Document pejQVjnqK5oX4dLYj5bJ7Z6OD

FILE NAME Brakes BRK DATE 1973 June 4 DOC BRK106 DOCUMENT DESCRIPTION Technical Report from Ford Motor - Asbestos Emissions from Brake Dynamometer Tests . dew ee ee we ee mee et eee mo eee dee Wee Cake ee ew es ed . ee enn FR.?P:94 REPORT No. 73-64 ASBESTOS EMISSIONS FROM BRAKE DYNAMOMETER TESTS OB) No by A. E. Anderson REPORT Mechanical Research Department and R. L. Gealer Chemical Engineering Department and R. C. McCune and J. W. Sprys Technical Services & Administration AY | se SCIENTIFIC ~.? 6 awe Tw . 4 RESEARCH RESEARCH RESEARCH SCIENTIFIC RESEARCH se TECHNICAL REPORT t., ous 8000 0086 81 % a TECHNICAL REPORT No. SR 73-64 SCIENTIFIC RESEARCH STAFF PROJECT NO DATE June 4 1973 FORD MOTOR COMPANY ASBESTOS EMISSIONS FROM BRAKE DYNAMOMETER TESTS by A. E. Anderson R. L. Gealer R. C. McCune J. W. Sprys SUMMARY Dynamometer tests of a production disc brake provided new information isokinetic- on asbestos fiber emissions during breakin use conditions Both ambient air and brake normal use and high cooling were sampled temperature clarification ally using 0.45 um filters Examination of test and background filters to maximize fiber detectability the use of required a process transmission electron microscopy at 40,000 X for detection and electron diffraction for positive asbestos was found to be identification converted to a of asbestos fibrous fibers Most of the material by the high lining flash temperatures of the braking surface Less than released as asbestos fibers The concentration 0.02 of the lining wear was of asbestos fibers in the was conservatively estimated at less urban atmosphere due to brake usage than 0.07 x 109 grams per cubic meter Based on this upper bound the use as a source of atmospheric asbestos of brakes was judged to be not significant APPROVED folm John E. Mayer Jr. Mechanical Research Manze . Manager Department f? 1 vw wt ry SV J. V. Petrocelli Manager Chemical Engineering Department , T. P. Hopkins Manager Technical Services & Administration 8080 0087 fens * INTRODUCTION Asbestos has been a major constituent of automotive friction materials for more than 50 years It is used to impart strength flexibility and heat resistance to a brake lining and to enhance friction and wear properties Most present brake linings use resin or rubber binders and chrysotile asbestos together with organic and inorganic friction modifiers and fillers The asbestos content varies with formulation from a low of 25 to about 65 by weight Minimum asbestos levels are found in some high performance European disc brake linings which are highly filled with metals and inorganic constituents linings in the U. S. average about 50 asbestos content Brake Of a total U. S. annual asbestos consumption of 800,000 tons 730 Mcg about 28,000 tons 25 Mkg of chrysotile asbestos are purchased annually for friction materials of all types 1 of this it has been calculated that brake lining wear consumes about 12,000 tons 11 Mkg of asbestos per year Roughly an equal amount remains on brake shoes at the time of replacement or is manu- facturing wastage Recent tests have shown that densely populated urban atmospheres often contain significantly higher asbestos concentrations than surrounding areas 2 Background asbestos levels in the atmosphere result from the natural weathering of asbestos rock and soil as well as from mining farming and excavating The generally higher urban concentrations suggest commercial and industrial sources Brake lining and clutch facing wear was suggested by Thomson 3 as a possible source for higher asbestos levels in the urban atmosphere : Ivnch 4 in a study underten by the Public Health Service reported the findings of several brake dynamometer and friction machine tests in which wear debris was trapped on a filter and subsequently examined by means of a transmission electron microscope TEM He concluded Reference 10 suggests 59,000 tons 53 Mkg is more correct 8000 0084 that free fibers from brake lining wear seem to be an inconsequential health factor in urban air pollution Lynch detected no free fiber from an automobile clutch and a bus drum brake but some free fibers were found in one test of an experimental disc brake With mounting concern over air quality in general and asbestos pollution in particular this study was initiated in 1970 to provide additional data on the asbestos emissions from disc brakes OBSERVATIONS OF LINING WEAR The near absence of free asbestos fiber from lining wear has been reported by Luxon 5 using ray diffraction and by Lynch 4 using the TEM transmission electron microscope Several authors have suggested that interfacial