Document wgyb0eQBVEY8Jp8nXN3N9JEXo

:). zm < z~ ~ mz ,~.... ~ m ' <mI ' )> n~ ::X: ;0, ,--0-..., G')\ -z< m (') 0 6 G"l R 0 (8\.... , 0. \ G-<"l' r .,~NVIRO~~-~NTAL RES~ARCH 12, 110-128 (1976) ----- ----- TEXT I -! Asbestos Exposure during Brake Lining Maintenance and Repair1 ARTHURN. ROHL, ARTHUR M. LANGER, MARYs. WOLFF, AND IRVING WEISMAN Environmental Sciences Laboratory, Mount Sinai School of Medicine of the City University of Nel<' York, New York, New York /0029 Received December 10, 1975 Data obtained on asbestos exposure of garage mechanics during brake lining maintenance and repair work show that fiber concentrations frequently in excess of regulated limits are I !- common. The presence of chrysotile. ranging from 2 to 15%, in brake drum dusts, was demonstrated by X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and electron microprobe analyses. Unaltered chrysotile was found, both in fiber and fibril fonn, in air and brake drum dust samples. The chrysotile asbestos content of personal air samples. taken duringautomobile brake repair work, was measured both by' optical and electron microscopic techniques. While a positive correlation exists between the types of measurements, the present technique of optically counting asbestos fibers may considerably underestimate the levels of total asbestos exposure. INTRODUCTION During the past decade, significant disease risk has been found associated with the inhalation of asbestos fibers in a number of occupational and environmental circumstances other than in asbestos mining, milling and manufacturing, where serious hazard was already known (Wagner et al., 1960; Newhouse and Thompson, 1965; Selikoff et al., 1964, 1965; Harries, 1968). Such exposures were found in the construction industry and in shipbuilding, as well as in other industrial settings where asbestos products were used. More recently, asbestos exposure has been suggested to occur during automotive brake lining repair and installation work, and measurable concentrations of asbestos fiber were obser'!'ed in the work environment of workmen involved in these operations (Hickish and Knight, 1970; Hatch, 1970; Boillat and Lob, 1973). With limited data available, however, uncertainty remained regarding the type and extent of asbestos exposure during this work. Some investigators have questioned whether free asbestos fibers survive the high temperatures produced during braking action (Lynch, 1968; Hickish and Knight, 1970; Hatch, 1970) contending that asbestos decomposes as a result of the high point contact temperatures produced at the . interface of the brake drum or disc and brake lining. We have sought to obtain information concerning asbestos exposure of workmen engaged in brake lining maintenance and brake shoe installation, by analysis of residual dusts recovered from brake linings and by direct measurement of the Il,;his research was supported by Center Grant ES00928 of the Nat ionaI Tnst itute of Environmental Health Sciences of the U.S. Department of Health. Education and Welfare. Assistance was also ,--provided in part by the Health Research Council of the City of New York HRC U 2329 and by the Ford Motor Company. - Copyright 1976 by Academic Pr-ess, fnc. 110 I- All righl s of reproduction in any form rest.:rved. FMSI 04724 -------------------------------- -------.-----------------------------------------------------------------------+-~ .... ..( llj_.: free asbestos fiber content of workroom air jn areas where these operations take place. In the United States, an estimated work force of at least 900,000 auto --mechanics and garage workers is potentially exposed to asbestos in the servicing of both brake and clutch linings. Furthermore, much brake dust enters the general environment during automobile use (Jacko and DuCharme, 1973), to add more to the burden of asbestos air pollution (Selikoff, Nicholson, and Langer, 1972). Asbestos in Friction Materials . , In the United States, an estimated J18 million pounds of asbestos is used annually for the production of brake friction materials (Jacko and DuCharme, 1973). After processing (cutting, grinding, punching), the asbestos in the material sold is approximately 103 million pounds per year. In addition, asbestos contained in automotive clutch friction materials amounts to 4.5 million pounds _annually. A;fajor Constituents ofBrake Linings 1 A number of materials is commonly used in the manufacture of the three major automotive brake lining components (binder, fiber reinforcer, and property mod- ifier). These are listed in Table I. Binder. The binders used in the automotive industry today are primarily phenolic-type resins, which are noted for high binding efficiency and ability to withstand pyrolytic breakdown. Other materials have been used, in varying pro-1 portions and in addition to resins, for binder improvement (Table J). I: TABLE I CoMMON COMPONENTS OF AUTOMOTIVE BRAKE LININGS" Binder and organic friction modifiers Fiber reinforcer Property modifier Phenolic-type resin Rubber Tire scrap Pitch Cork Gilsonite Cashew nutshell resin and particles Drying oils Chrysolite asbestosb (grades 4-7) Unaltered Calcined Mixed fiber Lead compounds Zinc compounds Antimony oxide Iron oxide Copper metal Brass chips Clay minerals Barite (BaSO.) Wollastonite (CaSiOJ Quartz (Si02) Cryolite (Na.AIF3) Rottenstone (SiOJ Coke (C) Coal (C) Gilsonite (C) Graphite (C) Carbon black (C) Molybdenum sulfide (MoSJ Fluorspar (CaFJ See Carroll, t962;Anderson, 1969; Anderson, 1973; Jacko and DuCharme, 1973; Bark,et al., 1975. 6 Chrysotile fiber constitutes about SO% by weight of most automotive brakes currently manufac- tured in the United States. rCOPYRIGHT +-- FMSI 04725 J: ~ w Iwl l ~ ....1 ~ z w z~ ~ ~ w -g 0 ~ 0 0 ~ 0 ~ <!) g 0uzw b I, i lm ~,o~z ~ l~,.... l;og 1~ ~~ :00 10 ':X: 0 ,::1 ' 0. 'o ,"'( .Z .gtmn : nC) n0z 0 0 C) -< ~: ~=-+12-D_ : ::_ _---==~~ - Fiber. For fiber reinforcement of the friction product, chrysotile asbestos isused almost exclusively. The mineral typically comprises from 40 to 50% of the -brake product. Fiber grades 4 through 7 are used, and occasionally, several sizesare admixed or even calcined to improve performance characteristics. l Modifiers. Perhaps the widest range of materials used in friction products are the property modifiers. Nineteen representative compounds are listed in Table 1. Modifiers are used for a number of purposes; they are included to increase brake shoe "density," making the brake surface able to withstand high pressures (e.g., barite); they are included as "lubricants" to reduce the coefficient of friction along the brake surface, and thereby prevent "grabbing" (e.g., lead compounds); they act as "friction agents" increasing the coefficient of friction and enhancin~ the braking action of the shoe (e.g. brass chips); they act as internal"abrasives," which help to "recondition" the braking surface and remove deposited decomposition products (e.g., rottenstone, quartz); they act as "heat sinks," reducing binder pyrolysis and fiber decomposition thereby extending the useful life of the lining (e.g., brass chips, metals, etc.). It is important to note that one major purpose of the reconditioning agents is to retard the formation of forsterite (a mineral not originally present in the brake material, but created by de hydroxylation and recrystallization of chrysotile asbestos at high temperatures) which may accumulate on the surface of the brake lining. The hardness of the forsterite (Mobs, 6.5-7 .0) is such that it tends to score and gouge brake drums and discs (hardness 3-3.5), degrading them prematurely~ Therefore, recrystallization of chrysotile to forsterite is an unwanted effect, hindered insofar as possible by the modifiers present in the matrix. Materials of Biological Interest Asbestos, quartz, and heavy metals are constituents of automotive brake linings, each warranting special consideration from the viewpoint of biological activity. The focus of this report is limited to the problem of chrysotile asbestos exposure. Mechanisms of Degradation of Brake Linings during Use 1 Brake wear is dependent upon many factors, such as the temperature generated at the surface of the brake shoe during braking operations. At any one time, only a small percentage of the rubbing area is in contact with the wheel, with "hot spots" generated, ranging up to 800 to l000C (Carroll, 1962; Anderson, 1969). It is not uncommon during moderate braking action, to attain temperatures as high as .500"C (Carroll, 1962). Some investigators have suggested that, in addition to bin- . :lder pyrolysis, chrysotile completely dehydroxylates under these conditions and "reduces to powder" where it is swept off the brake facing (Carroll, 1962). How- .ever, this hypothesis is oversimplified, in that other important processes, besides !thermal wear, contribute to shoe breakdown, and brake shoe degradation. (Bur- well, 1957). For example, the effects of abrasive wear and macroshear have been linvestigated'. When monitored by X-ray diffraction, chrysotile in brake materials displays structural strain and substructure fragmentation, caused by shear during !braking processes (Mizutani et al., 1973). This shear strain produces material +-- fa-t-ig~u.e ~w=h-i-ch-,.w::it'h-b-i-n=d--e=r- p-y-ro~ly-s--i-~=can c_ause brake lin.ing dis--in-te=gr-a.tion- at -- -+C-0-PY_R_I_G_H,_T_ _ _ - - - - - - - - - - - FMSI 04726 ~ I I i l I I. I f ' I ! fE~!?___ 11~ -temperatures far below those required for chrysotile dehydroxylation. Therefore, brake lining disintegration may liberate partially altered, or unaltered, chrysotile -fibers. Thermal Decomposition of Chrysotile Differential thermal analysis indicates that chrysotile undergoes dehydroxylation at 650 to 680oC and recrystallizes (anhydrous magnesium silicate to forsterite) (Mg2Si04) at about 810 to 820C (e.g., Martinez, 1%6; Daykin, 1971; Berry, 1971; Monkman, 1971; Harris, 1971). These temperature ranges are subject to great variation as a function of the chemistry of the fiber, particle size, instrumental variations, sample packing, etc. Also, forsterite has been noted to form, during prolonged static heating, at considerably lower temperatures (Bates and Comer, 1957; Martinez, 1966; Brindley and Hayami, 1965; Naumann and Dresher, 1%6). In general, temperatures in excess of 570C are required for dehydroxylation and incipient forsterite formation in chrysoti1e. Extensive study of both the thermal behavior of chrysotile and brake lining composition and design_ indicates that chrysotile fiber may survive in the decomposed lining dust. I I METHODS Analysis of Brake Drum Dust (Decomposed Lining) Ten samples of automobile brake drum dusts were collected and examined by optical microscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy with microchemical capability, for the pu[-pose of determining the presence or absence of chrysotile.2 Optical microscopy, employing polarized light, was generally not useful for detecting asbestos in brake drum dust. A number of factors are _considered re- sponsible for this phenomenon including the low relief and birefringence of chrysotile and the nature of the matrix, consisting largely of road dust, resin _binder, and pyrolyzed residue, which, in optical microscopic preparations, readily obscures the smaller asbestos fibers. .. X-ray diffractometry, in the continuous and step-scan mode, was performed on all dusts. Chrysotile reflections (hkl = 002; 020; 004) were observed in all ten samples. Quantitative determination of chrysotile content was made by compari- son of unknowns with calibrations of chrysotile dilution standards. The weight occurrence ranged from about 2-15%, with an average ranging from 3--6%. Lead compounds, quartz, calcite, mica, clays, barite, graphite, and alpha-iron particles ,were identified as well. In several samples, weak, diffuse reflections suggested the jP_resence of forsterite, but positive identification could not be made using this lt~chnique. ~dentification of Chrysotile by Electron Microscopy I 1 Transmission electron microscopy, ------- --- .. se-lec!ted-a-re-a-e-le-ctr-on diffraction, and elec- 1We acknowledge the cooperation of the United Automobile Workers, Local Union No. 259 and the Automobile De'alers Industrial Relations Association in helping us obtain these samples in auto 1 maintenance shops in the New York area. Each sample was taken from "a typical job" under way. at the time. 'l COPYRIGIH -i- I -~------ FMSI 04727 :X:' ~ w 1/) ~ ;;ii z1- ' w ~z ~ ~ w -g 0 t; g 0uz 0 ~ gC) ut0zw; ,. t': L ' '.. ! _l__ --------:T11-4-.D----- ------ --- __,_-- - .. --- - - - - --- ------ - - - - ~---- - - tron microprobe analysis of the brake dusts were carried out on each of the tensamples after preparation by a technique which disperses the dust particles in a -nitrocellulose film without altering particle size distribution. Free chrysotile fiberbundles and fibrils were observed in all ten samples (Fig. 1). Selected area electron diffraction analysis of representative fibers demonstrated the preservation of the chrysotile structure (Figs. 2A, B). Some patterns displayed arcuate reflections suggestive of interfibril rotation and intrafibril displacement (Figs. 2A, B). Occasionally, fibers were observed without characteristic chrysotile morphology, with r -----------mottled surfaces and obliterated fibrils, inQicating partial or complete recrystalli- zatio.JL-Eiectron diffraction--p-a-t-te-r-n-s-1obt-a-i-n--e-d--f-rom th.ese p..articles dis--played "" .li' Im I~ "0z' >3mz: .. _. .... "m' (1'1 m > n"' I a :::1 tQ. (;) -z< r\,.