Document 0JYpMmm9G1yJgEk9ZanZ23DoM

I JAMES D. CAL!..A.GHAN v.c.. Presiderot HILL AND KNOWLTON, INC. Public Relations Counsel 150 EAST FORTY- SECOND STREET NEW YORK, N.Y. 10011' 212-697-5600 ENVIRONMENTAL HEALTH UNIT / Dr E P S te fl Vice President Raybestos-Manhattan 205 Middle Street Bridgeport, Conn. 06603 August 27, 1971 Dear Gene: Bill Raines has asked me to send you the enclosed packet of materials dealing with brake linings to help in preparations for your meeting with Illinois Pollution Control Board personnel. For a quick rundown on what the scientific papers contain I am attaching to each of them a copy of the Summary and Evaluation sheets prepared at the time they were received in this office. The papers enclosed are: Bentley, M.L., "Control of the Use of Asbestos-Containing Friction Materials" Hatch, D., "Possible Alternatives to Asbestos as a Friction Material" Hickish, D.E. and Knight, K.L., "Exposure to Asbestos During Brake Maintenance" Knight, K.L. and Hickish, D.E., "Investigations into Alternative Forms of Control for Dust Generated During the Cleaning of Brake Assemblies and Drmns" Lee, G.L., "Rem011ing Dusts from Brake Assemblies During Vehicle Servicing -- Alternative Cleaning Methods" Luxon, S., "Technical Implementation of the New Asbestos Regulations" Roach, S.A., "Hygiene Standards for Asbestos" Smither, W.J., "Asbestos and Asbestosis" Although you probably have it, I am also enclosing a copy of the Lynch paper on brake linings. In addition you will find a selection of pages from a document, "National Inventory of Sources and Emissions: Cadmimn, Nickel, and Asbestos - 1968. Asbestos, Section III," that deal with friction materials. This report was prepared for the old Air Pollution Control Administration and was presented to them in February 1970. It has only recently become available to the public through a printing by the U.S. Department of Commerce Clearinghouse. If we can be of any further help, please let us know. JDC:rnnl Enc. cc: W.P. Raines \Sincerely, .%~. Callaghan FMSI 06472 SUMMARY AND EVALUATION Subject: Brief account of the work of the British Asbestosis Research Council in setting hygiene standards in asbestos friction products plants. Of some interest. Evaluation: This paper runs only two pages, of which the first is devoted to the background and organization of the ARC. A Working Group on Friction Materials has been conducting studies of dust exposure in factories making brake linings. The studies are not yet complete, and there is no report as to preliminary findings. Journal: Annals of Occupational Hygiene (British), January 1970. \ Title: 11 Control of the Use of Asbestos-Containing Friction Materials." 1 Summary: As given above. -xxx- FMSI 06473 l .l.~~..... . I ., - ~ l 1 Ann. Occup. lin;. Vol. 13. pp. 31-32. Pergamon l'r<u 1970. Printed in Great Britain CONTROL OF THE USE OF ASBESTOSCONTAINING FRICTION MATERIALS* M.' L. BENTLEY Mintcx., Cleckheaton, Yorks INTRODUCTION THis paper outlines the measures taken by the asbestos-using industry to find out the nature and cam.es of asbestosis, and the work it has carried out on environmental control. Particular reference is made to dust created during the manufacture and sub- sequent handling and machining operations of friction materials containing asbestos. It is rather less than 40 years ago that the need for control of asbestos dust in large quantities was first recognised and the Government Regulations which became law in 1933 have resulted in a considerable improvement in the health record of people employed in asbestos factories. In the 1950's, however, it became apparent that although the improvement had been dramatic, cases of asbestosis were occurring in people who had. joined the in- dustry since the dust control measures w~re introduced and it was also apparent that certain users of asbestos products, such as th~rmal insulation engineers or Jaggers were also being affected. As a result of this the three leading Companies in the asbestos industry, B. B.A. Group, Cape Asbestos and Turner & Newall, decided that further investigation into the nature and causes of asbestosis was necessa~y and they financed and set <tp the A~bestosis Research Council with this objective. Since then the Asbestosis Research Col.lncil (ARC) has continuously sponsored research at Cambridge,' Reading and other centres and has co-ordinated the work of its own research, medical and en- gineering teams concerned with this problem. ' Much of the increased awareness of health problems connected with asbestos stems from these research projects and the-industry's own experts are acknowledged, and have been consulted regularly, by Government Departments and other organisa- tions both in this country and overseas. The ARC has drawn up some Codes of Prac- tice on the h::.ndling of asbestos in those areas where the control of asbestos dust was thought advisable at that time. The ARC has also played an active part in the formu- . lation of the new Asbestos Regulations which arc expected to become law in about 12 months. Because of its considerable experience in using asbestos and asbestos products itself and its concern that these products should be used without risk, it set tlp an addi- tional committee last year with the principal object of intensifying the study of prob- lems arising in the working environment, dealing with those areas where it had only, *This paper W3S originally presented at a Conference on Exposure to Asbestos during Drake and Clutch Maintenance, held at Brentwood, Essex., March, 196\1. 31 FMSI 06474 I f I I I I r I I l I I I I I I t I I I I. I I i I I ~ ; I I .! r ~.s _.j \ ~.)1: l L ("" ' .I ) 32 . M. L. BENTLEY recently become apparent that some control might be necessary and helping those concerned with satisfying the requirements of the new regulations. This Committee is the Environmcntul Control Committee of the Asbestosis Research Council and it consists. of a number of working groups concentrating on the special problems of particular areas. One of these Working Groups is being devoted to the field of friction, materials, and has, as its constituent members, Small & Parkes {makers of Don materials), Fcrodo and Mintex. This Group, which has been fonned recently, is concerned with the users of friction materials, both at its major customers -the brake, dutch and car manufacturers-and also in the replacement and service field. Its concern has been, first of all, to establish whether or not a problem exists and, if so, how big a problem it is. To this end dust counts have been taken both in premises where friction materials are handled and serviced, and at customers' premises, by the three Companies principally involved. These tests have been taken by their own dust counting teams who have many years' experience in accurate dust measurement. This work is continuing and a picture is being built up of dusr counts likely to be encountered whilst carrying out typical operations during brake and clutch maintenance. Analysis of the dust found in brake dnuns is being carried out also to determine whether all the fibrous Just is asbestos or not. In addition to gathering and collating information.on a large number of dust readings in various types of service premises, the Working Group is preparing two codes of practice for users of asbestos-based friction materials which will be issued by the Asbestosi~ Research CounciL One of these is for the guidance of bulk users in factory premises carrying out, in some cases, operations similar to those carried out in our own factories, such as drilling and grinding; and the other is for the guidance of those engageu in servicing of brakes and clutches. The purpose of these Codes of Practice or Notes for Guidance will be to remind tousers oftheprincipal requirements of the new Asbestos Regulations to recommend the action that they should take to meet their requirements. The aim is achieve what is, after .all, the whole purpose of the Asbestos Regulations and the Asbestosis Research Cquncil's work-to reduce concentrations of asbestos dust to a safe level. The long experience of the ma nufacturcrs of friction materials in dust control over a wide variety of operations will enable them to recommend- measures and types of equipment to help the users to comply with the Regulations and protect the health of their emrloyccs. A further line of study is being followed to sec whether a satisfactory surfacesealing agent can be found in order to cut down the amount of dust given olr in handling a new lining, even though this amount is already small. It is not possible for us to take d;1st counts in every service garage in the country and the work of the Friction Materials Group has been (iirectcd to dealing with, and giving advice on, situations which nre likely to be typical of those found in service garages. It is: however, the intention to give as much help and advice as possible with the facilities that arc available and requests for help or advice directed t::> the Asbestosis Research Council will be passed on to th(' Working Group for action. ""'' Occup; I R WHATEVEI deny that the total t an operati be judged in using tl veloping v time rcqu concede fr inevitable. When presseclcaiJ sation aim objective 1 mental co fibre coun evaluated consideral: simple mer dusts nre 1 with the c1 method is is importa1 MET1 When< the clouus Tyndall De work. This pal Clutch l\hin FMS' 06475 -: ... I SUMMARY AND EVALUATION Subject: Discussion of the possible use of materials other than asbestos for auto brakes. Of interest and importance. Evaluation: The conclusion of the author is that asbestos is practically indispensable for auto brakes at the present time. If asbestos were not available, we could "eventually find a substitute, but it could well be at the expense of a considerable loss in performance, and also at a considerable increase in cost. 11 The author also emphasizes that there is no valid health reason why asbestos should be abandoned at the present time. He cites the tests demonstrating the very small percentage of asbestos fiber in brake lining dust and concludes that 11 the wear products from friction materials are probably no more dangerous to health than many c;~ther dusts and can be treated as 'merely dirty. 111 He also mentions that technical developments have reduced the quantities of asbestos needed in the pro~f-efficient brakes and clutches, 'Autho" 6 1 e r o d o Company), Journal: Annals of Occupational Hygiene (British), January 1970. Title: 11Possible Alternatives to Asbestos as a Friction Material. 11 Summary: As given above. -XXX- FMSI 06476 le industry red, in the figures for that over a ,Jcvcl of 12 crhauls on ticular in~urcs even described nc univer:ake dust, Industrial We have iifi'raction although ere seems :h occurs tween the iJ Hygiene 1 A1111. Occup. HYil Vol. 13, pp. 25-29. Pcraomon Press 1970. Printed in Great Britain January 1970 POSSIBLE ALTERNATIVES TO ASBESTOS AS A FRICTION MATERIAL* D. HATCH Ferodo, Chapcl-en-le-Frith, Derbyshire INTRODUCTION I HAVE been asked to talk on the possible alternatives to asbestos as a friction material. The facts are that if by "alternative" we mean a new or better fibre which might shortly be available as a replacement for asbestos in conventional friction materials, then I think the chances arc so remote as to be not worth considering. This is not to say that if the world supplies of asbestos dried up we wou!d not eventually find a subsfitute, but it could well be at the expense of a considerable loss in performance, and also at a considerable increase in cost. THE ROLE OF ASBESTOS IN FRICTION LININGS Having started on what may appear to bea rather depressing note, Jet us exa,nine the reasons why asbestos occupies the role of an ahtwst universal constituent in friction materials at the present time. The first automotive friction linings were made from cotton textile material im- pregnated with drying oils which were subsequently cured to form a strip of material which, while being flexible and conformable, still exhibited great mechanical strength. The-main function of the drying oil was to protect the cotton from attack by atmo- spheric oxygen, which, even at the temperatures reached by early brakes, would have resulted in the colton burning had its surface been exposed. A second function of the drying oil was to prevent the cotton from fraying under the influence of mechanical abrasion. As brake operating temperatures increased, it was found that cotton started to degrade and lose its strength even though still protected from attack by oxygen. In other words, it suffered thermal degradation instead of oxidative degradation. Around 1910, a technological break-through was achieved when it was discovered that textiles could be woven from asbestos and used to replace cotton, because asbestos neither burns nor loses its strength below about 500oC. However, as brake operating conditions became steadily more severe, a point was reached in about the middle 1940's when, despite the continual improvement of synthetic resins with which the asbestos textile was impregnated, further heat resistance was required, this time because the organic part of the composite was proving inadequate. The solution proved to be to mould brake Jinin_gs rram powdered resins, using short fibre unwoven *This paper was oC:ginully presented at a Conference on Exposure to_ Asbestos during Drake and Clutch Maintcnanc..:, held :t Brentwood, Essex, March, 1969. 25 r I I I I l I ~ I f fr I FMSI 06477 .