temperatures during braking could be high enough to decompose the chrysotile asbestos into fibrous thermal degradation products Ana- lytical relationships exist which permit calculation of interfacial tempera- tures 6 However several of the significant parameters are difficult to determine accurately for heterogeneous materials such as brake linings The asbestos crudes larger fiber bundles were calculated to reach their rapid decomposition temperature during normal braking at speeds above 56 MPH 25 m as an upper bound value and abo18vMe FH 8 m as a lower bound value An experimental approach was undertaken to provide closer bounds Added insight into the thermal decomposition of asbestos fibers trake lining wear was attempted by direct visualization of the frictional process A small laboratory friction test machine was constructed using a thermal shock resistant Vycor gless rubbing surface replacing the conventional cert iron in which the friction interface was directly viewed with a low power 7-50X binocular microscope 7 Scaled rubbing velocities were used to compensate for the thermophysical property differences between the glass and cast iron anna 2484 eee me ee I At a Wee eM ke Rl Moderate scaled velocities roughly equivalent to 12 MPH 5 m provided a view of intermittently incandescent asbestos crudes During the initial burnishing operation resinous material surrounding these asbestos crudes was observed to pyrolize producing microbeads of condensation products around the crude These organic products of resin degradation and the apparently powdered asbestos decomposition products were seen to smear into platelets often of such size as to be discernible to the unaided eye At higher rubbing velocities over 30 MPH or 13 the platelets formed a surface char layer under the action of more severe thermal and mechanical action The larger asbestos crudes then could be seen to glow with apparent depth and for greater time durations often several seconds The actual brake lining contact area was only a few percent of the total available surface with contact spots moving in a random manner with time From these friction visualization studies it appeared that local flash temperatures and severe mechanical action could be major factors in the breakdown of asbestos fibers for most brake usage Examination of the lining surfaces revealed the presence of non fibrous magnesium silicate in both crystalline Forsterite and amorphous phases Magnesium silicate is a thermal degradation product of chrysoti asbestos Forsterite transformations have been reported to occur at 600 over a period of hours Differential thermal analysis DTA studies in our laboratory indicated this transformation occurs within seconds at 820 C Special brake lining formulations were then prepared and tested . on the glass visualization apparatus and a Friction Assessment and Screening Test FAST machine Chemical reactions were found to take place at the friction inte.face which would require a flash temperature rise of 740 to initiate when an equivalent of 35 MPH 16 m rubbing speed was used on the FAST machine At this same speed melting of inorganic lining additives and =< metal particles confirmed brake flash temperatures up to 980 8080 0000 a ee ee eT. Bae ee oe a ewe eB ee ot ~~ te 40 Based on these findings it would not appear surprising for few asbestos fibers to be emitted from brakes in normal usage However some mechanical removal of fiber appeared possible during the first several brake applications with new linings Also high brake temperatures possibly could weaken the organic binders and cause increased fiber emissions TEST PROCEDURES Complete sample collection and examination procedures along with sample data calculations are included as Appendixes I II and III Briefly the tests were performed as follows a new Pinto disc brake assembly was installed on a single station brake dynamometer in a room which was cleaned - of extraneous asbestos sources Air from within the room was blown through a diffuser screen to provide a velocity distribution over the brake which approximated that of vehicle usage The air stream in front of and behind ft the brake was sampled isokinetically using matched 0.45 ...mfilters holders and air the system in pumps Figure 2. The brake exhaust schematic in Figure 1 and air was discharged out of the the actual test building setup The first pair of filters were used during the first 82 burnish stops to represent breakin conditions After further burnishing a second pair of filters collected samples during 560 normal use brake applications A third set of filters then were utilized in a high temperature