-. nm ....0 FIC:-T. Electronphotomicrograph of large chrysotile bundle in brake drum dust (38.000x magnifica- 0 tion). Other particles include_p_h_en~l re~ ~n~c:~11d ro~d-~ust d_eb~~: (;) :n 0nz -+---------- ---- COPYRIGHT 0.... 0 G) -< _..,L__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ -- - - FMSl 04728 r.-~' ' l i ~HEAl?. ______ --------- -i ----- - 115. - I I I F1c. 2. Selected area electron diffraction patterns obtained on fibers of chrysotile obtained during air sampling at brake repair shops. In A, the reciprocal a axis is marked a as are the layer lines in the (OKI) series. Indexing of upper right quadrant yielded 16 reflections corresponding to single crystal X-ray diffraction analysis of Whittaker and Zussman, 1956. Patte~n in (B) displays "smear- ing" of refiections in a ''clockwise" manner suggesting interplanar rotation. ---- --- .. . I- ---------- -- polycrystalline characteristics of multiple random reflections or Debye-Scherrer rings rather than the distinctive single fiber chrysotile pattern (Fig. 2B). Mic- rochemical analysis with a probe technique on the unaltered fibers showed them to possess the usual Mg:Si ratio of chrysotile. In addition to free chrysotile fiber bundles and fibrils, chrys'otile was also frequently observed projecting from the margins of binder fragments (Fig. 3). Free asbestos fibers present in the decomposed lining dusts were sized at 42,000x magnification. The results, seen in Table 2, show that most fibers are too small to be seen by optical microscopy; almost all of them are shorter.than 0.4 1-1-rn in length; virtually all are of respirable size (-5 ~J-ffi). Hatch (1970) in reporting on optical fiber counts obtained from brake cleaning operations with compressed air jet, found that 94% of the fibers fell in the 2-5 1-1-rn length category, while only 6% were. longer than 5 ,urn. Jacko and DuCharme (1973) made size distribution meas- ,urements of asbestos fibers in brake dusts generated during dynomometer tests,_ -using both optical and electron microscopy. They found, al magnifications of 22,000x that 30% of the fibers were from 0.25 to 0.50 1-1-m in length and that 60% were longer than 0.5 ,u.m. Some discrepancies between our data and those of Jacko and DuCharme may be attributed to their use of the lower magnification (22,000x VS 42,000X), at which fibers shorter than 0.20 1-1-m may not be easily seen Or identified on the electron microscopic screen. Thus, both the optical fiber count _ data in other studies and the electron microscopic fiber size distribution data_ rPYR=-- -+ I :r:, ~w! V~J zw~ ~z ~ ~ UJ "a2 l; g 8z 0 u 5 9 0 Mz t; FMSI 04729 .,,---r--------~------------------------------------------------------------------- ..... \,- . - -1 _L ------------- .------ -- - jt~"- ----~~....,.,--~~ll:'trJ!l'111""11:-~~g- ti j!O~ I...~~.. 1:>~:~ ,m I (II .' m> 1' ;nv ::t: 0 :J ' 0.. Qz gm Q i"i ~ n .0... 0 Q -< FIG. 3. Electron photomicrographs of brake drum dusts. Chrysotile is present in both free fiber and fibril form. Opaque granular material is road dust or_ phenolic binder,_~,_x iO,II(!O;_!J. ~9300;~ x30,000; d. x30,000. .,I - - --- ---- indicate that the chrysotile fiber population generated by brake wear is a strongly skewed one, with almost all fibers concentrated in the smaller than 5 11-m region. No attempt was made to size the asbestos-binder particulates. Personal Air Sampling during Brake Repair Work Personal air sampling for asbestos exposure during brake lining maintenance and repair was carried out at franchised auto dealer garages, taxi fleet repair shops, and a municipal truck repair shop, all located in New York City.3 Personal I - 1 I !Assistance in providing opportunity for sampling was given by the Dt!partment of Air Resourcest _ New York City. . .. --- ... - - T . .lC~PY:IG:ll- __ FMSI 04730 jHEAD-===-:~~ . .. : 117: \! CR:~=~~ELENGTH DISTRIBUTION OF 2 F1BERS IN BRAKE DRuM Dus-r' I 750-ISOOA 1500-2250A 2250-JOOOA 3000-3750A Sample N (%) N(%) N(%) N(%) Total <%> I J 2 . - - - - -" 34 - - - - 5 6 7 8 9 10 40 34 32 23 .- 20------ 25 26 37 57 17 23 9 so 26 29 30 6 41 II 6 - II - 32 25 26 :4 12 21 21 18 31 II % - ------ 87 70 7 96 - 78 12 56 2 99 17 97 10 75 31 79 ~' i Fibers counted and sized at 42,000x; all fibers have diameters from 250 to 500A. air samples were taken during and after brake repair work and at varying distan<!es from the work sites in other areas of the garages and shops. The latter samples were intended to provide information concerning levels of asbestos exposure which garage employees other than those doing brake work might experience. Asbestos Exposure during Automobile Brake Repair Work Air samples were first taken in the breathing zone of mechanics doing brake repair work. These peak exposure measurements were taken over periods of 3-8 minutes during which the workers were blowing dust from brake drums. The air samples, taken on membrane filters, were processed," and tiber counts made in accordance with the procedures which have been adopted by the Occupational Safety and.Health Administration (OSHA) of the U.S. Department of Labor (Bayer, Brown, and Zumwalde, 1975). Essentially, the analysis consists of count- ing fibers 5 to 100 JLm,in a fixed area of a Porton graticule, using phase contrast microscopy at a magnification of 400x. This microscopiC method enhances image contrast and allows large asbestos fibers to be readily seen and counted. When a vehicle is brought into a repair shop for brake lining. inspection or replacement, the wheel is removed and loose dust is removed from the drums and back plates, generally by means of a compressed air jet. A recent survey of brake repair establishments in Baltimore and Washington revealed that this is the stand- ~rd method in those cities (Castleman eta/., 1975)_. A similar situation exists in New York City. The cloud of dust that is produced is visible for several minutes afterwards (Fig. 4). Table 3 shows that fiber concentrations--are high in the operator's area under these conditions (an average concentration of 16 fibers/ml), and that there are significant concentrations at least 20ft away. Background or area sampling during the same operation shows that, at least 14 minutes after jet air blowing and up to 75 ft away, asbestos concentrations are still measurable even by optical microscopy. The data in Table 3 indicate that an asbestos concentration gradient, dependent on distance and time, is associated with this operation. It is evident that any person 65-75 ft away can be exposed. Current (interim) regula- _tions of OSHA prohibit concentrations of5 fibers/ml or more, longer than 5 JLm, as +OP:RIGHT .. + --- . - - ---~------- ~ ::r: ~ w CIJ ~....! ~~z ~ ~ w -g 0 g~~: ~ 0 ~o ; 9 0 tz~; ---------------~---------------------------------------------------------- -- FMSl 04731 __I --- --------- _IJ_B_E__ I- ---- ---1- .. - !'~ 4. Rernov_~l_c:lf_du~ !rom _b_rake drum an~- b~~k_ plat~ by pneu~a!ic_~_blowing-~ a!l~()~_!l~1 -----T -- - - - -1r-~~~---- --~- a time-weighted average for workers, and concentrations above 2 fibers/ml will be illegal after 1976~ Regulations set a peak concentration (maximum excursion) of 10 fibers/ml of air. Newly proposed standards are designed to set a limit of 0.5 fibers/ml (500,000 fibers/m3), with a maximum excursion of 5 fibers/m1. It was generally fourid that there was minimal, if any, effort to control dust in most garages. Workmen do not use respiratory protection. There was little aware- n-ess of the potential hazard of brake dust. -- In a single instance, brake drum cleaning was not done with a compressed air jet, but with a dry hand brush. Fiber concentrations were somewhat less (2.5 :;10 ~~m fibers/ml) at the operator level, but background levels 12ft away were the same as ' with air jet cleaning. I!g:X Asbestos Exposure during Truck Brake Repair and Installation Work Personal air sampling was also conducted at the New York Department of _ ; a.. I Sanitation truck'repair shop, where various kinds of brake application and repair. ,jQz m work are performed. Used truck brake linings are salvaged by grinding the surface to remove-grease-and dirt, and new linings are ground to expedite break-in. The 8 areI;n~ edges of new linings are beveled on a grinding wheel or arcing machine to a~oid :n l::::::::m~ (FOg. ~~oles drii!T~r punched into the brakdming, '!~l- t :2 no 6 Q FMS\ 04732. : J 12.__ TABLE 3 ASBESTOS CONCENTRATIONS DURING AUTOMOBILE BRAKE SERVICE Fiber concentration Operation Distance (ft) Number of samples (fibers/ml) Mean Range Blowing dust out of brake 3-S 4 16.0 6.6-29.8 drums with compressed S-10 3 3.3 2.0-4.2 air jet 10-20 2 2.6 0.4-4.8 Distance from operation (ft) Time lapse {min) Concentration (fiberslml) Background samples taken 10 0 0.3 at varying distance and - lapsed times, after brake drum blowing 20 12 so 0 .0.8 s 0.2 s 0.1 65 7 0.1 15 14 0.1 Distance Number of Fiber concentration (fiberslml) (ft) samples Mean Range Cleaning brake drums with dry brush 1-3 2 2.5 1.3-3.6 Background samples taken 3 minutes after cleaning brake drums with dry brush 12 3 0.1 0-0.2 Fibers S-100 p.m in length, counted by optical microscopy.. The new proposed Asbestos Standard ofthe U. S. Department of Labor records asbestos exposure in fiberslm3 , noting that a workman might respire approximately 8 m3 of air per working day, retaining an unstudied proportion of inhaled fibers. The above table omits reference to air content of fibers < S p.m in length. is then riveted onto a steel plate. Some of these operations are similar to those done during the manufacture of brake shoes. Table 4 summarizes the results of personal air sampling in the course of this work. During light grinding of truck brake shoes (Fig. 6), an average peak concentration of about 4 fibers/ml was found in the breathing zone of the operator. The data show that measurable fiber con- centrations are found 25 ft or more away. At a distance of 25 ft, for example, a concentration of 1 fiber/ml (1 ,000,000 fibers/mP) wa~ found. Much larger numbers of shorter fibers would simultaneously be inhaled. During the beveling of truck brake shoes on a grinding machine, very high concentrations offibers were found in the vicinity of the operator. The average of five air samples was about 37 fibers/mi. Area samples, taken up to 30ft away from this operation; demonstrated the presence of airborne fibers. It was of interest to note that, at the time of this -rmp~in_g, _fi:om- eight-"'- _1_5 otb~'- garnge_"!ehan_~cs _were working _within th~ COPYRIGHT +-- - - - - - J: ~ a..c..:. z~ w g~z w5z 1 ~ 0 ~ 9 0 Uoz!i !og:l.j 0 Mz ~ FMSI 04733 ,L . ---------- ---------------- ---I------ 12Q~D- ------ - - - - - - I -- TEXT I ! II I 1m Ftc. S. Beveling of truck brake linings at municipal garage. Arrow indicates accumulation of asbestos I --- .!~ dust. ;g : 0z ,3: perimeter and were exposed to asbestos. Fiber levels for other kinds of operations ;>,zm at the truck garage are given in Table 4. Boillat and Lob (1973) have reported fiber concentrations measured during . r- ,::mo I ">m' n::0 :I: drilling holes for rivets and grinding. They found values ranging from 0.3 to 29.2 fibers/ml; four of the nine values exceeded 5 fibers/mi. ~ A Comparison ofFiber Levels Visible by Light Microscopy and Electron Microscopy 0 ::l In the ten brake drum dust samples examined, it was found that asbestos fibers 0.. shorter than 0.4 jLm predominated (Table 2). The OSHA Asbestos Standard does sQz m not require that short fibers (< p.m in length) be counted or controlled. This oversight may have considerable biological significance in that 'small chrysotile () 0 fibers readily produce asbestos disease (Holt, Mills, and Young, 1964, 1965; --'--'6 n(;) __Da-.:i~!9_6~~~ott, Huth,_an~ Frie~ric_~ .12?2; ~ll_~~! Berry and .Jj__mb_!'~ll.~?_31- 0z COPYRIGHT ! . () 0,...... 0 (;) -< FMSI 04734 1 - - - - , - - - - - - ~-=---:::----HEAD TEXT -I 12ll l 1- 1 I I .,i - -------- - I -------F1c. 6. Renewing of municipal truck brake linings by light grinding to remove grease and dirt. Hilscher et al., 1970). Attention has recently been again called to the potential importance of this question (Bouhuys, 1975}. There is little published information on the numbers of, and sizes of, submicro'scopic asbestos fibers in occupational exposures. The present study affor~~. ~ opp<;irtunity to coiiec data ori the--relationship between submicroscopically- and optically-visible fibers for this specific industrial exposure. Eight air samples were selected for both light arid electron microscopic examination. Six of these were taken during brake drum dust removal operations with optical fiber counts recorded from 0.1 to 3.6 fibers/mi. The other iwo samples were taken during light grinding of automobile brake shoes." Preparation and Analysis ofAir Samples T.Uid-".One square centimeter sections of the eight membrane filters were mounted, <1<1>YnL O!! microscopic slid:: and. ashed in low temperat_ur~acti~atel COPYRIGHT _+- FMS\ 04735 I :X: I Ul ~~ WI !a..f.:.i.,l. z...:(\ w! ~, 0!z>Z!: !lII WI ~ 0 ~ <!)' O! 0uo.z..I :!;I ul 6~ 9 0 lzrl {5 :J _p-2.