Document gEJd9b3KkVJonGd44oopybZpQ

FILE NAME Manville JMA DATE 1970-1973 DOC JMA186 DOCUMENT DESCRIPTION Ford Motor Company - Memos & Test Results with BC Notes 7/5/98 Ford Motor Company Nov. 1970 documents refer to Ford efforts to substitute or control asbestos in making housing units for heaters and air conditioners Ford brake tests in 1973 demonstrate asbestos emmissions in brake wear products Asbestos Emissions from Brake Dynamometer Tests by A. Anderson R. Gealer R. McCume and J. Sprys Environmental Control Department Research & Engineering Center November 17 1970 003900A W W. P. O'Reilly - Cleveland Dist Off CC A. C. Smith N. W. Hendry - Asbestos H. M. Ball - GHQ W. P. Raines - GHQ H. G. Donovan J. Goldfield File C 1500 FORD MOTOR COMPANY PLYMOUTH MICHIGAN YOUR LETTER OF NOVEMBER 13 1970 I contacted Dr. George Bauer today in accordance told me that Ford was greatly concerned with the with your request He health hazards related to asbestos fiber usage and that he had been looking for substitute materials He further stated that his search had convinced him that other materials were equally if not more hazardous than asbestos fiber and that instead of using a dust control at their operations substitute they should improve the He asked if anyone from Manville could visit their plant and advise them on dust control procedures I informed Dr. Bauer that J. Goldfield and | expected to be in the Detroit area sometime within the next two weeks and would visit their plant to review the problem with him and Mr. Leonard Evans their Plant Engineer Emy E. M. Fenner EMF ems fy _ a | 037000 037000 Cleveland Office November 13 1970 E.M. Fenner - Finderne CC N.W. H.M. H.G. W.P. File Hendry Ball - - Asbestos GHQ Donovan Research Raines - GHQ FORD MOTOR COMPANY HARDWARE & ACCESSORIES 14425 SHELDON ROAD PLYMOUTH MICHIGAN DIVISION Lee - fa i . . This plant manufactures the Heaters and Air Conditioners for all Ford vehicles and the housing for these units is a molded poly- ester premix compound For chased from us in excess of 7T15 the past three years they have pur2000 tons of Asbestos Fiber grade Last month we heard through Dr. George Bauer a chemist and their formulator for this item that he was instructed to investigate possible substitutes for asbestos and that if we had any comments on the subject we rather than he should approach Ford about it Last week on the 5th of November Noel Hendry and I visited there and brought up the matter with our contacts seeking their advice They felt that although the subject had come up a presentation on our part would be premature at this time and I believe Noel is to write them to the effect that we have such a presentation and would be glad to offer it at their convenience Dr. Bauer was not present at this meeting Now on November 11th Dr. Bauer has contacted our distributor Mr. John Hastingosf International Fibers asking that someone from the M Environmental Control Department telephone him to discuss recommended asbestos dust levels Their ECD feels the asbestos dust in their operation exceeds the allowable limits and if so a dust they wish to know level of 2 fibers how per to reduce cc which the dust I think is Dr Bauer stated a little low At any rate may I suggest that you or someone in your group tele- phone Dr. 445-0600 George Bauer at Ford to discuss allowable in Plymouth Michigan asbestos dust levels Phone 313 Then would you kindly drop a note to Noel Hendry and me informing us of what transpired 455-080 1455 U.P. Reilly Reilly ! mct WPO mct 4 Thiefs son oe os Pogearch Pogearch & Development Center GS Vo _ 562 fl - fl - fl - fl - ASBESTOS EMISSIONS FROM BRAKE DYNAMOMETER TESTS A. E. Anderson R. L. Gealer R. C. McCane and J. W. Spys Meeting SAE Automobile Scientific Research Staff Ford Motor Presented at the 1973 National May Detroit 10 1973 Company Engineering SUMMARY by J. Axelson _ Dynamometer tests were made with a production disc brake and all airborne wear particles were collected on 0.45 um filters Asbestos fibers were detected and measured by the use of transmission electron microscopy at 40,000X and positive identi- fication was made by electron diffraction Mosotf the lining asbestos 99.95 porcent was found to be converted to a non- fibrous material by the high flash temperatures of the braking. surface Brake flash temperatures as high as 980C have been observed on a test machine estimate ' They that about 28,000 28,000 tons of asbestos are used each year by the friction materials industry in the U.S.