( . j ,, "~ ' I .J.t 26 D. HATCH asbestos to maintain the necessary strength and flexibility. This made possible the inclusion of heavy loadings of mineral and metal fillers which imparted greater heat resistance than could be obtained from resin and asbestos alone, and did so at the expense of a reduction in asbestos content. The last point is important in the context of asbestos substitutes. The question is often asked, "why can't asbestos be replaced by something like glass fibre which, after all, must surely impart sufficient strength?" The answer is possibly "it can", if merely the perfonnance of a textile lining is required, but at the temperatures commonly met in modern brakes, the gluss fibre melts even in depth below the operating surface. Furth::rmore, as a result of the embrittling effect of mineral and other fillers needed in today's brake lining, glass fibre is inadequate in imparting the necessary strength and flexibility. The same caP. be said to a greater extent, of the various types of rock wools and mineral fibres which have appeared on the market over recent years. It is interesting to note that not oply is the ultimate strength of asbestos almost three times that of glass fibre, i.e. 550,000 lbfin. but the modulus of rigidity is up to ten times as high, at a value of 30,000,000 lbfin. . Typical figures for other materials are say 100,000 lb/in. , for steel wool and down at 60,000 lb/in. for mineral wool. The current situation therefore, is that in drum brake linings of normal configuration \Jsed for passenger cars and commercial vehicles, there exists no substitute for asbestos which would not result in a deterioration of performance and strength. DISC DRAKE PADS Rates of energy dissipation continue to rise and we have now passed the point where moulded drum brake linings are adequate for a large percentage of passenger cars. In this country, nearly SO per cent of the passenger car axles are equipped with disc brakes, and for the second time in nearly half a century, there seem to be technical possibilities of reducing the asbestos content of friction materials. It is purely fortuitous that the friction materials med in disc brakes are designed to a stronger shape, that is, more or less square or circular pads of considerable thickness, supported, furthermore, by a metal plate of adequate stiffness. The friction material, therefore, docs not have to stand up to handling during assembly, does not have to withstand riveting, and could, from the point of view of bulk mechanical strength alone, be made without a high loading of fibrous rcinfo.rcement of any kind. There remains, however, thermal shrinkage and thermal shock, and in order to prevent the fonnation of tensile cracks normal to the operating surface, a percentage of asbestos fibre is still retained. Nevertheless, it cannot be said that the usc of asbestos in disc brake pads remains a technical necessity, and it is in this field of friction materials that some departure from resin-asbestos based composites could occur in the next few years on technical and performance grounds. FRICTION t.IATERIALS FOR CLUTCHES As yet, I h.ave confined my comments to brakes, but the development of friction materials for clutches has followed broadly similar lines. l n recent years, however, we have seen the start of a growing replacement of manual clutches by automatic transm to airb sinteret feature that th Clll seded < fricti01 of butt free m: Sur is a dr result c reduce in autc The siderin subject Thc pcratUJ becaus bccaus import white< but inc point i: of wat slow, t; produc the em asbestc occurri One w olivine but in ducts. by X-r. occasic has be< by VCr) the Jini \Vh survive ... FMSl 06478 ..:.::. ._;_: ..,;.;..1~ ~~- -~;,........,~. h,......,.;.;..:.,...,.~~~""'""""....,o:,';.. -~-u;r;....i.:,..u....,;.,:,..._;,;J ..;,.. ..;. ........,._.. ,.,..;d ......_...'.!.< ., .,.oc,,>...:...>i...._.._ . ". '.J..d I~ ,. . \ ~ possible the .I greater heat did so at the in the context 1s be replaced nt strength'!" 1!! is required, re melts even other fillers the necessary \'arious types over recent ,cstos almost idity is up to 1er materials ~raJ wool. al configuraubstitute for rength. :d tl oint )f passenger uipped with be technical purely formgershape, supporled, I, therefore, o withstand h :!lone, be Tc remains, r formation ftbrc is still brake pads that some :w years on of ftiction however, automatic Possible alternatives to asbestos as a rriction material 27 transmissions where the clutch packs arc immersed in oil and therefore do not give rise to airborne contamination. The friction materials used are, in any case, made from sintered metals or paper based facings in which the flbre is largely cellulose. This feature is made possible by the low operating temperatures, due in turn, to the fact that the materials are immersed in oil. Clutches for heavy duty manual shift gear boxes are, in the U.S.A., being superseded at a significant rate by lhc spider clutch. This is a type of clutch in which the friction material, instead of being in the form of a thin annulus, consists of a number of buttons rather like disc brake pads, and these again could be made from asbestosfree material such as sintercd metals'or cenncis (ceramic-metallic compositions). Summarizing the situation at the present time therefore, it can be seen that there is a drift towards the use of smaller quantities of asbestos in friction materials as a result of a number of purely performance considerations and design changes, that is, reduced amounts of asbestos in some disc brakes, and replacement by other materials in automatic transmis'sions and some dry clutches. OTHER FACTORS AFFECTING EXPOSURE TO ASBESTOS There a!e, however, several other factors which enter the equation when considering the exposure to a~bcstos during brake and clutch maintenance, which is the subject of this meeting. The first is that the durability of friction materials is {ncreasing, as is the temperature at which they will operate satisfactorily. I mention these facts not only because they tend to offset the adverse effect of increase in vehicle miles per year, but because they affect the whole chemistry of asbestos in friction materials. The second important point is that the type of asbestos liSCd in friclion materials is chrysotile or white asbestos, and is different from blue asbestos or crocidolite, not only in colour, but in chemical composition and also in chemical decomposition. The third important point is that under the influence of heat alone, chrysotilc asbestos decomposes by loss of water of crystallization at a temperature of around 600C. The process is rather slow, taking well over an hour to convert 50 per cent of the asbestos to its degradation products. Thc.sc form a series of iron magnesium silicate materials known as oli\ine, the end member of which is forsteritc. The olivine series of minerals are quite unlike asbestos; both physically _and chemically, being non-ftbrous, and in fact, widely occurring as the major part of many common rocks (basic and ultramafic igneous). One would not expect that a significant amount of asbestos would be converlcd to olivine during braking except under conditions of" very severe duty stich as a fade test, -but in fact it is exceedingly diiTicult to detect asbestos in friction material wear pro- ducts. It has only on rare occasions been possible to detect asbestos in wear products by X-ray diffraction methods, and one ha~ to resort to electron diffrilction, selecting occasional individual smnll ftbrrs to show its exislcnce. This rather surprising fact has been known for several years and current theory suggests that it is accounted for by very hjgh temperalures which arc said to exist at the points of real contact between the lining and drum or disc, even at bulk temperatures as low as 100C. Whether !his explanation is correct or not, it remains a fact that very little asbestos survives in the wear products after brakes or clutches have been used under normal '' FMSI 06479 .. ( ~ .... ... "' .;. 28 D. HATCII operating conditions. As the durability of brakes improves, further reductions will occur in the percentage of asbestos which survives the wear process, because each particle of asbestos is then subjected to more heat "treatment. Of the approximately 1 per cent or asbestos remaining in wear products, a large proportion is gro'und down during the wear process to much Jess than the 5 (..1. length at which particles are judged to be fibres. This is easy to understand when one considers that under n~rmal conditions a lining will lose about one-millionth of an inch of thickness for every 20 ft of sliding. Over recent weeks I have had regular tests performed in which employees' private cars, and tmcks from the Company fleet have been brought into the garage for brake cleaning. The dmms have been removed and in a gatage with no forced ventilation, all loose dust has been removed from the drums and back plates by the use of a compressed air jet. As each brake was cleaned, instantaneous atmospheric samples were rapidly taken by a hand-pump from the centre of the dust cloud. Several of the dust clouds were visibly filthy, and would, in my view, be avoided by the operator; the dust counts taken at the point of maximum dust density were as given in Table 1. TABLE J. DUST COUNTS DURING DRAKE CLEANING BY COMPRESSED AIRJET Test Non-fibrous Fibre count Fibre count No. above 21-' 2-51-' Above 51' Samples I 2 3 4 5 6 7 tO min average 2000+ 109 "402 607 475 1513 628 181 306 'll 17 21 0 37 49 35 50 54 2-1 25 37 5-3 82 32 08 The interesting points from this exercise are, firstly, the ratio of the number of particles of asbestos to the total dust particles of a similar size, showing a very small percentage of asbestos, and, secondly, the distribution of size of the fibrous element, suggesting that those particles over 5 fL must have been only just over. I am not suggesting for a minute that the practice of blowing out brake drums with a compressed air line is to be recommended, merely that an intense dust cloud of this composition is a lot less harmful than one might think. Unfortunately, at the present time, no corresponding data is available from clutches but one would expect the situation to be better than in brakes rather than worse, because on the one hand, surface rubbing speeds arc higher, giving rise to higher point contact temperatures, anJ on the other hand, wear rates are very much lower rest1lting in an even finer subdivision in the wear products. It in fric in the produ other to su~ necess Glass Steel' Miner Carbe Sinter and' . ........... ,_ ....~--~..-.~":"":";:<"'"-"';~~--,.-, ........~~-;.~...~"!"~:"'~~~..o..-.~~....,.;~.~Y-'""y-~."'',,.....,r.~~.....~':'""l7"....__... -.~--- FMSI 06480 . (-~-..t.&~.a- ....... .. ,.,,.. i luctions will ; ccause each ! proximately ]ound down J ; arc judged 1m1al condi- 1 ery 20ft of iJ ;-es' private I! for brake l cntilation, j c use of a j ic samples i :raJ of the 1 operator; :~ 11 Table I. Possible alternatives to asbestos as a friction material 29 POSSIBLE ALTERNATIVES TO ASBESTOS I have confined. my comments to an account of changes which are taking place in friction materials at the present time in the normal course of technical development, in the belief that, although the use of raw asbestos must be tightly controlled, the wear products from friction materials arc probably no more dangerous to health than many other dusts and can be treated as "merely dirty". If further evidence comes to hand to suggest that a substitute for asbestos must be found, then under the pressure of necessity, a list of possible replacements could be drawn up as follows:- Giass fibre Low stre1gth-low melting point-severe frictional instability. Steel wool Low availability-high cost-low strength-damage to drums. Mineral wool Very low strength-brittle to the extent of limiting mixing processes. . Carbon fibres 100/lb currently forecast to fall to 1 /lb in several years time. Still ten times too expensive. Sintered metals Probably the best possibility eventually, but cost will always be and cermets relatively high. I f I I i r ..i ~ 1ber of Y small 1 emcnt,_ l1swith i of this : Jtches j ;v_orse, : Hgher i lower I r I ~ I'' i I ~ FMSI 06481 v' SUMMARY AND EVALUATION Subject: Discussion of the preferred type of vacuum cleaner to use in cleaning auto brakes during servicing. Of some interest. Evaluation: Having determined that blowing the dust out of brake assemblies with a compressed air hose releases the most dust into the air, the authors investigated the use of vacuum cleaning equipment with two types of pick-up heads. It was determined that a brush on the end of the vacuum hose is more efficient than a funnel attachment. Journal: Annals of Occupational Hygiene (British), January 1970. Title: "Investigations into Alternate Forms of Control for Dust Generated During the Cleaning of Brake Assemblies and Drums." Summary: As given above. -XXX- FMSI 06482 ..;..-..~~~~u:-.:._..:_~..w.r-~~~~..t.::. :filfi!,w;.;,;;;,.-. * ,a'tt~~!fWD~..!ii~;.t.i'S..,..,a~.;.'..i,,dtWin" ~-A~Hwii-4'..,.-J........... ~' :# 1 dust concentra.inc.d but.was not ;;ought. INJQUE que was devised. eadily accessible ;ing the smallest vacuum cleaner. l'as then used to cd in water and :missions of dust ods, as shown in INIQUE Nere too low to leaning provides ~n brake assemts the discharge enables suitable rly part of 1968 1til such time as try were kno\vn 1r1mcnt and Mr January 1970Ann. Occ11p. 1/)"ll Vol. Jl, pp. 37-39. Pergamon Press 1970. Printed in Grcot Dritoin . INVESTIGATIONS INTO ALTERNATIVE FORMS OF CONTROL FOR DUST GENERATED DURING .THE CLEANING OF BRAKE ASSEMBLIES AND DRUMS* K. L. KNIGHT and D. E. HJCKJSil Medical Services, Ford of Briiain, Brentwood, Essex INTRODUCTION THr: MOSr usual method of removing the accumulated dust from brake drums and assemblies is by "blowing off" with a compressed air stream. This, of course, generates a dust cloud in which the operator works, proportionate in size to the drum/assembly being cleaned. We therefore investigated two al!ernative methods of controlling dust generated at a maintenance operation on commercial vehicles, as representing maximum likely exposure. Enquiries at the beginning of the invtstigation indicated that the- removal of dust is to allow inspection of the mechanism, rather than b~ing a maintenance procedure in itself. Our efforts were, therefore, directed towards the removal of loose dust from the parts of the brake mechanism which needed inspection, rather than achie.viqg total cleanliness. The criteria for evaluating the two methods devised were firstly, that the alternative method did not take significantly longer than the method already in use, secondly, that it was not more diHicult to carry out, and thirdly, that very little extra equipment was i1eeded. ALTERNATIVE METHODS EXAMINED The alternative methods examined were a vacuum funnel, and a vacuum brush. Vacuum funnel The funnel (sec Fig. I) comprised a steel cone with a connection point at its apex for an industrial vacuum cleaner; a flexible skirt, with a draw string attached at its periphery; and a small-bore side-entry for the injection of compressed air. In usc, the funnel was secured over the backplate of the brake assembly or over the drum and compres~ed air was injected to dislodge dust \vhile the vacuum cleaner extracted dust-laden air. The assembly was rotated around the total circumference to complete the cleaning operation. *This paper was originJIIy presented at a Conrercnce on Exposure fo Asbestos during Brake and Clutch Maintenance, held at Brentwood, Essex, March, 1969. 37 f I I I i' I I ! I FMSI 06483 . ..... .......... .4 1 38 K. L. KNIGHT and D. E. HICKISH Vacuum brush The vacuum brush shown in Fig. 2 consisted of a circular nylon bristle brush mounted on an angled handle and filled via the handle to the same vacuum cleaner. In use, the brush was used to remove dust from drums and assemblies under vacuum. EXPERIMENTAL PROCEDURE In order to determine which of these two methods was the better, the performance of each was compared with the traditional blow-off method, in two sepamte experiments shown in Table 1. TABLE. l. EFFECT Of CLEANING I>!E"mODS ON DUST CONCENTRATIONS Hour Activity Personal sampler Static sampler Peak sample particles/em fibres/em particles/em fibres/em particles/em fibres/em Personal sampler Static sampler Peak sample particles/em fibres/em particles/em fibres/em particles/em fibres/em 1 Background 2 Blow-off 5 Background 66 Funnel Brush cleaning cleaning 116 422 107 096 535 095 161 72 162 045 052 041 41750 87 415. 