-=.D_ _ TABLE 4 ASBESTOS CONCENTRATION DURING TRUCK BRAKE SERVICE 0 Distance Number of Fiber concentration (fiberslml) Operation (ft) samples Mean Range Renewing used linings by grindin&._ Background to grinding used linings " Beveling new linings Background to beveling new linings Punching rivets into brake linings Chipping rust off used brake linings Sweeping floor around grinder Background to sweeping floor around grinder 3-5 10 25 60 3-5 8 12 30 3-,-5 3-5 3-5 IS 10 3.8 1.7-7.0 2 1.5 1.2-1.7 2 0.8 0.6-LO I 0.2 5 37.3 23.7-72.0 I 0.6 2 0.4 0.3-0.5. I 0.3 2 1.5 1.9-2.0 2.4 3.6 3.1 __ Fibers 5-l()()_~m_iQJei:tl!.l.t. _counted b~ op_tical microscopy~ _ ---- ----! oxygen to remove organic materials. The ashed residue was dispersed in a drop of nitrocellulose solution. The dispersal was accomplished by a "rubout.. technique using the edge of a watch glass (Nicholson, Rohl and Ferrand, 1971). By this method large asbestos fiber bundles are broken into their constituent smaller fibrils and large agglomerates of inorganic materials, which normally obscure the presence of asbestos fibers, ar.e broken into particles small enough to allow virtu- m ally all asbestos to be seen. By placing a second slide over the ground residue and ~ nitrocellulose solution and then gliding the two slides apart, a thin film is pro- duced. The dried film is cut into segments which are then floated off in water. The 2 film is mounted onto Formvar-coated electron microscopic grids. Typically, four grids are prepared from each sample and one square on each grid is scanned in the ~, ~..... electron microscope at 42,000x magnification to determine the quantity of chrysolite present. By estimating the length and diameter of each fiber, and as- I~ suming a cylindrical fiber geometry, the mass of chrysotile per grid square is l)lo determined. Representative electron photomicrographs of chrysotile fibers and I~ ,fibrils are shown in Figs. 7 and 8. ,::J: 'Ia ':DI.. RESULTS A comparison of the optical microscopic fiber counts and the electron micro- l~m~ scopic totaJ asbestos mass calculations obtained from the eight samples is shown in Table-5~~Flgur~ 9~howi~g the same- data, is plotted on logarithmic paper.- and 1~'0 visual inspection indicates that a positive correlation exists between the optical _ anE_e_~ectron microscop~c-~esults, alth:ugll!_ the d~ta are lif!l_~ted ~d the ~mount of_ l n ~~ !n COPYRIGHT 1 ...0... :0 Q FMS' 04736 ---------- HEAD 123 i .l ,; _:o:...~ ~~-~ . ~~.' . *J{ ,:;.;{:<;:):>:',!:~. - .. ~ _-,:,,: ~~:f-t-.~. ~::~';t.;~<:-.' :~\~~-.:.r.:,/-:-':.:..-~-<- ~.-.t.~i/L--..,-;. .!.~: ~. ~~-:::. ~-i~.-.:"';~,J:~;.... .. ;':- :..:_"-~I:;;. ~,-~..~.t.:. 7..;,."':.;!~'-.~~--~~--' F1c. 1-Electron photomicrograph.ofair ~ample taken-during brake drum blowing (sac sample No.4, 1. .... !Table 5), Large numbers (70-100) of chrysotile, some of which are masked by granular particu~ ""''~obiY ro"" (65,000 ooool mgn;r .,;,,J, scattering precludes a regression analysis. For example, from these data it may be possible to predict that, during the grinding of new brake linings (Sample No. 8, Table 5), a worker could be exppsed to about 0.5 mg of asbestos daily in _circumstances in which the time-weighted TLV of 5 fibers/ml would not have been exceeded. Similarly, Fig. 9 shows that, since a microgram of asbestos represents on the order of 1 million fibers per cubic meter of air (of greatly varying diameters and lengths), extremely high concentrations of. submicroscopic fibers are present up to 65ft away from brake repair work (e.g., Sample No.5, Table 5), even though fiber levels in such a case are barely detected, if at al1, by the standard optical counting technique. These limited data indicate that the standard (OSHA) optical fiber counting method may be only a fractional indicator of total asbestos exposure, at least in the case of automobile repair work. They also indicate that the _total exposure is much higher than the OSHA technique records, in terms of -- --- -------- --- -r--- -------- - -- -~ COPYRIGHT X: ~: wl IIJ' ~....- ~z w ~ Z; ~~I! ~ 0 t; g 8 Z! 0 uag 0 tlzr;l FMSI 04737 .l- : J 124 _l~.- .... ... ....~ ----:--~-~ -----:--L~ ~.-~ . ..,,~~ . ,. . ~ . ---- 1' ,.I, --~- ..... ..!: ~ ..~ j I I I I I I I I I I ~m . -~-~:-~. :~.~; ';- . .,tr,;;t~~(~r~::~J1~2 ;:zm~ lo1c. 8. Electronmicrograph or air ------------ -------- sample of cluster of chrysotile fibrils in background sample (see 1-- -------l,.... sample No._J, Table~ (~~~x ~agnificatioT"_ _ _ _______ :>0 m C/1 'm )lo -asbestos fiber number, mass, and surface area. Additional studies relevant to this n. :>0 and other kinds of asbestos exposure are needed to confirm and extend these :I: 0 findings, It is important to note that .particles ()f asbestos-containing pulverized :aI. brake lining were not included in this mass determination. Their importance, in terms of biologic potential, is presently unknown. ~nm SUMMARYANDCONCLUS~NS ( 1) Chrysotile asbestos fiber is a major component of brake lining materials. ;g ~ Degradation of the lining is brou ht about b a combination of factors, which nGl n0z COPYRIGHT --1- ,0.... 0 G-<l --~---------------------------------------------------- FMSI 04738 '! : 125 J TABLES CoMPARISON OF OPTICAL AND ELECTRON MICROSCOPIC FtBER CouNTS Operation Optical microscopy (fibers/ml) Electron microscopy (p.glml) 1. Blowing dust off drum with air jet (10 ft away) 2.0 1.27 2. Background to blowing out brake drum (10ft away) 0.3 0.2 3. Blowing dust off drum with air jet (20 ft away) 0.4 1.1 : 4. Background to blowing out brake drum {20 ft ..w,.y) 0.8 0.1 l, S. Background to blowing out brake drum {65 ft away-7 minutes after blowing stopped) .I 0.2 6.J;~llllins_!lrakc;drum with hand brush 3.6 6.5 7-. Ught grindings of new linings before installation 4.7 53.0 ' 8. Light grinding new linings before installation 2.7 66.0 ~-----r.------------- -- .--- --1 - - - - -----~-- ' include thermal stress, material fatigue, and shearing. Modifying agents are in- eluded in brake linings which lower the contact temperature between the lining and wheel interface; this. in tum, prevents binder pyrolysis and chrysotile fiber dehydroxylation. The amount of chrysotile fiber which survives the braking oper- ation is related to a number of additional factors, including some which are exter- nal to the properties and quality of the lining itself. As a consequence, degradation may occur at temperatures signficantly lower than that required for the dehydrox- ylation of chrysoti1e, with the persistence of fibers. (2) Ten samples of dust were taken from automobile brake drums in New York City, and analyzed. Optical microscopy was of limited usefulness. X-ray diffrac- tion anaJysis, using both continuous and step-scan modes demonstrated the pres- ence of chrysotile in all dust samples. The proportion of chrysotile ranged from about 2..:.1s%, arid averaged about 3-6%. This included both free fibers-and - .,- . --~--- c hr ::. ys oti -: le which s ---,._-:-:-:-.-:~:.-; urv . - i.ve-.d .. in pulverized binder - --- ... -----. . as particulates. Forsterite, the -- - - _---~-- -:-:- --- . -~ I I UitroqrorN Mt cul:tk. me..,- elutrQft "'c.fOIUPf I +tmn -1- _Ftc. 9-:c-.omp;;;.,..Or~ mkro~.W< ~l>u ~"-~__._____ COPYRIGHT :r: I I~ eww<n I..X... wz$ z~ ~ >z ,w ,I ~I oI t;; o..... r 0uozo:! 51 - O..... I uQ:l wz t; FMSl 04739 .! .. ' ~ > J~ . I m I~ '2 ~ zm ~ ~~ ~ t' n::0 I :X ig Ia.. I iQ .~lgn~ c;l !f"i :o Zn 0oa..... -< _!126 u----~ -~ --:-_------- ------~--- - ----- - -- - -------------~-- -1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --- - - - - - - - - - - - - - - thermal t'ransformat.ion product of chryso'tile could not be unequivocally identified by continuous scan X-ray diffraction. (3) The presence of chrysotile asbestos in the ten dust samples was furtherverified by transmission electron microscopy, selected area electron diffraction and electron microprobe analyses. Chrysotile was found, both in fiber and fibril ~rm, with unaltered structure and chemical composition. Its frequency of occurrence was consistent with, but lower than the:qu~titative determination made by X-ray- diffraction- analysis: However, it should be noted that X-ray- dHTraciion analysis is based on both free fibers and fibers present in clumps; the latter would obscure the presence of discrete fibers on electron microscopic study. In addition to unaltered fiber, partially altered and completely recrystallized fibers were also seen. (4) Size distribution analysis at 42,()()0X magnification in the ten samples indicate that about four-fiftbs of all chrysotile, in fiber form, is shorter than 0.4 p.m in length. These fibers are too small to be seen by optical-microscopic techniques. :- (5) Personal air sampling was conducted during brake reparr workiii automobile garages in New York City. Standard optical microscopic procedures for fiber counting were used. In samples taken in the vicinity of repairmen blowing dust from automobile brake drums with compressed air, an average concentration of 16 fibers/ml was measured. Background and time-lapse samples indicate that measurable concentrations exist at least 75 ft from the work site and for at least 14 minutes after jet air blowing. (6) Personal air samples were taken at a municipal truck repair facility where various brake fabrication and application operations are performed. Grinding of truck brake shoes resulted in an average concentration of about 4 fibers/ml (4,000,000'ml). During beveling, an average fiber count of 37 fibers/ml was measured. Exposure levels during drilling, punching rivets, and cleanup were also measured: Backgroundmeasurements show that fiber concentration gradients areproduced during truck brake repair and application work. During light grinding of truck brake shoes, measurable fiber concentrations were found 25 ft or more away, as well as up to 30 ft from brake beveling operations. The background measurements, during both automobile and truck brake work, indicate that many toempioyees in garages other-than brake lining workers are potentiallyexposed asbestos, including other mechanics and shop management. (7} Eight air samples taken during automobile brake repair work were analyzed by other optical and electron microscopy. A positive correlation was found to exist between optical fiber counts(> 5 11-m) and the total chrysotile mass calculations based on sizing all fibers at 42,000x magnification. These data indicate that. standard (OSHA) optical fiber counts may be a useful-index of total free asbestos exposure during brake repair wor-k. They also demonstrate that the total free asbestos exposure, in terms of fiber number, mass, and surface area is much greater than the optical counting techniques indicate. (8) Attention is cal1ed to the fact that in addition to asbestos, other biologically active substances, including free silica and lead compounds, have been identified in brake lining dusts. Their concentrations in brake work environments are not I::::G:: 1~~ ;nvesti~;~~~- ~---- . ___ ___ __ __ _ FMSl 04740 '...' --rlf:~D ==-~~-=-~--~ -~--=~ -~-= =~ 127 (9) Potentially hazardous asbestos exposure exists during automotive brake servicing. It l'las been reported that approximately 900,000 persons are employed -in such work in the United States. It is recommended that stringent industrial hygiene measures to control exposure be implemented as rapidly as possible. 1. -----~-------~---- ----- --------------- ACKNOWLEDGMENT We thank Drs. A. E. Anderson. R. L. Gealer. and I. Eichen of The Ford Motor Company for their valuable comments in reviewing the manuscript. ----,- REFERENCES Anderson, A. E. (1969). Wear in brake materials. In Proc. Amer: Soc. Metals Wear Conference. Anderson, A. E., Gealer, R. L., McCune, R. C., and Sprys, J. W. (1973). Asbestos emissions from brake dynamometer tests. Soc. Auto Engin. Meeting, Detroit, Michigan, 14-18 May, 1973. Paper No. 730549. Bark, L. S., Moran, D., and Percival, S. J. (1975). Chemical changes in asbestos-based friction materials during performance-a review. Wear 34, 131-139. Bates, T. F., and Comer, J. J. (1951).1n Proc. 6th Nat'! Conf. Clays and Clay Mineralogy, Int. Monog. Sec. 6, 237-248. Bayer, S. G., Brown. T. A., and Zumwalde, R. D. (1975). Document TR-84, U.S. Department of Health, Education and Welfare, Public. Health Service, National Insitute for Occupational Safety and Health, Cincinnati, Ohio. Benj, E. E. (1971). Thermal analysis of various chrysotiles using evolved water analysis techtriques. In Proc. 2nd Inti Conf.. Physical-Chemical Asbestos Minerals, Louvain Univ. 6-9 September; 1911, paper 2:7.15 pp. .. Boillat, M.A. and Lob. M. (1973). Risk of asbestosis in workers employed in replac~.s_~!!!_o~obile_ - brake linings. Schweizerische Meditinische Wochenschrift 103, (39), 1354-1359. Bouhuys, A. (1975). Fibers and fibrosis. Ann. Intern. Med. 83(6). 