`` M estimates about 45,000 tons Less than half of 12,o0 r 10 2,00 00 tons is estimated wear away Amy Throughout Throughout the paper they use a safety factor of 10 to make only . sure they are stating maximum quantities For instance they found that 0.0023 percent of the lining wear was released as asbestos fibers but state this figure as less than 0.02 percent Likewise the concentration of asbestos fibers in the atmosphere from brake usage was calculated as 0.007 x s 10-9 10-9 gms per cu moter but was reported as 10 times that or : 0.07 x 10-9 gms per cu meter iiY Some of the pertinent data are given in the act aru e aa ctul al values without multiplying ' 10 as they did in the paper following table by the factor of Background in asbestos ambient test air Asbfe ibes r frt om bo rakes in exhaust air Total asbestos fiber in exhaust air asbestos Estimated brake in urban air Asbestos fiber from brake in airborn wear Qust Asbestos fiber released from lining wear 1.9 ^ 1.3 x 3.2 ^ 0.007 10-9 m 10-190-109-9 m x 10-9 mm3 m3 0.005 percent 0.0023 percent ' Extrapolated :from data on residence times for lead particles y : 15 ; Amy | nice 2 Asbestos Emissions from Brake Dynamometer Tests \* ns a Local Detro^flt atmospheric concentration ranges from 0.5 to . 13.1 x 10-9 gms per cu meter so the calculated value of 0.007 ^ 10-9 gms per cy meter is only of normal conditions accruing from all natural weathering of asbestos farming excavating This leads to a minor fraction sources including rock and soil mining their final conclusion Based on this upper bound the use of brakes was judged to be not significant as a source of atmospheric asbestos . ' CC ) oo 4 J. M. Hutcheson - Asbestos N. W. Hendry - 3 West G. Donovan - 3 West _ E. M. Fenner -14 North F. J. Solon - 1 West W. C. Streib Hy D Ctr S. Speil - D Ctr on + 1. SO 7 _. ASBESTOS EMISSIONS EMISSIONS FROM BRAKE oy - : 7 . DYNAMOMETER TESTS , . . by . . : \ E. A. E. Anderson R. L. Gealer R. C. McCune J. W. Sprys j Scientific Research Staff Ford Motor Company . } Dearborn Michigan 48121 , 1 : 4 SCIENTIFIC RESEARCH STAFF STAFF STAFF PUBLICATION PREPRINT ae | \ . 4 i ASBESTOS EMISSIONS FROM BRAKE | | DYNAMOMETER TESTS . | , | ; | by A. E. Anderson R. L. Gealer R. C. McCune J. W. Sprys Scientific Research Staff Ford Motor Company Dearborn Michigan : _ . o4 4 48121 ABSTRACT Dynamometer tesotfsa production disc brake provided new information asbestos fiber emissions during breakin normal use and high temperature use conditions Both ambient air and brake cooling air were sampled isokinetically using 0.45 um filters of Examination test and background filters required a process " . clarification to maximize fiber detectability the use of transmission electron microscopy at 40,000 X for detection and electron diffraction for positive identification of asbestos fibers Most of the lining asbestos was high ; _. found to be converted to a fibrous material by the flash temperatures x of the braking surface Less than of the lining wear was released as The asbestos fibers ~ , concentratioonf asbestos fibers in the . i due brake usage was conservatively estimated at less than urban atmosphere 0.07 x 107 _ grams per cubic meter Based on this upper bound the use of brakes was of _ judged to be not significant as a source atmospheric asbestos _ INTRODUCTION Asbestos has been a major constituent of automotive friction | materials formore than 50 years It used to impart strength flexibility heat resistance and to a brake lining and to enhance friction and wear proper- t ties 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 Brake linings in the U. S. average about 50 asbestos content S. Of a total U. ! 25 Mkg 730 Mkg annual asbestos consumption of 800,000 tons about 28,000 chrysotile 28,000 tons asbestos are purchased annually for friction materials ' of all types 1 Of consumes about 12,000 12,000 it th1i1s Mkg has be nbeen calculated that brake lining wear equal tons of asbestos per year Roughly an amount 1 remains on brake shoes at the time of replacement or is manufacturing wastage a 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 oo ; . natural weatherinogf asbestos rock and soil as well as from mining farming and excavating The generally higher urban concentrations suggest commercial commercial and industrial 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 Lynch 4 in a study undertaken 