Document 2R9EQqmZq2BQJJ4xGBJ0D9aRg

1 July, 1969 Mx' } It Lyneh Department of Hoalth, Kdocation and Wolfarc Public Health Servieo 10.X4 Broadway Cincinnati Ohio 45208 Doav Mv Lynch, Thank you for your letter of June 13,J969, and for tho oopy of your Paper entitlod 'Drake Lining Decomposition Products', Tho last aontenco in my summary of your oonoluslcmo was taken from the draft report which yon coni no in January, 1968, hut 1 aeo that your views have now ohangod, : X BUggost, therofore, that tho final part of my roferonoo to your work should road as followot "At lower hulk lining teirQ>oratures within tho normal operating rango, tho hinder bohind tho surfioe remains intaot, However, tho epot temperature at tho point of oontaot botween tho .lining and tho drum may bo hlghor than tho decotnpofcltion temporature of aoboatoa* Tho decomposition product, thereforo, inoludoa not free asbestos flbros but a different minoral, resulting from thermal metamorphosis#* X hope that this roforonco to your work is now aoooptablo to yon and unless 1 hoax* from yon to tho oontrary 1 will publish it in this foia Tours sinoerely, D K Hloklsh .Tndustx'lal Hygiene 8pseiall/t 8850 1/16# B006 1200 . PRODUCED BY FORD SCF-FORD-0600 li tI BRAKE LINING DECCiPOSITION PRODUCTS BY Jeremiah R. Lynch / -Occupational Health Program ' 1014 Brri.adv.-ay Cincinnati, Ohio 45202 U. S. DEPARTMENT' OF HEALTH, EDUCATION-, AND WELTARE ' Public Health Service . National Center for Urban and. Industrial.Health Occupational Health Prograta . Presented at the Engineers Round Table Thirtieth Anpual"KefctJ.ns^T ~ American Conference of <j>vifrnmentP.l Industrial Kygffcnists . St. Louis, Missouri, May 12-, 1968 ' 012S36 JWK007909 . . . ' brake liniks decomposition- products .. .! . ` ABSTRACT ' ` . . A number of Investigates have found asbestos bodies In the lungs of urban residents who were not occupationally exposed to asbestos. A relationship between the carcinogenic properties of asbestos and the urban excess of lung cancer has been suggested. The decomposition products of brake 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 a very small fraction of the asbestos escaped as free fiber while,the remainder was transformed Into some other, non-fibrous, mineral. A significant release of free fiber occurred only under conditions extreme enough,to produce b^ak^ failure. -, i*'v - G i< ono s JHK007910 BRAKE LINING DECOMPOSITION PRODUCTS ^ Jeremiah R. Lynch* Introduction .. ' " The-occurrence of coated fibers referred to as "asbestos bodies" In the lungs of urban populations not occupationally exposed to asbestos , . <. ' i . ' has been noted by several Investigators. The results of several autopsy series, as sunnnarlzed by Cooper, ^ are shown In Table i. Thomson, ^ in suggesting possible modes of exposure that could account for these bodies, stated "The average private'EStor vehicle wears out three or four sets of brake linings and one or two clutch linings In Its lifetime, and commercial and public transport vehicles wear out many more. These linings consist largely of csbestos which Is ground to dust as the ling9. .' . . wear, and most wear occurs in built-up areas. This alone in most cities . .* would Involve the discharge of many tons of asbestos dust and fibers in the streets each year." Since asbestos has been Implicated as a carcinogen^and lung cancer has a higher incidenceamong urban populations, the fate of the asbestos v?6rn from brake linings becomes significant. *0. S. Department of Health, Education, and Welfare . Public Health Service . Bureau of-Disease Prevention and Environmental Control /National Center for Urban and Industrial Health Occupational Health Program ' 1014 Broadway, Cincinnati, Ohio 45202 . JHK0Q7911 ' - -2- ' ^ . ' . Table 1 - . Asbestos Bodies in Human Lunes' * ' Location Cape Tovn (2) Miami (2). Pittsburgh (3) Johannesburg (A) Finland (5) Montreal (6) . San Francisco (1) ' 1963 1965 1965 1965 1966 1966 1966 X Positive 26 27 41 39 58 48 42 012839 i i JWK007912 ii | i -3- Brake Lining Composition `. * ' ' . . . * .* f The average coraposicion of typical brake linings of the type tested IS-shown In Table 2. Individual nixes may vary considerably from these averages. ' ' ' Table 2 . ' . ' - Brake Lining Composition . - Ingredient Asbestos Resins and Polymers Oxides and pigments Metals Carbon, graphite, etc. ' ' Automobile 55 28 9 3 5 1007. Truck . 33 48 16 2 1 1007. Each of these ingredients performs a'particular' function. The asbestos provides strength, heat resistance and selective decomposition .