use test of 41 brake stops ; speed All brake applications were made from a 40 MPH 18 s equivalent Fremdin and normal use tests employed trake torques corresponding to quarter g 2.45 sdeceleration This torque level was doubled for the high temperature tests During the normal use procedure the test filter was located for 20 brake applications at each of 28 grid locations in the exhaust duct throat to . insure a representative sampling of the air flow over the brake This test grid 8000 009 - whet wees ot ee ete Dems Lot - tw + 3 me - ee ne eee eee Ow er 8. tae Be ee -5- ee em ee ete. ow and filter may be seen in Figure 3 A central collection site in the test mid was used for the breakin test and the final high temperature test Samples of the three pairs of filters breakin normal use and high temperature use were subjected to a clarification process involving low temperature ashing to oxidize all organic material and mechanical action to separate the particles This assures maximum detectability of asbestos fiber 2 RESULTS AND DISCUSSION Transmission electron microscopy at 40,000 magnification was used in the search for fibers At this magnification the ultimate fibrils appear to be above one millimeter 0.040 inch in diameter Quantity length and apparent diameter measurements provided data for calculation of asbestos fiber mass p~ r unit of filter area Coupled with dimension mass and flow determinations from the dynamometer tests this data was used to calculate the emitted asbestos fiber concentration in the collected wear dust in the cooling air stream and from the brake fining worn The size distribution of collected fibers was not determined by this method since the clarification process involved sufficient mechanical action to reduce most fiber bundles to the ultimate fibril size Additional samples of the normal use test filters were examined on the TEM without recourse to the clarification process in an effort to determine the asbestos fiber size distribution Roughly 10 of the asbestos fiber was visible on the background sample based on the results from corres- , ponding samples after clarification The largest observed fiber bundle was c in in dienster and over 1.2 long A similar direct TEM search of the normal use test filter revealed about % of the asbestos fibers observed after clarification This reduced percentage of visible fiber was attributed to the greater concentration of obscuring matter in the test filter However the . largest observed asbestos fiber in the test filter 0.13 ...min diameter and over 1.2 ...mlong was about the same size as was found on the background sample BRAA .. The similar low fiber content of both background and test filters precluded a fiber size distribution estimate However it appeared that the quantity of the larger asbestos fibers on the test filter was no greater than that of the background filter This supports the observation from the lining wear visualization tests that normal brake wear degrades most of the asbestos fibers A brake lining grade of asbestos appears on the TEM as in Figure 4. The fiber bundles are composed of strong but weakly adhering fibrils of about 0.03 ...mroughly 1 microinch diameter Mechanical action causes the larger fibers to open into smaller fibers fibers even or fibrils as illustrated in Figure 5. with one of the larger fibers Figure 6 and Contrast these one of the more raw material typical fibrils Figure 7 from the normal use test filter The similar low fiber content of both background and test filters required clarification to permit an asbestos fiber count thus providing more accurate fiber mass determination but obscuring the actual fiber size distribu- tion Therefore the calculations of fiber concentration Table 1 were as asbestos mass per unit mass of lining wear dust and asbestos mass per expressed unit mass of lining worn Asbestos fiber concentration in the ambient air background and in the brake exhaust air test was calculated in units of nanograms 10 gra per cubic meter of air However the actual asbestos emissions from brake usage would be diluted substantially through mixing The asbestos concentration in urban air due to brake usage was estimated based upon existing automotive exhaust lead dilution data These calculations appear in Appendix III All the test results in lacle 1 have been reported as ten times the calculated test values to allow for possible losses in collection processing and counting These values therefore should provide upper bourds for asbestes emissions from brake usage For example the local Detroit Michigan atmospheri asbestos concentration ranges from 0.5 to 13.4 nanograms per cubic