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 a transmission electron microscope TEM 2, a He concluded \ that free fibers from brake lining wear seem to be an inconsequential health factor in urban air pollution * clutch and a bus drum brake but Lynch detected no free fiber from an automobile some free fibers were found in one test of an experimental disc brake " tWith mounting concern over air quality in general and asbestos pollution in particular 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 , ; } and " reported by Luxon 5 using ray diffraction and by Lynch 4 using the TEM ' transmission electron microscope Several authors have suggested that _ 1 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- nes nes 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 above 18 MPH 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 in brake 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 glass rubbing surface replacing the conventional cast 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 . b the thermophysical property differences between the glass and cast iron -3- \ v3 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 + . - 4 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 m ) 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 | 7 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 ribers for most brake usage Examination of the lining surfaces revealed the presence of fibrous magnesium silicate in both crystalline Forsterite and amorphous phases Magnesium silicate is a thermal degradation product of chrysotile asbestosj xv 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 ~ 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 interface which would require a flash temperature rise of 740 to initiate . 7 t. FAST machine an equivalent . At this same of 35 . . speed MPH 16 m rubbing speed was used on the . meltinogf inorganic lining additivaensd , metal particles confirmed brake flash temperatures up to 980 \ ot 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 . 1 : WEST 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 . , . ' distribution a diffuser screen to provide a velocity distribution . . : 1 \ _ room over was the blown brake through which which _ approximated that of vehicle usage The air stream in front of and behind the brake was sampled isokinetically using matched 0.45 mfilters holders and air pumps Note the system schematic in Figure 1 and the actual test setup in Figure The brake exhaust air was discharged out of the building The first pair of filters were used during the first 82 burnish stops stops to v represent Breakin conditions . After further burnishing a second Breakin : pair of filters collected samples during 560 normal use brake applications 4 . , A third set of filters then were utilized in a high temperature use test of 41 brake stops ; .. All brake applications were . made from a 40 MPH 18 m equivalent speed Breakin and normal use tests employed brake torques corresponding to . quarter g 4.9 sdeceleration This torque level was doubled for 7 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 of the air flow over the brake This test grid _ and filter may be seen in Figure 3. 3 \ A central collection site in the test grid 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 Ly 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 0.040 inch in diameter Quantity length and apparent diameter measurements provided data for calculation of asbestos fiber mass per unit of filter area J ' Coupled with dimension mass and flow determinations from . ., the dynamometer tests of 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 lining 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 4 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 mm of 0.20 in diameter and over 1.1 km l ng A similar direct TEM search the : normal use test filter revealed about % of the asbestos fibers observed after ay - clarification This reduced percentage of visible fiber was attributed to the greater concentration of obscuring matter in the test filter . .