* *v under stress. The resins and polymers hold the other Ingredients together. Various oxides are added as pigments and to improve the grip of the lining on the drum. Soft metals such as lead and brass improve wear while carbon and graphite serve as friction modifiers. Brake lining quality depends to a large extent on the type of binder OKt) . used. . Linseed oil, which begins to-decompose at about 450 F-, Is used for. light service brakes. More 'demanding service requires brakes made from ca'shew' type resins or oil modified, phenolic resin's 1 ;Thesc ingred!ents'- are _ mixed, either dry or with a solvent added,' formed, into- shape and cured' 012840 JUK007913 . -4- in an oven. The hardened lining Is chen cut, ground and sanded to the precise dimensions of the finished linings. ' The dust produced by the abrading operations in asbestos friction product factories (Figure 1) . contains free asbestos fibers thap are similar to Chose In industries `< where cancer is known to be in excess (10). The question to be resolved, . ,l _ '' . ' . therefore, is whether the dust produced by the normal wear of brake linings contains this same type of free asbestos fiber. - Test Methods '' ' . In an initial exploratory survey, the dust obtained from Inside automobile brake drums removed for brake relining was examined by electron micrograph. Figure 2, which is typical of the series, does not reveal any free fibers. However, this finding did not eliminate the possibility that free asbestos fibers were released and that they had escaped into the atmosphere. To examine this hypothesis a series of experiments as devised to permit sampling decomposition products of the .lining undjr simulated operating conditions. The tests (Table 3).were performed with the. brake testing machines in the laboratory of a major brake lining manufacturer. Most of the tests were performed on a friction-tcstir.g machine which used one-inch-square samples of the test lining. Heating and cooling apparatus permitted control of drum temperature from those.. encountered with Intermittent brake use to the maximum temperature which . .occurred only in'extremely rapid or.Vpariic" stops from high spee<f. ; . Other tests were performed on a brake-testing dynamometer which subjected 012841 JWK007914 a complete brake assembly to'a.series o stops and starts from different speeds and at different deceleration rates to simulate actual driving conditions. In these tests the drum temperatures varied according to the driving condition simulated. During each run at a test condition, a -sample was 'collected on an 0.8 ji pore size membrane filter. Electron - micrographs of these' filters were examined to determine the presence of free asbestos fibers and to quantify these fibers when more than a few occurred. . - 012S42 JHK007915 6 * . Table 3 Teat Results by Electron Micrograph Produc t Brand 1. Automobile A drum brakes 2. n B 3. tf C 4. * ifi C 5. . D French Test ' Method Friction Friction Friction Friction Friction No. of Samples 1 6 1 1,6 Conditions Presence of of Test-F Free Fibers 300-800 Few 250-800 None 5 300-700 Few 1 700-900 Numerous 5 300-800 Few I Free Fiber* <1 6 <1 '---10 <1 6. E Friction ' 5 300-700 Few 7. F Friction 5 300-800 Few German 8. C Fricticn 2 . 100-500 Few 9. * 10. M ft C Friction H Friction 1 600-700 Numerous 2 100-600 Few <1 <1 <1 w-15 <1 11. Automobile clutch J 12. Automobile ' disk brake K 13. Bus drum breke L 14. M 15. Truck drum ; f' brake (light) Dynamometer Dynamometer - Dynamometer Friction Friction" ' 1 1 1 2 ' io' norasl driving normal driving city driving 450-550 ; ;-300-80CV ] None 0 Few <5 None 0 None - FetT 0 : .y ^Height estimated from fiber volume. - 012843 JWK007 91 6 i ,! !' i *. ! ii t j ' 7- Results ' *. ' '' . . The object of the tests vij to determine what proportion of the asbestos known to be present In the lining appeared as free fiber In the decomposition product.* No attempt was made at a mass balance between the material worn from the lining andjthe decomposition product since It was not possible to collect all of tile decomposition product. However, the percentages obtained in the fraction of decomposition product examined are applicable to the total material worn from the brake and may be compared to the percentage of esbestos originally present. In all but a few tests the automobile drum brake linings showed less than IT-free. fiber In the decomposition product as compared to about . * 50% in the lining. An election micrograph of the decomposition product obtained from a typical test In this group Is shown In Figure 3. In those tests where e significant mass of free fiber