Document MoG4G4jkOQErOgyRJVzGxBEjL

FILE NAME Brakes BRK DATE 1986 DOC BRK097 DOCUMENT DESCRIPTION Journal Article - Asbestos Dust Exposure During Break Repair ause lung 285-294 h^/ufigkeit 218-219 .6 .6 Suppl American Journal of Industrial Medicine 10 63 712986 Asbestos Dust Exposure During Brake Repair K. R^delspergerPhD H. Jahn ING B. Br^...ckelING J. Manke PhD R. Paur MD and H.-J. Woitowitz Prof Dr Med * About 10,000 tons of chrysotile per year are used in the Federal Republic of Germany the production of friction materials During brake repair an unknown number of approximately 300,000 mechanics in automobile service stations are exposed to asbestos dust In a field study asbestos fiber concentrations during brake repair were measured Occupational histories and chest rays of brake service mechanics are being examined Ninety dust measurements in 76 service stations were made by phase contrast micros- copy and by scanning transmission electron microscopy By electron microscopy ex- tremely fine chrysotile fibers with lengths < 5 ...mwere identified in brake drum dust Fibers with lengths > ...mconstituted less than % of all chrysotile fibers counted in brake drum dust Short asbestos dust exposures were measured by light microscopy in 101 personal samples during blowing out of brakes and grinding and turning of brake linings During blowing out of car brakes as well as during grinding of brake linings the product of fiber concentration with length > 5 ...mand sampling time amounted to about 4-5 fibers min corresponding to a concentration of 106 fibers over 4-5 min For trucks and buses higher amounts of 5-10 106 fibers min were observed during these operations From occupational histories of 210 vehicle mechanics an average duration of employment of x -s = 21 -10 years and a mean cumulative fiber dose of x -s = 0.54 -1.1 106 fibers years were calculated Key words brake repair auto mechanic asbestos exposure light and electron microscopy occupational history fiber dose INTRODUCTION The amount of brake lining material used during 1975 in the Federal Republic of Germany was estimated to be 26,000 tons Ullman et al 1978 The asbestos content of brakes used in the FRG ranges from 10-70 weight- with an average of 35 weight- Infrared spectographic analysis of 18 samples of brake material resulted se in the following reading of chrysotile Jahn et al 1985 X -s = 30 -11 weightIn accordance with these data it would appear that the asbestos content of brake material increased from 9,000 year in 1975 to about 12,000 year in 1980 and dropped to 10,000 year in 1983 G Schmidt 1984 personal communication Institute and Polyclinic for Occupational and Social Medicine University Giessen Federal Republic of Germany Address reprint requests to Dr. K. R^delspergerInstitute and Polyclinic for Occupational and Social Medicine of the University of Giessen Aulweg 129 6300 Giessen Federal Republic of Germany Accepted for publication February 18 1986 3 * '1986 Alan R. Liss Inc. 64 R^delspergeret al A large percentage of the approximately 300,000 car mechanics in the F.R.G. have been exposed to asbestos dust during the cleaning of brake systems and the machining of brake linings It is the aim of this study to estimate the to asbestos dust for this large group of persons exposure Similar to earlier studies on the use of products containing asbestos Heider- manns et al 1978 R^delspergeret al 1980 Woitowitz and R^delsperger1983 a risk assessment is made on the basis of ) dust measurements during brake service 2 screening for fibrogenic reactions by chest rays and 3 evaluation of standard- ized work histories Our intent is to examine a group of about 400 vehicle to date 210 have been examined mechanics MATERIALS AND METHODS During the maintenance of automobile brake systems 90 dust measurements in 76 garages were taken with static and personal samples In general personal sampling was extended over the whole service operation which lasted 1 h or more but in some cases personal sampling was limited to certain generating work operations Therefore depending on the duration of the work operation sampling time varied from less than 3 min to more than 1 h Fiber concentrations were determined by light and electron microscopy Fibers with lengths > 5 ...mwere counted with phase contrast light microscopy using the reference method of the AIA Asbestos