898-899. Brindley, G. W., and Hayami, R. (1965). Mechanism of formation of forsterite and enstatite from serpentine. Min. Mag. 35, 189-195. Burwell, J. T. (1951). Survey of possible mechanisms. Wear, 1, I 19-141. Carroll, W. G. (1962). The manufacture of brake linings. Brit. Plastics August, 414-411. Castleman, B., Camarota, L. A., Fritsch. A. J., Mazzocchi. S., and Crawley, R. G. (1975). The hazards of asbestos for brake mechanics. Public Health Rep. 90 (No. 3) 254-256. Daykin, C. W. (1971). A study ofthe infrared spectra ofchrysotile and related minerals.ln Proc. 2nd Intt. Conf. Physical-Chemical Asbestos Minerals, Louvain Univ. 6-9 September, 1971, paper No. 2:6,7 pp. Davis. J. M. J. (1965). Electron-microscope studies of asbestosis in man and animals. Ann. N. Y. Acad. Sci. 132, 98-111. Harries. P. G. (1968). -Asbestos hazards in naval shipyards. Ann. Occup. Hyg. 11, 135-145. Harris, A. M. (1971). The effects of grinding on the structural and ihermal properties of chrysolite asbestosfibers.ln Proc. 2nd Inti. Conf. Physical-Chemical Asbestos Minerals, Louvain Univ. 6-9 September, 1971. Paper No. 3:2A, 6 pp. . _____ _ asaH-at-c2h,5D-.2(919.7-0-).--P-ossibl-e-alte.rna-t-ive-s-t-o--a-s-best-o-s-----f-rictio-;;-~-ater-i-a-l-: A-nn.--O-ccu-p-.--H-y-g-.--1-3-,- Hickish_. D. E. and Knight, K. L (1970). Exposure to asbestos during brake maintenance. Ann. Occup. Hyg. 13, 17-21. Hi1scher,.W., Sethi. S.. Friedrichs, K. H., and Pott, F. (1970). Zusammenhange Zwischen Asbestose and Faserll!.nge. Naturwisstnschaften S1, 356. . Holt, P. F., Mills, J., and Young, D. K. (1964). The early effects of chrysolite asbestos duson the rat lung. J. Path. Bact. 81, 15-23. Holt, P. F., Mills, J.. and Young. D. K. (1965). Experimental asbestos with. four types of fibers: Importance of small fibers. Ann. N. Y. Acad. Sci. 32, 87-97. Jacko, M. G. and DuCharme, R. T. (1973). Brake emissions: Emission measurements from brake and ~::::P from-~~~~ ~b;k ~~+ RepoL~~-= ._- . :x:rI ~I ~~ ~ zw~ a~ !I ~: 0 ~ Qi '0 I Uz ,i 0 ~u 9 0 .~z ~ FMSI 04741 ,.. ) ,~. ' l. .... ' I' m ~ ;a2 z; 0 I~ i mz ,.,i I ~ r- I I "'m m )>n::a :::t: II a ::l ~ !Qz 1m IO !06 j nC> ,n10 IZ I e> I -< t 128 ~ -- -- ------- -. ----!- --- --- - - --- 1 -Langer, A. M., and Pooley, F. D. (1973). Identification of single asbestos fibers in human tisues.ln of- ' Biological Effects of Asbestos (P. Bogovski, et al. Eds.)pp. 19-25. I.A.R.C., Lyon, France. Langer, A. M. Mackler, A. D., and Pooley, F. D. (1973). Electron microscopical investigation of - asbestos fibers.. Envir. Health Persp. 9. 63-80. - Lynch, J. R. (1968). Brake lining decomposition products.]. Air Pollution Control Assoc. 18, 824-826. McConnell, J. D. C. (1967). Electron microscopy and electron diffraction. In "Physical Methods in Determinative Mineralogy" (J. Zussman, Ed.), pp. 335-370. Academic Press, New York. Martinez, E. (1966). Chrysolite asbestos: Relationship of the surface and thermal properties to the crystal structure. Canada Mining and Metall. Bull. 69, 414-420. Monkman, L J. (1971). 'Some chemical and mineralogical aspects of the acid decomposition of chrysotile. In Proc. 2nd Inti. Conf. Physical-Chemical Asbestos Minerals, Louvain Univ. 6-9 September, 1971, paper No_ 3:2, 9 pp. Naumann, A. W., and Dresher, W. H. (1966). The influence of sample texture on chrysotile dehydra- tion. Amer. Mineral. S1, 1200-1211. Newhouse, M. L ( 196.5). Epidemiology of mesothelial tumors in the London area. Ann. N. Y. Acad. Sci. 132, 5~2. Nicholson, W. J., Rohl, A. N., and Ferrand, E. F. (1971'). Air pollution in. New York City. In . "Proceedings of the Second International Clean Air Conjp"ess. (H. M. Englund and W. T. Berry, Eds.), pp. 136-139. Academic Press, New York. Pott, F. Huth, F. and Friedrichs. K. H. (1972). Tumors of rats after i.p. injection of po~dered chrysotile and benz[a]pyrene . .Zbl. Bakt. I. Abt. Orig. ISS, 463. Selikoff, I. J., Churg, J., and Hammond, E. C. (1964). Asbestos exposure and neoplasia. lAMA 188, 22-38. Selikoff, I. I., Hammond, E. C. and Churg, J; (1968). Asbestos exposure, smoking and neoplasia. lAMA 204,(2), 106-112. Selikoff, I. J., Nicholson, W. J., and Langer, A. M. (1972). Asbestos air pollution. Arch. Envir. Health. 25, 1-13. Wagner, J. C., Berry, G. and Timbrel!, V. (1973). Mesotheliomata in rats after inoculation with asbestos and other materials. Brit. J. Cancer 28, 173. Whittaker, E. J. W., and Zussman, J. 1956. The characterization of serpentine minerals by x-ray diffraction. Min. Mag. 31, 107. ---,. --1--------------:------------- -------------------------------------;- -+C-O_P_Y_R-IG_I_IT----------------~-~-t- FMSI 04742 ... . ',...._~ .J -.!." " ' --.-A- -- ... . .. f . -...-;: :.:: ';-:.-..~: . -: _, .~.:j,. .l_:. ~ .... .:r. c i. - ... .:- ..=..-:' ... ~-I' .-- . !' .. -=:. .. - _!:..L,__.., _____ ...-J..,;..~-- ' _.......____ --- ---- _________ . ---~ -- -~~---'-~- -~ - _j 32 Proc. roy. Soc. Med. Volume 70 January 1977 l irregular or nodular interstitial opacities of limited extent and intensity on their films. Silica or asbestos exposure had occurred in 12 ~-~ of the work fon:e examined. Such exposures had occurred in various job categories in the titanium facility as well as in prior occupations. Eight of the 26 workers with abnormal X-rdys had had silica or asbestos.exposure. No clear pattern of restrictive disease in relation to X-ray findings could be seen. SW1ImllTy and Conclusions Clinically significant or symptomatic pulmonary disease was infrequent in a survey of 201 currently employed production workers in a plant producing titanium dioxide from ilmenite ore. Evidence of airways obstruction was found in 47% of all workers (including 38% ofworkers who had never smoked regularly). This abnormality was not frequently accompanied by disabling shortness of breath. Despite the fact that approximately 90% of the group of workers examined had worked for ~0 yean or more, radiological changes consistent with pneumoconiosis were relatively few. and unrelated. io the respiratory abnormalities observed. We conclude (with the caveats inherent in a prevalence study in which only half of the eligible long-term workers were examined) that occupational exposure associated with titanium production by the sulphate process may commonly cause undesirable irritation of the upper and lower respiratory tract and functional abnormalities of the lung, but does not result in an important incidence of serious occupational lung disease. Individual workers may. however, suffer unwanted abnormalities. These findings, of course, do not speak to the presence or absence of increased risk of malignant pulmonary disease. This is being separately studied. AcknoMledgment: This research study was supported in part by National Institute for Occupational Safety and Health Contract CDC-99-7491. REFERENCE Milltt A. CbuanJ: M & SdikoiT I J (1976) Amt:ric<~n Rnir of R~spiratory Diua.Ks Ill., Suppl. p 89 (abstract) ; ' Asbestos Content of Dust ! Encountered in Brake Maintenance and Repair I j by A N Rohl PhD, A M Langer PhD, J ~ R Klimentidis BA. M S Wolff PhD and 1 J Selikoff MD (Et~tirollmental Sciences Laboratory, A-fount Sinai School of Medicine ofthe City University ofNew York, New York, NY 10029) Asbestos in Brake Linings The composition of auto111otive brake linings in- I'I, cludes c.fu-ysotile asbestos.'fibre which comprises about 50'7~ o'f ~he fridion:material. The: exposure of g~rage workers to asbestos during brake lining maintenance and repair has recently been in- vestigated (Rohl et al. 1976). This important issue was studied because a large labour force is poten- tially exposed (over one million people in the United States alone). Consequently it was thought essential to determine if chrysotile fibre sunwes braking, and to measure the amounts liberated as an aerosol during maintenance and repair oper- ations. Investigators in the past have expressed doubt as to whether chrysotile fibres can survive the: high temperatures generated during braking (l:-nch 1968, Hickish & Knightl970, Hatch 1970). C:.hry- sotile is alleged to be subjected to temperatures in excess of 800C, which would cause its thermal transformation to forsterite or to an amorphous magnesium silicate phase. While 'hot :;pots' up to 1000oc may be attained (Carroll 1962), the heat distribution is nonuniform, and other processes. in addition to thermal wear. contribute to de- gradation of brake linings. For example, abrasion and macroshear may also cause physical break- down (Burwell 1957, ~.1izutani et a/. 1973)..-\c- cordingly, brake lining disintegration by these mechanisms may liberate partially altered or even :::~:dO;:::::i::::IISI .:. ;'~~-:~:::I:.:::: ~ Initially, ten samples of automobile brake drum dusts from brake repair shops in New York City were collected and examined by optical microscopy, X-ray diffraction. trdnsmission electron mic- roscopy and energy dispersive X-ray spectroscopy, to determine the presence or chrysolite. Opll'cal microscopy: The detection of chrysotile in brake drum dust by optical microscopy is hindered by the nature of the debris matrix, consisting largely of opaque pyrolyzed phenolic-type r~in binders and road dust. Chrysotilc. particularly small fibres, has low optical relief and low birefnngence, which further hinder its identilication. Only in rare instances have large fibres, with opucal ! ... .. -~ ... ....__...;:.:=~.....,.. ~~-- .-.. -......-,:-- ;. FMSI 04743 .' ___ ------- -- -.-_........__....'... . ... -- --.1 , ,..;, , -____...,.,....,_ ..... __...-.:. ........ --a..--- . .. -~--. - ake linings inlich comprises . The exposure 1g brake lining :ntly been inrnportant issue force is potenpeople in the it was thought : fibre survives 1ts liberated as td repair oper- ressed doubt as arvive the high raking (Lynch :h 1970). Chryempcratures in Jse its thermal an amorphous ,ot spots' up to 1962), the heat .er processes, in ~ribute to demple, abrasion ~hysical breaka/. 1973). Acltion by these altered or even ile brake drum ~ew York City optical microsJn electron mic- y spectroscopy, ,tile. of chrysotile in opy is hindered lrix, consisting 1olic-type resin le, particularly r~d low birefrintification. Only s. with op~ical S~ction ofOccupational MediciM Tab/~ I Qr}oolil~ asbestos content of brake drum duts X-#'11>' di./frociion (Slt'p-scon) !:;,;<'.f Great Britain Wcst~nnany .France orUnited States I 8I . America 10 Finland 5 Wcstcm Australia 7 No. po.ritil.Y!! 6e' se I 10 3 4 W<'ight ~rcmt M<'on !lDngr 1.1 0.7-2.3 2.4 o.s-J.l 2..5 4..5 2.~15.1 l.l 0.1-2.5 1.4 o.s-2.3 39 :zt .i2.4 1.1 1- I sample possibly positive Transmissiort rl~clron nticruscopy No. po.ilirr a 8 I 10 5 7 39 33 properties consistent with chrysotile. been obser- onstratc:d the preservation of crystal structure as "Ved with this technique. well (Fig 1). X-ray diffractometry: The ten brake dust samples . Fibr~ siz~ distribution: In ten brake dusts sampled were analysed by X-ray di!Tractometry, in both in New York City, free asbestos.fibres were sized continuous and step-scan mode. The diagnostic by TEM at magnification 42 000. The results reflection selected for chrysotile (3.66 A; showed that about 80% ofchrysotile is in free fibril lzk/=(004)) was step-scanned in the fixed-count form and is shorter than 0.4 Jlm in length. Over mode. By comparison with external standards, the 57% have lengths of about 0.2 Jlm. At magnifi- amount of chrysotile present can be determined. cation 40 000, such a fibre would be about 1 em Chrysotile reflections were observed in all samples, long. If lower magnification were used to scan for with weight percentages estimated to range from 2 asbestos, significant numbers of fibres might not bC. to IS (average 4.5). Lead compounds, quartz, detected. carbonate minerals, clays, halite (NaCl), graphite, It is obvious that most fibres are too small to be micas and alpha-iron were also identified in vari- seen by optical microscopy. The Asbestos Stan- ous samples:-- --- ----- - - - - - - - - dard adopted by the: Occupational Safety and Twenty-nine additional brake drum dust samp- Health Administration (OSHA) ofthe US Depart- les were collected by colleagues in four European ment of Labour is limited to optical microscopy countries and Australia. The samples were ob- and neglects to count or control fibres less than tained from areas representing variable circum- 5 Jlm long. On the other hand, accumulating stances~ such as driving conditions, friction evidence .suggests that such small asbestos fibres material composition. type of automobile and may produce disease (Holt et al. 1964, Davis 1965. climate. The results of X-ray di!Traction analyses Potter al. 1972, Wagner er al. 1973, Hilscher era/. arc presented in Table 1. Of the 39 total samples 1970. Bouhuys 1975). analysed (including 10 United States samples) Air sampling: Eight personal air samples taken chrysotile was found in 29. or about three-fourths. during brake repair work were selected for electron The mean chrysotile content varied from 1.4% in microscopic analysis. This was done in order to the seven Australian samples to 4.5% in the New positively identify cbrysotile in the samples and York City samples. to determine whether a systematic relationship The thermal breakdown product of chrysotile. existed between optically and submicroscopically ie. forsterite, which might ~ expected to form as visible fibres for this type of exposure. The memb- a result of recrystallization. was not unambigu- rane filters were ashed in plasma oxygen to elimin- ously detected in any sample. ate organic materials and the residue was prepared . Trarumission e/~ctro11 micro.~t'opy ( T,\-1): In order for electron microscopy by a rubouf technique lo verify the results of X-ray diiTraction analysis. (Nicholson eta/. 