Document 93Q47gjMJDOVoMrK5jrxMG8VR

Jeremiah R. lynch Notional Center for 'Jroan and Industrial Health TCaIRtIffs I 3e1xh3ib2it 6^D Brake Lining Decomposition Product! PLAINTIFF'S EXHIBIT wy-notowi A number of investigators Hay* found asbestos bodies in th* lungs of orbon resident* who were not oceuparionaily exposed to asbeitos. A relationship between th* carinogenic prop*rtis of asbestos and the urban excess of lung cancer has b*n suggested. TH* decomposition products of brake linings have b*n describad as a possible source of th*s fibers. Brak* tssting laboratory methods wr* used to test fiber mission from a variety erf friction products. Only a v*ry small fraction of th* asbestos escaped as fre* fiber while the remainder was transformed into tome other, nonfibrows, mineral. A significant release of fre* fiber occurred only under conditions extreme enough to produce brak* failure. Tsfete L Asoettas bodies in numtn 'ungv Location Year % POSitTV* Caoe Town (2) 'Si*mi (2) riraaurjn (3) Jcntnnesaurg (1) Finland (5) Montreel (4) S*n Francsco (1) 1963 1963 1963 1963 1966 1966 1966 2i H 33 51 a 12 TaMe It. Srstie lining composition. ingredient Automootie T.-uc* Asoestos Resms and eoymff Oxides and Metals Careon. graphite. tc. S3 a i 3 3 TOC 33 4 16 2 1 ~ 05* Mr. Lynch is Chief of the Lab oratory of Engineering, Ocnpe* (iocuI Health Program, Public Health Serriee. Department of Health, Education, and Welfare. 101* Broodwtv, Cincinnati, Ohio i.VJO! The occurrence of coated fibers re ferred to ss "asbestos bodies" in the lungs of urban populations not oc cupationally exposed to asbestos has been noted by several investigators. The results of several autopsy senes, os summarised by Cooper.1 are shown in Table I.1-4 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 sets of braks linings and one or two clutch linings in its lifetime, and commercial sad public transport vehicle* wear out many more. These linings consist largely of ssOestos which is ground to diut ss the linings wear, and most wear occurs in built-up areas. This alone in mo>i cities would involve the discharge <A many tons of asbestos dust and fibers in the ursets each year. Since asbestos hoe been implicated as a carcinogen* and lung cancer has a higher incidence' among urban popula tions, the fate of the asbestos worn from broke linings becomes significant. Brake Unlfif Campetition The average composition of typical broke linings of the type tested is shown in Table II. Individual mixes may vary considerably from these averages. Each of these ingredients performs a particular function. The asbestos pro vides strength, heat resistance, and selec tive decomposition under stress. The resins 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 as lead and brass improve wear while carbon and graphite serve u friction modifiers. Brake lining quality depends to a large extent on the type of binder used. Linseed oil. which begins to decompose at about 450*F, is used for light service brakes. More demanding service re quires brakes made from cashew type resins or oil modified phenolic resins. These ingredients are mixed, either dry or with s solvent added, formed into shape, and cured in nn oven. The hardened lining is then cut. ground, and sanded to the precise dimensions of the finished linings. The dust produced by the abrading operations in asbestos friction product lactones (Figure D contains free asbestos fibers that ore similar to those in industries where can cer is known to be in excess. " The question to be resolved, 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 automobde brake drums removed for brake relining was examined by electron micrograph. Figure '2. which is typical of the senes, does not reveal any free fibers. How ever. this finding did not eliminate the possibility that free asbestos fibers were released and that they had escajied into the atmosphere. -To examine this hy pothesis a aeries ot experiments was devised to permit sampling decomposi tion products of the lining under simu lated operating conditions. The tests (Table III) were performed with the brake testing machines in the laboratory of a major brake lining manufacturer. Most of the tests were periormed on * 8- tl ll#- Flfar* 1. trek* limnf factory dual Fleefe Z. Ouat from o>t drum. fiqmrm J. QacamoaaitiaA sroduct from norm#4 W**r of eraaa limn*. friction-teating machine which used drum brake linings showed less than ooe-incb-tquar* samples of the test 1% free fiber in the decomposition lining Heating and cooling apparatus product aa compared to about 60% in the permitted control of drum temperature lining. An electron micrograph of the from those encountered with inter decomposition product obtained from a mittent brake use to the maximum typical test in this group is shown in nperature which occurred only in remely rapid or "panic" stops from Figure 3. In those tests where a sig nificant mass of free fiber wuYeleased speed. Other testa were performed (Figure 4). the temperature was in an on a brake-testing dynamometer which extremely high range for the lining in subjected a complete brake aaaembly to question as evidenced by rapid drop in a aeries of stops and itarta from different the coefficient of friction. Had these apeeds and at different deceleration linings been subjected to like conditions rates to simulate actual driving con in a vehicle, the brakes would