International Association 1979 In addition counts of fibers of lengths 5 5...mand fibers of all lengths were made by scanning transmission electron microscopy at magnifications of 6,300 and 29,000 Since it is suspected that the mineral structure of fibers is altered during the braking process all fibers were examined by energy dispersive ray analysis and electron diffraction In addition to the dust measurements an epidemiological sectional study was planned for a group of 400 car mechanics who have been involved in brake maintenance for at least 10 years A standardized occupational history was adminis- tered to each individual and an extended medical examination made To date 210 occupational histories describing 459 different sets of working conditions under which brake maintenance is carried out have been evaluated . RESULTS Working Operations . The number of working operations which were registered in 76 automobile garages dufing dust sampling can be seen in Table The use of exhaust ventilation is also indicated Compressed air was used to blow out loose dust in 15 of 36 garages servicing cars and in 19 of 40 garages servicing trucks or buses Special exhaust ventilation systems were used during blowing operations in 8 of the car garages and in 10 of the bus and truck garages In addition to compressed air blowing brushing and the use of solvents were observed Only brake systems heavily contaminated with oil and dirt were cleaned with hot water Fitting of new brake linings for cars was done with special grinding machines in 20 garages Although each grinding machine was combined with an exhaust ventilation none of the filter bags were suitable for asbestos except in 3 garages i { , 1 4 i : j . 128 128 Or Bl M Tu b aw bF TA Mi _ _ Blo Dry RIV Gri Tu Con aPh Sixt dev Gri in for equ of | gar veh Co con thar of a bus 1 fi con grin mea lelsesss F.R.G. and the sure to Heider- 983 a service andardhanics ments in impling in some rations varied . Fibers sing the ddition canning Since it process fraction al study in brake adminisTate 210 er which tomobile ulation is servicing entilation Jin 10 of g and the .th oil and machines n exhaust \ garages Asbestos Dust Exposure During Brake Repair 65 TABLE I. The Number of Work Operations Releasing Dust Observed During Brake Repair in 76 Automobile Maintenance Shops Operation Blowing out dust Machine grinding of drum brake linings Passenger car n = 36 15 8 20 20 Truck bus n = 40 19 10 43 Turning of drum brake linings 34 11 aWith exhaust ventilation + For 17 of these systems the filter bag was not suitable for asbestos TABLE II Concentrations of Fibers With Lengths > 5 ...mDetermined by Phase Contrast Microscopy " Brake service in automobile repair shops Fiber concentration 106 fibres Passenger car Truck bus Operation Blowing out Dry brushing = 31 4 4 _ 0.10 0.09 n = 36 4 1 7 0.05 0.15 0.10 Riveting off and on Grinding by hand Machine grinding - 7 0.12 1 0.39 5 0.06 18 0.08 - Turning Combinations 11 0.04 5 0.08 of fibers with length > 5 ...mPersonal sampling for > 30 min Pshe asve econ ntramsetamsiucrreomsecnotpsy were made of personal air samples taken during brake service Standard deviations approximately equal mean values Grinding of brake linings was only done in 4 out of 40 garageussesderavitcuirnngitngrumcakcshiannde in one of these with exhaust ventilation Thirty garages In addition to the stationary machine special movable for fitting wbirtahkea lroitnaitnignsg cutting tool was used which could be mounted to the axle machine in 11 eofqutihpemetnrtuck Exhaust ventilation was also available for the turning servicing trucks In general blowing out and grinding only take a few min garages for each vehicle On the average the turning of brake linings takes about 30 min per vehicle Concentration of Asbestos Fibers Table II shows the results of 67 measurements of fiber Light microscopy concentrations during personal air sampling of brake repair work for periods of more than 30 min Values are specified for different working operations involving emission of asbestos dust during the maintenance of cars compared with trucks trailers and buses about 0.1.106 0.1.106 0.1.106 fibers 106 fibers = Average fiber concentrations were A 1 fiber of lengths > 5 for all but one of the working operations ...m concentration of 0.39 106 fibers of lengths > 5 ...mwas reached during