- 8 However the largest observed asbestos fibeirn the test filter 0.13 ...min diameter and over ' 1.2 mlong was about the same size as was found on the backgound sample -6- The similar AY a fiber size low fiber content of both background and test test filters distribution estimate However it appeared that the precluded quantity of the larger asbestos fibers on the test filter was no greater than that of the background filter the 4 This supports observation from the lining wear visualization tests that degrades normal brake wear most of the asbestos fibers A brake lining grade " . of asbestos appears on the TEM as in Figure 4 fiber bundles are composed of The 7 strong but weakly adhering fibrils of about 0.03 ...mroughly 1 microinch diameter Mechanical action causes the larger fibers to open into smaller fibers or even fibrils as illustrated in Figure 5 Contrast these raw material fibers with one of the larger fibers Figure 6 and one of the more typical | fibrils | + Figure 7 from the normal use The similar low fiber content test filter 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 \ exhaust in the brake exhaust airtest was calculated in units of nanograms 10-9 grams per cubic meter of air However the actual asbestos emissions from brake J would be diluted substantially through mixing The asbestos concentration usage in urban air due to usage was estimated based upon existing automotive exhaust lead dilution data These calculations appear in Appendix III All the test results in Table 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 bounds for asbestos emissions from brake usage For example the local Detroit Michigan atmospheric asbestos concentration ranges from 0.5 to 13.4 nanograms per cubic meter The -7 \ ; observed background asbestos value was 1.9 1.9 mfor the normal use test but is reporved in Table 1 as 19 mThe low asbestos emissions from . ; \ the test disc brake under normal use conditions is underscored by the addition ofbut 13 m1.3 mobserved in the undiluted exhaust air stream TABLE 1 a ASBESTOS EMISSIONS FROM NORMAL USE BRAKING a DynamometDaetra for a Production Disc Brake . Background in Asbestos Ambient Air 19 109 m- _ Asbestos Fiber from Brake in Exhaust Air 13 x 10 m -, Total Asbestos Fiber in Exhaust Air 32 x 109 m . Estimated Brake Asbestos Fiber in Urban Air 0.07 x 109 m . Asbestos Fiber from Brake in Airborn Wear Dust < - | | 0.05 0.05 | : Asbestos Fiber Released from Lining Wear 0.02 * Reported values are 10 times the observed test ; upper -.. values to provide . 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 about be % when averaged over the life of the linings | increase would High temperature brake usage also increased lining wear rates in this case by a factor of eleven Asbestos fiber emissions increased by less then a factor of three Frequent vehicle operation under such high temperature -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 . J atmosphere - 4 would still be under 0.06 of the lining wear The The t remaining remaining brake wear was mixture a mixture of fibrous fibrous organic 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 , 1 . } ' More precise values of brake dust from the ambient air lining asbestos emissions or the determination of their particle size distributions appear possible for these t . low fiber concentrations only by testing brakes in an asbestos free atmosphere This approac wahs used in an EPA sponsored study 9 where filtered air was flowed through sealed brakes at a flow rate greatly reduced from normal CONCLUSIONS brake , 1. Automotive usage provides a very small emission of asbestos fiber / . . t - less than 0.02 of the lining worn oe on a - 2. Automotive brake provides a very small asbestos fiber input to a t urban atmospheres estimated to be below 0.07 m Z, Intense local heating and severe local mechanical action causes the decom- position of most asbestos fiber in brake linings during typical usage ] ] a | a -10- SAMPLESAMPLE 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 and 3 of Gelman sampling pumps 35 mm diameter holders were used t t Thin metal cones of 12 included angle were fabricated and sealed to the filter of the entrance These exhaust air duct cones increased the tip entrarice velocity so isokinetic sampling could be achieved to that The cone : ips 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 4 } 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 the . where 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 g 2.45 s deceleration and with a two minute time interval This provided a peak rotor temperature ~ of 180 C 350 F The number of brake applications were selected to provide ~ about one gram of lining wear per test Breakin wear was monitored for the first 82 stops No sampling _ was performed for about 200 more brake applications