1971), which comminutes large the: brake dust samples were prepared for electron chrysotile fibre bundles into individual fibres and microscopic 'analysis by means of a technique fibrils. Large inorganic particles are likewise re- which disperses the dust particles in a nitrocel- duced in size. permitting all chrysolite to be seen lulose film without altering particle sizes. Both free and rrteasured. Chrysotile was identified in the chrysotile fibre bundles and tibrils were observed eight samples. in both fi_bre and fibril form (Fig:!). in all 39 samples. Most of the chrysotile retained By measuring a large number of fibres at magnifi- its char.tcteristic morphology without significant cation 4:! 000 and converting the: volumetric data alteration, and scrected area electron dill'raction into mass. a conccntr.llion per volume oi air is patterns obtained on representative fibres dem- determined. Comparison of optical microscopic ---.-----..,............~--------- FMSI 04744 .. ~--------------~-~---~,.~-----~_.~~----------~~--_.~--- ---~~-----~-----~~------~~------~~----------- ~, '~ ! 34 Proc. roy. Soc. Med. Volume 70 January 1977 .. fibre counts and the electron microscopic asbestos taxi fleet repair shops and a municipal truck repair m~t.ss calculations indicates that a positive cor- shop in New York City. Air sampling and analyti- relation exists between the two sc:ts or data. These cal methods for the determination of fibre con- results show fltat the standard (OSHA) optical centrations were in accordance with the OSHA fibre counts may be only indicative of the total techniques (Bayer 1!1 a/. 1975). Present regula)ions asbestos exposure. of OSHA prohibit asbestos concentrations of 5 fibres per millilitre (f/ml) or greater, longer than Asbestos Exposure of Workmen 5 ..m as a time-weighted average, and con- Aner the identification or chrysotile in the brake centrations above 2 f/ml will be illegal after July drum dusts. asbestos fibre exposure during main- 1976. Peak concentr.uions or maximum excursions tenance and repair was determined by personal air of 10 fiml are permitted by the regulations. sampling c-.uried out at auto!"obile repair shops, In brake lining inspection and repair, the wheel is removed from 1 monly removed frc means or a jet of ( garages in Baltirn shown that this is the shops (Castlt situation exists in Table 2 show that the breathing zon pressed air blowi gradient. diminish from the opcratio to 22 m from such able conccntratioll lf?~~:-~: ....:-:\:. ~- _.. :. r-~'~;~~;~~~~~!~ lv~~-;,.. ~ ; .-~:-,. ""'.'' ~- ... I _,. ~ .<~-: ''.o; ~- ,: ~-=-:~!-" ! :-=---:~:z .;.r:-'~ ..-; ! .-. =..-r:-: .. ,_ _:~~.. . -,. ~::~-:' ~-~j"- :. t. it~ .. ~~., ::\. '--~,,. 0 , ...., . . .! ~ - , ~~-,:;.~~,~~ ~-j;~~~><~ ., ~ , J::~:i~~---........:;.....! ,. --- ~-:- OT'1' . ,._ .. .; . . : _"j' Fig I EIC'cir.m plmrumicrnwaplr.< ofhrakl.' drum Ju.<IS. takt!n at rariou.< m<J_qnifkatinn.r. A, tht! numrrous ch~_,.rotile fibrils '""!I''hare ur~ru_qC'Itll!lllr. o{U.4 ~"' <1r lc.u ( x 311 lHHII. H, lur!lc" "'""locr.r ~I drry.<t>tilt/ihrc.< imlocclclttl ill. <1111/ protruJi11g from, OP<J'/IIC' partide. pf'lll~t~h~& pymli=ccl plrcuolic r.-.itlltill<lcr ( x J(IIHJtl). C'. drr.nutilc.fihrc hrmc//c ( x 45UtNJ). D, luryt' particle' in I<'J! cc:lllrt: uj plruwyruplr is tlrl.' sum<' us irr l', hur umwt he itk~rtificd at (o..- mugllificutiull ( x 5400) Fig 2 EltC'trOtr phot. u.uu.-iatc-J ,..;,J. opuq . ..... --:r--- ..- .. -~--- -~-..........----------- - ; - - : : - - - - - - - - - ' ..- -- - - - -~---- --,;-----....,...-FMSI 04745 ... ..,. -4- __....__t;---~ _ .....-!.-....- --......:.-- .__....:.._ _ .. - - - - - __ ..a..-.__ ...... __............_.. - - - - - - lruck repair Lnd analyti- r fibre con- the OSHA rcgulalions ations of 5 lorigcr than and contl aficr July 1 excursions ions. r, the wheel ' 1.. S~ction ofOccupa~iona/ MediciM 3S is renr~ved from the axle and loose dust is com- Personal air sampling was also conducted at monly removed from the drum and back plates by New York City Department of Sanitation where means of a jet of compressed air. A survey of 210 truck brakes arc repaired. Used linings are sal\'aged garages in Baltimore and Washington. DC has by machine grinding to remove dirt and grease shown that this is the method of choice in 80 ~ ~ of from the surface. New linings arc bevelled by the shops (Castleman et al. 1975). A similar grinding to reduce noise and improve break-in. 'Situation exists in New York City. The data in Accordingly. these studies relate to levels of as- Table 2 show that fibre concentrations arc hieh in bestos exposure which may be experienced. by th~ breathing zone of the operator during ~om workers engaged in brake lining manufacturing. pressed air blowing. An asbestos concentration Table 2 shows that fibre concentrations experi- gradient, diminishing with time and distance away enced during grinding ranged from 1.7 to 7.0 f;rnl from the operation. appears to occur. Persons up of air in the breathing zone of the operator. The to n m from such activity are exposed to measur- background or area samples for this operation able concentrations of asbestos. ranged from 1.2 to 0.2 fjml. with a general decrease -I : _, :~;:. ~: -:- ~: -~ :~::-:. ~~;,:,1/': ~ ~-.:""~ ~~ ~-, ...;- ......... - -: :~~ . :::. ~~- ..-~-- -~ ~: .--...-.j;.....: h q s u t i l ' filorils otrudi"!l } ; . , , , 5 Ullll). D. lurrJft' <100) Fig 2 /rc:tron phoromicmqraph.f of ptr.<nnal air sample.< rak~n durin_q hral.:~ npair ln,rk. Clumps of chrysotilr tire IUSociDt!d rith opaqu~ parric/.:s ofroad Just anJ resin binJtrs. A, B. x 6U ()()()_ c. D, x 72000 r-------~ -._..,._. ...,------=--,.......----- -- - - t I .~ - - FMSI 04746 11 I _..~I:- ..... 1 s: ..: l .a:, .. :a. I ---. .:i 36 ~roc:. roy. Soc:. Mtd. Volume 70 January 1977 Ttlhld PenGU!alr umpln. automobile .,.d truck bnk~ repair Automt>bilr 6ra/cr rrpoir Blowina dust rrom bnkc drums: Distance 1-I.S m Distance 1.5-3 m Distance 3-6m a.dc&round (S min after air t:towina. distance 3.~16 m) kpund (7-14 min after air jet blowina.distancc 19.~22.6m) Prak jibir COftUIItratiolt No. of (/ihrt!s fl' m1) -..plrs MNn Rongr 4 IS.O 3 3.3 2 1.6 i O.l 2 0.1 IJ 6.~29.4 2.CH.l IU-4.1 o.J-D.l o.J Tnd bra/cr::/i/' Rcuc..iua u Jininp by cdin& (distance 1-I.S m) 10 4.1 1.1-7.0 k1round to grindin& used liDinp: DislancC 3.3 1ft 2 1.5 1.2-1.7 Distance 1.3 m 2 0.1 0.~1.0. Dislancc 20.0 m 1 O.l BcvcDina new lininp 4 37.3 23.1-72.0. Back&round to bcvellin& new lininp: Distance 2.4 m I o.6 Distance 3.6 m .2 0.4 O..J-o.5 Disu.Dcc 9.1 m I 0.3 2l . ,. away from the operator. From six to ten other mechanics work within an area up to 20 m from this operation arc exposed to asbestos as well. Since a person breathes about one cubic metre of air an hour. multiplication of the fibre concentrations by one: million gives the number of fibres inhaled during this period. Fibre: con- ccntrations measured during bevelling of truck linings were as high as 72 f;ml and averaged about 37 fiml. Background counts were measured up to . 9.1 m away from this operation (0.3 fjml). Fibre concentrations measured during drilling holes for rivets and grinding ranged from 0.3 to 29.2 f/ml. as reported by Boillat & Lob (1973). Four of the nine values exceeded S f/ml Conclusions The existence of significant exposure: during brake senicing operations necessitates the following measures: ledge support under a grant from the National Institute of Environmental Health Sciences, ES 00928 and support by the Ford Motor Company. MSW wishes to acknowledge support under a post-doctoral fellowship from the NIEHS, ES02565. We arc: grateful to the following for assistance: in obtaining brake dust samples: Professor Donald Bowes, University of Glasgow, Scotland; Mr L B Bowes, Department of Labour and Industry, Adelaide, South Australia; Dr Trevor Turner, Adelaide. South Australia; Professor Jean Bignon, Hospital Laennec, Paris. France; Miiunu Harme., Geological Survey of Finland. Otaniemi, Finland: Dr G. Gail. Helsinki University of Technology, Helsinki, Finland: Dr K Robock and Dr W Klosterkotter. lnstitut fiir Hygiene und Arbeitsmedizin des Klinikum der Universitiit Essen, West Germany. (I) Implementation of industrial hygiene procedures to control exposure. (2) Clinical studies of garage mechanics to determine evidence of asbestos-related disease. (3) Epidemiological studies of the mortality experience: of exposed workers. In addition, the entire variety of dusts and other materials present in brake repair work should be characterized in order to determine its disease potential. especially silica and lead compounds. Ac:lcno"ledgmf!nt: The authors wish to acknow- REFERENCES BayerS G. Bro..., T A & Zumwalde R D (197S) Document TR-84. US Public Health Service. Cmcinaati. Ohio Boillal 1\1 A & Lob 1\1 11973) Scluri:viKht! mrJi=inischr Whrruchrift ]OJ. 39 BouhuysA (197S) AIIIUIIs oflntvnol Mt!dkw 13.191 BunoeUJT (19S7) Wrar I. 119 CarrotJWG (1%2) Briti.<h Plastics 35.414 Cnlloman B. Camarota LA. Fritsch A J, 1\fazzoc:dll SA CnlnRG (1975) PuNic H,alth Rcports90. 2S4 Da-isJ MJ (l96S) Annalsofthr Nr,. York Acadrmyo[Scirm:rs 131.91 HatdoD (19701 Annolo -f Ocr-upoJ Hlru..ts D a 1\a.i~:hr t.: ( 1970) AriiiDb.-{Ouuf"' Hll..,bcr W.s.mi S, Fri: (1970) .\.lltunris.nu:lwr Holt P F. !\I J &; , ..,.. (19f>.I)Jou..Uof Patho~ LJacbJ R (1961)Javrlllll/rlor Au !\lizutani \, Obno H 4. (19731 w...... n. :;s7 .Nk....._ W-I, Rolli A: (1971) In: l'rnl=dingsc . CODJUSS. Ed. H !\t EnE New York: pp l:;().-139 Pon F, HotlaF & Friede ( 1972) ZMtra6lall jiir i. Rolli A IIi. lao: A M. (1976) Enrir-ntal R \\'a&ncr J C. Berry G & (1973) Bririslr .knunal aj ..... . Neurotoxic P1 Certain Aliph: by Peter S Spence~ and Herbert H Sci (Departments ofp, Saul R Korey Dep1 Rose F Kemtedy C Albert Einsitin Co. Bronx, Nnr York. Durin2 the: s.umm ipheral neuropatl group of employ plant in Obio. U~ disease was chara sensory loss symrr the feet (ADen e1 affected indh.idual ment whe~ colol solvents, ~ue ap coated fabrics. F process required t containing methyl isobutylketone ( (MBK) wasgradu 1972 to replace th was in its maxima first case of peripi tly thereafter. Th into the printing d with other isolatt ; . individuals chron gested that this co ties. MBK prod1 --.~---------:----- - .. ~--~-;-~ --- -~---~-- ....-:- -- - - - : r - - -... - --~-- . FMSI 04747 ... .., ... "; . __ _______,.. .. '. . -~;:)i'r~.-~--- . __....... _ _ _ _ _............_ __ __.............._ ..... -~; ...........__. . . I .. ~~-------------- - ... ;. , .- te National ciences, ES r Company. >rt under a .e NIEHS, 11.ssistance in ;sor Donald nd;Mr L B lustry, AdelJmer, Adel:an Bignon, unu Harme, mi. Finland; Technology, and Dr W I ArbcitsmeEssen. West icc,. Cincinnati. i 103,39 cchlSI. usl31, 91 Section ofOccupational Medicine 37 Hatdo D (1970) An~111l1 ofOccupational Hygi.:nr ll. 2S Hklthob D I. Knight K L (1970) AturDL< "lOccupali<Htoll H:uicnr 13. 17 Hihdler \\', S..tbi S. Fridrichs K II & Pot! F (1970) Natur..wcnJtha_/1<'11 57. 356 Holt P F,,'\1ills J &. 'lounc D K (1964) Journil ofPatlw/ag} unJ Buctniolag}ll1. 15 L,..ctoJR (1961) Journal "/llw Air PollutiM CIUIIral As:wciation 18, 824 Mlataai '~ Obara H &: Nakajima K (1973) K'ur%3. 381. Nk.,.._ W J, Rohl AN &: Fetnaud F (1971) In: Proc:ttdings of the Sc<:ond International Clean Air Coasress. Ecf. H. M England &t W T Berry. Academic PI"CS$. N-Yorlc; pp 136-139 Poa F, Hath F & Fridric:hs K H (1971) aniTalblaufor &ktt:riu/O!fi<'. Abt. I. Originalc:. 135.463 Rohl AN, Lane.,. AM, WolfT !\1 S &. Wrismaa I (1976) Entiran-nlal Rr.'Warch 12. 110 Wper J C. Berry G &: limbml v (1973) BriiW. Journal ofCanar 28, 173 'I Neurotoxic Properties of ~ - Certain Aliphatic Hexacarbons by Peter S Spencer PhD . and Herbert H Schaumburg MD (Departmetlls of Patholog_v and Neuroscience, Saul R Korey Department ofNeurology, Rose F Kennedy Center, Albert Einstein College ofMedicine. Bronx, New York 10461, USA) several species of experimental animal (D~ckett et at. 1974. Mendell et al. 1914, Spencer, Schaum- burg. Raleigh & Terhaar 1975). These studies demonstrated that prolonged intoxieation by inhalation or subcutaneous injection caused the insidious development of symmetrical weakness first in the hindlimbs and later in the forelimbs. The first signs of peripheral neuropathy developed after 4 to 12 weeks or continuous inhalation of zoo- 600 parts/106 ofMBK, and after 12 to 16 weeks of intermittent inhalation of 1300 parts/10 of M BK. The onset of MBK neuropathy was associated with a reduction in the sciatic nerve conduction velocity (Mendell et al. 1974), an indication of nerve damage also found in rats and monkeys inhaling lOOOor 100 partsfiO" MBK intermittently for periods of 3 and 8 months respectively (Johnson 1975), the figure of 100 parts/106 being the recommended Threshold Limit Value in the United States. Recent studies have suggested that concurrent exposure to MEK and MBK will produce neuropathy more rapidly than in animals exposed to MBK alone (Saida eta/. 