35 210 075 759 104 125 635 016 084 129 155 010 016 41750 87 140 009 llO 020 158 022 122 018 310 057 , During the first hour of the day air samples were collected to determine background concentrations; during this period the near side front road wheel was removed. In the second hour samples were collected during dust removal from the near side brake as~embly by blow-off. Further background samples were taken during the fifth hour while the off side front road wheel was removed; and during the sixth hour dust dete1minations were made while either the funnel or the brush cleaning methods were us~. The personal samples were collected from the. breathing zones of mechanics en- gaged in the work and static samples were collected concurrently to simulate exposure of mechanics working in an adjacent repair bay. Short duration samples were also collected by means of a Drager pump from the operator's breathing zone at the peak period of dust generation. . All the samples were subsequently analysed for flbres in accordance with the technique iaid down in the Hygiene Standard for C/,rysoti/e Asb..,stos published by the British Occupational Hygiene Society ( 1968). Particle COllllls were limited to particles greater than I 11 dia. .,,. .....;.,.....~ ..-~~ :.. tf-=---- t. i ~-- r..~,:' ' .~: ~-~ I l ----~ FMSI 06484 Alternative forms of control for dust generated during the cleaning of brake a_sscmblics 39 DISCUSSION The results for the vncuum funnel l'S. blow-off experiment and for the vacuum brush versus blow-off arc shown in Table 1. It can be seen that the background concentrations during the firth hour had re-established at the original level after a 2 hr ]atent period and therefore the blow-off operation carried out during the second hout did not aOcct the concentrations observed in the vacuum funnel samples collected in the sixth hour. The funnel appears to reduce personal cxposme by 2 per cent for particles and 40 per cent for fibres; concentrations observed in the adjacent bay are . increased and a reductio:1 in peak concentrations of about 80:1 was achieved. During the second experiment there was more variability in the background concentrations between the first and fifth hours but the effect of blow-off on the vacuum brush test may be discounted. Perso)1al cxposi.1re by use of the brush is reduced by 75 per cent for both particles and fibres and the static samples show a reduction of 20 per cent for particles but an increase of 12 per cent for ftbres. A reduction of 80:1 in peak concentrations was again observed.. -CONCLUSION The experiments dem01istrated that the vacuum brush was better in reducing operator's exposure; it had the added advantages over the funnel of being easier to handle, comisted of fewer, simpler parts and was much quicker than the vacuum funnel. There are three major reasons for the relative incnicicncy of the funnel; its use increased brake cleaning time (and thus exposure time) by a factor of 8, it was difficult to obtain a good seal at the skirt, and imbalance occurn:d between the necessary air input and the capacity of the available exhaust system, with resulting leakage of dust. REFERENCE '. CmtMIITEE ON HYGIENE STANDARDS, BRITISH OCCUPATIONAL HYGIENE SOCIETY (1968) Hygiene Stomlards for Chrysotile Asbestos Dust. Pergamon Press, Oxford. D FMSI 06485 SUMMARY AND EVALUATION Subject: Study of asbestos dust exposure among British auto brake mechanics. Of interest and importance. Evaluation: 'This paper sheds additional light on the persistent speculation concerning brake linings and asbestos dust. The study was conducted among workers engaged in the repair and maintenance of brake drums "at the Service 1 Bay of a Ford Main Dealer in the Greater London area." During the dustiest part of the operation, the prelilnin3ry cleaning of the brake drum, workers were exposed to an average of fewer than two fibers per cubic centimeter of air. According to the recommended dose-time limits established by the British Occupational Hygiene Society, this means that a brake-maintenance worker could work for 50 years at this job with less than a one percent risk of contracting asbestosis. Journal: Annals of Occupational Hygiene (British), January 1970. Title: "Exposure to Asbestos During Brake Maintenance." Summary: Brake lining mechanics in an automobile service shop worked on two passenger cars and a truck, while two types of dust-measuring devices counted the amount of asbestos dust in the atmosphere. The personal exposure of the mechanics was below the limit corresponding to 50-year exposure, the hygiene standard of the Brit:ish Occupational Hygiene Society. "Samples of drum dust were examined by Dr. s. Holmes, and his tests showed that chrysotile was pre- sent only in trace quantities, or at most at 1 per cent, compared with the original lining content of 40-60 per cent. These findings suggest that there is a change in the physical and/or chemical form of the asbestos during its use as a brake material." -XXX- FMSI 06486 19701!1111. Occup, Hys:. Vol. 1J, pp. 17-21. P~rg3mon Press 1970. Printed in GrC3t Britain Janilary EXPOSURE TO ASBESTOS DURING BRAKE / MAINTENANCE* D. E. HICKISH and K. L. KNIGHT Medical Services, Ford of Britain, Brentwood, Essex EXPOSURE DURING CAR SERViCING - TllERE is little maintenance of passenger vehicle brakes involved at the manufacturers' premises, and therefore an investigation was carried out at the Service Day of a Ford Main Dealer in the Greater London area. This Dealer normally services 10-20 cars per day, but blowing-out of brake shoes and drums is not included in all r<?utine services. It is the blowing-out procedure which is the subject of the study. Air.sampling was carried out using membrane filters, the sampling and subsequent assessment being in accordance with the technique described in the Hygiene Standard for Chrysotile Asbestos Dust, published by the Dritish Occupational Hygiene Society (1968). Static samples were taken by the side of.the car (Fig. 1) and composite samples were also taken in the dust-cloud during the blowing-out procedure, continuing by the side of the car for the remainder of the sampling pefiod. Normally the mechanic takes care to blow the dust away from himself, so this sampling procedure should overestimate exposure. Two sampling periods of 45 minutes were used, and during the first period one Cortina Estate and one Anglia Van received brake blow-outs, and duJ;ing the second period one Cortina car was dealt with. The results arc shown in Table 1. 'J:'ADLE ]. ATMOSPH~RE SAMPLES DURING CAR BRAKI! SERVICE Location of samples l~t period Fibres/em 2nd period Time-weighted average By car 1-12 1-42 125 Dust cloud then by car 171 362 255 An estimate of the daily exposure of the mechanic engngecl on brake cleaning was obtained by a series of personal sample~ (r.ig. 2) covc.-ing an entire workshift, during which brake servicing was cMri.:C: uut on 11 vehicles. The results arc shown in Table 2. "'This papl-r was originally presented at a Conference on Exposure to Asbestos during Drake and CI~Jlcll Maintenance, held at B1:cntwood, Essex, March, 1969. 11 I Ii. I FMSI 06487 ~- ~ -~'~"' ,.,;,,.:=-~-., .t= i:;'e- a,.,...,.....:..;.,;;_,IOJi'Uii.'*.',.._......_..~;.L;.,.,:....-.,.:;.o:;,;;.;;""".... --~".-. .... . .....,...- '~. :; ~ y"n+rf.J~-~~ D. E. HlcKrsn and K. L.' K.Nrorrr TABLE 2. PERSONAL SAMPLES DURING CAR DRAKE SERVICE Sample 1 2 3 4 s 6 Time-weighted average Concentration (fibres/em) 063 1-12 021 096 038 079 068 EXPOSURE DURING TRUCK. SERVICING Maintenance of truck brakes involves a somewhat different type of operator exposure as the servicing is more complex, and therefore the number of vehicles dealt with is less. The larger size of wheels and drums, on the other hand, makes it difficult for the operator to avoid the dust cloud produced, and personal exposure could be higher than that during car maintenance. Further sampling was therefore carried out in a large fleet workshop with equipment similar to that used for the passenger car tests. Static samples, each of approximately 3 hr duration, were collected dming the morning and afternoon periods at three positions; at the bay adjacent to the one at which brake cleaning was carried out, at the next bay, and in the centre of the garage. Bral-:es were blown out during the morning, but not during the afternoon. The result~ arc given in Table 3. lADLE 3. GENERAL ATMOSPHERE SMIPLES DURING TRUCK DRAKE SERVICE Location of sample Concentration (fibres/em") Adjacent bay 2 Days away Centre or garage Morning Afternoon Morning Afternoon Mornjng Afternoon 028 007 017 007 049 Olf ~. ~- ff ,'i -.~ ~,. Personal samples wc~rc obtained from two men-the man engaged oil brake cleanin_s, and the man engaged on clutch repair work at the adjacent bay. The first period of 15-2 hr included the period of brake cleaning, and the second period of approximately 5 hr represented the remainder of ll;c shift. The reslrlts are shown in Table 4. 1.. I .I I .1. FMSI 06488 ( -"-.--~--- 1 "' "."" .. ..I "' . I l Exposure to asbestos durinc brake maintenanCe: TABLE 4, PERSONAL SAMPLI:S--TRUCK DRAKE SERV~CE Operator Concentration (fibres/em) Brake cleaner during cleaning after cleaning Time-weighted average Clutch repair-adjacent bay during cleaning after cleaning Time-weighted average 7{)9 o-os 17S 22S 011 079 19 SIGNIFICANCE OF EXPOSURE LEVELS l'he Hygiene Standard suggests that exposure should not exceed an accumulated level of 100 fibre-years/em. On this basis, a man exposed for the whole of his working lifetime of 50 years, should not be exposed to concentrations exceeding 2 fibres/em. While an exposure to asbestos of this length is somewhat improbable in the case of motor mechanics, nevertheless the results have been interpreted against this value, and the findings are summarized as follows: Car senicing While the standard may be exceeded in the dust cloud dpring actual brake clean- ing, the personal exposure of the operator studied was well below the standard. Truck servicing The standard is not exceeded during brake cleaning in the general atmosphere away from the immediate vicinity of the operation, but personal exposnres in the vicinity_ do exceed the standard. On a daily basis, the personal exposure levels are below the standard, although that of the brake cleaner approaches it. It should be noted, however, that in a fleet workshop, brake cleaning operations do not necessarily take place daily. ~- f f I t THE NATURE OF AIR-BORNE DUST Brake lining materials contain 40-60 per cent of asbestos, and it was somewhat surprising to find that particles of a fibrous nature were scarce in the air samples collected. In a laboratory investigation, specimens of dust were obtained by filing brake lining material, and after sieving through a 200-mesh sieve, these were examined microscopically before and after incineration. Samples of dust were collected from brake drums during car servicing and examined in similar manner. The results of the examination were expressed as the percentage of particles which were fibrolJS in nature, ;-~nd are compared in Table 5, together with a result from an incinerated thermal precipitator sample obtained during brake ckaning. ! ~ l f ,. I. ,~r:'C'i!.,...~~:~.:o---.'""":"'~........~,..;r!""!(.... -::~..-r:~:n:~:!'t'f:';~':-"~..-~~--:.~.~-~(:. --. ~"!7\.~~;~-~:~l"':"~~~~,..~ .. l I FMSI 06489 \. - ..1t ...r r .l ~ 1 1.I ] i j ~ ; j l l 20 D. E. HICKJSII and K, L. KNIGHT' TABLE S. ASSESSMENT OF FIBROUS FRACTIONS OF DUST SAMPLES Sllmple Percentage of parliclcs seen to be fibrous Sample Sample not incinerated incinerated Brake lining material 28 12-3 Brake drum dust 06 16 Air-borne dust 13 It is clearly shown that the percentage of fibres in the drum dust and airborne dust is much lower than that in the dust formed from the original lining material. Samples of drum dust were examined by Dr S. Holmes, and his tests showed that chrysotile was present only in trace quantities, or at most at I per cent, compared with the original lining content of 40-60 per cent. These fmdings suggest that there is a change in the physical and/or chemical form of the asbestos during its use as a brake material. Enquiries were made of research workers in the UK and USA as to whether they had observed a similar effect. LYNCH (1968) reported that tests on brake testing dynamometers had shown the presence of few or no fibres in the dust produced from bus and automobile brakes, except under severe braking conditions. In the latter instance, the brake' t~mperature reached 320-370C, compared with the design maximum temperature of 290-320C, and it appeared that, under these conditions, the binder decomposed and released part of the asbestos as free fibre. At lower bulk lining temperatures within the normal operating range, the binder behind the surface remains intact. However, the spot temperature at the point of contact between the lining and the dnnn may be higher than the decomposition tempe~ature of asbestos. The decomposition product, therefore, includes not free asbestos fibres but a different mineral, restilting from thennal metamorphosis. HourES (1967) in reporting the analyses described earlier in this paper, commented that the normal thermal decomposition product of chry~otile is forsterite, a non-fibrous crystalline magnesium silicate. However, our samples of brake dmm du:;t contained very little forsterite, but rather were mainly comprised of an amorphous magnesium silicate, which is non-fibrous. Little was known at that time about the structure and CO!Jlposition of this substance. Whilst there was no evidence to suggest that the material was a health hazard, this possibility could not be dismissed, and animal experimentation has been commenced in the U.S.A. CONCLUSIONS Our investigations show that exposure to asbestos during brake maintenance is not as severe as was anticipated, and in the situations we examined, the personal exposure of the operators was below the limit corresponding to 50-year exposure. It is however recommended that care should be exercised during brake cleaning to a.void inhalation of the dust produced, and the development of cleaning procedures whirh would re~ucc air contamination is desirable. The present trend towards the int be vol wo wil HOI LYI FMSI 06490 j I ~ I :l '1 l rirne dust I ~vcd that pmpared ~at th~re luse as a I I ih~r they rom'lg dynabus ;I nstance, i.Jm tern- ~ bi - 'f ing k.