machine The sampling time for this grinding of brake drum linings in a truck garage measurement was about 1 h time is about 1 h or Because of the short duration of dust generation sampling less Therefore the average fiber count for all measurements in Table II was only Se + 66 R^delspergeret al TABLE III Concentrations and Doses of Fibers With Lengths > 5 m Brake Service in Automobile Repair Shops Concentration and Fiber Dose" Fiber concentration X -s Sampling time t min [ 106 106 fibers fibers n m m.min m.min 1 /3 < 30 30 < < 60 t > 60 - 227 227 227 5.5 -5.8 0.47 -0.48 0.09 -0.06 0.08 -0.07 4.8 4.8 4.6 3.7 -2.5 7.4 5.5 aPhase contrast microscopy of fibers with lengths > 5 ...mAnalyses of 101 personal samples by phase contrast microscopy The effect of different sampling times is shown Personal sampling in the breathing zone eight fibers per 100 fields Because of this the precision of measurement is very low and the detection limit corresponds to a count of about one fiber per 100 fields for an unused filter ; In Table III 101 measurements with sampling times from < 3 min to > 60 min are compared For all working operations the average concentration decreased considerably as the sampling time increased For 14 short measurements with sampling time < 3 min the maximum concentration was 20 . 106 fibers The average reading was 5.5 - 106 fibers Because of the generally short duration of dust emission the average concentration decreased to less than 0.1 106 fibers if the sampling time exceeded 30 min In addition in Table III fiber concentration is compared with fiber dose which is calculated as the product of concentration and sampling time In contrast to the fiber concentration the fiber dose is generally independent of sampling time There- fore comparison of the emissions of asbestos dust during the different working operations is possible even if the sampling times are different Moreover fiber dose is a suitable parameter for estimating the exposure of workers during a short emission of asbestos fibers Table IV specifies fiber doses for fiber lengths > 5 ...mand for all sampling times From 40 measurements made during the repair of cars the average fiber dosesare about 4 106 fibers min for dry brushing and grinding and 5 - 106 fibers m min for blowing out Generally higher average values are obtained from 46 measurements during the repair of trucks and buses For machine grinding for example they are about 10 10---fiber min The doses can be compared to the limit value of 1 - 106 fibers with lengths > 5 ...mwhich has been adopted in the Federal Republic of Germany which results in a maximum permissible dose of 480 - 106 fiber min for an h shift Electron microscopy Fibers with lengths of 5...mon Nucleopore filters were counted at a magnification of ^ 6,300 in the scanning transmission microscope In comparison to the results shown in Table IV the dose of chrysotile fibers was considerably higher For instance an average reading of 20 106 fibers min was seen in three measurments made during blowing out of truck drum brakes A Operation Blowing out Dry brushing Riveting off and on Grinding by hand Machine grinding Turning Phase contrast mich Brake service was ' equal mean values reading of x - - ments made duri Static samp microscopy Co 5...mwere es than 1 h Fiber chrysotile meta study 1,219 fib examined by en percent of thesc Other stud Heidermanns et 1985 Rohl et al electron microso 1 weight- in braking operatio confirmed by o few fibers of le of dust blown |) observed at m the crystalline ... dispersive ra in brake drum ( 1985 Therefo magnification o chrysotile fiber Occupational The occup ics had been en of employment XS XS ) 1.106 1.106 fibers m.minm.min 4.8 4.6 -4.9 3.7 -2.5 7.4 5.5 les by phase the breathing > very low elds for an to > 60 . decreased ments with mThe duration of fibers ose which rast to the ne There- it working fiber dose short I sampling tiber doses 106 fibers d from 46 Ending for ith lengths ich results it TM filters ncroscope fibers was ./m min brakes A Asbestos Dust Exposure During Brake Repair 67 TABLE IV Dose of Fibers With Lengths > 5 m Brake service in automobile repair shops fiber dose [ 106 fibres min Passenger car Truck bus Operation n 40 X n = 46 Blowing out Dry brushing Riveting off and on Grinding by hand Machine grinding Turning Combinations nono 4.7 nono 4.0 nono - 8 5.3 1 9.3 