1976). Methytethylketone alone or MBK alone produce no neurotoxic effects (Spencer & Schaumburg 1976). The purpose or the present paper is to emphasize the importance of chronic testing of potentially neurotoxic compounds in experimental animals. to describe the range of hexacarbon compounds which have been identified as neurotoxic al!ents and. finally, to characterize and illustrate the pathological basis for the onset of the nervous system disease. A total of seven hexacarbon compounds have been tested in this study {Table 1). During the summer of 1973 an outbreak of per..: -~:; ipheral neuropathy developed among a large ,:Table 1 group of employees of a fabric manufacturing _H_n:_.:oca_r_bon__.,o_m_:pou__nds_,es_t_e_tl _ _ _ _ _ _ _ _ __ plant in Ohio, USA (Billmaier et al. 1974). The disease was characterized by distal weakness and sensory loss symmetrically in both the hands and the feet (Allen et al. 1975). The most severely affected individuals worked in the printing department where colouring inks, dissolved in volatile (II ...bexaneCH,CH.CH.CH.CH.CHL 121 mcthyl-n-butylketone CH,COCH:Cti.CH1CH, (31 :Z.S.hel<ancdioneCH,COCH:CH:CoCH, (41 2.~-hcxancdiol CH ,CHOHICH .I.CHOHCH, (5) 2.4-h.:xllncdione eli ,COCH .COCH :CH, (61 2.3-hcxancdioneCH,COCOCH:CH:CH, (7) 1.6-hexancdiol HOCH:CH,CH,CH:CH:CH10H solvents. were applied to the surfaces of plastic coated fabrics. For several years the printing The first compound. n-hexane, an important sol- process required the usc of a 9: I solvent mixture vent and a minor component or petrol. was indicted containing methylethylketone (MEK) and methyl- in several reports as a possible neurotoxic agent isobutylketone (MIBK). Methyl-n-butylketone (Herskowitz ct a/. 1971. Korobkin et al. 1975). (MBK) was gradually introduced in the summer of Rats were exposed continuously to atmospheric 1972 to replace the MlBK. Methyl-n-butylketone levels of 400 to 600 partstlOc. of 11-b.:xane for up to was in its maximal usc by December 197:! and the five months. 500 parts1l 0" being the US Threshold first case of peripheral neuropathy occurred shor- Limit Value for 11-hexane (sec a/.~o Schaumburg & tly thereafter. The recent introduction of M 8~ Spencer 1976). The second compound. mcthyl-11- into the printing department of the plant, coupled butylketone. the solvent implicated in the outbreak with other isolated outbreaks of neuropathy in of neuropathy, was administered to cats by sub- individuals chronically expos..-d to MBK. sug- cutaneous injection of 150 mg,rkg twice daily for gested that this compound had neuroto:o~.ic proper- periods up to six months (.vet ul.~u Spencer & ties. MJ!K pr"<!uccd peripheral neuropathy in Schaumburg 1976). The third compound, 2.5- _ _____..,. .,._.. .... -....... ....... ......-... ---~ -----~,-------------- . ~- ~- FMSl 04748 it i :: i ' I it !I !I "! ... .,.___ ASBESTOS INFOR~AI ldlq ~ 'd' " ' 1745 Jefferson DaVIS 1-\wy. Suite 509, Crystal Square 4 Arlington, Va. 22202 A- {_______.........__s_ +~ ---------- AIRBORNE ASBESTOS IN THE VICINITY OF A FREE\VAY J. ALSTE. D. w.nscii-lt and J. BAGG De.,anm~nt o Industri:1l Sc:i~nce, Uni..-ersity of Melbourne. P:~rkville. Victoria 3052. Austr<~lia (Firsc r~cei.t:ed 22 Do:co:ml>o:r 1915 wrJ in jincrl fnrm 16 fd>ruury 1976) Abstr:lc:t--A;bes:os fibr::s t:1ltcn from ircsn or worn brake: linings or c:olh:ctc:d from the atmosrhcre ncar a freeway '>~<ere eumin.:d by cte-_,;on mic:rosc:opy and electron diffraction. The: major eF.c:ct of braking :ippc::~rs to bo= in separ:uing bunches or fibres and reducing their avc:rage length but not in altc:ring their crysul structure.. The suggestion that grcss change> in the: .cryst:tl structure: :m: l:-r~Jught about by hc::1t generated. during b1"3lting is not supported by this work. Airborne samrlc:s were co!lc:ct;:d at points where: there: was consi.!.::rablc bro1kir.g and when: there ~as only slil!!lt 1:-r.r.king. .-\t th..: roint where sli-z!tt bral.;.in~ toolt place: the airborne: conc:c:ntration wa:i ..-cry lo" aml.:ould not b-.:: s;ubl;u.:\\ril~ measure:.!. At the: point whc:r: consid.:nblc: bnking occurred an. estimate: or 5 x 10~ m-' r;:rti.:t.:s was d.::tc:rmi~cd. .!:~Ch partido: consistin!:! or a small bundl.: of fiim:s. The majority or rartidc:s ha<! <2a maximum linar dimension ~un. 1:'\TROOLcrtO:-; The concentration of asbesto~ fibres in the atmosphere may rc:-.1ch high levels in the immediate vicinity of mining thc: asbt:s:os mineral or manufacturing as~stos products. It has b~n known for a long time that the inhalation of fibres at these concentrations is injurious to both man and animals (Merewether, 19301. A qual!tati..-e standard which hns b.:::n pro po:;.:d by th.: E.P.A. 1.\'l'w.~ Fuc:u.~. 1973) is th:1t there should ~ no .-isible emissions during the ham!ling and m:tnub;t!,;~e of ash.:stos products. One criterion for a r..'t.-orr.m-::1d::d quantitativ.: standard is that tho: cor.:.:entr:1tion ::.ho.1ld not exceed 5 x 10'' fibres m- 1 of kngth ~ 5 J:m for a 30 y exposure and ~hat this st:mlbrd shotJd become more rigorous aft.:r July 19-r. h.:comir.:; ::' x 10" libr..::; m-J (NIOSH. 197::': L.S. IJ..:pt. L::...~r. 19721. British ;md \\\:st G..:rman roru~.a!s .:gr;.:; \\ith tho.: m<lr.: ri:;urous stanJard suggcst.:d abu\.:. ::i.:::u!l' anJ \\'uit0witz. 19i.'l. E:\t.:nsiv.: \\Ork has t><.-.::-: ~:.:rr;~J out on th.: hc;tlth of woi\.:.ers ..::'iro~c.J in th;: in.!u~:ri~.-s produ..:ing airborne aslx:stos. :\.luch lo.:ss \\Ork ha; bc.:n carri.:J out on th..: pr..:s.:no: of asb..:stos in :b.: ..Ltmosph.:r.: Ltr :tway from an~ such i:1Jus.try. Asr..-..:.Js ;.as founJ in :til samrks t;t~.:n from the atm<.'>;";~..-n: of sc,cral citil!s in Euro('l! whid1 did h:t..-.: :m a~lxsto3 ir.c.Justry !Holt ;md Yot.inl,;. 1973}. The asbestos \\aS pr~nt chictly as sin);le fibres but :1 small fraction 01.-.:um.-d as -ag~lomer:ctc:s. ~0 ll!.!;tntitati'.: estima!~ uf con.:..:ntratiiJn w:J.s made ::,ut comr.:~;J tO Ot!. .;r '~l';'.:'lh.kJ pMlicubt..:-; It \\ ;tS Small. Pr~hmi:t::~\ ~ .:>\.;b :,,r :"'cw y,,rh, t:ll\ ,;~L"'''-'li con- 4:::ntr~lti,,n~ r~~:1~1a~ fr't'tn ll h.' f.!l ng. ~- J \\lth Jurh- rr~,..;;r; ....:..::"" .-\.CI Emirom..:s. P.O. fkn S. :"..:w. r-. .f!, \"t~i,I.);I~L \l,;,tt~l:~~- -t l'rl..",.:nt .~.:..::~..: ..~ C S l.R.O. D~\i;,oil'" t'f Tr:~~'rii~ . .~~~ \ ~~~i"'-''JU\..:. -\ ""',.(:;.r.!:.!. cate samplc:s differing by a factor of ~-3 ISelikoff. 1972: Nichol:>an er ttl.. 1973}. Asbestos was also found to be present in all 200 samples taken from the ntmo:S- . phere of 49 cities in tho: U.S.A. {Sdikolf. 19711. Th..- sourc.: or asbestos emissions in the: 'lbio!nce of asbestos mining and industry is a ""1tter of spccu- l:!tion but on.: stron~ possibility is from the: brake linings of automobiles. Thcs.: linin~s ;tre suh.i<.-ct.:d to considerable w~tr leading to the: rde:1:>..: of <Lsb..:stos dust. In one c:1rcul study the rci~IS.: of ast.~.~tos w;~s mc-o~sur..:d by surrounding th.: hr:1k..: drum with :t .:ul h:ctor and c:ipturing the tot:1l ..:mi:-sion (Jack<> <'t ul.. 19731. A total emission of 17.!\ ~lg km- I for r:ISS<:ll~..:r vehicles <md 5-l.S Jig km- 1 travdkd for light trucks were.: quoted as typical values. Not all this el!li,;,-il'n r..-ad1..:d tho: atmosphcre. sum.: depositing. url'tl the ground and som..: l>.:ing r..:t:1ineu b~ the br:tk..: dnt!!l. '"I"The.: fraclic'll which b..:..::tm.: airbtrnc ,,ti:t:;::..:d to h..: 7-.i'' u f'"1r pass-.:-ng~r \~hit..:l~s ~tnU 2.lJ .. l'a..'r tru...:k~. This r..-~.:;tr..:~ alsll g:m: the 1!:\pl!ct.:d rc:;ult th;u h.::1' y ~r::king proJu..-.:J llllre emis;ion than light k:1ki:tg. Although it is \cr_y dillicu!t to eorm:rt th..::>c results into ;1tmo.~pheric conc.:ntr:ttions dc;td~ only ,cry l..w conc.:ntr:1tio~s would h..: anticip;t:cd. Lynch {llJ(~J..:x:unined th du:>t fnm brak..: linings ;mel from tho: appcar:me.: tf the libr.:' Sllt!l!Cst~.J tl:;a the cry>t:ll structure of tho: libr.: was ll..-sra.!,.-J h~ h.:;:l rd..:~t,.:J during hr:tking. Holt an,! 't\ung (llJ-:'.~1 found 1h:11 fibr.:s Clllk..:t.:d by them fwm th.: ;1tnw-< pht.:r.: ~ho\\o:d \O.:f) liuk ._.,jJ.:nc.: of ltl~S lf cr~,t;tl linit~ . .':ll'. !h~.rdtr~. ftlll\\ in:: l.~nch"s -<u~s.:"t:,,!._ ~\'!1-.:~ .. :~-~ :::~~t htt1h.!::l:; tH~th:n~tl:.. \\o:r~.. .l l!h'r'"~ !ik~!~ ...n~\r...:: !~' .~:1 br..\~'- li:~;n~'- Th..: ~::!1~ \.,lth~ \.h.'i~ r~P''rh:d lh:: ..: \\.b h' .... ,_,::Hil;.; fi1Vf~ (l~."..:~~ tht.: p\l~:-.il,t~ t.."~>'tl~l !!"l.lt:~'ll th~:t ;.. r :!~'- ~~~,. ing~ t.:~. "".: !~.! n~. ~..: 1t..' t !1.: ~'-'!"'~'ll,, \..\ '':-.....-i' 1r.q ~' 'il :11 ~t:n:t''r!~\.-! ..- FMSI 04749 J. ALSTE. 0. WATSON and J. BACG EXPEIU;\IF.:"'T,\L .-\ numh:r or m.:thl><fs h:ue ~n propos.:d for the esti m.,u.n of asb.::otos p:trti.:l.:s in the atmosphere {Kco:nan .t::J J.:.upd. 196S: Lane ol (II.. 196~: Gadsden I!C ul_ 1970) :-.~- ;&i tho: pr.:s.:r.t time tho: only method of sullicicnl sen~i. ;;,-:ty and sdecti\ity for tho: very low concentrations in- ,..,:,.:.:1 is the d.:.:tron microscopy of sampl.:s collected on ><:it;'''!.: li!t~rs. Atmo>ph.:ric s;~mplcs were collected oil a :'>!i:tipore rih.:r (VSWP 0-H. 0.0:!5 I'm pore dia.) at an a~er a;.: tluw rate of 0.61 min -. A High-Volume sampler was ::t>Ji1ic:d by placing an aluminium fac.:-platc containing a :;:nal! rube ot:er the inlel to the: s.1mpl::r. A Millipore ::::er ilolc..:r was connc.:cted by a ph!Slic tub.: witb a rola ~:t.:r in:erpo:~o:d 10 the small tube on the face plate. Sa;npl.:s were rak.:n at thn:c locations. (i) on the: roof or t!:.: D.:partment of Industrial Science. University of Mel ~ourne. 10 m above strect.lc:wl and 30m from the nearest traific. (ii) OUUtde the Same building 0.8 m abO\"e Str=t b.:l. (iii) at the exit of the S.E. end of the Tullamarinc: f;.:cway. O.S m above ground level This last sampling point was so- m irom the: -po5ition where br:lkes wc:re applied :o r.:duc.: thc s;x:cd of vc:hict.:s from aprrox. 100 to 60 km h -. Thc tot:tl numb.=r or vehicles rassing all thrc:c lvo:ations during the total sampling period IYaS very similar and the: .mujo.~r dilfc:reno:.: was the abs.:ncc. locations (i and ii). or pn:scncc:. Location (iii). of extensive braking. The samplirt); p..riod was from 0:1.:00-17:00 h during :'1/ovcmbcr 1973; the weather was fine with only light winds o;:r this p.:riod. After the samrl.:s had been collected the :'-.t:!iiporc filters '''c:re coated with a carbon film. appro~. :o nm thickness. and then live small pieces (1.5 x 1.5 mm) cut out at random. Each small section was placed o~ a copp.:; grid. carbon film facing down. and the membt:ln.r matcriai removed by dissolution in acetone. Electron micrographs and diffraction patterns were obtained trom th:=se spccime:'IS using a Phillips EM :!00 microscope at :,u kV. The ei.:ctron diffraction patterns were calibrated by evaporatint aluminium on to the copper grid and by comparison inter-planar spacings. lf.hld). could be deter- mir.cd. Samples or fresh and v.-orn brake: drum linings were obtained from an automobile n:pair shop and wc:re crushed gently in a mortar and pc:stle with a fc:w ml of chlorororm. An electron microscopc grid covered with a smooth film of evaporated carbon was th::n dipped into this suspension and the: chloroform allowed to c:vaportot. RESULTS A:-iO DISCliS.'ilO:"' Figures and 2 show electron micrographs and diffraction patterns from a sample prepared from a fresh brake lining. The characteristic structure of chrysotile asbestos. long filaments each or which is a hollow cylinder (McCrone and Deily, 1973). is clearly visible in this micrograph. The electron diffrac tion patterns or chrysolite. have been determincd and ir:d:xed by Yada (1967, 1971). I: Table I the interplanar spacings determined from the pattern or fresh brake linings arc compared to Yadas values and the agreement is seen to be excellent Figures 3 and 4 show results for the dust from worn brake linings. The average length appears to be shorter than in the fresh lining bu1 the hollow cylin- drical structure is still obvious. The- diffraction pattern still ~onsists of well-defined rings and the interplanar spacings derived from these rings ate in good agreement with Yada's values (see Table 1). There was no indication from the diffraction pattern of the presence or forsterite. the name _given to thermally-degraded asbestos. It appears that for the wear this lining had received no significant changes in the crystal st-ructure due to excessive beating bad taken place:. Temperatures within brake drums may reach 873 K under racing conditions with severe and repeated brak.ing 0.1 J.Lm .a - .,-: ~- I .-.__... ..., ~ . --....-..c..,."t"-=:.- ~~~..- ~'---------------------------------------------------~~ Fig. I. Dust samp!e from cr~sh:d r.::w !::ak: H01ings. FMSI 04750 ; I { Airborne asbestos in the iciruty of a fr.:.:way sss I I i l I t ii t I t f l t l f l.l.. _.. Fig. 2. Diffraction pattoem f;om sample in Fig-. :. I I I I. 1 1 but would be expected to be very much lower under normal city driving. Chrysoti!e has bn shown to maintain its crystal structure until temperatures in excess of ~00 K are reached (Yada. 1971; Robock an.:! K!o~:.::k.:>t:::r. 197~). T!::~ obs.=rvation:> on the worn brak.: drums are then consistent with the lik.:ly temp.:ratur.:s re:.1chcd ~1nd the known thermal b<:h<IV iour ofchr:-sotil.:. Y;td:l (1967. 1971) h<~s shown that ekctron bombardment insiCc: the electron microscope em I:.:::J :,:. p:oduction of ,,morpho.>us mat.:rial iri th.: fibn.:s ;and. th.:rdon:. cxc.:s3(\".: .:xposurc: during c:xamination s!-..)uld be a\oil!.:J. Tabk L \..:'"~'vi .iti:~/1 :,,r ~!a::-solii~ and brak.: linin),!S. nm " tO-' \"alv:~ for chr:"t"'tik tYa<b. ~".!.<". ;n, Fr~~01 l:>r:ak.: !;~:::; Worn brak.: lining P!;an.: (Irk II ....~ll .:.':!') .:.:o 3.65 2.70 ~.611 ~51 2.-'J :.~u :.::5 .:!.15 D:! l.~il 1 ~~ : ..!~l : :s I 21 -:"_a-:11 ~~-' }.6:! :!.fl.:! ~:5~ 2.