Document rerpL15xqLVdg8r7rEaYEJ73a

^UPUCATB ENVIRONMENTAL RESEARCH 12, 110 --128 (1976) -I TEXT Asbestos Exposure during Brake Lining Maintenance and Repair1 Arthur N. Rohl, Arthur M. Langer, MaryS. Wolff, and Irving Weisman Environmental Sciences Laboratory, Mount Sinai School of Medicine of the City University of New York, New York, New York 10029 Received December 10, 1975 Data obtained on asbestos exposure of garage mechanics during brake lining maintenance i and repair work show that fiber concentrations frequently in excess of regulated limits are ! 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 form, in air and brake drum dust samples. The chrysotile asbestos content of personal air samples, taken during automobile 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 I 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 z fiber were observed in the work environment of workmen involved in these opera < 2oz0 tions (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 z free asbestos fibers survive the high temperatures produced during braking action (Lynch, 1968; Hickish and Knight, 1970; Hatch, 1970) contending that asbestos 20 decomposes as a result of the high point contact temperatures produced at the m > interface of the brake drum or disc and brake lining. n20 We have sought to obtain information concerning asbestos exposure of work x men engaged in brake lining maintenance and brake shoe installation, by analysis o3 of residual dusts recovered from brake linings and by direct measurement of the CL 'This research was supported by Center Grant ES 00928 of the National Institute 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. I 110 Copyright 1976 by Academic Press, fnc. AH rights of reproduction in any form reserved. r "" j -< i l \ | FMSI 04724 jHE-A_D..___________ I 111 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 118 million pounds of asbestos is used annu ally 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. Major Constituents ofBrake Linings * 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 1. ' 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-i 1! TABLE 1 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 . Chrysotile asbestos* (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 (SiOj) Cryolite (Na,AlF3) Rottenstone (SiO,) Coke (C) Coal (C) Gilsonite (C) Graphite (C) Carbon black (C) Molybdenum sulfide (MoS,) Fluorspar (CaFt) * See Carroll. 1962; Anderson, 1969; Anderson, 1973; Jacko and DuCharme', 1973; Bark, el al., 1975. * Chrysotile fiber constitutes about 50% by weight of most automotive brakes currently manufac. tured in the United States. COPYRIGHT FMSI 04725 GYNECOLOGIC ONCOLOGY and ENVIRONMENTAL RESEARCH I I ) -- 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 sizes are admixed or even calcined to improve performance characteristics. ' 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 enhancing 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 decompos ition products (e.g., rottenstone, quartz); they act as "heat sinks," reducing bin der 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 dehydroxylation and recrystallization of chrysotile asbes tos at high temperatures) which may accumulate on the surface of the brake lining. The hardness of the forsterite (Mohs, 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, hin dered insofar as possible by the modifiers present in the matrix. Materials of Biological Interest Asbestos, quartz, and heavy metals are constituents of automotive brake lin ings, each warranting special consideration from the viewpoint of biological activ ity. 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 1000C (Carroll, 1962; Anderson, 1969). It is not uncommon during moderate braking action, to attain temperatures as high as 500^0 (Carroll, 1962). Some investigators have suggested that, in addition to bin der 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. (Burwell, 1957). For example, the effects of abrasive wear and macroshear have been investigated'. 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 fatigue which, with binder pyrolysis, can cause brake lining disintegration at COPYRIGHT FMSI 04726 ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY _head______ __ ' ! 113 temperatures far below those requiredfor chrysolite dehydroxylation. Therefore, brake lining disintegration may liberate partially altered, or unaltered, chrysotile -fibers. Thermal Decomposition of Chrysotile Differential thermal analysis indicates that chrysotile undergoes dehydroxyla tion at 650 to 680C and recrystallizes (anhydrous magnesium silicate to forsterite) (Mg2Si04) at about 810 to 820C (e.g., Martinez, 1966; 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, 1966). In general, temperatures in excess of 570C are required for dehydroxylation and incipient forsterite formation in chrysotile. 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 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 purpose 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 [presence of forsterite, but positive identification could not be made using this technique. Identification of Chrysotile by Electron Microscopy Transmission electron microscopy, selected area electron diffraction, and elec- .-j : lWc acknowledge the cooperation of the United Automobile Workers, Local Union No. 259 and the Automobile Dealers Industrial Relations Association in helping us obtain these samples in auto , maintenance shops in the New York area. Each sample was taken from "a typical job" under way . at the time.;-- j COPYRIGHT FNISI 04727 GYNECOLOGIC ONCOLOGY and ENVIRONMENTAL RESEARCH J I <  '*! j- I | 1 : 114 5---------- ------------- j"" _ ______ ______ ______ ___ . 'L tron microprobe analysis of the brake dusts were carried out on each of the ten samples after preparation by a technique which disperses the dust particles in a -- nitrocellulose Film without altering particle size distribution. Free chrysotile fiber- bundles and fibrils were observed in all ten samples (Fig. 1). Selected area elec tron 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). Occa sionally, fibers were observed without characteristic chrysotile morphology, with mottled surfaces and obliterated fibrils, indicating partial or complete recrystalli zation. Electron diffraction patterns obtained from these particles displayed ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY Fic. 1. Electronphotomicrograph of large chrysotile bundle in brake drum dust (38.000X magnifica, lion). Other particles include phenol resin binder_and road dust debris. COPYRIGHT FMSl 04728 i Fig. 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. Pattern in (B) displays "smear ing" of reflections in a "clockwise" manner suggesting interplanar rotation. 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, chrysotile 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 pm in length; virtually all are of respirable size (-5 pm). 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 pm length category, while only 6% were longer than 5 pm. 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, at magnifications of 22,000x that 30% of the fibers were from 0.25 to 0.50 pm in length and that 60% were longer than 0.5 pm. Some discrepancies between our data and those of Jacko and DuCharme may be attributed to their use of the lower magnification (22,000 x vs 42,000x), at which fibers shorter than 0.20 fim 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. FMSI 04729 GYNECOLOGIC O N C O LO G Y and ENVIRONMENTAL RESEARCH t :*v f ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY Fic. 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, a. x 10.800; b. X9300; c. x30,000; d. x30,000. .............................. . __________ __________________ 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 /tm 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 1 '. 