Document 33D16xGn0X30MdoqOgGe5pMy

1 A/ 7/ 3/FFOD ASBESTOS AND HEAL'IH IN THE FRI CTION MATERIAL T XDUSTRY The Problem Exposure to asbestos dust is recognised as a potential occupational hazard. Among work people exposed to high concentrations of respirable asbestos dust, such as is known to have occurred before present day dust control measures and work procedures were introduced, cases of cancer and eabestosis have been reported throughout 47 19 the world. The difficulty of reliably identifying the occupational history of those whose health has been affected many years after has resulted in any contact with asbestos being regarded with caution. Regrettably, all and any materials containing asbestos have been attacked indiscriminately by those whose judgment has been influenced more by emotional concern for past victims of an industrial hazard than by a logical examination of the evidence- now available. ` Since friction material is widely ecognised as one of the products for which asbestos is an importan; ingredient it has attracted such attention. Indeed, the asbestos ihdustry, in reminding everyone of the vital role played by asbestos in brake linings, has stimulated such attention. Nevertheless the occupational health record of the asbestos friction material industry, although including a few' reported cases of asbestos-related disease, is good and has not been regarded as a major problem. However, the widespread use of friction material in all types -of vehicles and trie nature of its use (the abrading of the material by friction), has raised the question of a harmful pollution of the environment with a consequent danger to the health of the general public. The friction material industry( therefore, has two basic problems. T)(e ^Tirst, the occupational health pr ob 1 em^ha in many areas, been resolved. However, the industry must continue to ensure that those employed in the manufacture of these materials are not exposed to HWBUI0011568 2- - dust lcv.-ls '.inch are hssnful. An extension of problem .is the need to eaaire that workers employed in the use of friction / materials, either in the fitting of the products or the maintenance of vehicles, are also prevented from exposure to I'.-'-.v ifnl dust levels. `Die other he sic problem, that of the environment, is r.ore difficult to resolve, based as it is on emotional anxieties. It is extremely hard to convince people that these anxieties are in no vay justified hy the evidence. Gathering concern for the adverse effects on the environment1posed by ever-growing towns and industries has identified the r.otor vehicle and its use as a significant factor in pollution. Couple this with the spotlight directed on asbestos in recent years together with its classification as a carcinogen, and one can see how asbestos-hased motor vehicle components have become the target for an illogical attack. The automotive industry itself is already under attack for a number of reasons, (e.g. pollution, waste of resources and congestion) and would gladly drop the use of asbestos although for some years current models of motor cars will need asbestos material for replacements. The friction material industry itself must therefore dispel anxieties about asbestos-containing products in motor vehicles by ensuring that the existing reassuring evidence is properly understood and accepted. Tackling the Problem In order to tackle the problem most effectively, it is important that the origins, investigations and remedial measures involved should be veil understood. This is especially necessary since the existence of the friction material environmental problem is to a large extent based on confusing two very different phenomena; on the one hand the occupational health experience and dust exposure data related to manufacture (and more particularly fitting and servicing operations sometimes called paraoccupational), and on the other hand an assumed emission of similar dust into the general environment as a result of the daily wearing down of brake linings and clutch facings, in example of this confusion may be seen in the evidence given to the TJE Asbestos Advisory Committee, where claims that the general public are at risk are supported Bolely HWBUI0011569 1 3- ty to a :-u;.voy of rotor -vehicle paintc;n?nce work;rs. 2c 4 s' It is therefore important to recapitulate the facts relating to health hazards and the conditions vhich are believed to give Tise to then aa given in the literature. These facts will he reviewed under