Document nknX346OBkNb40nmyVE4N7d0a

+1Z\ \ MOUNfSINA! SCHOOL O e MEDICINE of The City University oj New York FIFTH jj anO IFUTH ETUSBT HBV TQFX, MT t 0 9 3 9 Orparttfml af Csmmumtf February 26, 1370 Or William S Pierson Chemistry Department, Scientific Research Staff Ford Motor Company P O. Box 2053 ' Dearborn, Michigan 48121 Dear Dr Pierson, X mi sure you ure aware of the moat recent Issue of the Annals jL Occupational Health (Great Britain) which is devoted to problems of asbestos exposure associated with brake drum re pair X think there Is a fair amount of useful material in it, although s.me additional perspectives and approaches might have beep included Concerning youi letter of January 28, 1970, the following comments might be useful First, we now have a fair amount of experience 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 (phxysotile) 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 Jaeatic, M Rubnitt, M, C Godwin anc; hobert W. Weiskopf "Tissue Response to Intraperi toneal Aviiesios wilt Preliminary Report of Acute loricity o Fvat-Irc, * to isoestos in Mice" in f>vIRCCfrvTAL tsSHAr'CH in v uch it was noted that fibers n .red wel. jeyond '00' C seemed particularly toxic a'.-1 ere r._. tolerated) on iatraperitoaeal injection in i .i.oenti animal We have no knowledge about this in It might be useful to repeat the brake dust studies Johns- Maaville 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" appr - mately the same results by electron microscop;, a. p. * ut 200031 -21 not aware of the magnification they used They felt that this was consistent with the theoretical calculations which showed that the point temperature at the true area of particle con tact could reach 2,000 C under the test conditions, well beyond the temperature at which Chrysotile 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 eoncerned, the following estimates are based upon several sources and arc, X think, accurate I have obtained them from two sources, and the two closely conform For 1965, the follow ing amounts weie used in the United States (in tons) \ \ Matexlal Tons Friction materials Asbestos cement Flooring Paper All other TOTAL 33,000 ISO,800 137,500 140 000 22a ,400 719,700 JS 5 25 19 19 32 100 \ \ There has heen some increase since 1965, but I think a relative percentage usage by the industry has not changed very much. With the advent of disc braltes, 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, I 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, J,-C\ Irvii^ J. SelMffSff, M D Professor \ s, \ l i \\ PS c 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 000035 p*.OOUcD t 3- Mineral fiber lor fireprooflag the steel structure Of this, anywhere froo 3 to 30% beecesea waste, More often at the higher end of the spectrum The fireproofing Material con tains 13-25% asbestos (the remainder being extruded glass, bentonite, etc ), Where adequate precautions are not taken, auch of the va^ta material ay become airborne Sven if only 10% does, a ton of asbestos or acre aay enter the city air.. 4 \ \ r \ \ i it pp.OD'UC'ES BY TO5