 exposure-years @ 125 mppcf >2.5 mppcf Estimation of the Safety Factors** in the present NIOSH Standard: r __ For 30 years, 4.17 mppcf SF 0.333+ 12.5 For 40 years, 3.13 0.333+ - 9.4 For 50 years. 2.5 >7.5 0.333+ ' ! received AUG 1 3 1972 HASKELL LABORATORY *According to private communication with Enterline August 7, 1973. **For all types of asbestos disease, cancers and asbestosis. DUP 0903241 SC-DP-04410