three headings, the first two covering the occupational areas of manufacturing and servicing, and the third heading covering that of the general environment. Fricticn Katerial Ksnufacture There is ample evidence to suggest that, in the icanufacture of friction materials, the concentration of ashsstos dust compares favourably with that found in most other asbestos operations. Vitbin the last ten years, efforts to observe a 2 i/ml standard have led to further improvements in dust control and there are many operations where levels veil below this are achieved. Very few cases of asbestosrelated disease arising from friction material manufacture have been reported. y In evidence .presented, to the UJf Asbestos Advisory Committee28, Ferodo Ximited, who have been using asbestos in brake and clutch linings since 1910, reported 8 cases of mesothelioma and 5 cases of asbestosis. The mesothelioma cases had all been exposed?in the manufacture of a railvayrbrake block between 1923 and 1933 or during the war years up to 1943, to crocidolite as well as to the chrysotile asbestos more generally used throughout the plant. The asbestosis cases were all involved in mixing processes where masks Bhould have been worn. In the same volume of evidence, a report from the two Cape Industries' factories manufacturing both textiles and friction material (one since 1901 and the other since 1923) cites 9 cases of asbestosis and no case of mesothelioma. Ferodo report that "many millions of man hours have been worked on finishing operations of asbestos-based materials: though the dust concentrations associated with these were at one time very high, there has not been a single diagnosis of asbestosis as a result of this exposure". In more recent years. '(1968 -.1976) however, average concentrations were well below 2 f/ml following continous improvements iii dust extraction methods.. ... * f/ml - Asbestos fibres per millitre HWBUI0011570 -4- An investigation in 1975 by He?d- :=nns, Kuhoen, Schu'tz end Prochszka1^ into dust hazards which sight be associated with the manufacture and use of asbestos-containing frlfction materials (updated in the Research Report of the German Earufsgc-noBsenschsften55 quotes concentrations of micro-dust in the range of 0.09 to 0.20 mg/m^ during grinding, drilling, sawing, turning and milling operations (the current TRK*value is 0.10 mg/or 2 f/ml^; on this basis the current range is 1.8 f/ml to 4 f/ml), on average just below or just above 0.15 mg/m^ or 5 f/usl. Maintenance Operations Involving Friction Taterials Operations such as drilling, grinding and bevelling (similar to these carried on in the finishing operations in friction material manufacture though not usually on a continuous basis), can occur in motor vehicle maintenance workshops especially those of public transport or carrier fleets. Such operations, unless subject to dust control, will emit dust containing asbestos. A number of surveys of such operations have been ca.rri.ed, ou.t m. G_ ermany 13,55,U,,K 2',10,'18.USA. 8,'11,'12>.20 and. elsewhere 197 21 28 and it is clear that^ under some conditions of workingr and where such operations are carried out continuously, dust concentrations above 2 f/ml (or the TRK of 0.10 og/m^) can be reached. There is seme evidence of effects on health among men engaged for a long period on such work. Medical and epidemiological investigations by Professor Voitovitz, Valentin and others'^ cn workers vho had been continuously exposed for at least 10 and up to 25 years to asbestos dust suggests a similar risk level for men employed on finishing operations (mainly grinding and drilling) in the automotive industry to the risk level of workers in the manufacturing industry ^5,35 + It was noted that the automotive industry group studied had had long exposure from a very early age."*^ A group of men carrying out brake maintenance services with exposure primarily during the cleaning and brushing out of brake drum dust gave little evidence of inhalation effects in spite of long years of exposure. * TRK = Technical Control Limit f" Cut of 94 workers (including 43 women) in manufecturln.r. the re were 3 probable cares of asbestoses and 11 "possible". A-rng 65 men employed 'r` J -n-?r---ng operateons on brake linings in Ihe automotive 1ncustry, 2 probable asbestosis cases were found and 10 "possible". ( "Possible" ~tj i ec.s on ine lung which megnt be fibrc.renic. ) c- Iss at i m- HWBUI0011571 - 5- I Professor Selikoff's irivestiRations 15 quoted indications of