Document RJaVpdOXx9R7J1Zr0N0jYdQBv

FILE NAME Brakes BRK DATE 1976 Feb DOC BRK057 DOCUMENT DESCRIPTION Journal Article - Airborne Asbestos in the Vicinity of a Freeway Aameeplerte Laviorumeet Val bt, pp. 63-50%. Porque Press 1976 Primed in Goont Detain, AIRBORNE ASBESTOS IN THE VICINITY OF A FREEWAY J. ALSTE D. WATSOanNd T J. Bagg Department of Industrial Science University of Melbourne Parkville Victoria 3052 Australia i <q ee 4 First received 22 December 1975 and in final form 16 February 1976 Abstract fibres taken from fresh or worn brake linings or collected from the atmosphere ncar a freeway were examined by electron microscopy and electron diffraction The major effect of braking appears to be in separating bunches of fibres and reducing their average length but not in altering their crystal structure The suggestion that gross changes in the crystal structure are brought about by heat generated during braking is not supported by this work Airborne samples were collected at points where there was considerable braking and where there was only slight braking At the point where slight braking took place the airborne concentration was very low and could not be satisfactorily measured At the point where considerable braking occurred an estimate of 5 ^ 10 mparticles was determined each particle consisting of a small bundle of fibres The majority of particles had a dimelin neas r di imeo nsin on 62 m The concentration of asbestos fibres in the atmos of mining the asbestos mineral or manufacturing asbestos products It has been known for a long time that the inhalation of fibres at these concentrations is injurious to both man and animals Merewether 1930 A qualitative standard which has been pro- posed by the EPA News Forus thise thar t the ere cate samples differing by a factor of 2-3 Selikoil 1972 Nicholson et al 19731 Asbestos was also found to be present in all 200 samples taken from the atmosphere of 49 cities in the U.S.A. Selikoff 1972 The source of asbestos emissions in the absence of asbestos mining and industry is a matot f se pecr a- lation but one strong possibility is from the brake considerable wear leading to the release of asbestos dust In one careful study the release of asbestos was and manufacture of asbestos products One criterion lector and capturing the total emission Jacko et al for a recommended quantitative standard is that the 1973 A total emission of 17.8 gkmf,,or passenger concensht our ld a not t ei xco eedn5 x 10 fibres m vehicles and 54.8 gkm travelled for light trucks of length < 5 mfor a 30 y exposure and that this were quoted as typical values Not all this emission standard should become more rigorous after July reached the atmosphere some depositing upon the 1976 becoming 2 ^ 10 fibres mNIOSH 1972 ground and some being retained by the brake drum U.S. Dept. Labor 1972 Gear nd Wm esta Gern man The fraction which became airborne was estimated propoas greae lwis th the more rigorous standard sug- gested above Schutz and Woitowitz 1973 Extensive work has been carried out on the worok f e worr kes rs exposed in the industries producing airborne asbestos to be 3.7 for passenger vehicles and 29 for trucks This researalcsho gave the expected result that heavy braking prod mou re c emie ssid on than light braking Although it is very difficult to convert these results Muchless work has been carried out on the presence into atmospheric concentrations clearly only very low of asbestos in the atmospfharearwaey from any such concentrations would be anticipated industry Asbestos was found in all samples taken from the atmosphere of several cities in Europe which did have an asbestos industry Holt and Young 1973 The asbestos was present chiefly as single fibres but a small fraction occurred as agglomerates No quanti- Lynch 1968 examined the dust from brake linings and from the appearancofe the fibres suggested that the crystal of structure the fibre was degraded by heat released during braking Holt and Young 1973 found that fibres collected by them from the atmos- tative estimate of concentration was made but com- pared to other suspended particulates it was small phere showed very little evidence of loss of crystallinity and therefore following Lynch's suggestion Preliminary results for New York city showed concentrations ranging from 11 to 60 ng mwith dupli- concluded that building materials were a more likely source than brake linings Present address A.C.I. Environics P.O. Box 8. Newport Victoria Australia + Present address C.S.LR.O Division of Tribophysics Melbourne Australia The aim of the work reported here was to examine more closely the possible contribution that brake linings could make to the asbestos concentration in the atmosphere 583 7 lg A ig WE ee SLE EATEN ake at an ne ants Se ne ort pose eens a San ke OM 584 J. ALSTE D. WATSON and J BAGG EXPERIMENTAL A number of methods have been proposed for the esti mation of asbestos particles in the atmosphere Keenan and Kupel 1968 Lane et al 1968 Gadsden et al 1970 but at the present time the only method of sufficient sensitivity and selectivity for the very low concentrations involved is