'Assistance in providing opportunity for sampling was given by the Department of Air Resources, New York City. _ ._ COPYRIGHT FMSI 04730 HEAD TABLE 2 Length Distribution of Chrysotile Fibers in Brake Drum Dust* Sample 750--I500A N (%) 1500--2250A N (%) 2250- 3000A N (%) 3000--3750A N (%) 1 40 34 11 11 2 32 3 ' 20 23 25 ' 32 25 -- _ 4 26 ' 37 26 5 57 17 ` 4 7 _' 6 23 9 12 12 7 50 26 21 ' 2 8 29 30 21 17 9 6 ' 41 18 - 10 10 11 6 31 31 Fibers counted and sized at 42,000x; all fibers have diameters from 250 to 500A. 117 : Total (%) 96 87 70 r~ 96 : 78 | 56 99 97 75 79 air samples were taken during and after brake repair work and at varying distances 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 fiber 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 /im, 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 ard method in those cities (Castleman et al., 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 20 ft 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_ tionsj}f OSHA prohibit concentrations of 5 fibers/ml or more, longer than 5 /zm, as COPYRIGHT GYNECOLOGIC ONCOLOGY and ENVIRONMENTAL RESEARCH FMSl 04731 ENVIRONMENTAL RESEARCH ond GYNECOLOGIC ONCOLOGY Fig. 4. Removal of^dust from brake drum and back plate by pneumatic air blowing at automobile] garage. 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/ml. It was generally found that there was minimal, if any, effort to control dust in most garages. Workmen do not use respiratory protection. There was little aware ness 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 fibers/ml) at the operator level, but background levels 12 ft away were the same as ' with air jet cleaning. . Asbestos Exposure during Truck Brake Repair and Installation Work Personal air sampling was also conducted at the New York Department of Sanitation truck repair shop, where various kinds of brake application and repair 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 edges of new linings are beveled on a grinding wheel or arcing machine to avoid __noise problems. (Fig. 5). Holes are drilled or punched into the brake lining, which __ COPYRIGHT FNIS1 04732 HEAD 119_ TABLE 3 Asbestos Concentrations during Automobile Brake Service"-6 Fiber concentration Operation Blowing dust out of brake drums with compressed air jet Distance (ft) 3-5 5-10 10-20 Number of samples 4 3 2 (fibers/ml) Mean Range 16.0 6.6-29.8 3.3 2.0-4.2 2.6 0.4--4.8 Background samples taken at varying distance and lapsed times, after brake drum blowing ' Distance from operation (ft) 10 20 12 50 65 75 Time lapse (min) 0 0 5 5 7 14 Concentration (flbers/ml) 0.3 0.8 0.2 0.1 0.1 0.1 - Distance Number of Fiber concentration (fibers/ml) Cleaning brake drums with dry brush Background samples taken 3 minutes after cleaning brake drums with dry brush (ft) samples Mean Range 1-3 2 2.5 1.3-3.6 12 3 0.1 0-0.2 " Fibers 5--100 /tm in length, counted by optical microscopy. - 6 The new proposed Asbestos Standard ofthe U. S. Department of Labor records asbestos exposure in fibers/m3, noting that a workman might respire approximately 8 m3 of air per working day, retain ing an unstudied proportion of inhaled fibers. The above table omits reference to air content of fibers < 5 /im 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 4ftbers/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/ml3) was 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 of fibers were found in the vicinity of the operator. The average of five air samples was about 37 fibers/ml. Area samples, taken up to 30 ft away from this operation, demonstrated the presence of airborne fibers. It was of interest to note that, at the time of this sampling, from eight _to__15 other garage mechanics were working within J.his COPYRIGHT FMSI 04733 120^ ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY Fic. 5. Beveling of truck brake linings at municipal garage. Arrow indicates accumulation of asbestos dust. perimeter and were exposed to asbestos. Fiber levels for other kinds of operations at the truck garage are given in Table 4. Boillat and Lob (1973) have reported fiber concentrations measured during 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/ml. A Comparison of Fiber Levels Visible by Light Microscopy and Electron Micros copy . In the ten brake drum dust samples examined, it was found that asbestos Fibers shorter than 0.4 p.m predominated (Table 2). The OSHA Asbestos Standard does not require that short fibers (< 5 p.m in length) be counted or controlled. This oversight may have considerable biological significance in that 'small chrysotile fibers readily produce asbestos disease (Holt, Mills, and Young, 1964, 1965; __Davis^ 1965 L Pott, Huth, and Friedrichs, 1972; Wagner, Berry and Timbrell, 1973; COPYRIGHT FMSI 04734 GYNECOLOGIC O N C O LO G Y ond ENVIRONMENTAL RESEARCH Fig. 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 afforded an opportunity to collect data on 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 re corded from 0.1 to 3.6 fibers/ml. The other two samples were taken during light grinding of automobile brake shoes.' .. Preparation and Analysis ofAir Samples . One square centimeter sections of the eight membrane filters were mounted, _ dust side downL on microscopic slides and ashed in low temperature activated COPYRIGHT FNISI 04735 l J 122 O T TABLE 4 Asbestos Concentration During Truck Brake Service" Distance Number of Fiber concentration (fibers/ml) v / Operation Renewing used linings by . grinding^ 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 (ft) samples Mean Range 3-5 10 3.8 1.7-7.0 10 2 1.5 1.2--1.7 25 2 0.8 0.6-1.0 60 1 0.2 . -- 3-5 5 37.3 23.7-72.0 8 1 0.6 -- 12 2 0.4 0.3-0.5. 30 1 0.3 -- . 3-5 2 1.5 1.9-2.0 3-5 1 2.4 -- 3-5 1 3.6 -- 15 I 3.1 -- __ " Fibers 5--100 nm in length, counted by optical 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, are broken into particles small enough to allow virtu 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 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 chrysotile present. By estimating the length and diameter of each fiber, and as suming a cylindrical fiber geometry, the mass of chrysotile per grid square is determined. Representative electron photomicrographs of chrysotile fibers and fibrils are shown in Figs. 7 and 8. RESULTS A comparison of the optical microscopic fiber counts and the electron micro scopic total asbestos mass calculations obtained from the eight samples is shown in Table 5. Figure 9, showing the same data, is plotted on logarithmic paper, and visual inspection indicates that a positive correlation exists between the optical . and electron microscopic results, although the data are limited and the amount of. COPYRIGHT ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY FMSI 04736 GYNECOLOGIC ONCOLOGY and ENVIRONMENTAL RESEARCH Fic. 7. Electron photomicrograph of air sample taken during brake drum blowing (sae sample No. 4, Table 5), Large numbers (70-100) of chrysolite, some of which are masked by granular particu lates, presumably road dust (65,000 total magnification). __ _ 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 exposed to about 0.5 mg of asbestos daily in cir cumstances 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 65 ft 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 all, 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 expo sure, 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 COPYRIGHT FMSI 04737 m Z fS 6 z ?m Z Fig. 8. Electronmicrograph of air sample of cluster of chrysotile fibrils in background sample (see sample No. 3, Table 5 (83,000x magnification). ______________________ _____________ 1 I" -------- ` ! ' CO m > asbestos fiber number, mass, and surface area. Additional studies relevant to this . 