while the linings and ' rotor developed essentially steady conditions -11- \ oe The normal use test was then performed on this burnished brake assembly Twenty brake applicat wei reomnas de under the same conditions with the test filter located sequentially at each of the twenty grid to locations The filter cone entrance velocity was adjusted match the grid i 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 central location for this procedure Thirty stops were made 0.5 g 4.9 sand minimal time interval until the rotor attained attained 410 770 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 + conditions and then corrected for humidity After use the filters were individually stored in covered glass containers Lining weights were taken after removal of wear debris but before they had cooled completely to minimize weight chan frog m e wats er absorption stored in a dry jar Between tests the linings were slight pad The relevant test data are included in the following table A drag caused the outboard lining to wear above expectations on the . normal use test ; rate calculations | Since this added work was not included in the lining wear the specific wear above the usual range for this lining No adverse effect on the test results would be expected to have resulted from this drag Similar pad drag effects may occur on cars when smooth road . conditions prevent pad knockback Test Brake Speed RPM . | -. + Brake Decel g Wheel Load kg Brake Applications Total Energy kW | Max Apply Temp C Total Lining Wear g Lining Wear Rate kW Breakin Normal Use Hi Temperature Use 535 40 MPH 535 40 MPH 535 40 MPH 0.25 2.45 s .0.25 2.45 s 0.50 4.9 s 257 567 lb 82 257 567 lb 560 257 567 lb 41 0.938 1.25 hr 6.405 8.54 hr 0.469 0.625 hp 115 240 115 240 410 770 1.10 1.17 in 1.17 0.051 hp 0.25 in 0.011 hr 1.07 2.28 2.28 ( in in 0.100 hr ee : enam en| a 7 ~~ I ad 4? ] 9 a = ut . oo -13- t y 5 | re a SAMPLE EXAMINATION APPENDIX II : PREPARATION co PREPARATION AND EXAMINATION i OF ASBESTOS CARRYING SAMPLES FROM TEST FILTERS i) All slides diches scalpels and other utensils used in the following . fy : ; preparations were cleaned in acetone followed by rinse in 200 proof ethanol "| 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 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 1 Several drops of a % solution of cellulose in amyl acetate were - placed on the 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 residue and and a smear obtained by pressing the two slides together and residue s^' 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 e 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 11 & 7 14= grids 8 Approximately 10 eletron eletron microscope grids 3 mm finder 1 were placed at random on the floating film and the film was lifted by putting a clean slide on top of the film and drawing the slide down through ! a # the water so as to trap the grids between the slide and the film which ' an t scould now cling to the slide { ' 9. A 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 ; Electron microscope 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 x chosen fibr foritl he purposoef determining an average fibril diameter accurately 1 . Measurements were then made visually that is each fibril fiber or asbestos was compared to known calibration marks on the electron microscope screen bundle to lengths to estimate the lengths be The length could be estimated to within 20 as determined by the photographic measurements The marks on the screen are 0.5 cm apart corresponding to 0.125 um when a magnification of 40,00i0s used furthermore impractical photograph e and approach | This was t. aken because it was to all the fibrils measurements were not as critical as diameter measurelength * 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 -15- " Sample . wt . ASBESTOS CONCENTRATION ON FILTERS | , Sample Identification : normal stop brakes cm Concentration of filter | 15.32 13 c - D Background for A - . , normal burnished brakes . - Background for C * 1.06 7.98 . 4.64 4.64 L ...; . high t 'mperature burnished brakes . 