Document 3JXXQD0pO54e1zqeKen9VoXy0

aia/7/3/ppod A3K>3T0S A1TD KPAI/TK ITT TPJS FRICTION HATRIAL IPJSTTSTPY The Probl era Hxposure to asbestos dust is recognised es a potential occupational hazard. Among vork 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 ashesLosis have been reported throughout the world. ' ' The difficulty of reliably identifying the occupational history of those whose health has been affected, many'yeers after has resulted in any contact with asbestos being regarded with caution and all materials containing asbestos being attacked indiscriminately. \ Since friction material is widely recognised as one of the products for which asbestos is an important ingredient, it has attracted, such attention. Indeed, the asbestos industry, in reminding everyone of the vital role played, by asbestos in brake linings, has stimulated such attention. T-e-rert.hcless the occupational health record of the asbestos friction material industry is good and only a few cases of asbestos-related disease are on record. Hovever, the widespread use of friction material in all types of vehicles has raised the question of potential pollution of the environment with an assumed consequent danger to the health of the general public. The friction material industry, therefor, has two basic problems. The fizoi, the occupational health problem, has in many areas beer, resolved, rowsvar, the industry must continue to ensure that those employed in the manufacture of these materials ere not exposed to dust levels vliich are harmful. An extension of this problem is the need to en-.uxa that workers employed in the subsequent use of friction materials, eiuher in the fitting of the products or the maintenance of vehicles, are not exposed -co harmful dust levels. O HWBUI0011643 I -2- The other problem for the industry, that of possible environmental pollution, is more difficult to resolve, based as it is on emotional anxieties (which are in no way justified by the evidence). A climate of concern for the effect on the environment of expanding towns end industries has led to the motor vehicle being included as a significant factor in this pollution. This fact together with the publicity given to asbestos and its classification as a carcinogen.^ have all combined to lead people to question the use of asbestos-based components in motor vehicles. ' The automotive industry is also under attack for a number of other reasons, (e.g. pollution, waste of resources and congestion) and would gladly be without the asbestos problem although it must accept that for 6ome years, current models of motor cars will need asbestos-containing material for . 1 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 made manifest and is properly understood. _- Tacklinc: the Problem j> In order to tackle the problem most effectively, it is important that the origins, investigations and remedial measures involved should be well 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 the subsequent fitting and servicing operations sometimes called "para-occupational") and on the other hand an assumed emission of similar dust into the general environment as a result of the daily wearipg down of brake linings and clutch facings. An example of this confusion may be seen in the evidence given to the TJK Asbestos Advisory Committee, where claims that the general public are at risk are supported solely by reference to a survey of motor 5 vehicle maintenance workers. It is therefore important to recapitulate the facts relating to health hazards and the conditions which are believed to give rise to them* HWBUI0011644 - 3- Tnese facts will be 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. Manufacture of Friction Materials There is ample evidence to suggest that, in the manufacture of friction materials, the concentration of asbestos dust compares favourably with that found in most other modern asbestos operations. Within the last ten years efforts to observe a 2 f/ml* standard have led to further improvements in dust control and there are now many operations where levels well below this maximum allowable concentration are achieved^. Very few cases of asbestos-related disease arising from friction materials manufacture have been reported. In evidence presented to the UK Advisory Committee,"* Ferodo Limited, 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 railway brake blocks between 1928 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 should have bean worn. In the same volume of'evidence, a report from the two Cape Industries'1 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 * f/ml (asbestos) fibres per millitre HWBUI0011645 4- - has not been a single diagnosis of asbeotosis as a result of this exposure". In core recent years (1968 - 1976) however, average concentrations were well below 2 f/ml following continuous improvements j.n dust extraction methods. An investigation in 1975 by Eeidermanns, Kuhnen, Schutz and Prochazka9 into dust hazards which might be associated with the manufacture and use of asbestos-containing friction materials (updated in the Research Report of the German Eerufsgenossenschaften quotes concentrations of