abnormalities in J2 out of 87 motor vehicle mechanics (6 out of 29 vith five or more years intermittent exposure shoved . signs on X-ray of changes consistent vith asbestosis). Another report of the sane investigation quoted 21% of 93 brake service mechanics Ehowing chest abnormalities not necessarily asbestos-related. (N.3. There vere no confirmed cases of asbestos-related disease.) Dust levels quoted in connection vith this investigation (in USA)^ refer to mean concentrations for blov-out of brake drums, grinding of used linings and bevelling of new linings of 15-9 3-8, and 37.3 f/ml respectively - much higher than any found by any other researchers. No information is provided as to the duration of these samples - they are frequently referred to as peak concentrations or the mean of a number of such measurements. It is also clear that in the case of bloving out brake drums, no asbestos fibres vere visible by optical microscopy; some chxysotile vas identified by X-ray diffraction. Fibres identified by electron microscopy were all below the minimum Bize specified in the definition of asbestos fibre (i.e. 5 P in length) It should he noted that the methods of sampling and the criteria for measurement of occupational environments did not conform to the methods used by governmental agencies and by other investigators in Germany and UK. . For comparison, concentrations of asbestos dust during brake maintenance reported by Eickish and Knight ' ' shoved an average daily exposure of 0.68 f/ml (range 0.21 to 1.12) during brake service of 11 cars. During truck brake service, the average vas 1.75 f/ml, vith peak, during cleaning of the brake drum, of 7-09 f/ml. The German investigation in 1975^ (now incorporated in the Berufsgenossensch&ften report ) recorded high concentrations in brake services department, and where machining was done without dust extraction. Althou, high concentrations of du^t were observed during bloving out, no cbryBotile asbestos could be detected by infra-red spectrometry, end the individual fibres which could be detected optically could not be identified as asbestos.* * O.OJ to 0.79 (equivalent, to 9.2 to 15.8 f/ml) end with background workshop atmosphere of 0.03 to 0.05 mg/m^ (equivalent to 0.6 to 1.0 f/ml). HWBUI0011572 / `J -6- The C-.r.ie.r<?l r.-iviromsat Because during the application of drum brakes, disc pads or clutch facings, small quantities of the surface of the friction material are worn a\.-ay and because these materials contain quantities usually between to 6Cof asbestos, it has been assumed by some that thereby large quantities of dangerous asbestos dust are being regularly discharged into the atmosphere. This, it is argued, creates a dangerous atmosphere akin to that vhich has produced asbestos-related disease (especially cancer) in some vorking environments. Since the estimated consumption of asbestos in friction material is annually over 40,000 tenB25 for Europe and over 50,000 tons in the ESA the amounts involved are substantial. An estimate carried out by the Bendix Corporation with the support of the ES Environmental Protection Agency (EPA) calculated that annually the amount of friction material Q vom away in brakes and clutches in the ESA is around 60,000 tons. (They calculate that 57,000 tons is the asbestos content i.e. 60jo. In Europe the content of brake linings iB nearer 3OJ0.) Eovaver it is clear from measurements made at a number of locations with heavy road traffic that insignificant quantities of respirable asbestos dust areso emitted ^ The most important factor in dispelling this anxiety is that the asbestos content of the wear products of friction material is not emitted into the atmosphere in the form of respirable asbestos dust. Indeed, a number of ambient air investigations indicate that it is difficult nowadays to find asbestos fibres in any significant quantity, regardless of size, in the atmosphere - even in the vicinity of asbestos manufacturing plants Keasureaents of the ambient air even in heavy traffic conditions do not show any significant level of asbestos. Again, in underground railway systems, where fierce application of asbeEtos-content brakes in the confined tunnel environment might be thought to create the worst conditions, no significant build-up of asbestos dust has been detected ^ The explanation 1b simple and is confirmed by a number of careful scientific investigations. The heat generated in the process of applying the brakes or the clutch (the reason in fact why asbestos