Document EBXdndydVLJ78qvZrGYMO0Jb

Ban m *Q*ild* / Q Cw< OA.TT 12/12/67 ' / L. V./ Thctchsr C.W.C. rQMi W. E. Ifesid, Jr., M.D. Msd. 3iv. "XH'CIT rr OATC v-10.11 not; i.:tsoukw t 'o.^MMoa oc CUtflFiiOSHOSTHAliiliffOIKfRJ For your interest ) .' ^ CURRENT STUDIES INDICATE THE TLV FOR ASBESTOS IS TOO HIGH ~ Evidence suggesting that the Threshold Limit Valuo (or expoeure to aeboetos-eontainim matt rial* i* too high waa p relented at tho Western Industrial Ham 1th Conference in San Francisco, September Z9*30 by Leroy Bailor, Rtatareh Specialist la Industrial Hygier at tho Uniwortity ot CalUornia'a School at Public Health <aerkoloy, Calif.), who report on studio* at insulation workoro in tho San Francitco Bay area. Somo of his informaci is summarised below; The midget impinger was used for environmental sampling for dust exposures both* the breathing sene and in general air. The membrane filter waa used in evaluating the environmental exposure to fibrous materials. Sample* were collected using Mi llpore Type AA filters In field monitor cases counseled to personal air samplers si attached to theworkrrn for periods ranging from 30 minute* to 2 hours. Tho flbtr> were counted by clearing a wedge<-thaped segment of tho fittor using a modified tee. nique of tho U.S. Public Health Service at <30 X magnification, using phase contras illumination. Although tho insulation workor In tho Bay aroa works with asbestos-containing produc <5% ot tho time, his overall tlmeweighted average exposure to asbestos'containing materials is below tho presently recognised TLV of 3 mppcf specified by the America Conference of Governmental industrial Hygienists. The three work areas in whiehth dueMevels were above the TLV (prefabrication, tearing out, and mixing) account for 1ms than 20% of his total wort time, however, tho incidence ef radiographic changes indicative of aabostoaia is ovor 2S% la man with 20 years or more of work. That tho present TLV far aaSestas ia not preventing aabettoaia ie supported by these observe tioas coupled with reports from somo asbestos industries which have experienced a d ereaaed incidence in aabeetosia fallowing a reduction in dust counts wall botdw the T 104 DUP 0900882 DU 022280