nicro-dust in the range of 0.09 to 0.20 mg/m^ during grinding, drilling, saving, turning end milling operations (the current TnH* value is 0.10 mg/m^ 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 or Fuch operations, unless subject to dust control, will emit duet containing asbestos. A number of surveys of such operations have been carried out in Germany UK usa 13.14k15.16,17 ar_ eisevvere 3i5*8 nd it .is clear that, under some conditions of working and where such operations are carried, out continuously, dust concentrations above 2 f/ml (or the TRH of 0.10 mg/m') can be reached. There is some evidence of effects on health among men engaged for a long period on such work. Medical and epidemiological 7 investigations by Professor V'oitovits, Valentin and others on workers who 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 (m? ;\ly grinding and drilling) in the automotive industry, to the risk 1 e-ve-Ts. of workers in the manufacturing industry 7,9 It was noted that the automotive industry group studied had had long exposure from a very early age. 9 A group of men carrying out brake f * TTil = Technical Control Limit + Out of 94 workers (including 43 women) in manufacturing, there were 3 probable cases of asbestosis-and 11 "possible". Among 63 men employed O in finishing operations on brake llnin/rs in the automotive industry. 2 probable asbestosis cases were found and 10 "possible". ("Possible" means shoving effects on the lung which might be fibrogenio.) HWBUI0011646 5- - maintenance services with exposure primarily during the cleaning and hrushing out of brake drum dust gave little evidence of inhalation effects in spite of long years of exposure. Professor Selikoff's investigations 19 quoted indications of abnormalities in 32 out of 87 motor vehicle mechanics (6 out of 29 with five or more years intermittent exposure showed signs on X-ray of changes consistent with asbestosis). Another report of the same investigation quoted 24% of 95 brake service mechanics showing chest abnormalities not necessarily asbestos-related and it is emphasised that there were no confirmed cases of asbestos-related disease. Dust levels quoted in connection with this investigation (in USA) 20 * 21 * refer to mean concentrations-for blow-out' of brake drums, grinding of used linings and bevelling of new linings of 1.5-9* 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 blowing out of brake drums, no asbestos fibres were visible by optical microscopy; some chrysotile was identified by X-ray diffraction. Fibres identified by electron microscopy were all below the minimum size specified ft in the definition of asbestos fibre (i.e. 5 pm in length) . It should be 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 Eicki.sh. and Knight 10 s howed 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 was 1.75 f/ml, vith peak, during cleaning - - of the brake drum, of 7*09 f/ml. f The German investigation in 1975 ^ (now incorporated in the Berufsgenossenschaften report ') recorded high concentrations* in the brake service department and * 0.03 to 0.79 mg/m^ and wi-gi background workshop atmosphere of 0.03 to 0.05 mg/m^. HWBUI0011647 6- - I whore rachirpng was done without dust extraction. Although high concentrations of dust were observed during bloving out, no chrysotile asbestos ccmld be detected by infrn-red spectrometry, er.d.-the individual fibres which could be detected optically could not be identified ss asbestos. The GeneralEnvironment 1>ar'nr the application of drum brakes, disc pads or clutch facings, F.'-.ell quant it ^rd of the surface of the friction rater* si are worn e.v&y. These materials contain between J/Cf/l to 60j' of aEtestos, and it has been assured by sons 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 which has produced asbestosrelated disease (especially cancer) in some working environments. Since the estimated consumption of asbestos in friction material is annually over 40,000 tons 22* for Europe and oyer. 50>000 tons in the USA the amounts involved '-re substantial. An estimate carried out by the F-endix Corporation with the support of the US Environmental Protection Agency (UFA) calculated that the amoimt of friction material worn away in brakes end clutches annually in the USA is around 60,000 tons, J (of vhich 57>000 tons is the asbestos content i.e. 60;'. In Europe the content of brake linings is nearer *&/.). Eowever it is clear from measurements made at a number of locations with heavy road traffic that insignificant quantities of i-espirable asbestos duet are so emitted. A The- most important'factor iri dispelling 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.^ Keasurement6 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 asbestos-containing brakes in the HWBUI0011648 7- - confined tunnel environment might be thought to create the worst conditions, no significant build-up of asbestos dust has been detected.?4 **25 26 The explanation is 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) is sufficient to destroy the original structure of the asbestos fibre. From-a temperature of 450C the chrysotile structure begins to convert to a non-crystalline amorphous phase, leading to a loss of stability.of the fibre structure. The mechanical strain applied during the braking process has a pulverising and grinding effect, leading to disintegration of the fibre structure. The German report 7 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 650C either 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 diffratcmatic methods). Examination of the residue of wear products in brake drums confirms that the asbestos content is usually less than 1% of the residue. 