is such a vital component) 1b sufficient to destroy the original - * y <r'- HWBUI0011573 i 7 structure of the asbestos fibre. From a tempera t'ure of 450C the chrysotile structure begins to convert to a non-crystalline amorphous phase, leading to a loss of stability of the fibre structure. When a mechanical strain is applied i.e. during the braking process, this leads' to disintegration of the fibre. The braking process^has a pulverising and grinding effect. The German report calls it "a kind of micro-milling so that the dust no longer contains any fibres". From a temperature of 650C a new crystalline structure develops called Forsterite, which will be fully developed at temperatures of above 700C. Generally, forsterite cannot be traced in brake lining dusts. This means that temperatures beyond 650Ceither do not occur or are only very short-lived. The decrease of the chrysotile content, however, indicates that temperatures beyond 450C are reached because the amorphous phase of the chrysotile cannot be traced analytically (by either infra red-spectrometric or X-ray diffractomatic methods). Examination of the residue of wear products in brake drums confirms that the asbestos content is usually less than 12 of ?- the residue. It has been suggested, that the dust escaping into ambient air may contain a higher proportion d>'f the fine respirable asbestos than dust left in the drams but careful studies designed to entrap this escaping portion of the wear product show that this suggestion is without foundation. Various investigations into the amount of asbestos remaining in the residues from friction processes have been carried out which indicate how minute is the fraction of asbestos released in the application of friction. The latest report 33^ from Germany, confirms that technical investi.gations in recent years have repeatedly shown that the dust generated by friction of the linings in use - as opposed to dust created during the finishing and handling of new linings - as a rule contains only traces of free chrysotile fibre, i.e. of the order of 1%. The working party was unable to provide clearer infra-red spectrographica1 evidence of chrysotile. Under phase-contrast and electron-microscopic scrutiny, the dust contained just a few isolated fibres which could not even be definitely identified as asbestos. This is consistent with the investigation by UK government and industry investigations in HWBUI0011574 8- gpA 1969 2 ' 3 which reported that the free asb',estos content of wear // products of drum brake linings rarelyf exceeded 1%. (in disc brakes the content was even lower.) p The Bendix investigations for^NIOSH/in USA in 1973 gave a range from 1.65% to 0.003% - only three tests were above 1% and the overall average was 0.23%. This study also determined that only 3.2% of the asbestos content of all the wear products over the whole range of US motor vehicles became airborne 5060 lbs. annually 8 . - estimated at The Ford Motor Company carried out a study based on dynamometer tests which showed brake usage providing less than 0.02% of the lining worn in the form of free asbestos, and estimated that concentrations of asbestos fibre in the urban atmosphere in US due to brake usage was less than 0.07 x 10-9 g/m3 (..07 nanograms) (less than one millionth of the 2f/ml standard for occupational control). Measurements carried out at points of heavy traffic concentrations in^ithe UK by:the Asbestosis Research Council, under the observation of the TUC Centenary Institute of Occupational Health, also found no greater concentration. Even in the underground railway system,' this survey found the asbestos content to be of the order 10-- 8 g/m 3 to 10 ^ g/m^. (lOngs to 100ngs).^* Finally, the conclusions drawn in the last two years by two eminent occupational health experts, commissioned by the European Economic Commission to report on, respectively, occupational risks and risks to the general public, are worth quoting. Dr John Gilson , reviewing asbestos as an occupational hazard in a general group in which he includes friction materials, says "Despite the thousands of products containing asbestos, evidence of ill effects from their use is very small". He adds the qualification that occupations involving brake shoe maintenance have been shown to be at risk, in the past. "Although most of the asbestos in brake shoes is degraded, the dust in the brake drums still contains a small percentage of asbestos". "The magnitude of the risk (of asbestosis and mesothelioma