5.37 F Background for ",- 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 0.0337 ...mwith distributions similar to that observed by other workers 10 From 45 fibrils of triple jet- milled chrysotile the chrysotile average was diameter determined to be 0.0316 pm with 1. standard deviation of 0.0063 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 _ Such a diffraction pattern is presented as Figure 8 by electron Measurement diffraction of diameters and correlation Ls spacings the of these measurements , 1 material Comparison with a known standard gives the . of these spacings with the ASTM interplanar File identtihefmaitee ris al as chrysotile asbestos The second method of identification is by appearance Figure 9a ' representasn asboef s ast beo sts os obtained in the TEM Fine lamellae are observed within the fibril which are parallel to the long axis - af + , . 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 -16- in changes in asbestos are represented in Figure 9b the fibril of Figure 9a has been changed to a So a . ta and calculated . | | | . | . Temp Use | Calculation est Bkgrd Pasic 564 0.564 Measured .27 | 0.00 | Measured .37 - 0.12 Measured .33 0.33 Measured .62 | 9.62 | Measured 48 1.07 4 ^ 5 .96 1.90 6 ^ 1 .1 7 7.4 8x 1 235 From Meas .0586 | 070 .0055 st 9 x 10 Measured | 11 ^ 12 x 100 .27 *** *** 2 33 ' 1.018 1.018 10 x 14 | 11 ^ 15 x 100 1 ^^^ 15 ^ 12 x 100 B to insufficient sample ackground filters -representative. -18-| A ESTIMATION OF BRAKE LINING ASBESTOAS SBESTOS 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 fe the 5) dispersed to be - have same residence times as the lead emitted from . 4 4 engine Assume an average mileage of 15 MPG from cars which emit 75 of the lead to the atmosphere When gasoline averaged 2.52 grams of lead per gallon the typical ~ lead concentrations in urban atmospheres were about 2 mJAPCA Sep. 1969 . 19 p 684 TypicaUl. 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 105 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 city city 10,000 2.3 10 2.3 10-5 10 x 1075 202 m 2 ng | | MPG 0.07 ng or [ gal .75 ng 2.52 Urban atmospheres vary in asbestos fiber : within within a a city city from time and from one time to another concentration from city to x This variation This variation does not correlate with expected automobile brake usage ! The concentration has been reported to reach 100 m 2 Thus it appears that the wear of brake lining - produces at most small fraction of the asbestos fiber in urban air This is surprising considers . is not when one that brake lining wear involves only 1.5 % of S. asbestos usage and that brake usage converts over 99.95 of this to fibrous dust rn| -1.9- \ CALCULATIONS OF COLLECTION EFFICIENCY LINING COMPOSITION ESTIMATE FROM LABORATORY ANALYSIS SiO2 al | MgO 16.3 17.8 Fe203 | 2.5 th A1203 . 0.3 HO 5.5 ---- -- -- 15.4 Zn Zn 3.9 Organic 38.3 Total - 100.0 Chrysotile Asbestos 42.4 4 WEAR DEBRIS ESTIMATE Decomposed Asbestos Decomposed Limestone . Zinc Metal - Inorganic j ~ ORGANIC fon Volatile J ~ Uncertain Low Volatility _ Organic Collectable Total Collectable| Collected on Filter Collectable Material not trapped by Pilter 36.9. 8.6 3.9 % 49.4 10.5 15.7 12.1 12.1 to 27.8 , 61.5 to 77.2 47 14.5 to 30.2 , ay This material presume presume presume om sh sho ow w show of This material presume ? REI ERENCES 1.. SullivanR. J. et al PreliminaAriyr Pollution Survey of Asbestos * i N.A.P.C.A. Publication APTD 69-27 a 1 Selikoff E. J. et al Asbestos 1969' Air Pollution Arch Environ ' Health Vol 25 1972 Thomson J. G. Asbestos and the Urban Dweller Ann N. Y. Acad Sci ' 132 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 1 x 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 7 Resolution Electron Microscopy Acta Crystal Vol A 27 1971 cg x Figure 1 Dynamometer test schematic . Figure 2 Dynamometer test setup Figure 3 Figure 4 i Figure 5 View brake assembly and test grid I TEM image of chrysotile asbestos fibers : : TEM image of partially opened fiber bundles Figure 6 TEM image of fiber bundle on normal use filter | Figure7 TEM image of fibril on normal use filter Figure 8 TEM electron diffration pattern of chrysotile fibril Figure 9a TEM image of fibril before a and after b electron beam damage 4 1 e. DYNO -| DRIVE MOTOR | TEST GRID t TEST FILTER TO EXHAUST| QO TEST } PUMP AND FLOWMETER TEST INERTIA { SCREEN DIFFUSER a DYNO DYNO TAILSTOCK BACKGROUND FILTER (Tf BACKGROUND PUMP AND FLOWMETER ~ FigT meterAnemo- HWiorte Ey and Test Filter Screen Pyrometr Infraed ===. = (i^' iTeSt Wire | _ AsemblyBrcke = Oo 2 fey amen we en : es Yves : wee : ve ; 5 ; 473 vated : ye qs ie mn, i . wieas) main. : 4 tw \ ro ^' f- - ( : \ 4 . ol 4 1 j 4 i t ' i $y wv ' . os : et he ' 1 tye sO ubee and ' . > ee wt ue ~ sw e e e ed v4? 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