meter The ROCO 0093 observed background asbestos value was 1.9 mfor the normal use test but is reported in Table 1 as 19 ng The low asbestos emissions from the test disc brake under normal use conditions is underscored by the addition of but 13 ng 1.3 ng observed in the undiluted exhaust air stream TABLE 1 ASBESTOS EMISSIONS FROM NORMAL USE BRAKING Dynamometer Data for a Production Disc Brake . Asbestos in Ambient Air Background . Asbestos Fiber from Brake in Exhaust Air Total Asbestos Fiber in Exhaust Air . Estimated Brake Asbestos Fiber in Urban Air . Asbestos Fiber from Brake in Airborn Wear 19 x 10 1 13 10 m 32 x 109 m 0.07 x 10 m Dust 0.05 . Aspestos Fiber Released from Lining Wear 0.02 0.02 * Reported values are 10 times the observed test values to provide upper bounds The lining wear rate during the first 82 breakin stops was found to be about five times above the normal use rate Asbestos fiber release during breakin was also higher an average sevenfold increase However since the breakin wear is less than % of the total lining wear the increase of emitted asbestos fiber resulting from this temporary sevenfold increase would be about % when averaged over the life of the linings High temperature temperature braze ge also increased lining wear rates in factor this case by a of eleven Asbestos fiber emissions increased by less ~ than a factor of three Frequent vehicle operation under such high temperature QNAAR Ans 8. conditions would lower lining life to levels far below present averages However even if all brake wear provided the same fiber emission rate as found in the high temperature use test the percentage fiber release to the . atmosphere would still be under 0.06 of the lining wear The remaining brake wear was a mixture of fibrous organic and inorganic matter Forty percent of the estimated 62 to 77 collectable wear debris were accounted for by the test filter on the normal use test The remaining 15 to 30 presumably were retained on the lining edges the caliper spindle rotor wheel and tire Accurate measurement of this material was not possible due to the added retention of dust from the ambient air More precise values of brake lining asbestos emissions or the determination of their particle size distributions appear possible for these low fiber concentrations only by testing brakes in an asbestos free atmosphere This approach was used in an EPA sponsored study 9 where filtered air through was flowed sealed brakes at a flow rate greatly reduced from normal CONCLUSIONS \ y, 1 Automotive brake usage provides a very small emission of asbestos fiber less than 0.02 of the lining worn 2. Automotive brake usage provides a very small asbestos fiber input to urban atmospheres estimated to be below 0.07 ng 3 Intense local heating and severe local mechanical action causes the decom- o position of most asbestos fiber in brake linings during typical usage 8000 0095 SAMPLE COLLECTION APPENDIIX DYNAMOMETER ROOM PREPARATION The normal brake cooling air was found to be more variant and higher in dust concentration than was the room air Consequently the supply air duct was removed and sealed To reduce the background asbestos level to a minimm the dynamometer room was thoroughly cleaned and vacuumed while maximum exhaust air flow was maintained All potential sources of fiber emissions were removed from the room and asbestos handling was curtailed in adjacent rooms A production Pinto disc brake assembly was installed on the single station brake dynamometer as shown on the schematic of Figure 1. The major elements of the test setup may be seen in the photograph of Figure 2. Cooling air was supplied from the room by means of a fan and diffuser screen Containment of all possible airborn wear dust was assured by fitting a rectangular collector nozzle to the exhaust air duct about two feet downstream of the brake Metal panels were installed below and beside the brake to further contain the cooling air flow and to help provide a representative air flow over the brake compared with vehicle service System parameters were adjusted until the air velocity distribution matched closely with actual usage and the air flowing over the brake assembly was fully captured by the exhaust duct This was confirmed using a smoke generator ; The exhaust dust threat was partitioned into 4 by 7 array of roughly three inch square grids Figure 3 The velocity profile within this grid was measured to provide mean values for each grid square 8000 0096 -10- SAMPLE FILTER PREPARATION Microporous membrane filters with 0.45 ...mpores were selected to assure high retention of asbestos fibrils and most of the wear dust powders A