<Jremains 1ing and )S. The UiHercnt T, comterite, a ,e drum ~ amor:eabout :cnce to 'be dis- lance is :ersonal !sure. ]ning to ;-cdures rds the Exposure to asbestos during brake maintenance 21 introduction of ..flow-line.. servicing at Dealers works, in which one individual may be engaged almost entirely on brake servicing, emphasises this point. Our environmental studies have not includcd maintenance procedures which involve the ft.ling or grinding of brake lining material, and we would envisage that these would give rise to considerably increased air contamination by cluysotile asbestos, with the attendant need for strict precautions to prevent the inhalation of fibres. REFERENCES CoMMIT'IEE ON HYGIENE STANDARDS, BRITISH QCCUI'ATIONAL HYGIENE SOCIETY (1968) Hygiene Standards for ChrysMile Asbestos Dust, Pergamon Press, Oxford. HOLMES, S. (1967) Private conununication. LYNCH, J. R. (1968) J. Air Pollut. Control Ass. 18, 824. I l t ~ ! ' i:. I I l l '. - , FMSI 06491 --~ SUMMARY AND EVALUATiON Subject: Comparative study of methods used for cleaning auto brakes during servicing. Of some interest. Evaluation: In British auto repair shops it has apparent~y be common practice to clean the dust from brake assemblies by blowing it out with a compressed air hose. The natural assumption that this process releases most dust into the air was confirmed by comparative tests using a vacuum cleaner, two types of brushes and rag wiping. However, it is noteworthy that the dust concentrations, measured by sampling devices, included relatively few fibers, which would presumably be asbestos. The author comments: "The results of fibre counts showed. that the numbers of fibres present in the high total dust concentrations obtained When an air line was used were of a low order of magnitude and hence the total dust concentration was used as a relative method to describe the dustiness of the environment." ~Author: Le:, G. L: (Br'itish Leyland Company). Journal: Arinals of Occupational Hygiene (Bri.tish), January 1970. Title: "Removing Dusts from Brake Assemblies During Vehicle Servicing -Alternative Cleaning Methods." Summary: "Vacuum cleaning provides a useful contribution towards obtaining satisfactory dust control when brake assemblies are cleaned." -XXX- FMSI 06492 idping those l II !Jcstosis ReIHing on the ling devoted ~til & Parkes jteen formed ~~customers jand service il exists and, iin premises Ises, by the 1r own dust lt~urcment. jr to be en- !intenance. detcmtine 1 ~~r of dust 'tring two 11 will be it! of bulk to th.-.~e iisfo. .: h remind JJmmend ;ve what iosis Re- 'lfe level. I over a ypes of ::health ;;urfacehand- ountry :l, and 1 ~ervice I jewith !~stasis Ann. Ouup. IIJ'Il Vol. IJ, pp. JJ-)(,. Pcr.,amon Prcsa 1970. Printed in Oreal Dritnin REMOVING DUSTS FROM BRAKE ASSEMBLIES DURING VEHICLE SERVICING- ALTERNATIVE CLEANING METHODS* G. L. LEE . British Leyland, Longbridge, Birmingham PRELIMINARY CONSIDERATIONS WHATEVER the criticisms may be from an occupational health point of view, few would deny that the operation of removing brake dusts with an air line is efficient in that the total time to perform the task is extremely short. The time required to perform an operation is of vital importance in industry and any process changes will always be judged relative to the time scale. In addition, the effort required from an operative in using the method should be minimal and it is easy to sec that the chances of de- veloping a technique of clcm~ing which v.il! reduce dust cmi~;sions but at the same time require no more tim.:! and effort are extremely slim. Quite clearly, we must concede from the very beginning that some increase in time and effort involved is inevitable. When viewed under nonnal lighting conditions, the' result of applying a com- pressed-air line to remove brake dusts is very dramatic. Unfortunately, mere dramati- sation alone is not adequate to describe the emission 0f dust from a process; more objective methods are needed. The conventionaf method of evaluating an environ- .mental condition is the measurement of the appropriate parameter (in this case- .fibre counts), referring the results to hygiene standards. In experimental work to evaluate dust control methods, simpler, "relative" techniques of measurement have considerable advantages and part of this work is concerned with applying a fairly simple method to define certain environmental conditions which prevail when brake dusts are removed by blowing out with a cQmprcssed t~ir line and compt~ring these with the conditions obtained when a dust control technique is applied. Because the method is a relative one, care to prevent errors from extraneous sources of variation is important. These sources of error are discussed later. METHODS USED TO EXAMINE ENVIRONMENTAL CONDITIONS When dusts are released in relatively small quantities it is often imj1ossiblc to sec the clouds under normal lighting conditions. They can be made visible using the Tyndall Beam effect and this has been employed extensively during the experimental work. This paper w:1s originally presented at a Conference 011 Exposure to Asbestos during Drake and Clutch Maintenance, held at Drentwood, Essex, March, 1969. 33 FMSI 06493 t r I ! f 'j i . 34 G. L. LEI! Mass concentrations of airborne brake dusts were determined at two positions by sampling through tared membrane f~ters. In the first position, a static sampler was placed close to the sources of dust emission. Generally, this sampling position was chosen to be in the area where the results of Tyndall Beam examinations had indicated that the highest dust concentrations were likely to be obtained. Secondly, a personal air sampling device wa~ worn by the operative in such a manner that tlie sampling bead was attached to the wearer's lapel, as near as practicable to the breathing zone. Samples for particle counting were taken, again in the operative's breathing zone, using a Konimeter, and membrane filter samples were also taken for subsequent fibre counts by microscopy, using the method described by ADDINGLEY (1966). Possible weighing errors due to static charges on membrane filters were prevented by weighing in a field of ionising radiation, as described by HIGGINS and DEWELL. The results of fibre counts showed that the numbers of fibres present in the high total dust concentrations obtained when an air line was used were of a low order of magnitude ami hence the total dust concentration was used as a relative method to describe the dustiness of the environment. The location selected for the experiments was in a workshop area, behind a glazed partition, and well away from access doors, so that comparisons of cleaning methods were not a!Jected by variations in local air movement. Smoke tests were carried out at each sampie period to confirm this point. CONDITIONS OBTAINED WHEN A COMPRESSED AIR LINE WAS USED TO REMOVE BRAKE DUSTS A commercial vehicle brake assembly, after removal of the brake drum preparatory to cleaning, is shown in Fig. I. In this particular case, the hub had also been removed for bearing replacement which facilitated cleaning operations. Jt should be noted that this is not always so and for the majority o'f our tests the inconvenience of the hub being present had to be contended with. A series of Konimeter samples were taken during typical operations and also after the process had ceased. The counts for these samples are summarized in Table I. TABLE I. RESULTS Of KONIMETER SAMI;LES DURING BLOW-OFF Sample Number of brake dust particles/5 em Taken at beginning of operation Taken approx. 20 sec later Taken npprox. 60 sec later Taken approx. 30 sec later. _Tak..!n approx. 30 sec later 5000 4500 4000 1800 580 It is seen that there is a progressive fall in count as the local dust cloud disperses. The first three figures arc approximate only, the numbers of particles co'llcctccl being too high for accurate counting. ,l. ----~.~- .....~...~.~~..--~~:r..~..-.:~~::"!' ........--;~:~--;""'7'1'.r:r~-~---.-!T"'l'~~~~.-....~ .. ~~--~... -..- .. ......,..,~,... FMSI 06494 '!Ut:' ..; L <")rli:..:0:..C.f' .' .~- 4 ,. ',', -~._ ~~-=-j"*' t' ' () positions by : sampler was : position was had indicated ly, ~ personal the sampling eathing zone. cathing zone, sequent fibre :16). Possible I by weighing I in the high low order of ::method to ind a glazed ing methods carried out NT m prepara1 also been l should be venience of > and also in Table 1. ...... .:: ._ .p~:p~~~~~~~ ~~ ~ -~~:'- ,~.,.~-:~~f~~ [ , ' ,. / -? -~ . ~ Il (:~ .~ ,;>~< . . ~ . _,1 <.t~. ~!J ) ; t ~\.. 1-~ /'. .., . .~ ~-,.:~~----~~~~.-~:~_~: ~-~~ ~ ...... .,,or?. ___ : . ..... , ,;, 1'!. ,~.-.;..,.~;.,;-.;,.:J'.rw:'.;...;..:..:.::-"'-""'-ii'-"'j; ;..~.--..2iJ~~--..~{ FIG. I. Brake assembly bcrore cleaning. i I I t i : .1... ~ ';! ~- Jisperses. led being (fu<in~: p. )4) FMSI 06495 r .. .1.--..~.;.:.~;..:.. ~--' ~- 1- Removing dusts from brake assemblies during vehicle servicing 35 A flXed sampling period of some 5 min was chosen for the determination of mass -concentrations-this being longer than required for the blowing operation but sufficient to cover that required for the alternative cleaning methods. The dust collected by the static sampler close to the brake assembly gave an equivalent concentration of 114 mg/m' and that for the personal air sampler 42 mgfm. It is probable that many of the particles included were larger than respirable size. The few asbestos fibres counted on membrane filter samples gave a concentration of the order 3-5 fibresfcm. ALTERNATIVE CLEANING METHODS I Initial approaches were to try the use of fixed and hand~held extractors to collect the dust particles removed by hand-bntshing with a small paint bntsh. Fixed ex- tractors, although reasonably efficient, were rejected because of restrictions which these placed upon the work by confining it to one area. Doth operatives and supervision were unhappy about being confined to one work area-preferring to retain flexibility and carry out the work as they had previously done, wherever the vehicle happened to be. Portable extraction equipment was clearly required and after some preliminary enquiries, a nvc industrial vacuum' cleaner was selected for use in experimental work. It is of fairly conventional type, powered by a !- h.p. motor and supplied with disposable paper bags in addition to the normal cloth bag. The paper bags arc fitted in a manner which allows them to be scaled fairly easily before removal. To trap any particulates which might pass through the paper and cloth bags, an ex- ternal, multi-layer filter was provided for fitting to the air outlet end of the cleaner.- Preliminary experiments established that some brake dust particles were passing the paper and cloth bags but these were trapped by the externally fitted filter. Sampling at the exit side of the filter established that no particles passed the filter. \,_- CONDITIONS OBTAINED USING THE VACUUM CLEANER AS A SOURCE OF EXTRACTION The first technique tried was to use the nozzle of the cleaner, hand-held as a source of local extraction whilst the dust deposits were disturbed with a small paint brush held in the other hand. The Tyndall Beam showed that some dust was escaping into the environment. Objective measurements arc summarized in Table 2. TABLE 2. RESULTS OF KONIMETER SAMPLES DURING BRUSIIJNG AND WITH LOCAL EXTJ\ACTION Sample Number of brake dust particles/5 cm3 Taken at start of process Taken ahoul I min later Taken about 2 min l:itcr Taken at" end of pr_oc~ss 1070 404 426 446 FMSI 06496 l l ! -~---- 36 The fixed sampler in the area of the highest concentration gave a dust concentration of21 mg/m and the personal sampler, 27 mgfm. An improvement in controlling the release of dust had been obtained but was not considered completely sati.sfactory and an alternative approach was sought. .CONDITIONS OBTAINED USING A MODIFIED TECHNIQUE Mter some preliminary experiments, the fo11owing general technique was devised. Firstly, the loose deposits of dusts inside the brake drum and on readily accessible surfaces of brake shoes and the brake assembly were removed, using the smallest brush supplied with the cleaner-the equipment being used as a vacuum cleaner. A much narrower, tubular brush, made from available materials was then used to remove deposits from less accessible surfaces. Finally, a rag, soaked in water and wrung fairly dry, was used to remove adherent deposits. No visible emissions of dust were observed but a few particles were detected by the objective methods, as shown in Table 3. TABLE 3. RESULTS OF KONIMETER SAMPlES DURING MODIFIED TECHNlQUE Sample Number of brake dust particles/5 em Brushing with standard brush Brushing with tubular brush Rag wiping 16-25 20-25 1-5 No .fibres were detected and the mass concentrations involved were too low to det~rmine. CONCLUSIONS The objective measurements made seem to confirm that vac'uum cleaning provides a useful contribution towards obtaining satisfactory- dust control when brake assemblies are cleaned. The design of the particular cleaner chosen prevents the discharge ofparticles back into the environment and the collection in a paper bag enables suitable disposal methods to be adopted. This work was completed in the early part of 1968 and subsequently the method described was recommended for use until such time as the results of studies being carried out elsewhere in the Motor Industry were known and detailed requirements subsequently formulated. Acknotrlcdgemenls-The assistance of Mr D. Smith of the Industrial Hygiene Department and Mr Young, Works Engineers, is gratefully acknowledged. REFERENCES ADfliNGLEY, C. G. (1966}, Ann. ocmp. Hyg. 9, 73. HIGGINS, R. I. and DEWELL, P. in lnslruclion Leaflel 3107/Al, C. F. Casella. i t t n tl \I fo pc th :w du th< Ch FMS\ 06497 SUMMARY AND EVALUATION Subject: Brief discussion of the British Asbestos Regulations as applied to brake maintenance in auto repair shops. Of interest and importance. ~valuation: This very short paper is important because the last paragraph confirms the American study by Lynch on the small amounts of asbestos in brake lining dust. The present author reports the results of tests performed in the Industrial Hygiene Laboratory of the British Ministry of Labour: "We have found that samples of dust from brake drums, when subjected to X-ray diffraction analysis, contained between 1 per cent and 3 per cent of chrysotile asbestos although the original lining material contained more than 40 per cent of asbestos. There seems little doubt that this is due to the considerable t'hermal degradation Which occurs consequent on the high temperatures generated by friction een the lining and the drum;" Journal: Annals of Occupational Hygiene (British), January 1970. Title: "Technical Ini.plementation of the New AsbestosRegulations." S~: The levels of asbestos exposure for brake mechanics appear safe. However, the exposure of particular individual workers will be increased if brake ~verhauls are conducted on a production line basis, making the development of adequate precautionary measures even more important. "Certainly, we should not be blowing out brake dust, even if it contafns only a few per cent of asbestos." -xxx- FMSI 06498 -...,:~~<< ;lJ,......._j,""'-\...._~.J.et''eir...lo..:....J'~~~t4.1L~~~~~ ........,ti'th"..; h*s~.