the electron microscopy of samples collected on suitable filters Atmospheric samples were collected on a Millipore filter VSWP 047 0.025 mpore dia at an average flow rate of 0.61 min A Volume sampler was modified by placing an aluminium plate containing a small tube over the inlet to the sampler A Millipore filter holder was connected by a plastic tube with a rotameter interposed to the small tube on the face plate Samples were taken at three locations ) on the roof of the Department of Industrial Science University of Melbourne 10 m above street level and 30 m from the nearest traffic ii outside the same building 0.8 m above street level iii at the exit of the S.E. end of the Tullamarine freeway 0.8 m above ground level This last sampling point was 50 m from the position where brakes were applied to reduce the speed of vehicles from approx 100 to 60 km h The total number of vehicles passing all three locations during the total sampling period was very similar and the major difference was the absence locations ( and ii or presence Location il of extensive braking The sampling period was from 08.00 17:00 h during November 1973 the weather was fine with only light winds over this penod After the samples had been collected the Millipore filters were coated with a carbon film approx 20 nm thickness and then five small pieces 1.5 ^ 1.5 mm cut out at random Each small section was placed on a copper grid carbon film facing down and the membrane material removed by dissolution in acetone Electron micrographs and diffraction patterns were obtained from these specimens using a Phillips EM 200 microscope at 80 kV The electron diffraction patterns were calibrated by evaporating aluminium on to the copper grid and by comparison interplanar spacings which could be deter- mined Samples of fresh and worn brake drum linings were obtained from an automobile repair shop and were crushed gently in a mortar and pestle with a few ml of chloroform An electron microscope grid covered with a smooth film of evaporated carbon was then dipped into this suspension and the chloroform allowed to evaporate RESULTS AND DISCUSSION Figures 1 and 2 show electron micrographs and diffraction patterns from a sample prepared from a fresh brake lining The characteristic structure of chrysotile asbestos long filaments each of which is a hollow cylinder McCrone and Delly 1973 is clearly visible in this micrograph The electron diffraction patterns of chrysotile have been determined and indexed by Yada 1967 1971 In Table 1 the inter- planar spacings determined from the pattern of fresh brake linings are compared to Yada's values and the agreement is seen to be excellent Figures 3 and 4 show results for the dust from worn brake linings The average length appears to be shorter than in the fresh lining but the hollow cylin- drical structure is still obvious The diffraction pattern still consists of defined rings and the interplanar spacings derived from these rings are in good agree- ment with Yada's values see Table 11 There was no indication from the diffraction pattern of the presence of forsterite the name given to thermally asbestos It appears that for the wear this lining had received no significant changes in the crystal structure due to excessive heating had taken place Tempera- tures within brake drums may reach 873 K under racing conditions with severe and repeated braking fe SONI Re ares EAT TN VN RE Re to teh ten BRL ER OOD RTE SPOIL TINE EN IEEE AER SIN re Es $FMaR aS STAH Sis CBETEM TNE catia ne LS ASAE 3 BOAT Se SEIS RA ESOAEO REDS ESET, BOSE: ts OSE Buttle ent obese Sis w emt ba fealty Fayed A . 2. Diffraction pattern from sample in Fig 1 but would be expected to be very much lower under normal city driving Chrysotile has been shown to maintain its crystal structure until temperatures in excess of 800 are reached Yada 1971 Robock and Klosterkotter 1973 The observations on the worn brake drums are then consistent with the likely temperatures reached and the known thermal behav- iour of chrysotile Yada 1967 1971 has shown that electron bombardment inside the electron microscope can lead to production of amorphous material in the fihres and therefore excessive exposure during exam- ination should be avoided Table 1. Values of dilikh for chrysotile and brake linings nm * 10 Values for chrysotile Yada 1967 1971 Fresh brake lining 7.30 x 4.50 365 270 7:30 Worn brake lining 7.21 tie 367 267 251 215 12182 Plane Chikh 007 130 020 002 2000 130 2011 1003 1003 220 040 202 1004 JO OL 330 1005 400 13663 13663 Samples taken either on the roof or at ground level near the Department of Industrial Science contained very low concentrations of asbestos fibres Fig 51 Although the rings in the diffraction pattern Fig 6 are more diffuse than from fresh linings the inter- planar spacings shown in Table 2. again match both the values for fresh linings and Yada's values Although the comparison in Table 2 enabled the presence of asbestos to be deduced no attempt was made to estimate the atmospheric concentration because of its very low value Samples taken at the exit from the freeway however contained a much higher