was released (Flgure*4), the temperature was in an extremely high range for the lining in question as evidenced by rapid drop in the coefficient of friction. Had these linings been subjected to like conditions in a vehicle, the brakes would'have failed. . ' Similar rcsults'werc obtained In the bus and truck drum braka tests and in the clutch test. The experimental model disk brake tested did releese some 0>57.) free fibers, but no conclusion can;be dpawn freti.s - single sample. . ' " ~\ "* " ' 1 012S44 JWK007917 -8- Discussion ---------------- -- .' < . ' . '. ' Except In all but the most extreme driving conditions, only a very small fraction of the 30 to 50% asbestos present .in a brake lining escapes into the atmosphere as free fiber. The question remains: What happened to the asbestos? A prevalent theory of brake operation holds that wear occurs not by abrasion of1 the ling by the drum but by the production of minute areas of intense heat at the points of contact between the di-uro and the lining. Decomposition, not only of the binder but of the asbestos as well, occurs at these locations since the break down temperature of asbestos-, about 90(1 F. is exceeded.. The decomposition products will thus include not free asbestos fibers,- but a different *- ' ,, mineral resulting from the thermal metamorphosis of the' asbestos. Some .independent experiments done at a brake lining- research laboratory^*^ have shown that all of the magnesium present in the . -. .. " e chrysotile asbestos orgir.ally in the lining can be accounted for in the ' ` . -- . " ) decomposition products. However, the characteristic X-ray diffraction . pattern of chrysotile asbestos had vanished. Thus, it is apparent- that under conditions in which asbestos is worn from the lining of a brake, the asbestos is destroyed.' Conclusion ... - . Only a very smell proportion of the asbestos worn from breke . -. linings is released as free.fiber; the'remainder is converted into"so'me.- other mineral as a result of the extreme temperatures generated at small ... ' * ' ' *. ' ' . * ' spots on the lining surface. Thus, although urban aJLr-. contains a-few ' 612S45 JWK007918 .- 9 free fibers as a result of brake lining wear, they represent a very ' small, proportion of . the total asbestos used in the manufacture of brakes. Hany sources of respirable fibers not associated with asbestos products have been Identified, and the free fibers from brake lining wear appear to be an inconsequential health facto' . I. in urban air pollution. .1 . . . 012 JWK0Q7 919 10 - ' References 1. Cooper, W. C.: Asbestos as a Hazard to Health. Arch, of Env. Health. 15:285 (19671. . " . '' ' 2. Thomson, J. G., R. 0. C. Kaschula and R. R. McDonald: Asbestos Is as a Modern Urban Hazard. S. Afr. Med. J. 37:77 (1963). 3. Cauna, D. R. S. Totten and P. Cross: Asbestos Bodies In Human bungs at Autopsy. JAMA 192:37 (1965). '' 4. Web6ter, I., In discussion of Thompson, S. F. : Physiological Effects of D20 In Mammals, Ann. N. Y. Acad. Scl. 84:736 (I960). . 5. Meurman, L.: Asbestos Bodies end Pleural Plaques In a Finnish series of Autopsy Cases,.Acta Path Microbiol Scand Suppl 181:107 (1966). 6. Aryllrel, L. and V. Thiirlbeck: The Incidence of Asbestos Bodies In the Lungs of Random Autopsies In Montreal, Canada. Med. Assoc. J. 95:1179 (1956). . . tni . _ ,7. Thomson, J. G.: Asbestos and the Urban Dweller. Ann. N. Y. Acad. ' ..Scl. 132:196 (1965). ' 8. Sellkoff, I. J., J. Churg and E. C. Hammond: Asbestos Exposure and Neoplasia. JAMA 188:22 (1964). '' * 9. Buell, P. and J. E. Dunn: Relative Impact of Smoking and Air Pollution on Lung Cancer. Arch, of Env. Health 15:291 (1967). ; 10. Enterlinc, P. E. and M. A. Kendrick': Asbestos Dust Exposures at Various Levels and Mortality. Arch. Env. Health 15:181 (1967). 11. Sinclair, D.: Study of Wear Dust from Brake lining. Johns-Manvllie Research and Engineering Center, personal communication (1967). 12. Cralley, L. J., R. C. Keenan, J. R. Lynch and W. S. Lalnhart, M.D. : Sources.' and Identification of Respirable Fibers'. Am. Indust. Hyg. Assoc. J.'29:2 (1968). .. 0!2S4 JKK007920 Figure l. Brake lining factory dust . i 012S43 JHK007 921  4r *rrara 4; -- 0 ; rN*^ J.- * -a '* ^) SO''** ' Wr \ ? Kr -<* /- -r*. : n. Ci 13 *- r^~Vv 0 'A- ,> rt * i> - o'* ^ ^ D . : 6 r> 0 ^ ` ,o (! -ft-C5 O' !>-, V? O'A o. .<> <5 . o-i-) rA i - <f * "O v O- O' -N / ,, /*> r-' ki ^tv k ,c pp V cr-C" O. P't \ . / ^ i> * ' -o ^al <; V r-V cf . . 5 o \ 'O r: o-k . PC k. . i '^ \i> V . t .*. '-". (ss l'^ .00 . /7 , 1% ?'?v? 00 '-\ ^- . . \vo e-*'V * 4 c V . *;- ox v- - * 2> -r ? 4^* o chv r c\/0 W~ VO..