-.l.~... t.r ax..;.n . .. .... ' ,.., ... ..;~~ ..... A1111. Occup. H)'[:. \'ol. 13, 1'1' 23-2~. Pergamon Press 1970. Prinled in Oreal Brilain January 1970 TECHNICAL IMPLEMENTATION OF THE NEW ASBESTOS REGULATIONS* S. LUXON H.M. FaciO!)' Inspectorate, Department of Employment and Productivity, Chepstow Place, Westbourne Grove, London W.2. THE NEW Asbestos Regulations were signed by the First Secretary of State on May 13 1969, and will therefore come into operation on May 14 1970. They are based on the concept that asbestos dust must be so controlled as to be at a level which will not be liable to cause injury to health. For the purp~ses of our discussion today, I believe we should take this to be a level of 2 fibres,'cm and 01 mgfm for chrysotile asbestos. A fibre is taken as being 5 p. or over in length with an aspect ratio of at least 3: l. This is of course the standard proposed by the British Occupational Hygiene Society (1968) <~nd is based on timeweighed average concentrations. There is a practical limit on the time over which samples can be taken if the exercise is not t.o become unnecessarjJy cumbersome and expensive. On this basis, a sample of 4 hr duration seems a reasonable compromise. If we accept this, as a practical sampling time then the overall standard becomes 2 fibres/em over this four hour sampling period. We cannot, however, afford to ignore entirely peak concentrations which will occur during this period, and it seems reasonable to expect that a concentration of. say 12 fibrcsjcm' should not be exceeded during any period of 10 min, i.e. we mig_ht regard 12 fibres/em' as a ceiling value. It must be remembered that we arc using the fibre count not as an absolute measure of concentration but rather as a conveniently measurable parameter to indicate the total asbestos in the air. The work leading to the formulation of the BOHS Standard referred to above related to conditions in the textile industry and not enough information is yet available on the relationship between mass of asbestos and fibre c-ounts in other industries. To further complicate the problem, it is not known what ftbre sizes are biologically active and, even if this were known, appropriate clutriation (i.e. the rejection of material not biologically active) would be very diflicult witli a fibrous . material such as asbestos. We, ourselves, arc making both fibre counts and total mass determinations by X-ray dimaction analysis in industries, such as the motor industry, where degradation of the fibres may occur, resulting in a substantial change in size distribution. HlCKtSII and KNJGIIT (1969) have described conditions during the servicing of braking systems. The figures they have quoted are, to a large extent, reassuring in 0 This p:~pcr was originally presented at a Conference on Exposure to Asbestos during Brake and Clutch lvlaintcnancc, held at Brentwood, Essex, March, 1969. 23 c f I ['f I I I I I' I FMSI 06499 ...~ ._,J I ~I 1 .l, l 1 1 l I l ~ 24 S. LUXON that they indicate that the levels likely to be found in many sections of the industry engaged in this work arc below the level of 2 fibres/em, which is considered, in the light of past knowledge, a safe one for chrysotilc asbestos. Their highest figures for the time-weighted average concentration over 4 hr, however, clearly show that over a period of 10 min we may have concentrations exceeding substantially the level of 12 fibres which are quoted above. I was interested to hear of the increasing tendency to carry out brake overhauls on a production line basis. This, clearly, must increase the exposure of particular in- dividual workers, making the development of adequate precautionary measures even more important and, in this connection, I hope the devices which will be described later to-day can be improved and developed to the point where they become univer- sally acceptable to the operator. Certainly we should not be blowing out brake dust, even if it contains only a few per cent of asbestos. In regard to this latter statement, perhaps 1 should say that work at our Industrial Hygiene laboratory confirms the _figures indicated in the previous paper. We have found that samples of dust from brake drums, when subjected to X-ray diffraction analysis, contained between I per cent and 3 per cent of chrysotile asbestos although the original lining material contained more than 40 per cent asbestos. There seems little doubt that this is due to the considerable thermal degradation which occurs consequeJit on" the high temperatures generated by friction at the interface between the lining and the drum. REFERENCES Asbestos Regulations (1969) Statutory Instrument 1969 No. 690. COMMITTEE ON HYGIENF. STANDARDS, BRITISH OCCUPATIONAL HYGIENE SOCIETY (!968) Hygiene Slumlords for Chrysolite Asbestos Dust, Pergamon Press, Oxford. 1-JICKISH, D. E. and KNIGHT, K. L. (1969) Ann. Occup. Hyg.,13, 11. j l t 1 I I l I POSSI I HAVE b< The fact: shortly b then I th This i even~uall. loss in pe Havin the reaso friction m The fi pregnated which, wh The main spheric ox resulted in drying oil abrasion. As bra degrade a In other '' Aroun< that textile neither bu1 conditions 1940's wh< asbestos t< because lh proved to 1 This P:ll Clutch Main FMSI 06500 '. SUMMARY AND EVALUATION Subject: Asbestos dust control standards in Britain and the u.s. and their relationship to occupational health. Of some interest. Evaluation: This paper is essentially identical with the one presented by the author at the Conference on "The Control of Asbestos in the Working Enviroill~Jent;" sponsored by the British Occupational Hygiene Society and the Asbestosis Research Council, London, June 18, 1969. That paper has previously been evaluated and distributed. The author is president of the British Occ~nal Hygiene Society. - - ) Author:(~'/ S. A. (London School of Hygiene and Tropical Medicine). . ./ Journal: Annals of Occupational Hygiene (British), January 1970 Title: "Hygiene Standards for Asbestos." Summary: Hygiene standards of the BOHS are discussed and compared with those of the ACGTII. The British standar_ds apply only to chrysotile, and recommend a lower TLV than the latest recommended by the ACGIH. -XXX- FMSI 06501 ... --------- -- --~-------------- I. ~. ~- Ann. Occup. HJr. Vol. B, I'P _7-JS. Pergamon Press 1970. Printed in Great Britain HYGIENE STANDARDS FOR ASBESTOS* S. A. ROACH London Schoo! of Hygiene and Tropical MediCine, Keppel Street, London W.C.l. As LONG as there is any airborne asbestos dust in the work environment there may be some small risk to health. Nevertheless exposure up to certain limits can be tolerated for a lifetime without incurring undue risks. A hygiene standard for asbestos was published in the U.K. by the Ministry of Labour in 1960 and was taken from the annual list of Threshold Limit Values of the . American Conference of Governmental Industrial Hygienists (ACGIH) (Committee on Threshold Limits, Annually). The British Occupational Hygiene Society formed a Hygiene Standards Committee in 1965 t<'l advise on hygiene standards. This Committee recommends the use of the ACGIH list of standards and supplements this with critical examinations of ACGIH and other standards considered unsatisfactory by British workers. The Hygiene Standards Committee has expert Sub-Committees, each of which is concerned with a specific standard. There is a sub-committee on asbestos dllSt in air, one on trichloroethylene vapom and its urinary metabolites, one -on airborne vegetable dusts in the textile industry, another on noise critcriil for hearing conservation and two new ones are coming into being; 'On cadmium oxide fume and silica dusts in air. It is important to take into account the economic consequences of any recommendations made as \veil as the benefits to health, and this is one reason why on each of these Hygiene Standards Sub-committees, scientific and medic~) experts from industry are included. The value of a standard rises in proportion to the number of people who become protected by it. A particular advantage of direct industrial reJ;resentation on hygiene standards committees is that the industry more readily identifies itself with the standards recommended. The Hygiene Standards Sub-committee on Asbestos, under the Chainnanship of Professor Lane, has developed new hygiene standards for airborne chrysotile dust {LANE et a!., I968). These were based on the results from a medical and environmental study at an asbestos textile factory in England, in which investigations were made on 290 of the men employed at this factory in the period of l 933- I966. The Sub-committee considered that the degree and nature of the risk associated with the standards should be specified and the method of the derivation of the st:mdard from the data presented should he described in detail. It was also considered that ti1e standards should give prominence to ihe gradu<~lly increasing risk in relation to the concentration rather than to the single figure threshold concept. Open recognition should be given to the possibility that people might be adversely :~ffectcd, even This paper was 01 i)!inally presented at a Confe1cncc on Exposure to Ashcslo5 durin~; Drake and Clutch Maintenance, held at llrcntwood, Essex, !\hrch, 1969. 7' B ) i I 1- l I ~ ! I I .l FMSI 06502 .. 8 S. A. ROACH when the recommended standards of air cleanliness arc maintained. It was recognised that to protect the hypersusceptible workers environmental control would have to be supplemented with medical examinations. It was evident from the data made available to the Sub-committee, and from the earlier American experience, that when concentration is held constant the prevalence of asbestosis was highest among those with the greatest duration of exposure. Over ll period of time, dust accumulates in the lungs and gives rise to asbestosis. However, some of the dust is removed from the lungs, for example, by being dissolved. Con- sequently, if it is assumed that none is removed and exposure is limited accordingly, a safety factor is thereby incorporated. The problem of relating prevalence with concentration and with duration of exposure was resolved by assuming that the cumulative amount of asbestos remaining in the lungs from a given exposure is equally dependent on the dust concentration and on the duration of exposure to that con- centration. The asbestos dust concentration had been measured at the textile factory con- cerned with several different instruments, including the membrane ftlter method, in which the number of fibres longer than 5 !.1. was counted. The dust concentration to which different workers had been exposed varied from 1 fibre/em to 27 fibres/em over periods from 10 years to 33 years. .,I The exposure of an individual was expressed as fibre years/em, that is, the product of the average concentration to which he was exposed during working hours and his years of exposure to this average. A curve was developed relating the prevalence of asbestosis to exposure expressed in this way. The principles on Mlhich this was based may be explained as follows. I I I l I j An individual's response to dose of any foreign substance can be expressed by a line (Fig. I). There is a dose which produces no response whatsoever. This is marked i I different is reprcs by the threshdd A. If the individual is given progressively higher doses, the response average 1 progress's correspondingly. The least positive response may be real but mercly In a 1 undesirable. A higher response may have sensory manifestations. A still higher about an response might be associated with observable physiological changes and overt clinical frequenc: effects. The highest responses of all would perhaps be signified by Joss of conscious- on either ness, or even death. In a r The degree of response may be conceived to be measurable objectively on a con- Exactly'' tinuous scale starting at zero, and the scales of dose and response could be chosen usually nr to Jinearise the relationship between them, as in Fig. I. The dose-response relation- affected b ship could then be described by the slope of the line and the point where the line the size fr strikes the dose axis. The slope of the line expresses the rapidity with which increases zero expo in dose produce increases in response in this individual. The steeper the slope the An ai1 greater the safety factor necessary in practice to allow for the inevitable occasional of men bei excursions or dose above the maximum desirable. Doses which ;5ivc zero response are never, in fact, known with absolute certainty can bema standard I since the sensitivity of measurements of response is limited. A response which can costs of ai just be detected in a man corresponds to another and higher dose, shown as threshold A cur\ B on Fig. l. Also, one is not normally considering just one individual. As with all clinically n other characteristics of man, the position and slope of a dose-response line varies from one individual to another. Each man's dose-response line is different with a their years Fig. 3. Th .. . ....,....~T~..,---~ ...,. .. ,. ......... ~;J,..~~_,..._.,..,.. .,-v.-t~_, .... ,..,.~~~ .. ~~,.....,~.::r-~-~~~~r.~~.r::- ~:~n-,~, P:":;--~~ FMSI 06503 .f" . ; rCCL. .sed (have to be ll1d from the l prevalence .l~ure. Over , However, ~ l\"cd. Con~ ccotdingly, ltcnce with j;j!! that the is equa1Jy p that con- 1 'ctory con!nethod, in ;1tration to :fibres/em i1e product 'rs and his l'alence of -;vas based ssed l-" a !is rn! ~d ; response lt merely Iill higher. Irl clinical ;Jnscious- lm acon- .e chosen /rcla.tion1 the line :imereases i;Jope the i:casionai 1:ertainty lbich can lbreshold with all j!L ..lrics :1 with a Hygiene standards for asbestos Individual response to dose 9 .. . ..-~ 0. 0:: Threshold 8 ~~---------------- Threshold A ~ Dose FIG. I. Individual response to dose. different threshold dose and a different slope. A partiq1lar population under study is represented by a family of dose-response lines centred around the line for the average man.. In a real population the threshold dose will vary frOJll one individual to another about an average value, as in other medical norms. It is to be expected that the size frequency distribution of threshold doses would be a hump-shaped curve tailing away on either side of the central value, as shown in the Fig. 2a. In a real field study it is established whether a man has or has not been affected. Exactly when or in what concentration he first developed the characteristic response is usually not known. A graph showing exposure against the total number of people affected by it would be a cumulative sigmoid curve, illustrated in Fig. 2b, derived from the size frequency distribution in Fig. 2a. This tails away down to zero response at zero exposure. An air quality standard is still associated with a. small but non-zero probability ofmen being affected by the contaminant in question. The risk of people being affected can be made as small as one wishes. Zero risk is the ultimate target and an air quality standard has to be a compromise bet ween the costs of bearing a heal!h risk and the costs of air contaminant control. A curve was fitted to the data from the textile factory 011 asbestosis, detected clinically and the exposure in ftbre years per ~m' of all the inclividuals under study over their years of. employment up to 1966. The bottom end of the fitted curve is !'