-'5 ---"''"'~.! :.1 J 1.7\1 ' .:.! .. ~~ i.::l 7.21 .J.60 .l67 2.67 2.56 2.-'7 :! ~" 2.10 1.15 1.55 I.J.l 1.1~ (001) (110) (0~01 (Ill I:! I (~Ill) ( 1.~1\) (.:!l.ll) (OOJ) (.:!~ll) (1!-'()) t)l.:!l (1~.,..1 (ll:'lll p~nt (t M15) t-ltKIJ (11(111 Samples taken either on the roof or at ground level ornear the Departmen~ Industrial Science contained very low concentrations of asbestos fibres (Fig. 5~ Although the rings in the diffraction pattern (Fig. 6) are more di!f~;;:: ::::m from fresh linings the i:lt::r- planar spacir.gs. sh;o...-n in Table 2. again match both the valu.:s for fr:::>h linings and Yac!a's valu-:s. Although th~ compo.!rison in Table 2 cmtbled the pres- ence of asbestos to be deduced. no attempt was mac.: !0 C~!!lll:tt;; [:;,: :Htr.~sphcric COnt.'Clltr~\tiOn beOUS~ of its \.;ry low \;tluc. S:1mpks tak.:~ a: th.: e:(it from the freeway. how.:;.:r. contairo.:t! a m_r.::h high.:r com:.:ntration of asb.:slos par:!d.:s 1F:_;;,;. 7 and l'l .:stimatct.J <~l an ;:\'eragc of 5 X 10~ p;rn;ch:s m- l 0\'Cr tho! 9 h S<tmp!!ng r..:rioo.l. Th.: ~.:n~r:!! arrc~tr~mcc of tho: fibre c!ust.:rs ;ulo.l !o1..: prc,.::;..:; , ..- ,~t!l.:r m:at.:rial i,; \.:ry simi!::r to that ..'i'~..:rvl.!:.: :.. - ~>;.: \\orn hrak~ lining l!ust. ..\g~t!n the <.!itTr;:ct!-..'n ~..::-~ms tiC' not show 'ign!t:::.tr.t ;tmounts o.>f ;,morr::vus mal.:ri;ll and march Y::t.h's \"alu.:' JTabh: 21. Tab!:: .:!. Valu.:s of .It1rk/J for .:hrysCltilc and airborne a~:.:.;,:os.. nrn x tn- 1 Vatu.:,. t~lr chr~,,l::k tY:aJ:t. I'H-. -!1 till.. II J.C.:\ uu~. ~ : ~ I ~'~i l.'n' ~:., Dcpt. lndutrial So:i.:no:o: Tull:tmu:!l.: fr.:.:w;a~ .:~it J.(.() ~.15 1.15 1.1:\ FMS' 04751 ' 0.5f-Lm II ----------.....,J. 1\L\~t. 0. W1\TSOS and J. BACG .,..,._,..r,.._.,. ~: ~... ;~----' ..... I i Fig. 3. Dust sample rrom worn brake lining. ...-__ _ ' Fi!;. ~. Ditfracciun palt.:rn rrom sample i:1 Fig. 3. FMSl 04752 or- 4 Airborne :r.sbestos in the llicinity a frc..-.:..,ay . 5!17 ---\. . .. .---.,.- . ... ..,-= j .. ._J l .:.r.:.:"" I -). Fig. 5. Atmospheric s:r.mple collected 0.8 m :r.bove ground level at ~lclbourne Uni~rsity. f I I I Ij I l (:) I i I I I AI. fU ~ H Fi~. 6. Dilfr.t.tion r-th:rn tru111 -..;unph: "' I :. i I i i ! '.....,__.J FMSI 04753 - - - - - - - - - - -----~---- ! . . !-~ !~ . .. \- - -f. ' ;...-- ,_ . . -.. ~?---' '~...-.:./: ' ~ -- ~ J. ,\1~11.1>. W.\f"'"' ;md J. 8AGG -~ . . .------c-,_...,~,-----? --'\ ~. ~... --I ... . ... --..'.... ...:-.,:.... ._... c' . _ ~.;. ',\ .....~. ~ -......:.--.:--. ....~- - . -~~ ;:... .;.,'"- ' .;.- ........ ._.J ...,-~--~"- -~-_-___ - ~ .... .\,. =- '0.2J.Lm I I -- Fig. 7. Atmospheric sample coll-=ct~ 0.8 m above ground level at the exit or Tullamarioc Freeway. Fi:;. ' Oo!Tr.~u,n p:tll<:m from sample in Fig. FMSI 04754 t .' . . : Ai[borne asbestos in tho: vicinity or a fre.:w:~.y 5!19 The particles consi~ted of small bundles of fibres together with other mat.:ria.l which may have con tained binder present in brake linings. Another possible source for this amorphous m:uerial consi,;tent with a loc-J.tion wh.:re braking occum:d is w.::u from tyr.:s. Measurements by other workers- (Piers.:>n and Br:u:h;tczk. 1975) h;we shown com.:entratior.s of airborne debris from tyre wear from 0.05 to 2.1 pg m- 1 The number of fibres in the bundl~ and th:ir size varied consid.:rably and no attempt was made to count inc.!i..idu:ll numbl:r of fibres. The majority of bundles did ha..e a maximum dimension ~:! pm. Although th* results are limited and of a prelimi nary n:1ture the following points can be made: (i) Electron diffraction has proved to be :-. metho4 of great sensitivity in the identification of asbestos partic!es suitable for the low concentrations found in atmospheric samples. (ii) Asbestos fibres from brake linings operated un der normal conditions ha\'e the same Cr) stal structure as asbestos from oth.:r sour.:..-.s.. The abs.:n.:e oi th::rmally-dt:!;.rad.:d mat.:rial c-J.nnot. tlt::n:fore. be tak::n as evid::nc:: that brakes have not contributed to a particul:l.r sample. (iii) The results from the samples coll.:c:ed at the freeway e:<.it suggest that emissions from brakes can become airborne. The concentration:; reached are very low. below the recomm.:nded e:<.posure standard (:-llOSH. 1972; U.S. Dept. Labor. 197:!J,. and consis- tent with the prediction by other workeri that only a small fraction or th~ total dust rorml!d t:::com.:s airborn.: (bcko. l!t ul., !973J,. .kknr.m1,,/",m.ur.~-TI::: :mth.,rs would like to thank Dr. J. V. Sa.ml.:rs. CS.I.R.O.. Di,iiion orTrib..,pb~si.:>. Univer sity or Mdbourn.:. ror considerable assistance :~.nd usc of electron microscop.: facilitiC$. Onr: of us. J. Alsto:. wishes to thank A.C.l Fibreglass for suppurt duri<lg this work. Rt:Ft:Rt:I'\O:S G..d,.:n J. A.. Parker J. and Smith W. L 1l'r0J ::J~t:rmina lion or chrysotilc in airborn.: ;~s::..:sto;; by .1n i.r. Sp...'CtrO metric technique. Aunu,;pht>ric Em:irom~fll 4. 667- 670. Holt P. F. and Young D. K. (1973) Asllr:sto" fibr::s in the atm.nphere or town;. Armospl1eric Em:iromnenr 7, 4Sl- 4SJ; 669-670. Jacko G. J .. OuCh:mne R. T: and Si!mers J. H. (1913) How mu~:h asb.:stos do vr:hicl.:s emif? Auro EII!J"!I 81. 3::1-40. Kr:en:m R. G. and Kupcl R.. E. .(196R} ~lodern t..'.<:hniquo:s for evalu:~.tin~ mixed environmental exposures .to fibrous and p:micubte dusts in th:: asb.:sto; industr}. Prt:print U.S.. Public H.::c~ltb Service. l':ational Centre for Urban and Industrial H.:-o~!th.. Cinndnati. OH. Lane: R. E. r ul. (196S) Hygiene stand:trds for chrysotilc asbestos du;t..11111. o,c11p. Hyg. 11. ~7-69. Lynch R. J. (196:i) 30th Annual M.:r:ting.. Am.:rican confer- ence of Govcrnm::nl Hy~i.:nists. SL Louis. ~10. McCrone W. C. and Deily J. G. (1973) Til~ Pt~rriclor Arias. Vol ). :!nt.l Elln. p. 586. Ann Arbor Sci::nc~ Publishers. Ann Arbor. M l. M.:rcwr:th..:r E. R. A. (19301 Tho: o.."CUrrfiCce of pulmonary fibrosis and Other pulmonary infott:li<lnS- in asbo:$tos work.:rS. J. /I:J. Hyg. ll. :!39-257. No~us Foetu (19i31 EPA s.:ts final emission sundacd for asb..-sto>. bcr} Ilium. mo:rcury. J. ..tir Polltot. Coiiii'OI .-ts.s. 23. J'}S. Nicl\.Jison W. J.. lam:er A. :1.1. a:1.d Sdik.Jif I. 119731 Asbestos in tho: atm~;ph.:r.: of to.... ns. .-t!ll:v.r'~ric ;,_ &"irOIIIII<'IIC 7. ~66-66$. NIOSH (197:!) Criteria for a r::commr:nc::d standard. O.:cupational cll.posur:: to asbcst.Js. Docum::nt HS:O.l 7:!-10:!o7 +tt97:!~ U.S. D.:pt. of H::alth. Educa!ion and Welfare. Pierson W. R. anJ Bra.;haak W_ W. 11~75) ln-tr:t!lk 'mr::asurcmr:ilt of airborne tyr::-war partieulatr: dcbri! J~ Air Pollur. Comrul .-tss. 25 .w.-&-4\15. Rohoc:k K. and 1\.lost.:rkotter W. (19731 Jn,,stigation~ in the cytotoll.icity of as~"Stos dusts. Sr.mlt 3J. :!N-:!l!~. Schutz A. anJ Woitowitt. H. J. (l'l13) T..clmi..:~tl st;uu.l:!rd valu~ for the admi~;ible wNkin~ pl;}~:c C<lm:.:ntr:ttton s,,,.,,of .:hn:sotik asllo:stos. 33. ~5-~5lt. SelikoiT 't J.. ~idtolson W. .J. anJ L:.u::;.:r A. M. \ 19721 Asb::stos air pollution. Arclr. fllirolf. llltl 25. 113. U.S.. O.:pt of Labor. (197!) W:tshin):lton lnf,,rmation docu- ment T1-366. Yada K. (1967) Study of chrysoti!:: asbc..-stos by a high resolution micro:;.;op.:. An~;~ Cry>t. 23. 7()..1.-707. Yad: 1\.. (19711 Study or microstructur..: of chrysotile a;h.;,to; hy hi,;:h r.:sohnion mi~:r,ls<."t>p}- .-t.ru Crysr. ,\27. 65)-(\(~ \ \ \ I I FMSI 04755 C> F .A.IVJ: E ~I C.A.. INC::.. 201 KING MANOR DRIVE. KING OF PRUSSIA. PA 19406 (2151 277-3900 April 20, 1979 Mr.. I. H. ''ieaver Corporate Director Envir. RAYBESTOS-~L~~TT~~ 123 E. Stiegel St. Manheim PA 17545 Control Dear Ike: I thought you would be interested in the enclosed report from Dr. Arthur Rohl of Mt. Sinai Hospital Medical Center. We have been anxiously awaiting the results of Dr. Rohl's tests and needless to say, are very pleased with the report and what he has to say about NI~ISK'S ASBESTO-CLE~L syste~s. Sincerely, NILFISK OF AMERICA, INC. /M )Ju'-q.&e~ Robert S. Magea in !j President I RSM:ds Enclosure ,I_<( (LfJ FMSI 04756 . .~ ,. April 11. 1979 ,.., ""'" .,.,... ,, ..:: . . ,._, j. , .._, . Mr. Robert S. Magdelai~, President Nilfisk of America, Inc. 201 King Manor Drive King of Prussia, Pennsylvania 19406 , c \ . . . . ... :... ; _,. ~::. _.; ~ ::-- Dear Hr. Magdelain: This will report the results of air sampling tests conduct~d, in October 1978, to dete~ne chrysotile asbestos concentrations during brake repair work. Our major objective was to determine the efficiency of the Nilfisk Asbestos System utilizing HEPA filters, particularly with regard to submicroscopic asbestos fibers. Studies conducted in our Laboratory and else~~ere have demonstrated that free asbestos fibers present in brake drum dusts are predooinantly shorter than Sum in length. In particular, it was found that about 75% of the fibers in such dusts were less than 0.3~m in length, as determined by transmission electron microscopy. Thus, the optical microscopic technique used by OSRA for determining asbestos levels in workplaces (in which only fibers 5~m or longer are counted) would overlook a large number of asbestos fibers in air samples. That is, the total asbestos exposure in terms of fiber nucber, mass and surface area would be significantly greater than the levels determined using the OSHA fiber-counting oethod. Therefore, it was of considerable interest to us to have an opportunity to test the efficiency of the Nilfisk Asbesto-Clene System. To do this personal air s~ling was carried out on the exhaust of a REPA-filtered vacuum dust collector and, simultaneously, on a garage mechanic cleaning a brake drum with the ~ilfisk brake encapsulation cylinder. Three su~h tests were made. Background air samples, also using personal air pumps, were taken. For each of the tests, a sample of settled dust was taken from the brake drum. The dusts were analyzed by x-ray diffraction in the stepscan mode to quantitatively determine asbestos contents, using a technique previously published. Asbestos was found in all three samples, ranging from 2.5% to 4.5% by weight. The membrane filters were analyzed by both transnission electron microscopy (X25,000) and by the standard OSE\ fiber-counting technique, employing phase contrast optical microscopy. The results are as follows: FMSI 04757 !!.. ' ~lr. Robert S. Mag~elain, President Page 2 April 10, 1979 Sai!!Dle Description Nanograms/cu =eter Fibers/milliliter (electron microscoo~) (ootical microscop~) N-1. N-2 . N-3 TEST ;.'!1 Background (70 feet from o~erator) Operator (breathing zone - 6 ft. fro~ dust collector) Dust collector (HEPA-filtered vacu~) 400 0 0 .0 0 0 TEST ~2 N-4 Background (70 feet fr~ operator) N-5 Dust collector (HEPA-fil~ered vacuum) N-6 Operator (breathing zone - 6 ft. fro2 dust collector) 615 0. 59,000 O.l2 0 o.s TEST #3 N-4 :Background (same as in Test ~2) "N-7 Operator (breathing zone - 6 ft. from dust collector) N-8 Dust collector (HEPA-filtered vacuum) 615 o 0 0.12 0 FMSI 04758 :l-Ir. Robert S. :l-Iagdelai.n, President Page 3 April 10, 1979 Remarks and Conclusio~s: The tests demonstrate that asbestos levels are virtually el!minated by the use of a system ~playing braka encapsulation devica connacted to a HEPA-filtered vacuum dust collector. ~ithout the use of such equipment, fiber concentrations during compressed air jet-blo~ing of brake druns ranged from 6.6 to 29.8 fibers/oilliliter. Ho~ever, when the Asbesto-Clene System was used, fiber concentrations on both the mechanic and dust collector e.."'t.