3n0 x and other kinds of asbestos exposure are needed to confirm and extend these oaa. findings.. It is important to note that particles of asbestos-containing pulverized brake lining were not included in this mass determination. Their importance, in terms of biologic potential, is presently unknown. Z mn ' SUMMARY AND CONCLUSIONS (1) Chrysotile asbestos fiber is a major component of brake lining materials. Q Degradation of the lining is brought about by a combination of factors, which n Onz COPYRIGHT O Oa -< FMSI 04738 HEAD 125 TABLE 5 Comparison of Optical and Electron Microscopic Fiber Counts Operation 1. Blowing dust off drum with air jet (10 ft away) 2. Background to blowing out brake drum (10 ft away) 3. Blowing dust off drum with air jet (20 ft away) 4. Background to blowing out brake drum (20 ft away) J. Background to blowing out brake drum (63 ft away--7 minutes after blowing stopped) . 6. Cleaning brake drum with hand brush 7-. Light grindings of new linings before installation 8. Light grinding new linings before installation . Optical microscopy (fibers/ml) 2.0 0.3 0.4 0.8 .1 3.6 4.7 2.7 Electron microscopy Oig/m3) 1.27 0.2 1.1 0.1 0.2 6.5 53.0 66.0 include thermal stress, material fatigue, and shearing. Modifying agents are in cluded in brake linings which lower the contact temperature between the lining and wheel interface; this, in turn, 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 chrysotile, 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 analysis, using both continuous and step-scan modes demonstrated the pres ence of chrysotile in all dust samples. The proportion of chrysotile ranged from about 2-15%, arid averaged about 3-6%. This included both free fibers and chrysotile^ which survived in pulverized binder as particulates. J^orsterite, th i 1 I GYNECOLOGIC ONCOLOGY ond ENVIRONMENTAL RESEARCH _Fic. 9. Comparison of optical arid electron microscopic fiber counts. COPYRIGHT ii ! FMS1 04739 thermal transformation product of chrysolile could not be unequivocally identified by continuous scan X-ray diffraction. -- (3) The presence of chrysotile asbestos in the ten dust samples was further- verified by transmission electron microscopy, selected area electron diffraction and electron microprobe analyses. Chrysotile was found, both in fiber and fibril form, with unaltered structure and chemical composition. Its frequency of occur rence was consistent with, but lower than the quantitative determination made by X-ray diffraction analysis. However, it should be noted that X-ray diffraction 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 42,000x magnification in the ten samples indi cate that about four-fifths of all chrysotile, in fiber form, is shorter than 0.4 /xm in length. These fibers are too small to be seen by optical microscopictechniques. -- (5) Personal air sampling was conducted during brake repair work in 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/m3). During beveling, an average fiber count of 37 fibers/ml was meas ured. Exposure levels during drilling, punching rivets, and cleanup were also measured. Background measurements show that fiber concentration gradients are produced 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 employees in garages other than brake lining workers are potentially exposed to 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 /xm) and the total chrysotile mass calcula tions 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 work. 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 called 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 known, and warrant investigation._______________ _______________ __ ____________ r COPYRIGHT ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY FMSl 04740 'head' 1 _1 I ..... | 127 ... -- (9) Potentially hazardous asbestos exposure exists during automotive brake servicing. It has 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. 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. (1957). In Proc. 6th Nat'l 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. Berry, E. E. (1971). Thermal analysis of various chrysolites using evolved water analysis techniques. In Proc. 2nd Inti Conf. Physical-Chemical Asbestos Minerals, Louvain Univ. 6-9 September, 1971, paper 2:7 15 pp. . Boillat, M.A.. and Lob, M. (1973). Risk of asbestosis in workers employed in replacing automobile brake linings. Schweiierische Medizinische 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. (1957). Survey of possible mechanisms. Wear, 1, 119-141. Carroll, W. G. (1962). The manufacture of brake linings. Brit. Plastics August, 414-417. 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. In Proc. 2nd Inti. 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 thermal properties of chrysotile asbestosfibers. In Proc. 2nd Inti. Conf. Physical-Chemical Asbestos Minerals, Louvain Univ. 6-9 September, 1971. Paper No. 3:2A, 6 pp. __ __________ __ ____ _ ________ Hatch, D. (1970). Possible alternatives to asbestos as a friction material. Ann. Occup. Hyg. 13, ...... 25-29. ................... "" ' ........... .. ~ Hickish, D. E., and Knight, K. L. (1970). Exposure to asbestos during brake maintenance. Ann. Occup. Hyg. 13, 17-21. Hilscher. W., Sethi. S., Friedrichs, K. H., and Pott, F. (1970). Zusammenhange Zwischen Asbestose and Faserlange. Natun-issenschaften 57, 356. , Holt, P. F., Mills, X., and Young, D. K. (1964). The early effects of chrysotile asbestos dus on the rat lung. J. Path. Bad. 87, 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 . clutch linings from selected mobile sources. EPA Report. 68-04-0020. ___ _____ - - - - -j COPYRIGHT FMSI 04741 GYNECOLOGIC ONCOLOGY and ENVIRONMENTAL RESEARCH I I ... 128 ^ Langer, A. M,, and Pooley, F. D. (1973). Identification of single asbestos fibers in human tisues. In 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 ControlAssoc. 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). Chrysotile 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 mineralogies! 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. 51, 1200-1211. Newhouse, M. L. (1965). Epidemiology of mesothelial tumors in the London area. Ann. N. . Acad. Sci. 132, 579-602. . 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 Congress. (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 powdered chrysotile and benz[a]pyrene. Zbl. Bakt. I. Abt. Orig. 155, 463. . Selikoff, I. J., Churg, J., and Hammond, E. C. (1964). Asbestos exposure and neoplasia. JAMA 188, 22-38. Selikoff, I. J., Hammond, E. C., and Churg, J. (1968). Asbestos exposure, smoking and neoplasia. JAMA 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 Timbrell, 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. : ENVIRONMENTAL RESEARCH and GYNECOLOGIC ONCOLOGY COPYRIGHT FMSI 04742 Xr .A. hr. { 32 Proc. roy. Soc. Med. Volume 70 January 1977 .. ' irregular or nodular interstitial opacities of limited extent and intensity on their films. Silica or asbestos exposure had occurred in 22% of the work force examined. Such exposures had occur- red in various job categories in the titanium facility as well as in prior occupations. Eight of the 26 workers with abnormal X-rays had had silica or asbeslos.exposure. No clear pattern of restrictive disease in relation to X-ray findings could be seen. - Summary and Conclusions Clinically significant or symptomatic pulmonary disease was infrequent in a survey of 207 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 % of workers who had never smoked regularly). This abnormality was not freq- uently accompanied by disabling shortness of breath. Despite the fact that approximately 90% of the group of workers examined had worked for 20 years or more, radiological changes consistent with pneumoconiosis were relatively few. and unrelated to 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 occu- pational exposure associated with titanium pro- duction 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. . Acknowledgtnent: This research study was sup- ported in part by National Institute for Occu- pational Safety and Health Contract CDC-99-74- 91. . - Asbestos Content of Dust Encountered in Brake ' Maintenance and Repair r by A N Rohl PhD, A M Langer pho, R Klimentidis ba, M S Wolff PhD and 1J SelikotT md (Environmental Sciences Laboratory, Mount Sinai School ofMedicine ofthe City University ofNew York, New York, NY 10029) - ' Asbestos in Brake Linings . The composition of automotive brake linings in eludes chrysotile asbestosTibre which comprises about 50% of the friction material. The exposure of garage 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 survives 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 (Lynch 1968, Hickish & Knight 1970, Hatch 1970). Chry- 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 spots' up to 1000C 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, Mizutani et al. 1973). Ac- cordingly, brake lining disintegration by these mechanisms may liberate partially altered or even unaltered chrysotile fibres. . . REFERENCE Miller A, Cbuang M & SdikofT I J .. (1976) American Review of Respiratory Diseases 113, SuppL, p 89 (abstract) ... 