>hown in Fig. J. T'Jc tine~ points relate to three of the groups of workers studied. The exposure I f .I t i j ! t ---- -----.,_ --'-~--~---- - ----- -------- FMS' 06504 .. 10. s. A. ROACII Population response to dose .. ...E 0 a. . E ..=...:- .'i c; ..::.>. > -~ .~ 0 .O..i E z::> Threshold dose FIG. 2a. Population response to th.rcshold dose. .. E 2 D. E ~ ..~ ~ 0 ::> ":;0: :0 .!: .0... E z::0 D9se FIG. 2b. p,,;-.ulation response to dose. ~ I i is shown on l I prevalence i i basal rales. rt Basal ral I 'and there is tI posure. On: l rales. j A proble ! said to be at ! mon by ever: exposure. Tl other similar it to .zero. It benefits to th cost of dust < be economic, The benefits taminant exp benefits to th One cone! an accumulal affected to tlu is, for exampl FMSI 06505 .J Hygiene standards for asbestos 11 Response to chrysotile asbestos exposure 40 , ,,,' ..o; 30 ..1! ,,,,' .13 -. /.......c.. 2Q u .!: ... ~ c ...~ IL ~~~~~2~5~o------~s~o~o------~7~5bo.-------.~ooo : Exposure (fibre years/em) Flo. 3. Response)o chrysotile asbestos exposure. is shown on the horizontal axis, expressed in fibre years per em and the corresponding prevalence is on the vertical axis, showing the proportion of people with crepitant basal rales. Basal rales is the earliest clinically demonstrable effect on the lung due to asbestos and there is a steadily increasing prevalence of basal rales with increase in dust exposure. Only groups with near zero dust exposure show zero prevalence of basal rates. A problem arises when it is appreciated that there is no exposure which can be said to be absolutely free of risk. There is no single threshold exposure held in common by everyone. ~here is, consequently, this gradually increasing risk in relation to exposure. The application of dust control to meet a TLV, an MAC, MAK value, or other similar hygiene standard will limit and control the risk but is unlikely to reduce it to zero. It has to be remembered that asbestos is very widely used and brings real benefits to the community at large. A standard could be made so stringent that the cost of <_lust control is prohibitive, that the production and usc of asbestos ceases to be economic, production and use is discontinued and the associated benefits are lost. The benefits gained by reducing the risk of asbestosis through reducing air contaminant exposure have to be weighed against the possible loss of direct and indirect benefits to the commlmity from the usc of the material. One conclusion from the exposure-response curve fitted to the data was that for an accumulated exposure of I00 fibre years/em, it is probable that the risk of being affected to the ~xtent of having early clinical signs will be less than 1 per cent. That is, for example, a concentration of 2 fibres/em' for 50 years of such exposure while . , FMSI 06506 . .l ,I\ .: ' I :r I 12 . s. A. ROACH . .. . at work, 4 flbresfcm for 25 years~ or 10 fibres/em for 10 years. The British Occupational Hygiene Society Hygiene Standards Sub-committecon Asbestos expressed the view that a proper and reasonable objective would be to reduce exposures to below this level and thereby reduce the risk of contracting asbestosis to less than 1 per cent of those who have a lifetime's exposure to the dust. For such workers, who may possibly work for 50 years, the long term average concentration to which they are exposed would need to be Jess than 2 fibres/em. For others, who will be exposed to. asbestos dust in air for shorter periods, the long term average concentration need not be so low, as long as their exposure will amount to less than 100 fibre years/em. The possibility was considered that short periods of very high concentration for a few weeks or less might be disproportionately important in determining the risk of asbestosis. However, the evidence for this was not conclusive and the committee were satisfied that the risk can be satisfactorily expressed with respect to an average concentration over 3 months and can safely be kept below 1 per cent by ensuring that a man's accumulated exposure does not rise above 100 fibre years/em. The exposure measured by making fibre counts on membrane filter samples can be converted into exposure measured with an impinger, the American method, by examining the results of side-by-side comparisons of the two instruments. Such comparisons made by the United States Public Health Service in asbestos textile plants have shown that an accumulated exposure of 100 fibre years/em corresponds to 15 mitlion particle years/ft' by standard impinger methods (AYER, LYNCH and FANNE,.1965). The present American Threshold Limit Value is a concentration of 5 million particlesjft> (mpjft) which, if it persisted, would result in an accumulated exposure of 250 million particle years/ft' over 50 years. These American hygiene standards, called Threshold Limit Values, are a system for summarising published information on air contaminants in a convenient form for the day-to-day practice of industrial hygiene. The present American standard for 8-hr averages is thus 17. times higher than the British standard for 3 monthly averages. However, there is a published intention to revise the American standard in view o~ recent knowledge. However, the difference between the American and British standard is not primarily clue to conflicting evidence on the adverse affects of asbestos. It is because of a different attitude now adopted over the degree of protection which ought to be given against asbestosis. The American Threshold Limit Value of 5 mp(ft3 was recommended by Dreessen and his co-workers in 1938 after studying 541 employees in 4 asbestos textile plants where massive exposures to chrysotile occurred (DRESSEN et al., 1938). Only 3 doubtful cases of pneumoconiosis were found at the time of the study in those exposed to dust concentrations under 5 mp/ft, whereas numerous well-marked cases were found above 5 mp/ft'. A conference held in 1965 on the biological effects of asbestos called attention to the very real probability that the 5 mp/ft> limit recommended by Dreessen is inadequate to give complete working-lifetime protection against all forms of asbestos (SCHALL, 1965). Medical data on which the limits had been based were inadequate; more than half of the asbestos workers studied by Dreessen and his co-workers were under 30 years of age and thus had insufl1cient exposure time for much asbestosis to FMSI 06507 [ ...,-.~.~~.........-~ ., _. , .. ,. .. . ... ~ Hygiene standards for asbestos 13 io;h Occupa- :oressed the :s to. below 1 I per cent ., who may .:h they are exposed to lll need not <em. :ation for a the risk of committee .:m average suring that tmples can nethod, by nts. Such itos textile Jt'responds .YNCI[ and ' ration of 5 \:Umulated , ~a~' .~m 1ient fonn 1 standard :1 monthly 1 standard l. 1 1s not pri- . cause of a ght to be 'Dreessen tile plants '!doubtful t'd to dust ere found . tcntion to 1 1 is inadc- asbestos adequate; ~crs were ~cstosis to develop. Of the 105 workers exposed to Jess than 5 mp/ft, 82 had worked Jess than S years and only 4 had more than 10 years exposure. Moreover, it was a "point-intime" study; many of the ill were missing, the dead uncounted, and were not considered in the over-all evaluation of the limit. The British Hygiene Standard5 Committee finalised its views in November 1967 after studying the British data, and these views were immediately communicated to the ACGIH TLV committee. In May 1968 the ACGJH (Committee on Threshold Limits, 1968) proposed changes to its hygiene standard. The. new asbestos limit, while taking into account the British views, had to be based on American experience and consideratio.ns applicable to the American industrial scene. Recent evaluation of the health experience in asbestos plants in the U.S.A. had, nevertheless, indicated that the 5 mp/ft' limit was not sufficiently low to protect workers exposed for 30 years, a period rarely exceeded in America. In accordance with these findings, the 5 mp/ft' limit was made a ceiling value below which all concentrations should fluctuate. This corresponds to a time-weighted average concentration over a shift of 2 mp/ft. Since the count by Impingcr procedure often consists primarily of extraneous particulates, an alternative fibre count was recommended, using the membrane filter method in which fibres greater than 5 p. in lengtp are counted as in Britain. On this basis, for a time-weighted 8-hr average limit by Impinger count of 2 mp/ft', the corresponding limit based on the fibre count is 12 fibres/em. This limit is intended to reduce to an insignificant risk, the occurrence of asbestos disease :1111011g those exposed for 30 years to all forms of asbestos. The intended changes in American TL:Vs give two years' notice and objections to them should be conveyed to the TLV committee of the ACGIH. All objections arc given the most serious and sympathetic consideration' and users are strongly advised to take advantage of this if they have reason to question the proposed changes. The standards of the British Occupational Hygiene Society recommend that a person's accumulated exposure to chrysotile asbestos should not exceed 100 fibre years/em. It is probable that the risk of being affected to the extent of having early clinical signs of asbestosis will be less than 1 per cent if the conditions comply with these standards. It is believed that this is the first time a hygiene standard has been associated with such a specified degree of protection. The standards refer essentially to an average concentration during working hours over 3 months of 2 fibres/em. In an envir-onment where this 3 monthly average just equals 2 fibres/em, the concentration within this period will sometimes be above this value and sometimes below. The maximum 8-hr average will thus be somewhat higher than 2 fibres/em'. The proposed change in the American TLV is to a maximum 12 fibres/em' 8-hr average, which if exceeded on a shift demonstrate5 noncompliance. Thus, there may be a rough degree of consistency between the hygiene standards from the two countries' organisations, so far as this is possible. The Factory Inspectorate in their work have often only a short tinie during a day to come to a judgment on conditions and are considering a development of this, applying a maximum for even shorter periods, of a few minutes, which if exceeded would indicate a probability that the Asbestos Regulations arc not being complied with. There is a growing body of information on chrysotilc dust and other asbestos dusts from many countries, and it is hoped that in future the views from difl'crent I f .I t I.. ! -I I t ' FMSt 06508 14 S. A. ROACH parts of the World will be sought so that standards for testing air cleanliness can, as. far as possible,. be held in common. Even so, the risks that'may be tolerated can vary from country to country and from one situation to another within a country. The air quality attained in industry in different countries does differ and, no doubt, will continue to differ. A wealthy country can afford to spend more money on aircontaminant control. Also, a country very conscious of the slightest risks to which its workers may be exposed through their occupation may be expected to have different standards from one which is not, where other health risks may be so much the greater. The benefits to the community from the use of inexpensive asbestos products have in some measure to be weighed in the balance against the benefits to the health of the workers that would accrue by reducing asbestos dust exposure. Tl1e British Occupational Hygiene Society Sub-committee on Hygiene Standards for Asbestos has not yet decided whether their chrysotile standards would be suitable for amosite or crocidolite dust, nor whether they give sufficient protection against lung cancer or mesotheliomas. The ACGIH, on the other hand, make no distinction 11. between different types of asbestos in their standards. In this country it should be remembered that the Senior Medical Inspectors' Advisory Panel on Problems arising l from the use of Asbestos considered that the evidence to date on balance indicated that a particular significance must be given to crocidolite as a cause of mesotheliomas l (Ministry of Labour, 1967). That Panel recommended that other types of fibre should be substituted for crocidolite wherever possible and where this is at present impossible .special precautions should be taken to reduce the risks of inhaling the material to the lowest possible level. Whatever measures may be adopted to control ! asbestos dust, the Panel urged that these be even more rigidly applied to crocidolite. I The Factory Inspectorate is also developing procedures for testing hygiene standards in factories and is seriously considering the adoption of especially rigid requirements __ --where crocidolite is used. To derive hygiene standards for an air contaminant which provide a known degree of protection against a health hazard, it is necessary to have a body of data showing the !!mount of air contaminant to which people are exposed and the corresponding effects or lack of them in the people. It is also necessary to have a grasp of the consequences to industry and users of limiting and controlling emissions of the contaminant. Our present information is very imprecise, particularly in terms of the practical consequences of specific hygiene standards. In developing recommendations for a hygiene standard, the British Occupational Hygiene Society Sub-committee found that knowledge of the relationship betw.een exposure and risk was not the . greatest area of uncertainty. A much more difficult and contentious problem was to decide on what, in fact, was an acceptable level of dust control. More information is needed, for example, ori the expense of dust control. Where this is done by ventilation it is important to know what is the minimum amount and what kind of local exhaust ventilation and dilution ventilation is necessary to achieve a given degree of air cleanliness in a work place, since costs tend to climb as the cube ef the air flow. Research is needed to determine the balance between local and general ventilation which produces a specified. degree of ccn!rol at minimum cost. By setting <icwa the capital cost, installation cost, running and rnaintenancc costs, it becomes possible to grasp mo1 kind of in be ab!e to This d equation, dard. Ho AVER, H. E. CoMMITTEI!. Trans.