matched pair of Gelman sampling pumps and 35 mm diameter holders were used Thin metal cones of 12 included angle were fabricated and sealed to the filter entrance These comes increased the tip entrance velocity to that of the exhaust air duct so isokinetic sampling could be achieved The come tips were carefully matched in size Flowmeters and differential pressure indicators were installed in the system to monitor the filter airflow during each test and to set the tip entrance velocity before each test Tests were performed on the unused filters to determine their weight change with variation of humidity Filter weights were measured on a microbalance to the nearest 10 micrograms Filters were placed in the center of the designated exhaust duct grid and at a fixed position upstream of the brake but below the diffuser screen This latter background filter was located where the upstream air velocity equalled the average over the test grid In this way the sampling was isokinetic with essentially equal volume flows through both filters TEST PROCEDURE All brake stops were conducted from the same speed equivalent 40 MPH or 18 m to maintain fixed air flow conditions Burnish and normal use brake applications were at 0.25 8 2.45 sdeceleration and with a two minute time interval This provided a peak rotor temperatur of 180 350 The number of brake applications were selected to provide about one grem of lining wear per test Breakin wear was monitored for the first 82 stops No sampling vas performed for about 200 more brake applications while the linings and rotor developed essentially steady conditions -- -- -- A --ABO The normal use test was then performed on this burnished brake assembly Twenty brake applications were made under the same conditions with the test filter located sequentially at each of the twenty grid locations The filter come entrance velocity was adjusted to match the grid velocity at each relocation Four grids were used to monitor exhaust velocity Slight adjustments were sometimes required to compensate for drift which appeared to be external wind initiated A third test was performed to provide an estimate of the fiber emissions from a hot brake assembly As in the breakin test the test filter was positioned in a central location for this procedure Thirty stops were made at 0.5 g 4.9 sand minimal time interval until the rotor attained 410 C 770 This temperature was then maintained by adjusting the application time interval Ten additional stops were made as the brake was allowed to cool All filter weight determinations were performed at equilibrium then conditions and individually stored corrected for humidity After use the filters were in covered glass containers Lining weights were taken after removal of wear debris but before they had cooled completely to minimize weight changes from water absorption stored in a dry jar Between tests the linings were | The relevant test data are included in the following table A slight pad drag caused the outboard lining to wear above expectations on the normal use test Since this added work was not included in the lining wear rate calculations the specific wear is above the usual range for this lining No adverse effect on the test results would be expected to have resulted frm this drag Similar pad drag effects may occur on cars when smooth road conditions prevent pad knockback 8000 0098 Test Brake Speed RPM Brake Decel g Wheel Load kg Brake Applications Total Energy kW Max Apply Temp C Total Lining Wear 6 Lining Wear Rate kW if Breakin 535 40 MPH 0.25 2.45 2/12 257 567 lb Normal Use Hi Temperature Use 535 40 MPH 535 40 MPH 0.25 2.45 s 0.50 4.9 s 257 567 lb 257 567 lb 82 560 41 0.938 1.25 hr | 6.405 8.54 hr 0.469 0.625 hp 115 240 115 240 410 770 1.10 1.60 1.07 1.17 0.051 1 0.25 0.011 hp 2.28 0.100 12 8000 0095 APPENDIIXI SAMPLE EXAMINATION PREPARATION AND EXAMINATION OF ASBESTOS CARRYING SAMPLES FROM TEST FILTERS 1. All slides dishes scalpels and other utensils used in the following preparations were cleaned in acetone followed by rinse in 200 proof ethanol 2 An area of measured dimension was selected at random from the test filter cut and placed particle side down on a clean glass slide | Several drops of acetone were placed on the filter segment to partially dissolve and secure it to the plate The samples were ashed for a period of two hours by using a low temperature asher at a chamber pressure of 0.5 torr 70 Pa oxygen and power of 200 watts Several placed argos on the of a % solution of cellulose in amyl acetate were residue and a clean watch glass was used to grind the mixture \ for a period of five minutes A second clean glass slide