9 Analysis ofBrake Drum Dust Initially, ten samples of automobile brake drum dusts from brake repair shops in New York City were collected and examined by optical micros copy, X-ray diffraction, transmission electron mic roscopy and energy dispersive X-ray spectroscopy, to determine the presence of chrysotile. Optical 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 resin binders and road dust. Chrysotile. particularly small fibres, has low optical relief and low biretnngence, which further hinder its identification. Only in rare instances have large fibres, with optical FMSI 04743 ake finings inlich comprises . The exposure lg brake lining :ntly been inmportant issue force is polenpeople in the it was thought : fibre survives its liberated as id repair oper- ressed doubt as irvive the high raking (Lynch :h 1970). Chryemperatures in ise its thermal an amorphous iot spots' up to 1962), the heat er processes, in iribute to demplc, abrasion physical breakal. 1973). Acition by these altered or even ile brake drum Mew York City optical micros>n electron micy spectroscopy, >tile. of chrysotile in opy is hindered trix, consisting olic-type resin le, particularly nd low birefrintification. Only s, with optical Section ofOccupational Medicine . , Table 1 Ckrysodk asbestos content of brake drum dusts X-ray diffraction {step-scan) No.,>/ iies Great Britain 1 West Germany 8 France ** - 1 United States of - America 10 Finland 5 Western Australia 7 No. positive 6m " 5m 1 to 3 4 39 . 29 I sample possibly positive Weight percent Mean Range 1.8 0.7-13 14 0.5-31 13 . 4.3 1.8 1.4 x=14 1.1 10-13.1 0.8-13 0.5-13 Transmission electron microscopy No. positive 8 8 1 10 s .. 7 39 - - 33 ' properties consistent with chrysotile, been obser- onstrated the preservation of crystal structure as . ved with this technique. well (Fig 1). X-ray diffractometry: The ten brake dust samples Fibre size distribution: In ten brake dusts sampled were analysed by X-ray diffractometry, 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 Ak/=(004)) was step-scanned in the fixed-count form and is shorter than 0.4 pm in length. Over ; mode. By comparison with external standards, the 57 % have lengths of about 0.2 pm. At magnifi amount of chrysotile present can be determined, cation 40 000, such a fibre would be about 1 cm j 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 be ; to 15 (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) of the 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 pm 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 diffraction analyses Pott et al. 1972, Wagner et al. 1973, Hilscher et al. ! - are 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 chrysotile in the samples and York City samples. to determine whether a systematic relationship 1 . The thermal breakdown product of chrysotile. existed between optically and submicroscopically Le., forsterite, which might be 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 Transmission electron microscopy (TEM): In order for electron microscopy by a 'rubout' technique lo verify the results of X-ray diffraction analysis, (Nicholson et at. 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 chrysotile to be seen lulose film without altering particle sizes. Both free and measured. Chrysotile was identified in the chrysotile fibre bundles and fibrils were observed eight samples, in both fibre and fibril form (Fig 2). in all 39 samples. Most of the chrysotile retained By measuring a large number offibres at magnifi its characteristic morphology without significant cation 42 000 and converting the volumetric data alteration, and selected area electron diffraction into mass, a concentration per volume of air is patterns obtained on representative fibres dem- determined. Comparison of optical microscopic s' T TT FMSI 04744 34 Proc. roy. Soc. Med. Volume 70 January 1977 fibre counts and the electron microscopic asbestos mass calculations indicates that a positive cor relation exists between the two sets of data. These results show that the standard (OSHA) optical fibre counts may be only indicative of the total asbestos exposure. Asbestos Exposure of Workmen After the identification or chrysotile in the brake drum dusts, asbestos fibre exposure during main tenance and repair was determined by personal air sampling carried out at automobile repair shops. .w taxi fleet repair shops and a municipal truck repair shop in New York City. Air sampling and analyti cal methods Tor the determination of fibre con centrations were in accordance with the OSHA techniques (Bayer et at. 1975). Present regulations of OSHA prohibit asbestos concentrations of 5 fibres per millilitre (f/ml) or greater, longer than 5 pm as a time-weighted average, and con centrations above 3 f/ml will be illegal after July 1976. Peak concentrations or maximum excursions of 10 f/ml are permitted by the regulations. In brake lining inspection and repair, the wheel is removed from 1 monly removed fr means of a jet of c garages in Baltim shown that this is the shops (Castli situation exists in Table 2 show that the breathing zon pressed air blowi gradient, diminish from the operatio to 22 m from such able concentratioc Fig I Electron photomicrographs ofbrake drum dusts, taken at various magnifications, a. the numerous chrysolitefibrils - t hare average lengths of0.4 p>n or less ( x JO 000). H. large numbers of chrysotilefibres imbedded in. and protrudingfrom, . opaque particle, probably pyrolized phenolic resin binder ( x JO 000). c. large chrysotilefibre bundle (x45 000). D. large particle in left centre a] photograph is the same as in c. but cannot be identified at lots magnification ( x 5400) Fig 2 Electron phot associated with opaq I FMSI 04745 I Section ofOccupational Medicine 35 iruck repair ind analytir fibre conthe OSHA regulations ations of S longer than and conil after July 1 excursions ions. r, the wheel is removed from the axle and loose dust is com monly removed from the drum and back plates by means of a jet of compressed air. A survey of 220 garages in Baltimore and Washington. DC has shown that this is the method of choice in 80 of the shops (Castleman el al. 1975). A similar Situation exists in New York City. The data in Table 2 show that fibre concentrations are high in the breathing zone of the operator during com pressed air blowing. An asbestos concentration gradient, diminishing with time and distance away from the operation, appears to occur. Persons up to 22 m from such activity are exposed to measur able concentrations of asbestos. Personal air sampling was also conducted at New York City Department of Sanitation where truck brakes are repaired. Used linings are salvaged by machine grinding to remove dirt and grease from the surface. New linings are bevelled by grinding to reduce noise and improve break-in. Accordingly, these studies relate to levels of as bestos exposure which may be experienced by workers engaged in brake lining manufacturing. Table 2 shows that fibre concentrations experi enced during grinding ranged from 1.7 to 7.0 f/ml of air in the breathing zone of the operator. The background or area samples for this operation ranged from 1.2 to 0.2 f/ml. with a general decrease i t i ti 3J^rs hrysutiiefibrils olnu/inqfrom. 