in those working regularly in this employment) is not known but is likely to be small". Professor Zielhuis,25 in his report on public health risks concludes "There is'evidence of no excess risk of mesothelioma from asbestos HWBUI0011575 pollution which has existed in the neighbourhood of chrysotile and amosite mines . There is no evidence of a risk to the general public at present." Later he repeats this view in his general conclusion "There is no established evidence that true ambient exposure, as prevalent in Western European countries, at this moment carries such a definite risk; however, there exist too many uncertainties to deny such a risk, though if the risk was substantial it is likely it would have been detected bynow" . Conclusion There can be an occupational health risk in the loanufacture' of asbestos-based friction materials, but experience has shown that such risk, limited though it is, can be effectively controlled by well tested equipment and work procedures. Standards based on extensive experience in the industry have been established and equipment is available for their maintenance /o that any occupational health risk can be controlled. In many countries these standards are enforced by legislation, but trade and industry have an obligation as with any occupational safety problem to-implement effective risk:prevention measures developed by competent and experienced technicians. In certain uncontrolled conditions there may be a para-occupational hazard. The industry can provide information to ensure that users understand under what circumstances such risks can arise and that they are informed how these can be avoided 5,6,22,3^ The available data indicates that the.general public is not at risk. The industry`needs to consider how'most effectively to ensure a proper understanding of the facts*which justify this assurance'among opinion-formers in the press, government offices, trade unions, consumer groups and environmentalists. -___ r_ -- HWBUI0011576 BIBLIOGRAPHY Lynch, J.R., National Center for Urban and Industrial Health, USA."Brake Lining Decomposition Products" Journal of the Air Pollution Control Assocn. Vol.18, No.12 December 1968. Conference on Exposure to Asbestos during Brake and Clutch Maintenance. Brentwood, Essex, England. March 1969 a) Lee G.L: British Leyland, Longbridge, Birmingham. "Removing Dusts from Brake Assemblies during Servicing Alternative Cleaning Methods". b) Hatch,D., Ferodo, Chape1-en-le-Frith, Derbyshire, England "Possible Alternatives to Asbestos as a Friction Material " c) Knight, K.L. and Hickish, D.E., Medical Services, Ford of Britain, Brentwood, Essex. "Investigations into Alternative Forms of Control1' for Dust generated during the Cleaning of Brake Assemblies and Drums". d) ~ Hickish, D.E., and Knight, K.L., (as above) "Exposure to Asbestos during Brake Maintenance." UK Annals of. Occupational Hygiene. Vol.13 1970. Dufficy, B.L., Ferodo, Chape1-en-le-Frith, Derbyshire, England. Personal Communication - Asbestos Content of Wear Products from Friction Materials. June 1969. Walther,E., (formerly) Pneumoconiosis Research Unit, Penarth, Wales. "Dust Problems in the use of Asbestos Products". Proceedings of the International Conference on Pneumoconiosis. Johannesburg, S.Africa. 1969. "Asbestos Based Friction Materials etc.- Control and Safety Guide No.8". Asbestosis Research Council, Environmental Control Committee, P. 0 Box 18, Cleckheaton, Yorkshire, England.Dec. 1970(Latest revision - March 1977) HWBUI0011577 Bib]iography . (Contd) I 6. "Safe working with Asbestos - Friction/and Anti-Friction Materials". ARC - See Item 5. 7. Santorelli, Zedda, Aresini and Ghezzi; "Respiratory Physiotherapy of Asbestosis". La Medicine del Lavoro 63 (7-8) 269 - 281 July 1972. 8. Jacko, DuCharme, Somers; Bendix Corpn. and Environmental Protection Agency, USA "Brake and Clutch Emission during Vehicle Operation". Automobile Engineering Meeting, Detroit, Michigan, USA May 14-18 19.73. 9. Anderson, Gealer, McCune, Sprys; Ford Moter Company USA. "Asbestos Emissions from Brake Dynamometer Tests". (Ref.as 8) 10. Bentley, M.L.; Mintex, Cleckheaton, Yorkshire, England. Personal Communication - Asbestos Dusts - test during drum brake maintenance. May 1974 11. Rohl, Anderson, Nicholson, Langer; Mount Sinai School of Medicine, N.Y, USA. "Asbestos Exposure during Brake Lining Maintenance and Repair". American Industrial Hygiene Conference, Miami. USA. (Abstract 223) May 1974. 