concentration of asbestos particles Figs 7 and 8 estimated at an aver- age of 5 10 particles m 3 over the 9 h sampling period The general appearance of the fibre clusters and the presence of other material is very similar to that observed for the worn brake lining dust Again the diffraction patterns do not show significant amounts of amorphous material and match Yada's values Table 2 Table 2 Vabies of APK for chrysotile and airborne asbestos mm 10 Values for chrysotile Yada 1967 1978 Arki 365 02 22154 154 220 022 x0 950 121 80 Dept Industrial Seme 165 2.20 2.20 2.20 150 12 Tullamarine freeway ext 300 215 215 175 175 tas Dust sample from worn brake lining ... Fig 4. Diffraction pattern from sample in Fig 3 Fig 5. Atmospheric sample collected 0.8 m above ground level at Melbourne University eX Bsfas ae 5a =si SarIP Se ee SEIS : as on Sate etS LI N NR R R 1a AE ge 0s D seipt hages OEE ee 7" e ceot Fig 7. Atmospheric sample collected 0.8 m above ground level at the exit of Tullamarine Freeway +. ee on a ras re omy \ ; i | we - bee Che oor Be Airborne asbestos in the vicinity of a freeway 589 are Atmospheric 4 667 mat The particles consisted of small bundles of fibres metric technique Atmospheric Atmospheric Environment together with other material which may have contained binder present in brake linings Another poss- 670 Holt P. F. and Young D. K. 1973 Asbestos fibres in the atmosphere of towns Atmospheric Environmen 7 481 ible source for this amorphous material consistent 483 669 670 with a location where braking occurred is wear from Jacko G. J. DuCharme R. T. and Somers J. H. 1973 tyres Measurements by other workers Pierson and How much asbestos do vehicles emit Auto Engng 81 38-40 Brachaczk 1975 have shown concentrations of air- Keenan R. G. and Kupel R. E. 1968 Modern techniques borne debris from tyre wear from 0.05 to 2.2 gm for evaluating mixed environmental exposures to fibrous The number of fibres in the bundle and their size and particulate dustsin the asbestos industry print varied considerably and no attempt was made to count individual number of fibres The majority of bundles did have a maximum dimension < m U.S. Public Health Service National Centre for Urban and Industrial Health Cinncinati OH Lane R. E. et al 1968 Hygiene standards for chrysotile asbestos dust Ann Occup Hyg 11. 47 69 Although these results are limited and of a prelimi- Lynch R. J. 1968 30th Annual Meeting American confer nary nature the following points can be made ence of Government Hygienists St. Louis MO ) Electron diffraction has proved to be a method of great sensitivity in the identification of asbestos McCrone W. C. and Delly J. G. 1973 The Particle Atlas Vol 3..2nd Edn p 586. Ann Arbor Science Publishers Ann Arbor MI particles suitable for the low concentrations found in Merewether E. R. A. 1930 The occurrence of pulmonary atmospheric samples fibrosis and other pulmonary infections in asbestos ii Asbestos fibres from brake linings operated under normal conditions have the same crystal structure as asbestos from other sources The absence of ther- workers J. Ind Hyg 12. 239-257 News Focus 1973 EPA sets final emission standard for asbestos beryllium mercury J. Air Polha Control Ass 23. 398 degraded material cannot therefore be taken Nicholson W. J. Langer A. M. and Selikoff L. 1973 as evidence that brakes have not contributed to a Asbestos in the atmosphere of towns Atmospheric En- particular sample iii The results from the samples collected at the freeway exit suggest that emissions from brakes can recommended vironment 7. 666-668 666-668 NIOSH 1972 Criteria for a standard Occupational exposure to asbestos Document HSM 72-10267 1972 U.S. Dept. of Health Education and become airborne The concentrations reached are Welfare very low below the recommended exposure standard NIOSH 1972 U.S. Dept. Labor 19721 and consis- tent with the prediction by other workers that only a small fraction of the total dust formed becomes airborne Jacko et al 1973 Acknowledgements authors would like to thank Dr. 3. V. Sanders C.S.I Division of Tribophysics University of Melbourne for considerable assistance and use of electron microscope facilities One of us J. Alste wishes to thank A.C.L Fibreglass for support during this work REFERENCES Gadsen J. A. Parker J. and Smith W. L. 1970 Determina- Pierson W. R. and Brachaczk W. W. 1975 traffic measurement of airborne wear particulate debris J. Air Pollut Control Ass 25. 404-405 Robock K. and Klosterkotter W. 1973 Investigations in the cytotoxicity of asbestos dusts Staub 33 279 283 Schutz A. and Wonowitz H. J. 1973 Technical standard values for the admissible working place concentration of chrysotile asbestos Stawh 33. 445 450 Selikoff I. J. Nicholson W. J. and Langer A. M. 1972 Asbestos air pollution Arch Environ Hith 25. 1-13 U.S. Dept of Labor ment T2-366 T2-366Study Yada K. 1972 Washington Information docuof chrysotile asbestos by a high resolution microscope Acta Cryst 23. 704 707- Yada K. 1971 Study of microstructure of chrysotile asbestos by high resoluton microscopy Acta Cryst A27 tion of chrysotile in airborne asbestos by an i.r. spectro- 659-664