7 9.0 _ nono 3.9 _ nono 3.9 4 9.9 _ - 21 8.6 14 3.8 5 4.4 Phase contrast microscopy of fibers with length > 5 ...mPersonal sampling for < 3 to 2 60 min service was done most commonly for one car or one axis Standard deviations approximately equal mean values reading of x - s = 35 45 106 fibers min was obtained in eight measure- ments made during turning of truck drum linings Static sampling away from the working operation was also evaluated by electron microscopy Concentrations of less than 0.03 106 asbestos fibers with lengths 5...mwere estimated from these background counts when sampling time was more than 1 h Fiber counting by light microscopy is nonspecific for asbestos Apart from chrysotile metal fibers and other fibers may be released from brake linings In this study 1,219 fibers with lengths > 5 ...mfrom air samples in repair garages were examined by energy dispersive ray analysis and electron diffraction Seventy percent of these fibers were identified as chrysotile Other studies have been reported on the chrysotile content of brake drum dust Heidermanns et al 1978 Jacko et al 1973 Lorimer et al 1976 R^delspergeret al 1985 Rohl et al 1977 Williams and Muhlbaier 1982 Rohl et al 1976 In several electron microscopic studies brake drum dust showed an asbestos content of less than 1 weight- indicating a partial physical breakdown of chrysotile fibers during the braking operation leading to a large number of short thin fibers These results are confirmed by our study As shown in Figure 1 at a magnification of 6,300 only a few fibers of lengths 5...mare seen After air sampling on Nucleopore filters of dust blown from brake drums numerous fibers usually of lengths < 2 ...mwere observed at a magnification of 35,000 x50,000 and x60,000 Since alteration of the crystalline structure of these fibrils is possible electron diffraction and energy dispersive ray analysis were also done It was found that the thin fibers observed in brake drum dust did not differ from fibrils of chrysotile R^delspergeret al 1985 Therefore in brake drum dust even under electron microscopy evaluation at a magnification of 6,300 chrysotile fibers of lengths 5 5...monly form % / of chrysotile fibers of all lengths measured at a magnification of X29,000 Occupational Histories The occupational histories of 210 car mechanics were evaluated These mechanics had been engaged in brake maintenance for at least 10 years The average duration of employment as a car mechanic was x -s = 21 -10 years 68 R^delspergeret al ian all typ 83 dru tru bus ma bee dos car des car fib acc yea fibe was The mec TAR Dust Fig 1. Asbestos fibers in brake drum dust Scanning transmission electron microscopy at different magnifications Upper left 6,300 upper right ^ 35,000 lower left ^ 50,000 lower right x60,000 x60,000 Whereas at a magnification of 6,300 lower borderline = 14 ...monly a few fibers are visible at higher magnifications numerous unit fibrils are observed at different it x60,000 x60,000 e visible at Asbestos Dust Exposure During Brake Repair 69 Since most of the mechanics had more than one employment position altogether 459 job profiles were described Nine car mechanics gave descriptions of jobs where they had not repaired brakes themselves but had been exposed to asbestos dust generated by others Table V shows the percentage of job profiles that involved brake maintenance work and the number of vehicles with brake repairs per week classified according to type of vehicle The average number of clutch repairs per year is also shown In 60 of the job profiles mechanics repaired car brakes averaging 4.6 jobs per week In these cases the duration of repair work was approximately 2 On average the brakes of trucks or buses were repaired 2.6 times per week by those who did such work The average duration was approximately 4 h The duration was about 2 h for all other vehicles e.g. fork trucks Clutch repair also took an average of h Mechanic work activities during brake and clutch repair specified according to type of vehicle are shown in Table VI In almost all repairs either blowing out 7583 or dry brushing 54-59 of drum brakes took place Machine grinding of drum brakes is described in 25-36 and grinding by hand in 55-75 of the jobs for trucks buses and cars whereas turning 6-64 was mainly restricted to trucks and buses The cutting and drilling of brake linings