} Ohio, U CoMMITTE!! Governn DREESSEN,~ and TRu Wasil. I"\ LANE, R. E. occup. JJ MJNISTRYOI Medical SCHALL, E.! . , I' A+.._ FMSI 06509 . .. ..~~~,.~ ,.~~<A:.;,.";,,""'aai~~liLw~~~-tSin , ... ,~ . ),._i,-~~~-~~.:..Uc.M~...,....... ' ..,''.' iness can, as ted can vary H)'. d. no doubt, nney on air~ks to which :we different , the greater. ,oducts have :~calth of the :c Standards I be suitable tion against l distinction :l should be icms arising :e indicated sotheliomas )CS of fibre ; at present nhaling the j to control croc 1,ite. ,c stanaards :quirements c a known ~dY of data J the corre. a grasp of .ions of the nms of the 1a1cndations -committee :as not the dem was to rol. Where 1 111ount and to achieve ;,, the cube H'ntilation ~down the possible to Hygiene standards for asbestos 15 grasp more firmly the consequences of adopting particular hygiene standards. This kind of infom1atio.n is needed throughout the field of asbestos dust control so as to be able to weigh up the costs of achieving high air cleanliness. This does not reduce the choice of an air quality standard to 'a mathematical equation, nor does it avoid the need to exen::isc wise judgment in the choice of stan.dard. However, the judgment can become a little less arbitrary than at present. 'REFERENCES AVER, H. E., LYI'CH, J, R. and FANNEY, J. H. (1965) A1111. N.Y. Acad. Sci. 13.2, 274. CoMMITIEE ON THRESHOLD LIMITS (1968) Supplemental Documentation of T/ucsiUild Limit Values. Trans. Am. Conf. Governmental Industrial Hygienists 1968, p. 188. 1014 Broadway, Cincinnati, Ohio, U.S.A. CoMMITIEE oN THRESHOLD LL\IITS (1969) Threshold Limit Values for 1969. American Conference of Governmental Industrial Hygienists, 1014 Broadway, Cincinnati, Ohio, U.S.A. DREESSEN, W. C., DALLA VALLE, J. M., EDWARDS, T.l., MILLER, J. W., SAYERS, P.R., EASON, H. F. and TRICE, M. F. (1938) A study of asbestosis in the asbestos textile industry. Pub!. Hlth Bull., Wash. No. 241. LANE, R. E., BARNES, J. M., HICKISH, D. E, JoNES, J. G., RoACH, S. A., and KING, E. (1968) Ann. occup. Hyg. 11, 47. MINISTRY OF LADOUR (1967) Problems arising from the usc of asbestos. Memorandum of the Senior Medical Inspecior's Advisory Panel, HMSO, London. SCHALL, E. L. (1965) Arm. N.Y. A cad. Sci. 132, 316. f t I l I i t I ! ., FMSI 06510 SUMMARY AND EVALUATION Subject: Brief discussion of the various forms of asbestos and their effects on health. Of some interest. Evaluation: This very short paper, running to three printed pages, was presented to provide background information to a conference on possible asbestos exposure to maintenance workers on auto brakes and clutches in Britain. The author points out that currently disc brake pads, brake linings and clutch facings contain 50 percent chrysotile asbestos. However, newer developments indicate that the percentage of asbestos in the mix is likely to deciine, perhaps down to a minimum of 30.percent asbestos. Disc brakes require less asbestos fiber than drum brake linings, and it is estimated that more and more passenger cars produced in the U.K. will be equipe~~-~~~r~akes. ,.-------- ....... Author: Smither, W. J. (aroup Medical Adviser, Cape Asbestos Company). ~-------- Journal: Annals of Occupational Hygiene (British), January 1970. Title: "Asbestos and Asbestosis." SuliDIIary: As given above. -xxx- FMSI 06511 ASBESTOS AND ASBESTOSIS* W. J. SMITHER Group Medical Advbcr, Cape Asbestos Company, 114 Park Street, London W.l. THE FORMS AND USES Ol" ASBESTOS CoMMtRCIALLY important asbestos fibres fall into two main groups. The first of these is chrysoti\e, and the second comprises the amphiboles. Both groups arc . fibrous silicates, but they diiTcr in geological origin, in chemical composition, in molecular structure, in fibre size and strength, and in other characteristics. Chrysotile, white asbestos, comes from many different places. There arc slight chemical and physical variations in the fibres from different sources, but b.1.sical\y all have the same molecular structure. On the other hand, the amphiboles comprise at least three separate types, whose molecular structme is very similar, but whose chemical and physical properties differ more widely. Amosite (amber) and crocidolite (blue) are of commercial importance in this country, whereas anthophyllite is a Finnish fibre not used here. The relative amounts of each fibre in world producHon is shown in Fig. I and the areas or main use in Fig. 2. Asbetos. Annual world out put -3,000,000 tons Chrys.o1i le (while) 2,600,000 tons 93% Crocidolite (blue) (Soul h AI rico) 110,000 tons 3i a/o Amosite (South Alrico) 90,000 ton 3% Anlh{lrh:iltilc (1'1nlond) 10,000 ton" 1D/0 Conodo USSR S.t.lrico USA Europe Other 1,250,000 750,000 250,000 100,000 100,000 350,000 FIG. I. World production of asbestos. This paper was originally prc:;cntcd :1t a Conference on Exposure to Asbestos during Brake .and Clutch Maintenance, held at Btcntwood, Essex, March, 1969. 3 I' \ FMS\ 06512 .' .. w.4 J. S~tniiER Asbestos Annual consumplion-3,000,0001a!IS Where it is used Where it is mined Othcrs Belgium Italy France JAPAN UK Germany Chrysotile Others USA Southern AI rico .. USSR USA ' . USSR Canada Blue Crocidolile I I J =S.Africo Amosote Anth ophyllite S.Airico 1 Fi nlond r--: Flo. 2. Areas of usc of asbestos. The difTerent characteristics of asbestos fibres dictate their u~cs, their applications and their mode of packing and handling. For example, amosite can be pressure packed and paffetized, whereas chrysotife fends itself more reauify to containerization. By far the greatest usc of chrysotilc is in the asbestos cement inuustry. Amosite is used mainly in insulation and building products. Crocidolite, due to its excellent acid resistance, finds its major application in the manufacture of bartery boxes in 'this country. It is added to the pitch mixture in wwpencd dissoluble bags. v . brak1 con It in tht percc now with pads It is c be cq Tl is the physi1 is bei the fil .n lining cavity becon AI pcrioc sists o intcrf< the sh Th calciu1 C O i l CCI any C\ itself. Ex of the mcsotl workc1 uncom freque1 The r~ invcstiJ FMSI 06513 1cations rcssurc ization. 1osite is :nt acid in this Asbestos and asbestosis s Very broadly it can be said that current friction materials, whether they be disc brake pads, passenger car and commercial vehicle brake linings or clutch facings, contain 50 per cent chrysotile asbestos. The new trends of development, particularly in the fields of disc bntke pads and commercial vehicle brake linings; indicate that the percentage of asbestos included in the mix is likely to decline. Some new materials now contain approximately 40 per cent asbestos, and newer mixes can be foreseen with an even lower percentage, probably down to a minimum of 30 per cent. The pads for disc brakes require less asbestos fibre than conventional drum brake linings. It is estimated that more and more passenger cars produced in the U.K. will in future be equipped with disc brakes, particularly on the front wheels. THE BIOLOGICAL EFFECTS OF ASBESTOS The variation existing in the biological effects of the different types of asbestos is the subject of considerable interest and research, and the extent to which the physical and chemical characteristics of the asbestos itself influence biological effects is being investigated. The role of trnce clements and contaminants associated with the fibres has also to be considered. The chief biological effects of asbestos are confined to the lung and the pleura, or lining of the lung and chest cavity, and to the peritoneum, or lining of the abdominal cavity. A few cases of skin corns. have occured in asbestos workers, but these arc becoming much less common. All types of asbestos., if inhaled in fairly high concentrations over a considerable period of time, may cause fibrosis of the lungs. This disease, called asbestosis, consists of thickening of the Jnng membranes with resultant stiffening of the tissues and interference with oxygen uptake. The interference with gas transfer is the 1'cason for the shortness of breath which causes the disability associated with asbestosis. The amount of exposure required to produce fibrosis of the pleura, with or without cakium deposition in the scars, is more debatable. Jt may be that shorter, Jess concentrated exposures, particularly in youth, leave this mark upon the pleura. fn any event this particular e!Tect of asbestos inhalation causes lillie or no disability in itself. Exposure to asbestos may lead to further complications, e.g., heart failure, cancer of the lung, or, rarely, to m<Jlignant changes in the pleura or peritoneum, known as mesothelioma. Cancer of the lung has been shown to be more common in asbestos workers who smoke, just as it is in the general population. Mesotheliomas are very uncommon throughout the world, but in some areas they have been associated more frequently with exposure to crocidolite than to chrysotile, amosite or anthophyllite. The reasons for this arc at present obscure, but arc being sought intensively by inves-tigators in many different countries. I t l' I ~I FMSI 06514 B~ LINING DECOMPOSITION PRODUCTS In recent years, some individuals have pointed at brake lining wear as a pro- bable source of asbestos contamination of the ambient air. In this paper, Jeremiah R. Lynch of 'the National Center for Urban and Industrial Health, HID~, refutes this theory by shmving that in all but a few extremely severe automobile ' braking tests, less than one percent asbestos fiber could be found in the collected dust. He concludes that hrake lining wear is "an inconsequential health factor in urban air pollution." ,I ; ' . L ... ,. FMSI 06515 ~I Jeremiah R. Lynch National Center for 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 occupationally exposed to asbestos. A relationship between the carinogenic 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 a very small fraction of the asbestos escaped as free fiber while the remainder was transform~d into some other, nonfibrous, mineral. A signifkant release of free fiber occurred only under conditions extreme enough to produce brake failure. Table 1. Asbestos bodies in human lungs. Location Year Pos%itive Cape Town (2) Miami(Z) Pittsburgh (3) Johannesburg (4) Finland (5) Montreal (6) San Francisco (1) 1963 1965 1965 1965 1966 1966 1966 26 27 41 39 58 48 42 Table 11. Brake lining composition. Ingredient Automobile Truck Asbestos Resins and polymers Oxides and pigments Metals Carbon. graphite, etc. 55 28 9 3 5 100% 33 48 16 2 1 100% :\[r. Lynch i~ Chief of thl' L;th- oratory or Engineerill!!;, ( ltTilpa- tional Health l'rn~-:ram, l'tthlit: Health :->ervice, I >epart llll'"' of Health, Educ:atiun, and \\'dfare, 1014 llru:ulwny, Cineillltati, ( lhio 4520:?. 824 The occurrence of coated fibers referred to as "asbestos bodies" in the lungs of urban populations not occnpationally e:\-posed to asbestos has been noted by several investigators. The results of several autop"y series, as summarized hy Cooper,' are shown in Table 1. 1 ... Thompson,' in suggestiqg possible modes of exposure that could account for the~e bodies, stated: The average private motor vehicle wears out three or fonr 'ets of brake lining,; and one or two clutch lining~ in it ... lifetime, and commercial and public trnn>port vehicles wear out many more. The"e linin!!:" cnn,i;t. largely of a;be~to; which i" ground to dn.-t a.'S the linings wear, and n1o:-:t wear ot,nr~ in built-up area.o. This alone inmn'' !'itie' would involn~ the di;char~t!' of man~ t>n,; of a.~be4o" dlht an! fiber,; in the street,; each year. Since asbestos has been implicated as a carcinogen and lung cancer has a higher incidence among; urban populations, the fate of the asbestc"' wom from brake linings becomes ~ignificant. Brake Lining Composition The a\erage compo~ition of typical brake linings of the type te.-;trd i,; o::hown in Table II. Indi\iclual mixes may \ary considerably from these aHrages. Each of the~e ingredient~ performs a particular function. The a,;bc~to.-5 provides strength, heat rc~i~t::ltlcc, and sc\eetive dPcomposition undt>r -trc~s. The rr;:ins and polymers hold thP other ingrediPIIb to~cthcr. Yari<Hh oxiclc~ arc added a;; pi~1nents and to impro\e the grip of the lining on the drum. Soft metub such as lead and hra>"s improve wear while carbon ami graphite serve as friction modifiers. Brake lining quality depends to a lar~e extent on the type of binder u>ed. Linseed oil, which begins to decompo:'e at about 450F. is used for light senice brakes. :\lore demanding ~enice requires brakes made from ea:-;hew typp resins or oil modified phenolie re:3ins. These ingredient~ are mixed, either dry or with a solvent added. formed into shape, and cured in an ovet. The hardened lining is then cut, ground, and Eanrled to the preei~e dimensions of the fini~he:l linings. The dw<t prcKluret.l by the abrading operations in asbe~t05 friction prod net factories (Fi,!!;nre 1) contains free a~hesto5 fiber~ that are similar to those in industries where cancer i8 known to be' in excess. 10 The question to be resolved, therefore. is whether the dust produced hy the normal wear of brake linings eontain,; this ~arne type of free a~be~to5 fiber. Test Methods In an initial exploratory survey, thP dust obtained from im:ide automobile brake drums removed for brake relining; was examined by electron micro~raph. Figure 2, which is typical of the ~erie:;, doe,; not reveal any free fiber>. However, this finding; did not eliminate the possibility that free asbesto.~ fibers were relea~eJ and that they had esrapc<l into the atmosphere. To examine thi~ hypothesis a series of experiments was Je\i~ccl to pNmit >;amplinJ?; decontposition procluC'ts of the lining un<!Pr ..-imulate<l opPtating; eonclitions. The tr<b (Table Ill) were performed with the brake testin~ mac:hines in the laboratory oi a major brake lining nmnuf:1eturcr. :\lost of the tests were performed on a Journal of the Air Pollution Control Association FMSI 06516 ..,. .., 4L'.... . .... 