have ditions. In these testa the drum tem failed. peratures varied according to the driv Similar results were obtained in the ing condition simulated. During each bus and truck drum brake testa and in run at a test condition, a sample was the dutch test. The experimental model collected oa an 0-8 * port ties membrane disk brain tested did release tome filter. Electron micrographs of these (>fi%) free fibers, but no conclusion filters were-examined to determine the can be drawn from a angle sample. presence of free asbestos fibers and to quantify these fibers when more than a few occurred. Except in all but the most extrema driving conditions, only a very small fraction of the 30 to 50% aabanos pres ? The object of the tests was to drtar- ent in a brake lining eacapaa into the atmoaphare aa free fiber. The question mine what proportion of the aebartos ^ remains: What happened to the ae- knows to be present in the lining ap bartos? A prevalent theory of brake peared aa free fiber in the decomposi operation holds that wear occurs not tion product. Xo attempt was made 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 the points of contact position product since it was not pos between the drum and the lining. De sible to collect all of the decomposition composition, not only of the binder but nroduct. However, the percentages of the aabeetoa aa mall, occurs at these tamed in the fraction of decompoai- locations since the breakdown tem- a product examined are spptimble pareton of aabemoa, about' 900*7, is a tbit total material worn from the asceedad, Decoraposition products will brake and may be compared to the include not free asbestos fiben, but a parentage of asbestos originally promt, rlMhwnt mineral resulting from thermal i ' la ail bat a few tails the automobile metamorphosis of asbestos- ^jecembeOtiHI Votema U. Ho. 12 1 rifere - Oecompeerage pruct lro<n 8r Hnmeattaaure. cs 1 a i.v- $5 Hi It .-t I* [U Table 111. Tret results tty siacgoo micrograph. Test Product Brand Method Presence No. of Condibons of Free %'Free Ssmoies of Test-F Fibers fiber* 1. AutamoMe A dram brazes Friction S 300 no Few <1 2. AutemoMe B dram braitee Friction 6 250-00 None 0 X AutemoMe C dram braze* Friction 5 300 - 700 Few <1 4. AutemoMe C drum brafeee Friction l 70S-KS Numerous -10 5. * lilBWBftj* 0 Friction omm French amaa 5 300-100 Few <1 4. Autemeeie Friction arum brakes 7. Automoose F Friction drum German brazes 5. 300 - 700 Few <1 5 XX-no ftw <1 I. Autnmecse G Friction arum brazes 2 100 * 300 Pew <1 . AurnmeOSe G Friction dram 1 (00*700 Numerous -13 brazes 10. AutacnoMe H drum Friction 2 8 8 Few <1 brazes u. AutemoMe J .^Dynamometer 1 Normal None 0 dutch dftving 12. AutemoMe K Dynamometer 1 Normal Few <3 disk driving brake a Bus drum L brake Dynamometer t City None driving 0 14. Bus drum M Friction brake 2 ' 430*990 None 0 IS. Truck drum F Friction broke (Hgm) 10 300-B0 Few <1 w**gm iiawim (ram fiber vatuma. Soma independent expenmenu dooa at a brake liaise research laboratory11 have shown that all at tha magnesium present in the ehrysociis asbasto* orig inally in the fining can be accounted for in the decomposition products. How ever, the ehaiacteratie ^ray diffrac tion pattarn of ehryeotib 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. CencJwsiesi Only a very small proportion of the asbestos worn frpm brake Haines is released as tree fiber; the remainder is converted into soma other mineral as a result of the extreme temperatures geacrated at small spots on the lining sur face. Thus, although urban air con tains a few free fibers as a result of brake lining wear, they represent a very small proportion of the total asbestos used in manufacture of brakes. Many sources of respirable fibers not Mandated with asbestos products have been identi fied,l> and free fibers from brake lining wear seem to be an inconsequential health factor in urban air pollution. 1. Cooper. W. C., "Asbestos ss s haxard to health.1' Arch, of *. Health. IS: 2S5 (1967V 2. Thomson, i. G., gwKnU, R. 0. C., end McDonald, R. R_, Ajbestows as s modem urban hazard,'' 5. Afr. Hod. J. 37 : 77 (1963). X Canna. D., Totten. R. S., and Grose, P., "Asbestos bodies in human lunfs at autopsy'' JAMA, 192 : 37 (1963). 4. Webster, 1., in discumioa of Thorny son. S. F., "Phywologieal effect of DrO in mammals," Ana. .V. 1*. Aced. Sol, 64:736(1960). X Meunaan. L., "Aebestae bodies and pleural plaques in a Fiaieh series of autopsy cease," Ada Path Mietahitl. Semi Supply 111: 107 < 1966). 6. ArvilreL L. and Thuribeek. W.. `The incidence of sabsstos bodies in the lungs of randon autopsies in Mootrrei. Canada, Med. Aseec. J., 45: 1179 (1966). 7. Thomson. J. G., "Asbestos and the ur ban dweller," Asa N. Y. Acad. Seu, 132:196(1963). X Selikoff, I. J.. Churf, J., and Ham mond, . C., "Asbestos exposure and neoplasia.'' JAMA, 1U: 22 (1964). 9. Buell. P. and Dunn. J. E.. "Rdatirr impact of smoking and air pollution on lung cancer," Arch. of E>w. Health. 13:291(1967). IX Eateriine. P. E. and Kendrick. M. A*. "Asbestos dust exposures st various levels end mortality,'* ArcA. Eiu. Health, 13:1S1 (1967). 11. Sinclair, D., "Study of wear dust from brake lining," Johns-Manvtile Rss sou Eng Ctr., personal communication (1967). IX Cralley, L. J., Keenan. R. G.. Lynch. J. R., and Lambert, W. S.. "Sourer and idantificatioo of respirable fibers. Amer. Ind. Hvg. Assoc. J-, 29: l-'O (1968).