reported in 11-26 of the jobs mainly occurred before 1960. Since then precut and predrilled brake linings have been used From dust measurements and occupational histories as shown in Tables VI dust exposures expressed as a cumulative fiber dose can be calculated as follows A dose value as shown in Table VI is equivalent to the dose for the maintenance of one car Dose values per car can be calculated if the frequency of work operations described in Tables IV and VI are known for a particular job Taking the number of cars repaired per year Table V and the duration of employment the cumulative fiber dose per job can be calculated All jobs of the car mechanics are taken into account The unit of measurement fibers min is converted into fibers year assuming 240 working shifts per year each of 480 min duration The cumulative probability distribution function of cumulative fiber dose for fibers with lengths > 5 ...mis shown in Figure 2. For % of the 210 workers there was no measurable fiber dose since they were only indirectly exposed as bystanders The median value is 0.3 - 106 fibers years for about % of the vehicle mechanics the cumulative fiber dose exceeds 1.106 1.106 1.106 fibers - years Thus the TABLE V. Occupational Histories of 210 Vehicle Mechanics With Potential Exposure to Abestos Dust No. of employment histories repair reporting reporting brake or clutch repair work by vehicle No. of vehicles rerpepairedaired per week Brake repair n % X - Passenger car Truck bus Other vehicles Clutch repair 275 8475 209 8475 32 8475 278 61 4.6 -4.6 2.6 -3.9 3.7 -5.0 1.8 -2.0 Percentage of 459 employment histories of 210 vehicle mechanics In 33 histories mechanics were exposed only as bystanders etre 70 R^delspergeret al TABLE VI Occupational History of 210 Vehicle Mechanics With Potential Exposure to Abestos Dust Operation Passenger cars 198 Trucks buses No. of jobs - 100 133 Percentage of job profiles that involved indicated operation Mixed 78 Blowing out 76 Dry brushing u Riveting off and on 86 Grinding by hand 75 Machine 75 83 54 59 93 87 56 55 grinding Turning Cutting and drilling 36 25 33 36 64 33 14 11 26 Four hundred nine jobs of 210 car mechanics In 50 other jobs the mechanics did not perform brake repairs of passenger cars trucks or buses 99 % 95 M 210 90 rn. distribution distribution 70 - distribution distribution l | ! l a | ! | \ I Cumulative 10 | Cumlative ---- Cumulative \ Cumulative 0 25 Fibre dose | | | It | 1 1.5 2 3 length > 5...m [ 106 fibres * years Fig 2 Exposure of 210 vehicle mechanics during brake maintenance Cumulative probability distri- bution function of cumulative fiber dose for fibers with lengths > 5 ...mFor 99 of all mechanics exposure is less than 3 106 fibers - years For two further mechanics % doses of 7 and 13 106 fibers years are calculated average value amounts to x + s = 0.54 - 1.1 106 fibers . years This corresponds to an exposure of about 6 months with an asbestos fiber concentration of 1. 1. 106 fibers with lengths of > 5 ...m In 1981 Nicholson et al estimated about 350 asbestos cancer deaths per year among car mechanics for the United States This number was based on an average fiber exposure level of 0.1 to 0.3 106 fibers Compared to our results of an average dose of 0.54 106 fibers years during an average period of 21 years that tion brak CON low fibe Blov less : Con sam fibe fibe micr fiber unce taine data the c to the been roofe and I expo mw and p has b been out a are c ACK Proje REFE Asbest e to Abestos Mixed 78 83 59 84 Ma ey 55 metr 33 gaes i 33 26 perform brake 3 ars bability distriall mechanics 17 and 13.106 13.106 13.106 years This centration of ths per year an average results of an of 21 years Asbestos Dust Exposure During Brake Repair 71 that concentration estimate seems to be at least four times higher than the concentration estimated in our study Four cases of mesothelioma have been observed among brake repair workers seen as patients in our Polyclinic Paur et al 1985 CONCLUSIONS Asbestos dust measurements in garages during brake service operations show low fiber concentrations typically about 0.1 106 fibers average and also low fiber doses : The working conditions are generally characterized by short exposure Blowing out and machine grinding take only min and the time taken for turning is less than 1 h per vehicle All results are considerably below the