1 Figure 1. Brake lining factory dust. z.Figure Dust removed from brake drum. Figure 3. Decomposition product from nor mal wear of brake lining. friction-testing machine which used one-inch-square samples of the test lining. HE.'ating and cooling apparatus permitted control of drum temperature from those encountered with intermittent brake use to the maximum temperature which occurred orilv in extremely rapid or "panic" stops froin high speed. Other tests were performed on a brake-testing dynamometer which subjected a comp"lete brake assemblv to a series of stops and starts from diffe~ent speeds and at different deceleration rates to simulate actual driving conditions. In these tests the drum temperatures \aried according to the driving condition simulated. During each run at a test condition, a sample was collected on an 0.8,. pore :-ize 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. Results The object of the tests was to determine what proportion of the asbe:;tos known to be present in the liuing appeared as free fiber in the decompo:;ition product. Xo attempt was made at a mass balance between the material worn from the lining and the tlecompositiou product since it was not possible to collect all of the decomposition product. However, the percentages obtained in the fraction of decomposition product examiner! are applicable to the total material worn from the brake and may be compared to the percentage of asbestos originally pre~ent. In all but a few tests the automobile drum brake linings showed less than .1% free fiber in the decomposition product as compared to about 50% in the lining. An electron micrograph of the decomposition product obtained from a typical test in this group is shown in Fip;ure 3. In those tests where a ~ig nificaut ma!'s of free fiber was relea~ed (Figure fl, the tcmp<'rature "as in an extremely hil!;h ran)!;e for the liuing in question as evideuced by rapid drop in thr> coefficieut of friction. Had the~e lining;s been subjected to like conditions in a vehicle, the brakes would have failed. t;imilar re:;ults were obtained in the bu~ allll truck drum brake te~ts and iu the dutch te,-t. The experimeutal morlel disk brake tested did release some (>5%) free fibers, but 110 conclu~ion can be drawn from a single sample. Discussion Except in all but the most extrer.1e driving conditions, only a \ery small fraction of the 30 to 50% a:>beo.:tos present in a brake lining escape:; into the atmosphere as free fiber. The question remains: "'hat happened to the asbestos? A prevalent theory of brake operation holds that wear occurs uot by abrasion of the lining by the drum but by the production of minute areas of intense heat at the poinb of contact between the drum and the lining. Decomposition, not only of the binder but of the asbe~t.o:; as .....en, occurs at the"<' lotations sinte the brcaktlown temperature of asbestos, about 900F, i~ exceeded. J)ecompo~ition products will i,dwle not fne asbestos fibers, but. a different miucr~l resulting from thermal metamorphosi,; of asbesto~. December 1968 Volume 18, No. 12 .Ill' f. J LY Figure 4. Decomposition product from brake lining at fa1lure. FMSI 06517 825 .; ., ,_A Table Ill. 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 6 300.800 Few <1 drum brakes 2. Automobile B Friction 6 250 SOD None 0 drum brakes c3. Automobile Friction 5 300 700 Few <1 drum brakes c4. Automobile Friction 1 700-900 Numerous -10 drum brakes 5. Automobile 0 Friction 5 300 800 Few <1 drum French brakes 6. Automobile E Friction 5 300 700 Few <1 drum brakes 7. Automobile F Friction 5 300-800 Few <1 drum German brakes 8. Automobile G Friction 2 100-500 Few <1 drum brakes 9. Automobile G Friction 600-700 Numerous -15 drum brakes 10. Automobile H Friction 2 100-600 Few <1 drum brakes 11. Automobile J clutch Dynamometer Normal driving None 0 12. Automobile K Dynamometer disk Normal dliving Few <5 brake 13. Bus drum L Dynamometer brake City driving None 0 14. Bus drum M Friction 2 450-550 None 0 brake 15. Truck drum F Friction 10 300.800 Few <1 brake (light) Weight estimated from fiber volumea Some independent experiment~ done at a brake lining re,earch Jahoratoryu have shown that all of the ma!!;ne,.;ium present in the chrysotile a,.;he~to' originally in the lining ran he acr<Hmted for in the decomposition producu-. However, the charaetcristic X-ray diffraction pattern of chrysotile aHhe,.;to" had vanished. Thus, it is apparrnt that under conditions in whirh a,.;lw~to:< is worn from the lining of a brake, the asbestos is destroyed. Conclusion Only a very small proportion of the asbestos worn from brake linin!!" is released as free fiber; the remainder is converted into some other minrral as a result of the extreme temperatures generated at ~mall spots on the liuinp; ,.;urface. Thus, although urban air mntains a few free fibers as a result of brake lining wear, they reprctient a \'Cry small 126 proportion of the total asbestos used in manufacture of brakes. ;\!any sources of respirable fibers not associated with a~bestos products ha,e bren identified, 1 ~ and free fibers from brake lining wear seem to be an inconsequential health factor in urban air pollution. References I. Cooper, W. C., "A:;be,tos as a hazard to health," Arch. of Env. Health. 15: 28.> (1967). 2. Thomson, J. G., Ka,chnla. R. 0. C., and 1\fcDonald, IL H., 'Ashe,to,is as a modern urban hazard," S. Afr. .\led. J. 37: 7i (I !lG:{). 3. Cnuna, D., Totten, H. S., and Gross, P., "Asbestos bodies in human htni,'S at antopsy," .TA.\IA, 192: :ri < l!lli.">). 4. Webst.er, 1., in di>cussion of Thompson, l:;. F., "l'h~,iolo![i<al Pifed of D20 in mnmmab," r\nn. X. }".Acari. Sci., 84: 7:~fi (I !lliO ). .i. :\Icurman, L., ,\,llt-,.tos bodies and pleural plaques iu a Fini'h "rics of autopsy c:c,es," Aria l'ath .II icrobiol. Scant/ Suppl., 181: 107 (I!Jli6). 6. Aryilrel, L and Thurlbe~k, W., ''The incidence of a.'bestos bodies in the lungs of randon autopsies in Montreal, Canada. Med. Assoc. J., 95: 1179 (1966). 7. Thom~on, J. (;., "A:;bestos and the urban dweller," Ann. N. Y. Acad. Sci., 132 : 1!l6 (196.5 ). 8. SelikofT, I. J., Churg, J., and Hammond, E. C., "A:;bestos exposuri' and neoplasia," JAMA, 188: 22 (l\l64). !l. Buell, P. and Dunn, J. E., "Helntive impact of smoking and air pollut,ion on lung cancer," Arch. of Env. Health, 15:291 ( l!lfi7). 10. Enterline, P. E. and Kendriek, ~1. A., "A,.;bestos dlL~t expo'!tre; nt various levels anti mortality," Arch. Env. Health, IS: lSI (1967). II. Sinclair, D., "Htudy of wear <ltbt. from hrnke lining," .Johns-,\lanville H.., and Eug Ctr., personal r.ommunica\ ion 11 U61 ). l:l. Cralley, L. J., Keenan, IL U .. L.ntch, J. lt., and Lainhart, W. S., ~our<'t' and identification of re;pimhlc f1hcrs," Amer. Ind. !Jyg. A~soc. J., 29: l:!!J (196!!). Journal of the Air Pollution Control Association FMSI 06518 ---=====-==-r PB 192 252 i.~ NATIONAL INVENTORY OF SOURCES AND EMISSIONS: CADMIUM, NICKEL, AND ASBESTOS- 1968. ASBESTOS, SECTION III David (W. E.) artd Associates Leawood, Kansas February 1970 , "T1 3e-n: - L,e0n (II CD za Distributed 1 1 1 'to foster, serve and promote the nation's economic developme11t and technological advancement.' CLEARINGHOUSE FOk FEDRAL SCIEN~I:~ ~NO TCHNiCAliNFORMATION .......Ge t~E-.:.fi.t :~:WN M OiC.PARTiftEnT ur COIIIMERCE/Natlcnal Bureau of Standarcl:m This document has been appro1ed for public release and sale. I. I -----_,....,_,_______ ' --- ........., -6- )'"" J .-.~-~ >. ~':~. :...; ..,...-"' ' .... ~, ,., "':"'"-!":""';~." r ASBESTOS IMPORtlf'/'. I' . /fr Durinq 1968, asbestos imports wale 737,909 short tons, Approx- im~otalimately S4 percent of the was from Canada and 5 percent wa~ off~from the R.epabllc Africa.Y " ,, .)., .. ~r.~?.: . : ASBESTOS ElCPOR'l'S s, during 1968, were 41,236 short tons,2:J - Bureau of Mines Minerals Yearbook - 1968 ')~: :..-:.\ .'~{ .. -7J t:.~-:~. .. l.~l '. :!.~~{~~;~~.::- .~~~ ;.~~:.~~-~_\:~;. ~~: ;REPROCESSING . ' ... The apparent COMumption of asbestos 1n tbe United States, durinV 196B, has been reported at 817,363 short tons.~/ FRJCl'ION MMERIAIS Asbestos is regarded as indispensable in most types of friction materials. It is used as the Pr-imary constituent 1n brake l1ninqs aDd Clutch facings for motor vehicles, end other commercial end industrial equipment. l!rclke linings are of two principal types. In the early days of the automoblle, virtUally all braltebends -re of woven asbestos febricl but now the molded type is used extensively. Molded linings consist of asbestos fibers bonded with en organic matrix. Metallic reinforcing 'is commonly added, and the shaped product are thoroughly cured. ChrysoUle asbestos is required, rengirig,in fiber length fro~ the very short grades to those j&~st under spinning grades. In the United States the use of asbestos 1n friction material durlnq ., 1968 was about 104,000 short tons.~/ Reproceuinq plants producin9 friction materials ere listed in Appendix A. 3: ~ en0 1- Bureau of Mines Minerals Yearbook - 1968 2- Estimate based on reports from reprocesaing companies end date Ul from the 1967 Cen1ua of Manufacturers, N 0 .~~~~~-. ~- ~--------------~--------------------------~----------..------~~--~--------------.-------------------------------~~----~--~..- l-29- fiber, were sold to a contractor during 19 68 for use on roads. It Is reported that an appreciable amount is used in Vermont for I roads. _1 I This could not be confirmed, since permission to vis! the mine and mill was denied. l Construction 1 Workmen in all trades In the construction industry come In con- 'I Il II I ,, I .1 tact with asbestos. Heating duCts are often Insulated with asbestos, and steam piping is nearly always covered with a material contain- ing asbestos. Electricians strip asbestos insulation from wires, and the carpenter saws asbestos siding, wallboard, and shingles. As a result, there Is asbestos released to the air around the con-; struct!on sites. Asbestos emissions to.the atmosphere at construction sites are I. I estimated at 61 short tons for 1968. Brake Linings .I Motor vehicle travel durinQ 19 68 totaled one trillion miles, and replacement brake linings were required for about 25 to 30 million I vehicles. It Is the usual practice, when 1nstal11ng new brake Un!ngs, !I "T1 en3: 1- May-Timothy C.; Asbestos; Mineral Facts and Problems; Bureau of Mines Bulletin 630- 1965 I 0 I<c.n .N.... ! I -3o- toUt the linings to the drums by grinding, and the amount of grinding required varies dependin9 on the condition of the brake drum, Data concerning motor vehicle bcake llnings: Vehicle miles during 1968 1,010,000,000,000 Mileage life of brake linings 27,500 Brake lining sets on new vehicles 10,718,000 Pounds of asbestos per set of brake linings 3 Assumed loss to atmosphere during grinding and fitting - percent 0.5 Based on the above, the emissions factor is 10 pounds per ton of asbestos processed, and the asbestos emissions to the atmosphere during 1968 were 190 tons. Steel Fireproofing Several spray-on materials that contain asbestos are used extens!vely on steel columns and other structures as a fire protection measure. The application f"f such .materials Is often required by code. Even though the building frame may be covered by a temporary enclosure when the material is sprayed, the workmen are exposed to an atmosphere that Is virtually saturated with asbestos fiber. Asbestos emissions to the atmosphere, due to the use of spray on fireproofing during 1968, are estimated at 15 short tons, -31- based on an emissions factor of 1 0 pounds per ton of asbestos applied. Motor Vehicle Use It is obvious that there are ~ubstantial particulate emissions from the wear of motor vehicle brake linings and clutch facings. This has. been reported as a primary source of asbestos emissions to the atmosphere: however, there are conflicting reports indicating that the asbestos fiber has been destroyed by the heat of friction. In this report the estimate of emissions does not Include an amount for the wear of motor vehicle brake linings and clutch facings. I I I I 1 .I I -32- pounds per ton of asbestos applied iS calculated for the use of insulating cement. 1 - Fifteen percent of the insulating cement worn away during use, 2 - Dust collector efficiency - 89 percent (average) Asbestos emissions to the atmosphere during 1968 due to the use of tnsuiating cement are estimated at 25 sho,t tons. Insulating Cement Insulating cement that contains asbestos Is used extensively In I I all types of boilers. It Is used for pointing up joints and cracks In stack and breechlng linings, and for surfacing block Insulation I that is ins~alled !"'side breechinq s, ducts and ~:~cc..,omlzers. During the boUer operation, as the flue gas passes through the boUer some of fhe insulating cement 11 worn away and carried along through the dust collector, up the stack, and Into the -n atmosphere, sen: Baaed on the following assumptions, an emissions factor of 33 - '' 0 Q) en N N !I I I' I' I 1 -34- I I ASBESTOS MINES IN THE UNITED STATES ~ LOCATION Asbestos Manufacturing Company faquays Mining Corporation Metate Asbestos Corporation tAuFORNIA Gila County Gila County Glla County 1// Atlas Minerals Corporation ;' Coalinga Asbestos Company (1) Pacific Asbestos Corporation (2) / Union Carbide Corporation / / Fresno County Fresno County Calaveras County San Benito County NORTH CAROUNA / I Com~Powhatan Mining Yancey County VERMONT I GM Corpora~n Orleans County I I (l) - -!.d by ]ohns-ManvUle Corporation (2Jl::ed by H. K. Porter Company, Inc. during 1968. I., 3: -CJ) e0n Ul N (,) tl %f) -35- REPROCESSING PLANTS PRODUCING ASBESTOS FRICTION MATERIALS CALifORNIA H. Krasne Manufacturing Company Silver Line ~ake Lining Corporation Lasco Brake Products Corporation, Ltd. LOCATION Los Angeles Los Angeles Oakland CONNEQriCUT H. K. Porter Company, Inc. Raybestos-Manhattan, Inc. Middletown Stratford ILUNOIS Gatke Cotporation Grizzly Brake Division of Mar Pro Inc. The L, S. Miley Company Johns-Manville Corporation Chicago Chicago Chicago Waukeg~n mJ2.IA!!A Raybestos-Manhattan, Inc. H. K. Porter Company, Inc. World Bestos Company (sub. of Firestone Tire & Rubber Co,) Crawfordsvllle Huntington New Castle J)!;NTUCKY H. K. Porter Company, Inc. Richmond MASAQHUSETTS Auto FrictiOn Lawrence MICHIGAN American Brakeblock - Division Ambes Corp. Birmingham Amoricaq Brake Shoe Company Troy ~ ~..,.-..,, .-...:- ..... -, ~-------- ----------------------------------------------------------'-~--- -36- NEW IERSEY Jcnns-Manville Corporation Rf,ddaway Manufacturing Gompany, Inc. Raybestos-Manhattan, Inc. H. lC. Porter Company, Inc. Manville Newark Passaic Trenton NEW YORk Bendix Corporation Troy NORTH CAROLIN.A Southern Fri::Uon Materials Co"mpany Charlotte OHIO American Brake Shoe General Motors Corporation Maremont Corporation Cleveland Dayton Paulding PENNSYLVANIA Raybestos-Manhattan, Inc. H. K. Porter Company, Inc, Manheim Pittsburgh TEXAS Standco Brake Lining Company Fouston TENNESSEE ., Bendix Corporation VIRGINIA sen: American Brake Shoe Cleveland Winchester Qec.nn (Thomas Register, Dec., 1968 Ed., Fortune-1966 Plant & Product Directory of the 1000 Largest U.S. Industrial Corporations; U.S, .Np. Department of Commerce.) I -37- I // / REPROCESSING PLANTS PRODUCING ASBESTOS CEMENT PRODUCT~' / I ; / ALAI!AMA LO<kroN U. S. Cast Iron Pipe Company kruston GAF Corporation /Mobile Cement Asbestos Products Company f Woodward / '.,/ CALIFORNIA f /i / Southern Pipe & Casing Company / Johns-Manville Corporation j Azuza Long Beach Johns-ManvUle Corporation j Pittsburgh Certain-Teed Products Corporation/ Riverside Certain-Teed Products Corporatioii Santa Clara Johns-ManvUle Corporation ,, / Stockton ' ,. CONNECTICUT ..f Tile Roofing Company / GEORGIA . ,;' Stratford Uniroyal, Inc. /' GAF Corporatio"/ i i ILLINOIS Hogansville Port Wentworth Acme Asbe tos Covering & Flooring' Company Asbestos Magnesia Materials Company Fllntkot Compar.y Wester Slate Company Fel-Pr , Inc. John Manville Corporation Chicago Chicago Chicago Elmhurst Skokie Waukegan S. Gypsum Company East Chicago .