5 000). o. turqe 400) ' Fig 2 Electron photomicroqrapks of personal air samples taken duriitq brake repair Work, dumps of chrysolite lire associated with opaque particles oj road dust and resin binders, a, 8. x 60 000. C, D, x 72 000 FMSI 04746 X 36 Proc. roy* Soc. Med. Volume 70 January 1977 ' Table 2 Pcnoul sir umpK automobile sod truck brake repair Automobile brake repair Blowing dust from brake drums: Distance 1-1.5 m * Distance I5>3 m Distance 3-d m Background <5 min after air jet blowing, distance 3.6-16 ra) Background (7-14 min after air jet blowing distance 19.6-22.6 ra) Peakfibre concentration No. of (fibres per ml) samptes Mean Range 4 13.0 3 32 2 12 2 OS 2 0.1 62..60--2492.4 03-42 01-02 Ol 13 Track brake repair -' Renewing used linings by minding (distance 1-1.5 in) Background to grinding used linings: Distance 3.3 ra Distance 8.3 m Distance 20.0 m . Bevelling new linings Background to bevelling new linings: Distance 2.4 m Distance 3.6 m Distance 9.1 m ` to 2 2 1 4. 1 2 1 23 42 12 OS 372 0.4 1.7-72 12-1.7 06-1.0 . 02 23.7-722 06 02-02 03 . *# away from the operator. From six to ten other mechanics work within an area up to 20 m from this operation are exposed to asbestos as well. Since a person breathes about one cubic metre of air an hour, multiplication of the fibre con centrations by one million gives the number of fibres inhaled during this period. Fibre con centrations measured during bevelling of truck linings were as high as 72 fiml and averaged about 37 f/ml. Background counts were measured up to 9.1 m away from this operation (0.3 f/ml). 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 servicing 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, ES 02565. We are 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, Adel aide, South Australia; Dr Trevor Turner, Adel aide, South Australia; Professor Jean Bignon, Hospital Laennec, Paris, France; Maunu Harme, Geological Survey of Finland. Otaniemi, Finland; Dr G. Gaal, Helsinki University of Technology, Helsinki, Finland; Dr K. Robock and Dr W Klosterkotter. Institut fur Hygiene und Arbeitsme- dizin des Klinikum der Universitat Essen, West Germany. . (1) Implementation of industrial hygiene pro cedures to control exposure. (2) Clinical studies of garage mechanics to de termine evidence of asbestos-related disease. (3) Epidemiological studies of the mortality ex perience 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. Acknowledgment: The authors wish to acknow REFERENCES Bayer S G, Brown TA6 ZumwaWe R D (1975) Document TR-84. US Public Health Service, Cincinnati, Ohio . Boillat MA & Lob M -* 11973) Schweizerische medizinische Wochenschrifl 103,39 BouhuysA (1975) Annals ofInternal Medicine 83,898 Harwell JT (1957) Wear 1.119 *- Carroll WG (1962) British Plastics 35,414 Casllcman B, Camarota L A, Fritsch A J, MazzoccM S It Crawlev R G (1975) Public Health Reports 90.254 . Davis J MJ (1965) Annals ofthe New York Academy ofScience* 132,98 Hatch D 11970) Annab of Occupo HickKh D A Knight K (1970) Annab ofOceupa Hilscber W, Sethi S, Frii j (1970) Satunrisscnschut HoltPF.MObJ 4 You (19(A) Joum^of Pathol l i Lynch J R (1968) JournJefthe A a Mizutani V, Ohara H A (1973) HVor Z3L 3S7 Nicholson W* J, Rohl A ! (1971) In: Proceedings* J Congress. Ed. H M Enc ii New York: pp 136-139 Pott F. HutkFA Friedr (1972) ZentnJbtaztJur i Rohl A N, (wgrr A M, (1976) Environmental R> Wagner J C, Berry G A (1973) British Journal oj Neurotoxic Pi Certain Aliph; by Peter S Spencei and Herbert H Sc! (Departments ofP Saul R Korey Dept Rose F Remedy C Albert Einstein Co. Bronx, New York. During the suram ipheral neuropatl group of employ plant in Ohio, U! disease was chara* sensory loss symtr the feet (Allen e\ affected individual ment where color solvents, were ap coated fabrics. F process required t containing methyl isobutylkctone ( (MBK.) wasgradu 1972 to replace th was in its maxima first case of pcripl tly thereafter. Th into the printing d with other isolate individuals chror gested that this co tics. MBK. prodi FMSI 04747 ie National ciences, ES r Company. >rt under a e NIEHS, assistance in >sor Donald n*d;*Mr L B lustry, Adeljmer, Adel:an Bignon, unu Harme, mi, Finland; Technology, and Dr W 1 ArbeiismeEssen, West ice, Cincinnati, i 103,39 cctrfS& ces 132,98 i Section of Occupational Medicine 37 HafcfcD (1970) Antutls ofOccupational Hvgicne 13,25 HZcItbh D E A Kniphl K L ' f (1970) Annatx o/Occupatitmal Hygiene 13.17 Hibcher W, Sethi S, Friedrichs K H A Pott F (1970) Haturwissvnschaftcn 57. 356 ' Holt P J A Young D K (1964) Journo! ofPathology ant! Bacteriology 87.15 LjnclJR (1968) Journalofthe Air Pollution Control Association 18,824 Mlzntaoi Y, Obara H A Nakajima K (1973) Wear 23.382 - Nicholson WJ, Rohl A*N A Ferraud E F (1971) In: Proceedings of the Second International Clean Air Congress. E<f. H. M England A W T Berry. Academic Press. New York; pp 136-139 Pott F, Huth F A Friedrichs K H (1972) Zentralblattfur Baktvriolouie. Abt. I. Orieinate. 155.463 RoM A N, Langer A M, Wolff M S & Weismao 1 (1976) Environmental Research 12.110 Wagner J C, Berry G A Timbrril V (1973) British Journal ofCancer 28,173 several species of experimental animal (Duckett et al. 1974, Mcndell et al. 197.4, Spencer, Schaum burg, Raleigh & Terhaar 1975). These studies demonstrated that prolonged intoxication by in halation or subcutaneous injection caused the insidious development of symmetrical weakness first in the hindlimbs and later in the forelimbs. The first signs ofperipheral neuropathy developed after 4 to 12 weeks of continuous inhalation of 200 600 parts/106 of MBK, and after 12 to 16 weeks of intermittent inhalation of 1300 parts/10" of MBK. 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 1000 or 100 parts/106 MBK intermittently for periods of 3 and 8 months respectively (John son 197S), the figure of (00 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 ! i Neurotoxic Properties of exposed to MBK alone (Saida et al. 1976). Methylethylketone alone or MBK alone produce no neurotoxic effects (Spencer & Schaumburg 1976). ; Certain Aliphatic Hexacarbons The purpose of the present paper is to emphasize the importance of chronic testing of potentially : by Peter S Spencer PhD . neurotoxic compounds in experimental animals, to and Herbert H Schaumburg md describe the range of hexacarbon compounds i (Departments of Pathology and Neuroscience, which have been identified as neurotoxic agents | Saul R Korey Department ofNeurology, and, finally, to characterize and illustrate the i Rose F Kennedy Center, pathological basis for the onset of the nervous Albert Einstein College ofMedicine, . system disease. A total of seven hexacarbon com ; Bronx, New York 10461, USA) pounds have been tested in this study (Table 1). : During the summer of 1973 an outbreak of pier-. 1 . ipheral neuropathy developed among a large .'Table 1 group of employees of a fabric manufacturing Hexacarbon compounds tested _ _________ __ j plant in Ohio, USA (Billmaier et al. 1974). The (!) /r-bexaneCHjCHvCHXHXH.CH, i disease was characterized by distal weakness and (2) methyl-ff-butylkeione CH,COC'HXH .CHjCHj sensory loss symmetrically in both the hands and (J) 2^-hcxanedione CH3COCH .CH .Coen, (4) 2.3-hexancdiolCH,CHOH(CH.I.CHOHCH, `. j the feet (Allen et al. 1975). The most severely (5) i4-hexanedione CH ,COCH .COCH .CH3 1 affected individuals worked in the printing depart (6) 2.3-hexanedtoneCH,COCOtH.CH.CH, (7) 1.6-hexancdiol HOCH.CH.CH.CH.CH.CHjOH ment where colouring inks, dissolved in volatile 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 use of a 9:1 solvent mixture vent and a minor component of petrol, was indicted | containing methylcthylketone (MEK) and methyl- in several reports as a possible neurotoxic agent I isobutylkctone (MIBK). Methyl-/i-butylkeione (Herskowitz cf al. 1971. Korobkin et al. 1975). ! (MBK) was gradually introduced in the summer of Rats were exposed continuously lb atmospheric | 1972 to replace the MIBK. Methyl-n-butylketone levels of400 to 600 parts/106 of w-hexane for up to was in its maximal use by December 1972 and the five months. 