was then placed over the mixture of cellulose and residue and a smear obtained by pressing the two slides together and then sliding them apart The films thus formed were permitted to dry and then removed by scoring the * edge of the slide with a scalpel and floating the film free from the slide in a distilled water bath It was found that the film was most easily removed from the slide introduced in Step 6 Sample preparation techniques outlined below are similar to those . reported by Selikoff et al in Reference 2 8000 0160 8 Approximately 10 election microsome mids 7 m finder grids were placed at random on the floating film and the film was liited by putting a clean slide on top of the film and drawing the slide down through the water so as to trap the grids between the slide and the film which should now cling to the slide 9. carbon layer of approximately 0.06 ...mwas deposited on the film to prevent charging during examination in the transmission electron microscope (TEM Direct examination specimens were prepared by depositing a carbon layer on the dust side of the test filter and dissolving the filter in acetone microscope Electron i refnce grids were used both to support the sample and to provide grid location reference marks TEM EXAMINATION AND COUNTING PROCEDURES Approximately ten electron microscope grids were prepared for each of the five filter samples analyzed Four grids were arbitrarily selected from each sample and two grid squares on each grid were scanned for asbestos The individual grid squares are approximately 90 ...mon each side and were examined at a TEM magnification of about 40,000 For each grid area scanned photographs were taken where possible of the first last and one randomly chosen fibril for the purpose of determining an average fibril diameter accurately Measurements were then made visually that is each fibril fiber or asbestos bundle was compared to known calibration marks on the electron microscope screen ' to estimate the lengths The length could be estimated to within 20 as determined by the photographic measurements The marks on the screen are 0.5 ca spart corresponding to 0.125 ...mwhen a magnification of 40,000 is used This approach was taken because it was impractical to photograph all the fibrils and furthermore length 1: lurements were not as critical as dieptter dieptter measure- ments in determining fiber volume Where both measurement methods were used the values providing the greatest indicated brake asbestos levels were chosen The results are shown in the following table 8000 0101 Sample A B C A ASBESTOS CONCENTRATION ON FILTERS | - Sample Identification Concentration cmof filter normal stop brakes 15.32 Background for A ~ normal burnished brakes 1.06 7.98 Background for C 4.64 Q high temperature burnished brakes 5.37 F Background for E- E- not used insufficient sample - ; | Blank - unused filter 0.33 From photographic measurements of 120 chrysotile fibrils the asbestos fibril average diameter was determined to be 0.0337 ...mwith distributions similar to that observed by other workers 10 From 45 fibrils of triple jetmilled chrysotile the average diameter was determined to be 0.0316 um with a standard deviation of 0.0063 ...m ASBESTOS IDENTIFICATION Asbestos can be identified in the transmission electron microscope in one of two ways The first and absolute method is by electron diffraction Such a diffraction pattern is presented as Figure 8. Measurement of diameters and correlation of these measurements with a known standard gives the interplanar spacings of the material Comparison of these spacings with the ASTM file identifies the material as chrysotile astestos The second method of identification is by appearance Figure 9a represents an image of asbestos obtained in the HEM Fine lamellae are observed within the fibril which are parallel to the long axis This appearance is characteristic of chrysotile asbestos fibrils Because of the nature of the . electron beam radiation and heat damage can occur in the material markedly ANG 0102 altering the appearance Such changes in asbestos are represented in Figure 9b The fine linear appearance of the fibril of Figure 9a has been changed to a mottled structure 8000 0103 010 0 QF a Sa :t APPENDI IIXI DATA REDUCTION The following table contains the pertinent test data and calculated results from the brake dynamometer tests Test Sample 1. Air Filte Flr ow Breakin Normal Use BkTa est r | Bkd ard Test| Bkard 3 2.22 2.22 | 23.00 21.80 Hi Temp Use Test |Bkgrd 0.564 0.564 Calculatio Basis Measured 2. Filter pickup mg 0.36 0.10 | 1.56 0.90 0.27 | 0.00 Measured 3. Filter Asb Conc.ng/c 15.32 1.06 | 7.98 4.64 5.37 | 0.12 Measured 4 Blank Conc.ng/cm| 0.33 0.33 | 0.33 0.33 0.33 | 0.33 Measured 5 Filter Area 6. Filter Asbestos enfi ng 9.62 | 9.62 9.62 144.2 | 73.59 9.62 9.62 | 9.62 48.48 | 1.07 Measured 4 7 Asb.Conc in Air ng | 64.95 | 3.19 85.96 | 1.90 6 ^ 1 8. Lining Asb in Exh Air ng 61.8 1.29 84.1 7 Asb on Lining ng | 137.2 29.7 47.4 8x1 flow 10. Duct filter 1235 1235 1235 From Meas 11. Lining mg | 0.169 0.0367 0.0586 9 x 10 12. Lining worn mg 1100 1600 1070 Measured 13. Asb released as 0.015 14 Lining dust on ng 0.26 *** 15. Lining dust in air ng | 321 16. 