Document 5Db6RMmY9DoZkE6BG9Kr4MN45

MOUNJ SINAI SCHOOL OF MEDICINE of The City University o) New'York FIFTH AVlisUt AND iooTH STREET-NEW YORK, N.Y. I#QJ DfparimfBl of Community Tititctnt February 26, 1970 Dr. William R. Pierson Chemistry Department, Scientific Research Staff Ford Motor Company P.O. Box 2053 ` Dearborn, Michigan 48121 Dear Dr. Pierson: ' I am sure you ure aware of the most recent issue of the Annals jI Occupational Health (Great Britain) which is devoted to problems of asbestos exposure associated with brake drum re pair. I think there is a fair amount of useful material in it, although some additional perspectives and approaches might have beeii included. Concerning youv letter of January 28, 1970, the following comments might be useful. First, we now have a fair amount of experience }n evaluating the asbestos content of ambient air under varying circumstances. It is apparent that unless electron microscopy is undertaken at at least 31.000X direct magnification most of the fibers (fibrils) will not be seen. This is especially true when, as is usually the case, the mounting technique tends to separate the fibers into their unit fibrils (chrysotile). We are currently studying whether higher magnification would be preferable, from the same point of view. Second, insofar as change in the nature of the fibers is con cerned, your remark is perceptive. There is an addendum to a paper of JuraJ Jacatic, M. E. Rubnitz, M. C. Godwin ar.c Hubert W. Weiskopf "Tissue Response to Intraperitones! At-ht-scos wait Preliminary Report of Acuti luricity o- Kvac-lr*. *co Asbestos in Mice" in ENVIRC-'-'.,.!F'?Ai RESEARCH li. wiich it was noted that fibers n* jted wei. beyond TOO' C seemed particularly toxic *' \ . t*re r.vv tolerated) on lntraperltoneal injection in * -.i .mental animal. We have no knowledge about this in It might be useful to repeat the brake dust studies. Johns- Manville has undertaken some studies on this problem and found that almost all of the chrysotile could no longer be detected by "light microscopy or x-ray diffraction". However, light microscopy would be inadequate; they did, also, ge* ippr .- mately the same results by electron microscopy, a. pi. i w,, SCF-FORD-0630 -2 - not aware of the magnification they used. They felt that this waa consistent vlth the theoretical calculations which showed that the point temperature at the true area of particle con tact could reaqb 2,000 C under the test conditions, well beyond the temperature at which chrysotlle decomposes thermally. Surely the matter could be settled by an appropriate test de sign. This should be undertaken. Insofar as the quantity of asbestos used for brake linings is concerned, the following estimates are based upon several sources and arc,, I think, accurate. I have obtained them from two sources, ai$d the two closely conform. For 1965, the follow ing amounts weie used in the United States (in tons): Material Tons Friction materials Asbestos cement Flooring Paper All other 33,000 180,800 137,500 140.000 228,400 TOTAL: 719,700 5 25 19 19 32 100 There has been some increase since 1965, but 1 think a relative percentage usage by the industry has not changed very much. With the advent of disc brakes, the asbestos industry antici pates a decrease In the total tonnages used in the future, in brake linings. To repeat, while it is my informed guess that brake linings contribute less than is commonly assumed to asbestos contamin ation of the ambient air, 1 think this should be documented, precisely because of common assumptions. Should you think this would be useful, we would be happy to explore with you such assistance as we might be able to offer in an appropriate investigation. Sincerely yours, ^. C\ Irvli^ J. SeliiWff, M.D. Professor IJS:sa P.S. To judge the comparitive contribution of another asbestos use, for example, one could consider the sprayed insula tion industry. Here, an average New York high-rise office building would use approximately 200 tons of sprayed gOOO c mineral liber lor fireproofing the steel structure. Of this, anywhere from 3 to 30% becomes waste, more oftea at the .higher end of the spectrum. The fireproofing material con tains 15-25% asbestos (the remainder being extruded glass, bentonite, etc.). Where adequate precautions are not taken, much of the wa^te material may become airborne. Even If only 10% does, a ton of asbestos or more may enter the city air.