~aust were not detected, as verified by transmission electron microscopy. An inportant exception to this is observed in Test ~2. the s~ple taken on the operator. Prior to this test, this mechanic had worked on brake jobs wi~hout using the Asbesto-Clene System and without changing his work clothes. This exposure hac resulted in cont~nation of ~is clothes, reflected in the high residual asbestos concentration of 59,000 nanograms/cubic ~eter and 0.5 fibers/milliliter. In contrast, the operator in Test #1 and Test f-3 wore clean coveralls. This poin::s up the need to adhere to the OS~~ regulations concerning special clothing, change rooms, etc. to cinimize cont~ination. The background asbestos measurements, of 400 and 615 nanograffiS/ cubic meter, are consistent with other background measure=ents taken during brake repair work. They are the result of residual contamination of the garage by asbestos. This study has been unique and fortunate in two respects; first because of the great interest and importance of determining chrysotile asbestos levels in such circ~tances. The data indicate that the Asbesto-Clene Syste~ represents an outstanding advancewent in industrial hygiene procedures to control asbestos exposure. It has also been a pleasure to work with you in preparing and conducting these tests. If there are any questions regarding the results or conclusions in this report, please do not hesitate to contact me. ~~~ Arthur N. Rohl, Ph.D. Environmental Sciences Laboratory ANR:jm FMSI 04759 u~ccnw~an Correpondlence Asbestos Health Hazards There have been a lot of stories lately about the hazards of breathing airborne asbestos fibers. Is asbestos still u5ed in !:ra~ lining$? If is common practice to bloW the brake dust out with compressed air.to clean the brakes. Docs this present a health hazard? Is there a risk to motorists from brake dust in the air near streets and highways? Ken Bohn Louisville, Kentucky Asbestos is the name for a family of silicate minerals that occur in nature in the form of ultra-fine, brittle fibers. Asbestos has a high nsistance to heat and is still commonly used as insulation or molded (with other materials) into clutch and brake linings. In molded form a,bestoS is safe but when the fibers are nleased (from wear or from cutting or sanding the moldedmaterial), they present an insidious health hazard The fibers are so brittle that when they are broken, they tendto disintegrate into particles too small to be seen (an electron microscope is needed to see the smallest, most harmful particles). According to current medical research, usually there is no sign of asbestos-relateddiseasefor I0-35years after the fint exposure to asbestos particles. After this incubation period, the fibers can cause asbestosis, a disease characterized by seven scarring of the lung tissue, and mesothelioma, a cancer ofthe lining ofthe chest and abdomen. Asbestosis usually doesn't kill directly. Its victims genera'lly succumb to related respiratory infections such as bronchitis or pneumonia. Exposure to asbestos fibers also greatly increases the risk ofcancer ofthe lungs and esophagus, stomach, kidneys and larynx. Cases have beenfound wherefamily memben ofworkers exposed to asbestos fibers developed asbestos-related diseases just from exposure to asbestos fibers on the worker's shoes and clothing. Motorists and pedestrians ha\'e little to fearfrom inhaling brakedust. There is some brake dust in the air near streets and highways. but the numberofparticles is very smallandthey tendto settle out ofthe air, so the overall risk is virtuallv nonexistent. To reduce the risk of asbestos-related diseases, avoid contact K"ith asbestos particles, especially airborne particles. It's usually a good practice to clean any component before reassemb~y. but' with brakes and clutches, it's better to leave the brake or clutch dust in place, where it does no harm, rather than to use compressed air to blow it out and risk inhaling the asbestos fibers. Ifyou must clean the parts, use a vacuum system or rinse the parts in solvent and 'Wear disposable gloves. Clutch or brake linings should" 't be allowed to soak in the solvent, as this can damage the lining material. Discard the used solvent and wash your hands immediately so you don't spread theparticles around To cut or sand clutch or brake linings, use a ventilation system designed to suck in the asbestos dust before it can be inhaled and wear a dust or paint mask. To clean brake dust from the wheels, use a detergent solution and rinse with a hose or use a high-pressure cleaner at a self-service car wash. Information on health risks associated with asbestos exposure is available from NM!wAL CANC.t--t! INSTITca ................ . -: . .. .. . - ........ /-9 FMSI 04760 , '"'"" -..~,-Knowand understand the 1aw- OSHA will soon be around ... asbestos is a danger to your employees ~ Last month, we introduced the pro- industries (the miners were .under posed changes in the asbestos regula- another law). Of the nearly one million tions and briefly outlined some of the standards your shop must meet to obey Use of the common sense them. This month, we will taKe a closer N IOSH guidelines will mean look at some of the specific ~tandards affecting your business, show how much danger is involved in handling greater shop safety and could help you pass OSHA asbestos and present some of the solu- industrial hygiene inspection. tions parts and equipment manufacturers have developed. When the 1974 asbestos inhalation law went into effect, most of the concern was for those employees involved in milling, fabrication and construction . A dust collection sysum designed for use with Ammco Tools, Inc.'s brake shoe grin ders (Model 8925) efficiently collects, con tains and disposes of asbestos dust ground off brake shoes, according to the company. No external power source is required, as a built-in suction fan pulls dust from the sur- tons of asbestos "consumed" in the United States in 1972, approximately 77% was used in the construction industry. However, further statistics reveal that only 500,000 workers are exposed to asbestos in mining, milling, fabrication and construction. Compare that number with the nearly one million American workers exposed to asbestos while installing and/or maintaining clutch and brake linings! A smaller per- face of the brake shoe and deposits il in a centage of the total asbestos is con- sealable disposable plastic bag. Once instal- sumed but a larger percentage of led, the brake shoe grinder is said to meet or c..:;:.~~,exceed Federal Clean Air Standards set by the OSHA Act of 1970. ''A r America's work force is exposed. But how serious is the exposure? A 1975 study done by Dr. W.J. Nicholson of Mt. Sinai Hospital detailed in a paper entitled "Asbestos Exposure During . . .~~''- ~-.~~:!.11 Ff' ... : .!~r;~;,,.~i't ;1 . . ...,......,--~':'";j'.r:;r'il ., .. ~\~~ Brake Lining Maintenance and Repair" .' '' rey~als some interesting statistics. Before studies were undertaken, it was thought that the heat involved dur- ing the use of brakes caused a chemical 3: breakdown, transforming the asbestos ,.~ in the linings into a relatively harmless 0 dust. The data presented in the paper ....... en ..a. indicates that workers engaged in car and truck brake service are exposed to potentially hazardous levels of ai~ome ; ~ asbestos dust. 1-4 BRAKE AND FRONT END - ....~. 4 ,., .. ' ... .,. "'~-- T ..,.....-,.. - - - ,-.-~--~~- .... ,..,;.. ...... .......Spe~;i~,.br)lke..setvicing.,opo~tions.- .per cubic .ceatimeter.Specifically, the studied included blow-out of au- Federal Register ~tates "The 8-hour tomobile brake assemblies, grinding of time-weighted average airbome con- used truck brake linings and bevelling centrations of asbestos fibers to which of new truck brake linings. Average any employee may be exposed shall not peak asbestos air concentrations for exceed two fibers, longer than five mic- these three activities based on personal ron, per cubic centimeter of air." samples taken within 10 feet of the The measurement is done by using a operator were, respectively, 10.5, 3.75 membrane filter method with an elec- and 37.3 fibers (greater than five mic- tronic microscope costing between rons in length) per cubic centimeter, up $500-$1 ,000. Obviously, this is too to 19 times worse than the recom- costly for most brake shops. Some in- mended limit. surance companies will undertake this The study concluded that "during measurement for their acccunts, pro- brake lining maintenance and repair, viding the insurance company has an workmen in garages, service stations industrial hygiene division. Also, some and brake repair shops are exposed to state .OSHA offices will help. asbestos and thus may be subject to Regardless who does it, the employer serious cancer risk. Others, at some is responsible for taking the measure- distance from the repair work, (includ- ment. An explanation of the membrane ing those who are within 75 feet) are filter method (which is the only accept- perhaps subject to the same hazard." able method according to OSHA} can This study, and others that have been be found in the Asbestos Information undertaken, has established in the scientific community a basis for studying the extent of asbestos-related disease in brake servicing personnel. A recent re view of scientific literature, quoted in an ASIA news bulletin, states that "the association between asbestos exposure and [tumors of the chest and abdominal membranes] has revealed at least four cases of these rare tumors in persons who were employed in jobs involving automobile brake servicing." (Researchers have just begun to pinpoint this industry. Other related cases are expected to be found.} Now that the scientific community and the federal government are convinced The Brake-0-Vac brake assembly cleaner has been redesigned by Per-Lux, Inc., to meet OSHA requirements by at/aching the unit to an approved shop vacuum. Whe11 at/ached to a standard air hose, dust, asbes- tos and other foreign matter can be vac uumed off brake assemblies in seconds. Automatic or manual models, plus quick change adapters from 9 in. to 12 in., are [;;t'i'"~~~.,;~': ;.::r,~ -~:. \~ ~~--a>v~.;"a.';~:.i,,~,l.:a"".:/b'>"-';l.;',e,~?.,:~,1;::.,-J~~,",i. :-'.;.","~"")~>.I''..,..'-:.~.:.\...,..._ ,".'..:.-1~:'.1.\'i.". .n~'' i~ . n .. ,. . :.. \ (;.. ">.:." 01. .. . J. of the risk involved in brake servicing, it is time for the individual shop owner to comply with the standards established by the Dept. of HEW and stated in the Airborne Asbestos regulations. The law states that airborne asbestos fibers must be below a certain count k'a- Ij ' ..., . :,:1i {;f..<... . ;, ~- "!'( :.' ). . :.,\J;.~ ~1t~i\;,~::~U' .. ;,!l;t_'._?".'~ ,fj. " ' .. . . ..'. ,.~..'.-.,:. .a MAY 1976 15 Y-10 . (?) .v -. -;;. Association's ''Recommended Work If possible, an area should be des- of a new assembly. Practices: Fabrication and Use of As ignated for all brake and clutch repairs. Dust should first be cleaned from bestos Friction Materials." It takes 11 -Entrances should be posted- wittrwam-: - ~--:-- - brake drums, brake backing plates, complicated pages to explain the pro- ing sign saying: "Asbestos dust hazard. ; brake assemblies and clutch assemblies cedure. Avoid breathing dust. Wear assigned . using an industrial type vacuum cleaner A toll-free call to OSHA's Chicago protective equipment. Do not remain in equipped with a high efficiency filter office revealed that the industrial area unless your work requires it. Brea- 1. system. After vacuum cleaning, any hygiene inspectors will look favorably thing asbestos dust may cause ashes ' remaining dust shall be removed using on indications of voluntary compliance. tosis and cancer." (fhe Chicago office is quite willing to During brake servicing, an air answer any questions on this and any purifying respirator, either single usc or l a rag soaked in water and wrung until i nearly dry. Under no circumstances should compress~d air or dry brushing other OSHA regulations. T.he toll-free with replaceable particulate filter(s), as number is: 1-800-621-0523). approved by the Mining Enforcement be used for cleanmg. . Durin~ arcing and riveting opera- and Safety Administration of NIOSH, !tons, respirator should also be worn. The National Institute for Occupational Safety and Health has suggested the following procedures for asbestos brake and cluts:h servicing in order to will be worn during all procedures starting with the removal of the wheels and including reassembly. Such a respirator should also be worn during all clutch Grinding (arcing) machines should be provided with local exhaust ventilation such that worker exposures maintained at least below the 1976 asbestos stan- reduce exposures: procedures from removal to installation 1 dard. ' Industrial vacuum cleaner bags Tempo Products Co. offers this brake{ containing asbestos dust and cloths clutch service vacuum (Model AB-7515)for dry recon!ry ofasbestos fibers. The vacuum is equipped with a four-stage filtration sys tern wirh secondary fail-safe protection that is said to assure maximum asbestos filter entrapmenr. Each unit includes ;:omp/ete instructions and all elements necessary for the safe collection and disposal of asbestos used for wiping brake and clutch assemblies should be sealed in plastic bags and labeled with the following warning label printed in letters of sufficient size and contrast to be readily visible and legible, "Caution, contains asbestos fibers. Avoid breathing dust. fibers. According to the manufacturu, it Breathing asbestos dust may cause as- has bun certified to comply with current bestosis and cancer." regulations by an environmental laboratory when used as instructed. l!k...,..,@i'~ All floor cleaning in areas where brakes and clutches are repaired should be done with a high efficiency industrial vacuum cleaner. Although adherance to the above procedures should minimize any con- tamination of work clothing, appropri- ate portions of the OSHA asbestos reg- ulations concerning special clothing, change rooms, etc. should be followed. ., s: CJ) ,0. >.: e~n N '16 Compliance to this law will mean not only a safer shop for your employees but it will mean a cleaner and neater shop. Also, be sure your employees understand the severity of this problem so that compliance procedures become -~~ . <. ;;;.:;., standard operating methods in your shop. BRAKE AND FRONT END MAY 1976 --~(_...,_.~--.r"l.' ---..,..- .....,.._ ~_.."""'" .ww.cp .~-..,....w~ DATSUN Z, s10: 610, 710, 8210, MAZDA AX213 camber problems solve_d! ~~\;~~:, .... '<> Mac Pherson Comrol Struts. they're good, but they have a problem-lillie or no camber adjustment. New you have a quick solution. Install preciSIOn engineered camber bushings. G1ve your customers better tire wear or more respons1ve handling. Give yourself that extra adjustment margin so necessary on cars altereo or wreckeo. Install quickly lor fast profits. Simply remove lower control arm; press out old and slip 1n new bushing; retnstall and align. Easy! No dnlhng, no wetd.ng, no grin01ng, no dilficult adtustment. FAR Performance Inc., Dept. BF1, 2240 De La Cruz Blvd., Santa Clara, CA 95050 toll free 800SJ8791l Calif. 408-249-7990 collect v~ tr::J llr,:;,Performancel"c. =-... Circle II on Service Card . 17