5 Ast in wear dust 0.053 0.0023 0.61 754 6400 6400 0.0055 C.27 333 0.018 11 ^ 12 2 10 x 14 11 ^ 15 15 + * ** *** Value calculated based on normal use background due to insufficient sample Corrected for flum volume difference throust test and background filters Filter in one cont location and thus possibly representative -18- ESTIMATION OF BRAKE LINING ASBESTOS DILUTION IN URBAN ATMOSPHERE The concentration of asbestos fiber from the brake lining wear debris is assumed to be the same as was found in the normal usage dynamometer test and to be dispersed and have the same residence times as the lead emitted from the engine MPG Assume an average mileage of 15 | the lead to the atmosphere from cars which emit 75 of When gasoline averaged 2.52 grams of lead per gallon the typical lead concentrations in urban atmospheres were about Mg JAPCA Sep. 1969 19 p 684 Typical U. S. cars wear 202 grams of lining per year and drive 10,000 miles per year The normal use dynamometer tests provided asbestos fiber amounting to 0.0023 2.3 x 10 of the brake lining worn Allowing a factor of ten to provide an upper bound in this determina- tion the asbestos concentration in urban atmospheres from brake wear should be less than 10 5 10,000 105 10 2.3 x 202 [ ] \ 2 Kg m MPG Po 2.52 gal .75 0.07 or 25 Urban atmospheres vary in asbestos fiber concentration from city to city within a city and from one time to another This variation does not correlate with expected automobile brake usage The concentration has been reported to reach 100 13 2 Thus it appears that the wear of brake lining produces at most a small fraction of the asbestos fiber in urban air This is not surprising when one considers that brake lining wear involves only 1.5 of U. S. asbestos usage and that brake usage converts over 99.95 of this to fibrous dust 3000 0105 CANSULATIONS CANSULATIONS OF COLLECTION EFFITEROT LINING COMPOSITION ESTIMATE FROM LABORATORY ANALYSIS 8102 MgO F8203 Al2O3 20 CaCO3 Za Organic Total 16.3 17.8 2.5 0.3 5.5 15.4 3.9 38.3 100.0 Chrysotile Asbestos 42.4 WEAR DEBRIS ESTIMATE Decomposed Asbestos Decomposed Limestone Zinc Metal Inorganic ORGANTOORGANTO ORGANTO Volatile Uncertain Low Volatility . Organic Collectable Total Collectable Collected on Filter Collectalls Collectalls Material not trapped by filter 36.9 8.6 3.9 49.4 10.5 15.7 12.1 12.1 to 27.3 61.5 to 77.2 47 % 14.5 to 30.2 30.2 * This material presumably on shoe edges caliper rotor wheel and tire AAAA Aline REFERENCES 2. Sullivan R. J. et al Preliminary Air Pollution Survey of Asbestos N.A.P.C.A. Publication APTD 69-27 1969 2. Selikoff E. J. et al Asbestos Air Pollution Arch Environ Health Vol 25 July 1972 Thomson J. G. Asbestos and the Urban Dweller Ann N. Y. Acad Sci 196 1965 Lynch J. R. Brake Lining Decomposition Products J. Air Pollution Control Assoc 18:12 1968 Luxon S. Technical Implementation of the New Asbestos Regulations Ann Occup Hyg Brit Vol 13 1970 Rabinowicz E. Friction and Wear of Materials John Wiley 1965 Anderson A. E. Wear in Brake Materials ASME Wear Conf 1969 Anderson A. E. et al A New Laboratory Friction and Wear Test for the Characterization of Brake Linings SAE Trans pp 561-9 1968 Jacko M. G. et al Brake and Clutch Emissions Generated During Vehicle Operation SAE Preprint 730548 1973 10. Yada K. Study of the Microstructure of Chrysotile Asbestos by High Resolution Electron Microscopy Acta Crystal Vol A 27 1971 8000 0107 oe ee . eet aN ow! e ed wk * 2 te ee - o8 4 - ONV MOTORDRIVE ONYDy3LMs ONYSOVE diWNdYILWMOTA IVE MIOLSTIVL INERTIA TEST TEST GRID TEST INERTIA DIFFUSER DIFUSER TEST AS'Y Qiy9 1S43aL BACKGROUND Y3LIWMOT4BACKGROUND FLOWMETR LSNVHX3 R008 010s a ae _ som ayOIg 1821 kiquas y pug s9414 sel puo Py . . : te e oe ee F: . . 4 2 puno6490salts "UNYOR YPSa} de pomvuny Difuser Difuser GO vew ra BOON 01069 see Ce en wo tne 6 es Me ee giaqy soyaqse aTyzoshyD Jo sPewl WAL 4 IMI Ts 9009 01117 1 wii tot sy boy sy o' vf | *gaTpunq s9qfy pouado ATTeT Ied Jo sBumy WAL = amBTA 9000 0112 o- Oe ee ran . 8 ee wee > * SS eee wee 429TS , 28N Tem1ou, uo atpung Jaqis Jo aFemy WAL 9 FMITS 0113 8800 @1:23