500 parts/10" being the US Threshold ifirst case of peripheral neuropathy occurred shor- Limit Value for n-hexane (sec also Schaumburg & > tly thereafter. The recent introduction of MSBpeKncer 1976). The second compound, mcthyl-n- i into the printing department of the plant, coupled butylketonc. the solvent implicated in the outbreak ' with other isolated outbreaks of neuropathy in of neuropathy, was administered to cats by sub | individuals chronically exposed to MBK. sug- cutaneous injection of 150 mg/kg twice daily for gested that this compound had ncurotoxic proper periods up to six months (.ver also Spencer & ties. MBK produced peripheral neuropathy in Schaumburg 1976). The third compound, 2.5- FMSI 04748 ASBEsTosl'N^fiMK t \m-Ksaoownnn------------------ ;-------- 1745 Jefferson Davis Hwy III ? Suite 509, Crystal Square 4 Arlington, Va. 22-02 f Vol W pp. 53J-549. Pergatooti Press I97S. PnAcd m Great Britain. I I AIRBORNE ASBESTOS IN THE VICINITY 1 OF A FREEWAY \ t \ J. Alste*. D. Watsonf and J. Bagg Dipartment of Industrial Science, University of Melbourne. Parkville. Victoria 3052. Australia (First received 22 December 1975 and in final form 16 February 1976) Abstract--Asbestos fibres taken from fresh or worn brake linings or collected from the atmosphere near a freeway were examined by ele-.,ron microscopy and electron diffraction. The major effect of braking appears to be in separating bunches of fibres and reducing their average length but not in altering their crystal structure. The suggestion that gress changes in the crystal structure are brought about by heal generated during braking is not supported by this work. Airborne samples were collected at points where there was considerable braking and where there was only slight braking. At the point where slight braking took place the airborne concentration was very low and could not be satisfactorily measured. At the point where considerable braking occurred an estimate at 5 s I0? m"1 particles was determined, each particle consisting of a small bundle of fibres. The majority of particles had a maximum linear dimension <2 pm. . INTRODUCTION The concentration of asbestos fibres in the atmos phere may reach high levels in the immediate vicinity of mining the asbestos mineral or manufacturing asbestos products. It has been known for a long time that the inhalation of fibres at these concentrations is injurious to both man and animals (Merewether. 1930). A qualitative standard which has been pro posed by the E.P.A. (News Focus, 1973) is that there should be no visible emissions during the handling and manufacture of asbestos products. One criterion for a recommended quantitative standard is that the concentration should not exceed 5 x 10" fibres m-3 of length Si 5 /;m for a 30 y exposure and that this standard should become more rigorous after July 19"6 becoming 2 x 10" fibres m'3 (NIOSH. 1972: L.S. Dept. Labor. 1972). British and West German proposals agree with the more rigorous standard sug gested above .ichut/ and Woitowitz. 1973). Extensive work has beer, earned out on the health of workers exposed in the industries producing airborne asbestos. Much less work has been carried out on tlte presence of asbestos in the atmosphere far away from any such industry. Asb.--.tos was found in all samples taken from the atmosphere of several cities in Europe which did have an asbestos industry iHolt and Voung. 1973). The asbestos was present chietly as single fibres but a small fraction occurred as agglomerates. No quanti tative estimate of concentration was made bet com pared to other suspended particulates it was small. Preliminary rjv-!t> tor New Y'ork city -bowed con centrations ranging from 11 to 69 ng m'3 with Juph- *Preseii! aCC.'-ss: AC" 1 Ensironics. P.O. Box S. Newpar1.. Victoria \u>;r_!:a. * Present C'.SI.R.O. Division of TriSapiis-ues. Melivurne. Australia. cate samples differing by a factor of 2-3 ISelikoff. 1972; Nicholson vt/.. 1973). Asbestos was also found to be present in all 200 samples taken from the atmos phere of 49 cities in the U.S.A. (SelikofT. 1972). The source of asbestos emissions in the absence of asbestos mining and industry is a matter of specu lation but one strong possibility is from the brake linings of automobiles. These linings arc subjected to considerable wear leading to the release of asbestos dust. In one careful study the release of asbestos was measured by surrounding the brake drum with a col lector and capturing the total emission (Jaeko or /.. 1973). A total emission of 17.S pg km '1 for passenger vehicles and 54.S /ig km*1 travelled for light trucks were quoted as typical values. Not all this emission reached the atmosphere, some depositing upon the ground and some being retained by the brake drum. The fraction which became airborne was e-tim.itcci to be 3 7",, for passenger vehicles and 2.9",. I'or trucks. This research also gave the expected result that heavy braking produced more emission than light braking. Although it is very difficult to convert these results into atmospheric concentrations clearly only very low- concentrations would he anticipated. Lynch (196S1 examined the dust from brake linings and from the appearance of the fibres suggested that the crystal structure of the fibre w as degraded by lic.it released during hraking. Holt and Y'oung (1973) found that fibres collected by them from the atmos phere showed very little evidence of loss of crystal linity. end. therefore, following Lynch's suggestion. eonJa.i.-J building materials were a more likely source !b.-.:i brake linings. Tlte .um ofllic woik reported here was to examine more cio-ciy the possible centi ibimoii that 'make fil ings could make to the asbe-lo- ivicci'irnlioii m atmo'pheie FMSI 04749 5.'4 J. Alste. O. Watson and J. Bagg EXPERIMENTAL A number of methods haw been proposed for the esti- m.itioti of asbestos particles in the atmosphere (Keenan Kupel. 1965: Lane ( of.. 196S: Gadsden et al.. 1970) ha; at the present time the only method of sufficient sensi;;v:ty and selectivity for the very low concentrations in volved is the electron microscopy of samples collected on suitable filters. Atmospheric samples were collected oh a Miilipore niter (VSWP 047. 0.025 pm pore dia.) at an aver age itow- rale of 0.6 I min''. A High-Volume sampler was modified by placing an aluminium face-plate containing a small tube over the inlet to the sampler. A Miilipore filter holder was connected by a plastic tube with a rota meter interposed to the small tube on the face plate. Samples were taken at three locations, (i) on the roof of the Department of Industrial Science. University of Mel bourne. 10 m above street.level and JO m from the nearest traffic. (ii) outside the same building 0.S m above street level, (hi) at the exit of the S-E. end of the Tutlamarine freeway. 0.S m above ground IcvcL This last sampling point was 50 m from the position where brakes were applied :o reduce the speed of vehicles from approx. 100 to 60 km h~'. The total number of vehicles passing all three locations during the total sampling period was very similar and the major difference was the absence, locations (i and ii). or presence. Location (iii). of extensive braking. The sampling period was from (M:00-I7:00 h during November 1973; the weather was fine with only light winds over this period. After the samples had been collected the Miilipore fitters were coated with a carbon film, approx. 