existing German Technical Guiding Concentration TRK of 1 106 fibers with lengths > 5 ...mwhen a minimum sampling time of 1 h is taken Electron microscopy of brake drum dust does not indicate a high occurrence of fibers with lengths > 5 ...mhowever there are very high concentrations of short fibers Mass concentration of asbestos estimated from scanning transmission electron microscopy indicates the mass of fibers as < 1 weight- R^delspergeret al 1985 Fiber concentrations for certain working operations are characterized by low fiber counts and therefore by a high uncertainty factor Furthermore there is a high uncertainty in the knowledge of the frequency of different working operations ob- tained using a standardized occupational history However the inconsistency in these data inasmuch as it is measurable has no great influence on the calculated size of the cumulative fiber dose The data also allow the ranking of the workers according to the severity of exposure An average value of a cumulative fiber dose of 0.54 106 fibers years has been obtained This dose is one order of magnitude lower than an estimate made for roofers cutting asbestos cement at building sites R^delspergeret al 1980 Woitowitz and R^delsperger1983 It is about one order of magnitude above the environmental exposure which in the Federal Republic of Germany is usually less than 1,000 fibers mwith lengths > 5 ...m Some changes in working conditions have taken place Nowadays only precut and predrilled brake linings are used Machine grinding is less frequent for cars and has been replaced by turning in the case of trucks and buses Exhaust ventilation has been introduced almost universally during grinding and to some extent during blowing out and turning These changes have to be mentioned when cumulative dose values are calculated from results of dust measurements and occupational history ACKNOWLEDGMENT Supported by the German Federal Ministry for Science and Technology Bonn Project No. 01 VD 2900 REFERENCES Asbestos International Association AIA 1979 Reference method for the determination of airborne asbestos fibre concentrations at workplaces by light microscopy Membrane filter method London en 72 R^delspergeret al Hauptverband der gewerblichen Berufsgenossenschaften e.V. ed Heidermanns A Prochazka R Riediger G Woitowitz H Valentin F K^...hnenG Sch^...tz H Henke R Woitowitz RH Holzhauser der gewerblichen Berufsgenossenschaften V. Bremsendiensten Reinhalt Jahn H R^delsperger K Br^...ckel B Manke J Woitowitz H 1985 Asbeststaubgef^/hrdung in Luft 80-83 Jacko MG DuCharme RT Somers JH 1973 Brake and clutch operation Automobile emissions generated during vehicle engineering meeting Detroit Michigan May 14-18 pp 1-20 Lorimer WV Rohl AN Miller A Nicholson WJ Selikoff IJ 1976 Asbestos exposure of brake repair workers in the United States Mount Sinai J Med 207-218 Nicholson WJ Perkel G Selikoff IJ 1981 Cancer from 1980-2000 In R. Peto M. Schneidermann occupational asbestos exposure projections Spring Harbor Laboratory pp 87-111 Eds Banbury Report No. 9. New York Cold Paur R Woitowitz H R^delspergerK Jahn H 1985 Pleuramesotheliom bei Bremsreparaturen im Handwerk nach Asbeststaubgef^/hrdung 366 Kasuistische Beobachtungen Prax Pneumol 362 R^delspergerK Woitowitz H Krieger HG 1980 Estimation of building sites Biological effects of Mineral exposure to asbestos dust on Fibres Vol 2 J.C. Wagner Lyon Scientific Publications No. 30 PP 845-853 R^delspergerK Br^...ckelB Jahn H Manke J Woitowitz H 1985 Asbestemission bei gen Reinhalt Luft 26-31 Bremsvorg^/n- Rohl AN Langer AM Klimentidis R Wolff MS Selikoff IJ tered in brake maintenance and repair Proc Roy Soc Me1d93727-A3sb7estos content of dust encoun- Rohl AN Langer AM Wolff MS Weisman I 1976 Asbestos repair Environ Res 110-128 exposure during brake maintenance and Ullmann D Eggersdorfer R K^nigR 1978 Analyse der Asbestindustrie Bericht des im Auftrag des Umweltbundesamtes Bericht 4/78 Berlin Erich Instituts Williams RL Muhlbaier JL 1982 Asbestos brake Schmidt Woitowitz H R^delspergerK 1983 emissions Gesundheitsrisiko Environ Res 70-82 Berichte 475 313-324 bei der Anwendung asbesthaltiger Produkte so shet Nee | AN Sic REIN SA R N EE A RaS 2 EATele ee <2 = wine sercamieee ee $s mansnk Nit 0 Key v INTP asbes used 1 reside expos Pipe 1 repres conce about mortal years local u Environ Address Cancer ! Accept