* i '. t J w ^/ * \P. tc :c"; > U- * .. vdOO. *? -j Figure 2. Dust removed from brake drum: 012S4-? JWK007922 V r . *. \#i } j fri. i \ i- i. f i* - * ' : ' { < i . * f . i t *. 1 'tr Figure 3. Decomposition product from normal yvear - . of brake lining . .. 012850 JWK007923 i \ . . Figure 4. Decomposition product from brake lining c at failure . 0 I 285 JWK007924 \- 2 H * A COPY Public Health Service - BSS TO: Asst, to Chief for Epidemiology and Field Studies, DOH FROM: Engineering Section SU3J: Report bn Brake Decomposition Tests At the New-York Academy of Sciences Conference on the Bio logical Effects of Asbestos" It was stated: ll) "The average private motor vehicle' wears out three or four sets of brake linings and one or two clutch linings In Its lifetime, and commercial and public transport vehicles wear out many more. These linings consist largely of asbestos which Is ground to dust as the linings wear, and most wear occurs In built-up areas. This alone In most cities would Involve the discharge of many tons of asbestos dust and fibers in the streets each year." This statement was meant to explain, In part, the presence of "asbestos bodies" observed In the lungs of non- occupatlonally exposed residents of Cape Town, South Africa, and Miami, Florida. To Investigate this possibility, a study of the mode of dis integration of brake shoes under simulated operating conditions was undertaken by using test facilities made available by the American Brake Shoe Company laboratory at Kahwah, New Jersey. These tests were made as part of the Division of Occupational Health's overall epidemiological study of the asbestos processing Industry. . Automobile brakes are composed of from 30"50X asbestos (usu ally chrysotlle) held together with various resins and con taining such other Ingredients as carbon, brass filings and rubber. Theoretically, a brake wears by abrasion of the sur- . face by the drum and by thermal decomposition of the binder. The question to be resolved was: What fraction, If any, of the asbestos Is liberated a3 free fiber In the wearing process undezj^yarlois operating conditions. (1) Thomson, J.G.: Asbestos and the Urban Dweller, Annals of the New York Acad, of Science, VI32, Art. 1 (196-214), Dec. 1965 / rx*- ,4ncl r 011950 JVIK007 833 -e- Asst, to Chief for Epidemiology and Pi eld Studies, DOH -- 4/8/66 At the Kahwah laboratory a number' of brake testing dynamom eters were available which could simulate various operating conditions. These machines were set to test a variety of typical brakes and air samplea of the decomposition products were taken on membrane filters. Electron micrographs were made of the deposits thus collected and a number of fields were scanned for the presence of fibers. Where significant numbers of fibers were found an estimate of the fraction of the decomposition product which was fiber was made by sizing all of the particles and fibers seen. The results of these tests are as follows: Decomposition of Brake Linings No. Type of Brake Condition of Presence % Fiber Test of Fibers (mass) 1 Disk Brake Normal' driving Few <5 2 Bus Brake City driving None 0 3 Automobile 100-200 P drum Few temperature 4 Automobile Brake 300-500 F drum temperature *0 . <1 5 Automobile Brake 600-700 F drum Numerous temperature 15 6 Automobile Clutch Normal driving None 0 7 Bus Brake **50-550 P drum None temperature 0 8 Automobile Brake 100-300 P drum None temperature 0 9 A.-Vu*Ttom.. -obile B' rake 400-600 P drum Few temperature r'O 10 Bus- Brake **50-550 F drum None temperature 0 One clump of fibers still largely coated with binder and having a roughly rectangular shape. 011951 JWK007 834 -3Asst, to Chief for Epidemiology and Field Studies, DOH -- 4/8/66 In only one case (No. 5) did the percentage of fiber approach the percentage of asbestos in the brake; and that was at a temperature of 600-700 F as compared with normal meiziDua operating temperatures for automobile brakes In the range of 550-600 F. It appears that when the design temperatuxe of a brake is exceeded., the binder decomposes and releases part of the asbestos as free fiber. At lower operating tempera tures the asbestos worn off the lining remains encapsulated In the binder and few free fibers occur. Thus, although urban air would undoubtedly-contain a few-free asbestos fibers as a resuit of disintegrating brake shoes, they would represent an extremely small percentage of the total asbestos used In the manufacture of brakes. Jeremiah R. Lynch Senior Sanitary Engineer Engineering Section Research and Technical Services Branch t 01J952 JWK00783S