Document 2j6mKJNDk5vzEGEm8N2QGmOog

4 ?A-00265 Jtmnlah R. Lynch National Center (or Urban and Industrial Health Brake Lining Decomposition Products A number of investigators have found asbestos bodies in the lungs of urban residents who were not oc cupationally exposed to asbestos. A relationship between the carfnogerdc properties of asbestos and the urban excess of lung cancer has been suggested. The decomposition products of broke linings have been described as a possible source of these fibers. Brake testing laboratory methods were used to test fiber emission from a variety of friction products:...Only o very small fraction of the asbestos escaped as free fiber while the remainder was transformed Into some other, nonfibrous, mineral. A significant release of free fiber occurred only under conditions extrema enough to produce brake failure. i : Kbfl' r Table I. Asbestos bodies In human lungs. Location Year Positive Cape Town (0 Miami (2) Pittsburgh (3) Johannesburg Finland (6) Montreal (6) San Francisco (l) 1963 26 1965 27 1966 41 1966 39 1966 6B 1966 49 1966 42 Table It. Brake lining Composition. Ingredient Automobile Truck Asbestos Resins end paiytnera Oxides end pigments Metal* Carbon, graphite, etc. 55 28 9 a 6 10#5t 33 48 16 2 m . Air. Lyuoh Is Chiet of the Lab-, oratory of Bng(nearing, Occupa tional Health Program, Public Health fWvica, Department nf Health, Education, and Welfare,' TD14 Broadway, Ctaolwiati, Ohio 45202. The onourmnoft of coated fibers re ferred to os "aabestoB bodies" In the lungs of urban populations not oc cupationally exposed to asbestos has been noted by Beveral investigator*. The results of several autopay series, os summarised by Cooper,1 are shown in Table I-1-* Thompson,1 in suggesting possible modes of exposure that could account for these bodies, stated: The average private motor vehicle wears out three or four set* of bndco linings and wie or two ohrtoh linings in its lifetime, and commercial and pdblrn transport vehlolee wear out many mors. These lmbt&eonaiRt largely of asbestos which Is ground to dust ss the finings wear, and most wear occurs in built-up areas. This alonoln most cities would involve tbs discharge uf many tons of asbestos dust and fibam in the streets oachyew. Slnca asbestos has been implicated ss a carcinogen1 and lung cancer has a higher inoldcnoe* among urban popula tions, the fate of the asbestos worn from brake linings becomes significant Brake Uning Composition The average composition of typical1 brake finings of the type tested is shown in Table II. Individual mixes may vary considerably from these averages- Each of these ingredients performs a particular funotion. The asbestos pro vides strength, beatresistance, and selec tive decomposition, under stress. The rosins and polymers hold the other in gredients together. Various oxides are added as pigments and to Improve the grip of the lining on the drum- Soft metals such os load and brass improve wear while oorbon and gmpbito serve art friction modifiers. Brake fining quality depends to a large extent on the type of binder used. Linseed oil, which begins to decompose at about 45QF, is used for light service brakes. Mora demanding service re quires brakes made from cashew type resins or oil modified phenolic resins. These ingredients are mixed, either dry nr with a solvent added, formed into shape, and cured in an ovil' The hardened lining is then out, ground, and sanded to the preoiss dimensions of tho finished linings. The dust produced by the abrading operations fix asbestos friction product factories (Figure I) contains tree asbestos fibers that are similar to those in industries where can cer is known to be in excess.10 Tbe qoestion to be reeolvod, therefore, b whether the dust produced by the normal wear of brake linings contains this same typo of free asbestos fiber. Test Methods Iu on initial exploratory survey, the dust obtained from inside automobile broke drums removed for broke refining was examined by electron micrograph. Figure 2, which is typical of tiro series, does .not reveal any free fibers. How ever, this finding (fid not eliminate the possibility that free asbestos fibers wore rdeasod and that they had escaped Into tbe atmosphere. To examine this hy pothesis a series of experiments was devised to permit sampling decompose. turn products of the lining under simu lated operating conditions. Tho teals (Table HI) were performed with tbe broke testing machines in the laboratory of a major brake fining manufacturer. Most of tbe tests wore performed ou a fri< on lini per fro mi ter exl hi{ on i as ! SP< , ml ' dii pe 1 tn| ; ru co fi) fit : Pt S R( x kj P< tl a w P w P 0 t t t f 1~irnl # Ho 41. PntlxHnn Pfmtrnl AftSOdatjCn SCF-FA-6180 P-EXHIBIT-013 tnotion-testing maohine which used drum brake linings showed less than e onotach-aquare eamplea of the test lining. Heating and cooling apparatus 1% free fiber in tbe decomposition product os compared to aboufc50% in the permitted control of drum temperature fining. Au electron micrograph of tha jarom those enoounterod with inter decomposition product obtained from a y >0 mittent brake use to the maximum temperature which occurred only in typical test in this group is shown In figure 3. In those tests where a sig k. extremely rapid or "panic" stops from nificant mass of free fiber was released y highspeed. Other tests were performed on a brake-testing dynamometer which (Figure 4), the temperature was in an extremely high range for tbe lining in ft subjooted a complete brake assembly to question as evidenced by rapid drop in id a series of stops and starts from different the coefficient of friction. Had these w speeds and at different deceleration linings been subjected to film conditions y rates to simulate actual driving con in a vehicle, tho brakes would have 03 ditions. In these tests the drum tem foiled. 