1 It haB been suggested that the dust escaping into ambient air may contain a higher proportion of the fine respirable asbestos than dust left in the drums but careful studies designed to entrap this escaping portion of the wear product show that this is not so. Various investigations into the amount of .asbestos remaining .in the residues from friction processes have been carried f out which indicate how minute is the fraction of asbestos released in the application of friction. The latest report, 7 from Germany, confirms that technical investigations in recent years have repeatedly shown that the dust generated by friotion of the linings in use - as opposed to dust created o HWBUI0011649 -6- / during the finishing and handling of new linings - as a rule contains only traces of free chrysotile fibre, i.e. of the order of IJo. The working party was unable to provide clearer infra-red spectrographical evidence of chrysotile. Under phase-contrast and eloctron-nicroscopic 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 1969 which reported that the free asbestos content of wear products of drum brake linings rarely exceeded 1?j. (in disc brakes the content was even lover.) The Bendix'investigations Tor 1TI0SH in USA in 1973 gave a range from 1.65/= to O.OO^o - only three tests were above 1o and the overall average was 0.2J:. This study also determined that only 5.2?j of the asbestos content of all the wear products over the whole range of US motor vehicles became airborne - estimated at 50^0 lbs. annually. 13J _ y = o.oo7 The Ford Kotor Company carried out a study 28 based on dynamometer tests which showed that during brake usage less than 0.02J' of the lining wear was released in the form of free asbestos. The study estimated that concentrations of asbestos fibre in the urban atmosphere in the US due to brake usage was less than 0.07 x 10~^ g/m^ (.07 nanograms) (less than one millionth of the 2 f/ml occupational control standard). 1'essurements carried out at points of heavy traffic concentrations in' the UK by the Asbestosis Research Council, under the observation of the TUC Centenary Institute of Occupational Health, also found Ho greater concentration. Even in the underground railway system, this survey found the asbestos content to be of the order 10** g/nr to 10*"f g/m . (10 ngs to 100 ngs/m3)24 ' . Finally, some observations made within the last three years by two eminent occupational health experts, on occupational risks and risks to the general public, are worth quoting. * HWBUI0011650 9- - Tr. John Gilson, ' reviewing nsbootos 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 pdds the qualification that occupations involving brake shoe maintenance have been sbovn to be at riGk in the past. "Although nost 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 employ-r.ent) is not Imown but is likely to be small." Professor 22 V:ielbnis, in his report on public health risks, concludes "There is evidence of no excess risk of mesothelioma from asbestos pollution vhich has existed in the neighbourhood of chrysotile and arosite mines. There is ,r.c.evidence of a risk to the general public at present". Later he repeats this view in hir. general conclusion "There is no established evidence that true anVe-nt exposure, as prevalent in Vestem European countries, at this moment carries such a definite risk: however, there exist too many urcc-rte.-'ritics to deny such-a. risk, though if the risk .was substantial it is likely it would have been detected by now". nryniviTOhs 1 There can be an occupational health risk in the manufacture of esbestos- h- ?ed friction : atarids. However, experience, has shown that this is a very l.% i 'ec health r'nkand that it can be effectively controlled by well tested equipment? and.Work procedures. ', "ta.n':srds based on extensive experience in the industry have been established and equipment ic available to maintain these standards so that the occupational health risk ran be controlled. In many countries these standards are enforced by legislation, but in any case trade and industry have an obligation,.as with any occ\ipational safety problem, to implement the- effective risk prevention measures which1 have been developed by competent and experienced technicians. HWBUI0011651 I - 10 - liter.in?! c ' ~o1 ( 0 r:c r.i 1 In cortc;n conditions involvinj rorv'ci.nj;, etc , there nay te ?. v.ara- ccc-ip'iiion'l. ; -,ic."rn. ;';'V'rt>y c^n provide infor >eti.on to cnsur-s that v-Tncrs -oonnddeerrsstra.nnd MnlcvL- v'.ai chreur.tlrnccs ruch r.icVs can arise and l ow they ct?i he avoided.30,31.32,33. 1 r. l .? Z.y.rzt If few-* to tell the-, so. Itth UZ. TPS1 O HWBUI0011652