20 nm thickness, and then five small pieces (1.5 x 1.5 mm) cut out at random. Each small section was placed on a copper grid, carbon film facing down, and the mem brane materia! removed by dissolution in acetone. Electron micrographs and diffraction patterns were obtained from these specimens using a Phillips EM 200 microscope at SO kV. The electron diffraction patterns were calibrated by evaporating aluminium on to the copper grid and by comparison interplanar spacings. df/iM) could be deter mined. Samples of fresh and worn brake drum linings were obtained from an automobile repair shop and were crushed gently in a mortar and pestle with a few ml of chloroform. An electron microscope grid covered with a smooth film of evaporated carbon was then dipped into this suspension and the chloroform allowed to evaporate. RESULTS AND DISCUSSION ' Figures I 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 of which is a hollow cylinder (McCrone and Delly, 1973), is dearly visible in this micrograph. The electron diffrac tion patterns of chrysotile have been determined and indexed by Yada (1967, 1971). If, Table 1 the interplanar spacings determined from the pattern of fresh brake linings are compared to Yada s values and Che agreement is seen to be exccIlenL 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 but the hollow cylin drical structure is still obvious. The diffraction patternstill consists of well-defined rings and the interplanar spacings derived from these rings are in good agree ment with Yada's values (see Table 1). There was no indication from the diffraction pattern of the presence of forsterite. the name given to thermally-degraded asbestos. It appears that for the wear this lining had received no significant changes in the crystal structure due to excessive heating had taken place. Tempera tures within brake drums may reach S73 K under racing conditions with severe and repeated braking Fig. I. Dust sample from crushed new brake linings. FMSI 04750 Airborne asbestos in the vicinity of a freeway 5S5 i 1 i > ii \ \ l t Fig. i Diffraction pattern from sample in Fig. !. but would be expected to be very much lower under normal city driving. Chrysolite has been shown to maintain its crystal structure until temperatures in excess of sOO K are reached (Yada. 1971; Robock and Kiosterkor.sr. 197?). The observations on the worn brake drums are then consistent with the likely temperatures reached and the known thermal behav iour of chrysotile. Yada (1967. 1971) has shown that electron bombardment inside the electron microscope can lead to production of amorphous material in the fibres and. therefore, excessive exposure during exam ination should be avoided. Table 1. k a!ue u;'aiH/) for chrysolite and brake linings. nm x 10"1 Values for chf'^oiilc (Yada. tv.-T. !97ll Fror* brake hre-.c Worn brake lining Plane (HO \,,U) 4.o*J 4.50 3.65 2.70 2.60 2.51 24J 130 2.15 1.S2 l.SO ! 53 : 4(3 ..'5 i :i 4-I* 3.62 2.62 152 2.45 2.24 113 1.79 f4 132 in 7.21 4.60 3.67 2.67 2.56 2.47 2 2* 110 1.75 1.55 1.33 1.19 (001) (HO) (0201 (0021 (200) (130) (201) (003) (220) (040) (2(12) |IVU| (330) |IN|s) |4u0l (IKiiil Samples taken either on the roof or at ground level near the Department of Industrial Science contained very low concentrations of asbestos fibres (Ftg. 5). Although the rings in the diffraction pattern (Fig. 6) are more diffuse than from fresh linings the interplanar spacing*. shown in Table 2. again match both the values for fresh linings and Yada's values. Although the comparison in Table 2 enabled the pres ence of asbestos to be deduced, no attempt was made to estimate the atmospheric concentration because of its very low value. Samples taken a: the exit from the freeway, how ever. contained a much higher concentration of asbestos particles tr:cs. 7 and S) estimated at an aver age of 5 x 105 particles m" J over the 9 h sampling period. The genera! appearance of the fibre dusters and I'ae presence v other material is very similar to that observed " the worn hrake lining dust. Again the diffraction n...terns do not show significant amounts of amorphous material and match Yada's values (Table 2). Table 2. Values of i!{liU) for chrysotile and airborne asbestos, nm x 10"' Values for chrysotile (Yada. I9(.". !-i'!i |H0 3.65 t* tilt 2 ! 5 i2 lr I.MI . -ui 1.21 >i, Dept. Industrial Seienee > 65 2.20 I..Ml 1.2s Till lama rine freewav exit 3.60 2.15 1.75 MS FMSI 04751 J. Ai.vrt:. D. Watson and J. Bagg Fig. 5. Dust sample from worn brake lining. .1 Fig. 4. Diffraction pattern from sample in Fig. 3. FMSI 04752 Airborne asbestos in the vicinity of a freeway ' 587 Fig. 5. Atmospheric sample collected 0.8 m above ground level at Melbourne University. J I a i. fir > Fig. 6. Drlfr.iUum pattern trom simple in I i FMSI 04753 SSS .* 1^ i. Aish. I). Wacsun and J. Bagg s. .* - s Vv \ .\ : s*/' | F\. > 0l:r.kw\K>n paiicrn from sample in Fig. FMSI 04754 Airborne asbestos in the vicinity of a freeway 539 The particles consisted of small bundles of fibres together with other material which may have con tained binder present in brake linings. Another poss ible source for this amorphous material consistent with a location where braking occurred is wear from tyres. Measurements by other workers (Pierson and Brachaczk. 1975) have shown concentrations of air borne debris from tyre wear from 0.05 to 22 ,ug m"3. The number of fibres in the bundle and their size varied considerably and no attempt was made to count individual number of fibres. The majority of bundles did have a maximum dimension <2 fim. Although these results are limited and of a prelimi nary nature the following points can be made: (i) Electron diffraction has proved to be r. method of great sensitivity in the identification of asbestos particles suitable for the low concentrations found in atmospheric samples. (ii) Asbestos fibres from brake linings operated un der normal conditions have the same crystal structure as asbestos from other sources. The absence of ther mally-degraded material cannot, therefore, be taken as evidence that brakes have not contributed to a particular sample. (iii) The results from the samples collected at the freeway exit suggest that emissions from brakes can become airborne. The concentrations reached are very low, below the recommended exposure standard (NIOSH. 1972; U.S. Dept Labor. 1972). and Consis tent with the prediction by other workers that only a small fraction of the total dust formed becomes air borne (Jacko. ft (if., 1973). Acknowleiltivnienfs--The authors would like to thank Dr. J. V. Sanders. C.S.I.R.O.. Division ofTribophysics Univer sity of Melbourne, for considerable assistance and use of electron microscope facilities. One of us. i. Aisle, wishes to thank A.CL Fibreglass for support during this work. REf-KRKNCKS Gad sen J. A.. Parker J. and Smith W. L. ilVaj Determina tion of chrysolite in airborne asbestos by an i.r. spectro- melric technique. Atmospheric Environment 4, 667 670. Holt P. F. and Young D. K. (1973) Asbestos fibres in the atmosphere of towns. Atmospheric Environment 7, 481- 4S3; 669-670. . Jacko G. J.. DuCharrae R. T. and Somers J. H. (1973) How much asbestos do vehicles emit? Auto Eiu/ny 81. 38-10. Keenan R. G. and Kupel R..E. (1968) Modern techniques for evaluating mixed environmental exposuces to fibrous and particulate dusts in the asbestos industry. Pre-print U.S. Public Health Service. National Centre for Urban and Industrial Health. Cinncinati. OH. Lane R. E. ft ul. (1968) Hygiene standards for chrysolite asbestos dust. Him. Occnp. Hyy. II. 47-69. . Lynch R. J. (1968) 30th Annual Meeting. American confer ence of Government Hygienists. St. Louis. MO. - McCrone W.C. and Delly J. G. 11973) The Partivle Atlas. VoL 3. 2nd Edn. p. 5S6. Ann Arbor Science Publishers. Ann Arbor. Ml. Mereweihcr E. R. A. (19301 The occurrence of pulmonary fibrosis and other pulmonarv infections in asbestos workers. J. InJ. Hyy. 12. 239-257. News Focus (1973) EPA sets final emission standard for asbestos beryllium, mercurv. J. Air Pullut. Control Ass. 23. 393. ' Nicholson \V. J.. Lunger A. M. and Sctifcolf I. 11973* Asbestos in the atmosphere of towns Atnvspheric En vironment 7. 