1) peratures varied according to the driv Similar results were obtained In the re ing condition simulated. During each bus and truck drum brake tests and hi n- run at a test condition, a sample mu the dutch test. The experimental model h collected on an 0^i< pore use membrane disk brake tested did ideate some is filter. Electron micrographs of these (>6%) free fibers, but no conclusion ho filters were examined to determine the can be drawn from u single sample. AS presence of free asbestos fibers and to Discussion . quantify these fibers when more than a few ocoumd. Except In all but tbe most extreme driving conditions, only a vary small Figure 4, Decomposition produot Irom brake Ilwngattallufo- ho Results ite fraction of the SO to 60% asbestos pres ent in a brake lining esoapes into the The object n( the tests was to deter atmosphere as free fiber. Tbe question mine what proportion of the asbestos remains: What happened to the se- known to be present in the fining ap beitosf A prevalent theory of brake IV- peared as free fiber in the decomposi Operation holds that wear occurs not thc tion product No attempt was mnde at by abrasion of the lining by the drum a mass balance between the material but by the production of minute areas worn from the lining and the decom of intense heat at tbe points of contact position product since It was not pos between the drum and the lining. Do- sible to collect all of tire decomposition oomposltion, not only of the binder but product However, the percentage of tiie asbestos as well, ocours at these obtained in the fraction of decomposi locations since the breakdown tem tion product examined ore applicable perature of asbestos, about 900F, is the to tho total material worn from tha exceeded. Decompoation products will y brake and may bo compared to the include not free asbestos fibers, but a .er- pereen togs of asbestos originally present different mineral resulting from thermal j a In all bat a few tests the automobile metamorphosis of asbestos. 2/12/2003 WED 10:32 FAX 312 996 1899 UIC LHS CHICAGO @004 Table III. Test results by electron micrograph. Test Product Brand Method Presence No. of Conditions of Free % Free Samples of Test-F Fibers Fiber* 1. Automobile A Friction drum brakes 2. Automobile B Friction drum brakes 3. AulomobHo C Friction drum brakes 4- Automobile C Friotion drum 6 500 - 800 Few <1 8 230 - 800 None 0 B 300- 700 Few <1 1 700 - 800 Numerous -10 5. Automobile D Frtcdon drum French brakes S 300-900 Few <1 6- Automobile E Friction drum S 300-700 Few Cl brakes 7. Automobile F Friction s 300- 800 Few <1 t; drum German tj brakes 8. Automobile G Fricdon drum brakes 2 100-500 Few Cl I 9. AutomobPe G Friction drum 1 600 - 700 Numerous ~15 brakes 10. Automobile H drum brakes Friction 2 100-600 Few d n. Automobile J dutch Dynamometer 1 Normal None driving 0 12. Automobile K Dynamometer 1 Normal Few disk driving <5 brake 15. Bus drum L Dynamometer 1 City None brake driving 0 M- Bus drum M Friction brake 2 450-550 None 0 16. Truck drum F Friction brake 10 200 - 800 Few Cl Weight oittMed from fiber volume- Some independent experiments dona at a brake fining rcsearoh laboratory" have shown that ell of the magnesium present in the ohtywrtile asbestos orig inally in the fining can be accounted for in the decomposition products. How* ever, the characteristic X-ray diffrac tion pattern of chrysotile asbestos had vanished. Thus, it is apparent that under conditions in which asbestos is worn from the lining of a broke, the asbestos is destroyed. Conclusion Only a very small proportion of the asbestos worn from broke finings is released as free fiber; the remainder is . converted into same other mineral as a result of the extreme temperatures gen erated at smell spots on the lining sur face. Thus, although urban air con tains a fewfree fibers os a result ol brake lining wear, they represent a very small 828 proportion of tiro total asbestos used In manufacture of brakes. Many sources of roapirablo fibers not assootated with asbestos products have been identi fied,11 and free fibers from brake lining wear seem to be an inconsequential health factor in urban air pollution. References 1. Cooper, W. O., "Asbestos as a baasxd to feaKh." An*, of Btis. HtW. Hi 285(1987). 3. Thomson, J. CL, R. 0. CL, and MnTwmaM, R. R.. "Asbestoais as a modem urban hassra," & Afr. Mid. J.SV 5 77(1963). 3. Cauna, D., Totten, R. S., sod Grew, ?., "Asbestos bodies in human loan at autopsy," JAMA, 192 : 87J198G). 4. Webster, X, in discussion of Thomp son, 8. F., Thysinlogical effect of DiU in mammsls," AiuuN. Y. Acad. ScL, 84:788 (1900). 5. Meurnmn, X, '`Asbestos bodies and pleural plaques in a Finish sense of autopsy eases," Acta Path Microbiol Stand Supply 181:107 (1988). 8. Aryilrel, I>. and Tbudbosk. W.( `The biodenoo of asbestos bodies u> the lungs of randan autopsies In Montreal, Canada. Med. Auoc. J., 93: 1)79 7. Wmwm, X G_ "Asbestos and the w* bon dweller," Atm. N. Y. Acad. So., 182:198(1985). 8. Befikeff, I. J.jChurg, J, and Ham mond, B. C~ "Asbestos exposure and neoplasia."/AifA, 188: 22(J8M). 9. Buell, F. and Bonn, J. FL "Relative hspaot of smoimig end aa pajteto1 on lung eoaaer," Anh. ojBits. Boom, IS: 391 (1987). U). Entertine, F. E. and Kendrick, M-. A-, "Asbestos dost exposures at vsxjou* lends and monaltty/' Arch. Boo. htahh, IS: 181 (1987). 11. Sinclair, D., "Study of wear dust from brakelining," Johu-MaavlllgBas wl Eng Obr., personal communication (MW). 12. Craliey, L. J., KeenanJR. 0-, Lynch. J. JCand Loinhart, W. 8.. and identification of respirable ab**o> Amer. jnd. Hyg. Assoc. J., 29: 129 (1988). Journal of the Air Pollution Control Association -j Do