Document GKVNbe98j3x1NV25XRB178Q3n

FILE NAME: Kaiser Gypsum (KG) DATE: 1993 DOC#: KG095 DOCUMENT DESCRIPTION: Letter to the Editor from Morton Corn, Johns Hopkins, RE "TLVs for Asbestos" - American Journal of Industrial Medicine American Journa of Industrial Medicine 23:959 (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 or [Am. J. Ind. Med. 21:765-766 (1992)] by Warren A. Cook, who died on April i, 1992. Dr. Cook indicated that in asbestos-in-air counting after sampling collectioi i by midget impinger, a correction factor for the count was used based on the % cot iposition of asbestos in the mineral combination of the bulk material. The factor vas used to correct the Millions of Particles Per Cubic Foot (mppcf) count result ng from microscopically counting collected fibers and particles. I was a student in industrial hygiene at tht Harvard School of Pubjic 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 tn 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 impin;;er sampling in the 1950s and 1960s and never utilized such a correction factor. At the American Industrial Hygiene Conference 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 impingi rs 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 r lidget 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 expos ares 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 as having been corrected by the factor mentioned by Dr. Cook. Morton Corn, PhD The Johns Hopkins University School of Hygiene and Public Health I altimore, MD 21205 REFERENCE Cook WA (1991): TLVs for asbestos. Am J Ind Med 21:' 65-766. Address reprint requests to Dr. M. Corn, Division of Ei ivironmental Health Engineering, The Johns Hopkins University School of Hygiene and Public Heal h, 615 North Wolfe Street, Baltimore, MD 21205. Accepted lor publication September 10, 1992. 1993 Wiley-Liss, Inc.