12. Nicholson, W; Mount Sinai School of Medicine, N.Y. USA. "Asbestos Exposure during Brake Lining Maintenance and Repair" - June 1975. (Believed to be full version of abstract quoted above - 11) 13. Heidermann, Kiihnen and Schiitz (Dust Research Institute of Federation of Industrial Trade Associations (Berufsgenossenschaften), Bonn. W Germany), and Prochazka; (Bavarian State. Institute for Industrial Safety, Munich) "Investigations into the Hazards produced by dust of asbestos-containing friction linings". June 1975. 14. Sebastien, Bignon and Bonnard; Centre de Perfectionnemont Technique, Paris. "La Pollution Atmospherique Urbaine par 1 Asbeste . Journees d'Etude sur la Toxicologie Xndustrie11e, Paris , June 1975. HWBUI0011578 Bibliography (contd) 15. Marsh, J.H.; Raybestos-Manhattan, Connecticut, USA. Personal Communication. Reports of mesothelioma among brake service mechanics in Boston, Mass, and Santa Clara California - N.I.O.S.H. and Selikoff. August 1975. 16. Lorimer and Rohl; Mount Sinai School of Medicine, NY, USA. "Asbestos Exposure of Brake Repair Workers in the US". International Conference on Occupational Health, Brighton, England. September 1975. 17. Nicholson; Mount Sinai School of Medicine. NY, USA. "Comparative Mortality Experience of Three Cohorts of Asbestos Workers. International Conference on Occupational Health,See Item 16. 18. Cross, A.A.; Chairman, Environmental Control Committee, ARC. . England. "Asbestos Dust in Friction Materials". September 1975. 19.. Rubino, G.F.: Istituto Medicina del Lavoro, Torino,Italy. "Identification and Survey of Asbestos Occupationally Exposed Populations". September 1975. 20. Rohl. Langer, Wolff'and Weissman; Mount Sinai School of Medicine, NY, USA. "Asbestos Exposure during Brake Lining Maintenance and Repair". Environmental Research 12, 110t128 (1976). December 1975. 21. Kogan, F.M.; Sverdlovsk Institute of Labour, Hygiene and Industrial Diseases,US SR "Asbestos and Prevention Measures against Dust Harmful to the Health of Workers". (Chapter V). 1975 22. "Recommended Work Practices - Fabrication and Use of Asbestos Friction Materials". AIA - Asbestos Information Association of North America, Washington USA. 23. "Hygiene Standards for Airborne Asbestos Dust Concentrations for use with the Asbestos Regulations 1969". U.K. Dept, of Employmen H.M. Factory Inspectorate, Technical Data Note 13 (Rev) 1975. HWBUI0011579 Bibliography (contd) I 24. Rohl, Langer, Klimentidis, Wolff, Selikoff; Mount Sinai School of Medicine, NY, USA "Asbestos Content of Dust Encountered in Brake Maintenance and Repair." Proc. Royal Soc.Med; 70:32-37 Jan.1977. 25 Zielhuis, Prof. R.L.; Coronel Laboratory, University of Ansterdam,Netherlands. "Public Health Risks of Exposure to Asbestos." Report of a Working Group of Experts prepared for the Commission of the European Communities., DirectorateGeneral for Social Affairs, Health and Safety. 1977. 26. Gilson J.C.; former Director of Medical Research Council Pneumoconiosis Unit, Penarth, UK. "Occupational Risks of Exposure to Asbestos" (Section 6.1-3(v) a Report prepared for Commission of European Communities (as 25). 1977. 27. International Agency for Research on Cancer. I.A.R.C. Monographs on Evaluation of Carcinogenic Risk of Chemi'Cals to Man. Vol.14 Asbestos. Lyon,France. 1977. 28. "Selected written evidence submitted to the Advisory Committee on "Asbestos 1976-77" Health and Safety Executive, UK. 1977. Johns-Manvi11e; Denver, Col orado,USA. Boston Subway - Cobra Brake Lining Emission 1977. 30. Asbestosis Research Council, Rochdale, England. Personal Communication. "Investigation into levels of airborne asbestos dust in the London Underground etc"1978. 31. Vinton Laboratories, Surrey, England. "Asbestos in the Underground - no cause for alarm". 32. Cross, A.A, former Director General, Asbestos International Association, London. "Progress in the Control of Asbestos Dust in the Workplace". International Conference on Pneumoconiosis, Caracas. November 1978. HWBUI0011580 Bibliography (contd) 33. German Federation of Industrial Accide/nt and Safety Insurance Corporations E . V . Berufsgenossenschaften ( Bonn ,W . Germany) . Research Report - Asbestos. "Investigations into Health Hazards through Dusts by Brake-Linings containing Asbestos". (Analytical epidemiological and animal investigations) December 1978. 34. ' "Friction Materials Work Practices Guide". Friction Materials Standards Institute. Paramus, New Jersey, USA. October 1978 5 October 1930 HWBUI0011581 Chief Editor Wiley-Interscience Pub!ication HWBUI0011582