Document ppJj2E6VrvKnRBpQDmOpJQDbj

FILE NAME Threshold Limit Values TLV DATE 1993 DOC TLV008 DOCUMENT DESCRIPTION Medical Journal Letter to the Editor - RE TLVS for Asbestos American Journa of Industrial Medicine 959 1993 LETTER TO THE EDITOR Re TLVs for Asbestos Key words asbestos TLV ACGIH dust measurements I write to comment on the letter to the Edi cr Am J. Ind Med 765-766 1992 by Warren A. Cook who died on April 1992. Dr. Cook indicated that in asbestos counting after sampling collection by midget impinger a correction factor for the count was used based on the % composition composition of asbestos in the mineral combination of the bulk material The factor was used to correct the Millions of Particles Per Cubic Foot mppcf count resulting from microscopically counting collected fibers and particles I was a student in industrial hygiene at the Harvard School of Public Health 1955-56 and learned the midget impinger airborne dust evaluation technique from Dr. Charles A. Williams a distinguished instructor in a course on dusts their prop- erties and evaluation The use of such a correcti | factor was never mentioned Nor is it noted in the classic text of the 1954 edition of Industrial Dust by P. Drinker and T.F. Hatch I performed extensive midget impinger sampling in the 1950s and 1960s and never utilized such a correction factor At the American Industrial Hygiene Confere Confere ice and Exposition held in Boston MA June 1-5 1992 I personally asked a number of senior industrial hygienists about this factor all had utilized midget impingers impingers to sample for asbestos Only one had ever heard of the correction factor none had ever used it It is very clear today that the 5 MPPCF rudget impinger TLV was not suffi- ciently protective of workers Consequently it is very important to clearly understand how it was utilized to better appreciate the exposes exposes exposes and corresponding risk levels of the past I conclude that the correction factor cited by Dr. Cook was not widely utilized if used at all in industrial hygiene pract ce with the midget impinger Values of mppcf reported in the literature should not be viewed viewed as having been corrected by the factor mentioned by Dr. Cook Morton Corn PhD The Johns Hopkins University School of Hygiene and Public Health Faltimore MD 21205 REFERENCE Cook WA 1991 TLV for asbestos Am J Ind Med 21. 65-766 Address reprint requests to Dr. M Corn Division of Eldironmental Eldironmental Health Engineering The Johns Hopkins University School of Hygiene and Public Health 615 North Wolfe Street Balumore MD 21205 Accepted for publication September 10 1992 '1993 Wiley Inc.