666-668. NIOSH (1972) Criteria for a recommended standard. Occupational exposure to asbestos Document HSM 72-10267 +(1972). U.S Dept, of Health. Education and Welfare: Pierson W. R. and Brachaczk W. W. (1975) In-tratlic measurement of airborne tyre-wear particulate debris J. Air Pollut. Control Ass. 25. 4W-405. Rohock K. and Klostcrkotter W. (19731 Investigations in the cytotoxicity of asbestos dusts. Sntuh 33. 279-283. Schulz A. and Woiiowit/. H. J. (1973) Technical standard values for the admissible working place concentration of chrvsotiic asbestos Stuuh 33. 445-450. SclikofT L J.. Nicholson W. J. and Lunger A. M. 11972) Asbestos air pollution. Arch. Environ, lllth 25. 113. U.S. Dept of Labor. (1972) Washington Information docu ment T2--366. ' Yada K. (1967) Study of chrysolite asbestos by a high resolution microscope. Arty Cryst. 23. 704-707. Yada K. 11971) Study of microstructure of chrysolite asbestos by high resolution microscopy. Hern Cryst. A27. 659-664 April 20, 1979 Mri I. H. Weaver Corporate Director Envir. RAYBESTOS-MANHATTAN 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 NILFISK'S ASBESTO-CLENE systems. Sincerely, NILFISK OF AMERICA, INC. Robert S. Magdgdain President RSM:ds Enclosure FMSI 04756 M#v' VT *>* t^i : t\ hwiiyr *'s >4^ <<x :^7^ THE MOUNT SENA! MEDICAL CENTER OV; OUST.W i- I.1-V: VLW: XIW S.V F APR 4 C Ilia'S * TN'V V'.-V " MLFISA CRN^vW. / Mount Sinai School ot MoTcir.e The Mount Sinai f io-pitul P^R. April 11, 1979 1 ............. . ' C^r; n r *j fi _r * : * ' Mr. Robert S. Magdelain, President Nilfi.sk of America, Inc. 201 King Manor Drive King of Prussia, Pennsylvania 19406 Dear Mr. Magdelain: This will report the results of air sampling tests conducted, in October 1978, to determine chrysotlle asbestos concentrations dur ing 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 elsewhere have demonstrated that free asbestos fibers present in brake drum dusts are predominantly shorter than 5um in length. In particular, it was found that about 75Z of the fibers In such dusts were less than 0.3um in length, as determined by transmission electron microscopy. Thus, the optical microscopic technique used by OSHA for determining asbestos levels in workplaces (in which only fibers Sum 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 number, mass and surface area would be significantly greater than the levels determined using the OSHA fiber-counting method. . Therefore, It was of considerable interest to us to have an oppor tunity to test the efficiency of the Nilfisk Asbesto-Clene System. To do this personal air sampling was carried out on the exhaust of a HEPA-filtered vacuum dust collector and, simultaneously, on a garage mechanic cleaning a brake drum with the Nilfisk brake en capsulation cylinder. Three such tests were made. Background air samples, also using personal air pumps, vrere 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 step-- scan mode to quantitatively determine asbestos contents, using a technique previously published. Asbestos was found In all three samples, ranging from 2.5Z to 4.5% by weight. The membrane filters were analyzed by both transmission electron microscopy (X25.000) and by the standard 0SK\ fiber-counting technique, employing phase contrast optical microscopy. The results are as follows: . FMSI 04757 Mr. Robert S. Magdelain, President Page 2 April 10, 1979 Sample Description Nanograms/cu meter (electron microscopy) Fibers/milliliter (optical microscopy) N--1 N--2 N-3 TEST ?1 Background (70 feet from operator) Operator (breathing zone -- 6 ft. from dust collector) Dust collector (HEPA-filtered vacuum) 400 0 0 0 0 0 N-4 N-5 N-6 N-4 NT-7 N-8 Background (70 feet from operator) Dust collector (HEPA-filtered vacuum) Operator (breathing zone -- 6 ft. from dust collector) TEST 3 Background (same as in Test #2) Operator (breathing zone -- 6 ft. from dust collector) Dust collector (HEPA-filtered vacuum) 615 0 59,000 615 0 0 - 0.12 0 0.5 0.12 0 0 FMSI 04758 Mr. Robert S. Magdelain, President Page 3 April 10, 1979 Remarks and Conclusions: The tests demonstrate that asbestos levels are virtually eliminated by the use of a system employing brake encapsulation device connected to a HEPA-filtered vacuum dust collector. Without the use of such equipment, fiber concentrations during compressed air jet-bloving of brake drums ranged from 6.6 to 29.8 fibers/nilliliter. However, when the Asbesto--Clene System was used, fiber concentrations on both the mechanic and dust collector exhaust were not detected, as verified by transmission electron microscopy. An important exception to this is observed in Test #2, the sample taken on the operator. Prior to this test, this mechanic had worked on brake jobs without using the Asbesto--Clene System and without changing his work clothes. This exposure had resulted in contamination of his clothes, re flected in the high residual asbestos concentration of 59,000* nanograms/cubic meter and 0.5 fibers/milliliter. In contrast, the operator in Test 1 and Test #3 wore clean coveralls. This points up the need to adhere to the OSHA regulations concerning special clothing, change rooms, etc. to minimize contamination. The background asbestos measurements, of 400 and 615 nanograms/ cubic meter, are consistent with other background measurements taken during brake repair work. They are the result of residual contami nation 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 circumstances. The data indicate that the Asbesto-Clene System represents an outstanding advancement 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. ANR: jm Arthur N. Rohl, Ph.D. Environmental Sciences Laboratory r FNISl 04759 * TAAcK YscIMiSSiD ' Correspondence --- - -- - - Asbestos Health Hazards There have been a lot of stories lately about the hazards of breathing airborne asbestos fibers. Is asbestos still used in brake linings? It is common practice to blow the brake dust out with compressed air.to clean the brakes. Does this present a health hazard? Is there a risk to motor ists 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. As bestos has a high resistance to heat and is still commonly used as insulation or molded (with other materials) into clutch and brake linings. In molded form as bestos is safe but when the fibers are released (from wear or from cutting or sanding the moldedmaterial), theypresent an insidious health hazard. Thefibers are so brittle that when they are broken, they tend to 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 as bestos-relateddiseasefor 10-35years after the first exposure to asbestos particles. After this incubation period thefibers can cause asbestosis, a disease characterized by severe scarring of the lung tissue, and mesothelioma, a cancer ofthe lining ofthe chest and abdomen. Asbestosis usually doesn't kill directly. Its victims generally succumb to related respiratory infections such as bronchitis or pneumonia. Ex posure to asbestos fibers also greatly in creases the risk ofcancer ofthe lungs and esophagus, stomach, kidneys and larynx. Cases have beenfound wherefamily mem bers ofworkers exposed to asbestosfibers developedasbestos-related diseasesjust from exposure to asbestos fibers on the worker's shoes and clothing. Motorists and pedestrians have little to fearfrom inhaling brakedust. There issome brake dust in the air near streets and highways, but thenumberofparticles is very smallandthey tendto settle out ofthe air, so the overall risk is virtually nonexistent. To reduce the risk of asbestos-related' diseases, avoid contact with asbestosparti cles, especially airborneparticles. It's usu ally a good practice to clean any compo nent before reassembly, but' with brakes and clutches, it's better to leave the brake or dutch 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 shouldn "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. 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