Document kD7Ey77EyRya2nwG9RYgDQyOE

FILE NAME Brakes BRK DATE 2003 DOC BRK134 DOCUMENT DESCRIPTION Research Paper - Asbestos in Friction Materials Levin et al Missing First Page 640 J. L. LEVIN ET AL or emitted as olivine or forsterite particles p ) An therefore trapped that 99.9 of the mass of original asbestos industry lab reported silicates during brake fibers was broken down into nonfibrous magnesium Williams & Muhlbaier 1982 p 70 These investigators did usage that while brake usage was responsible for a minor fraction of acknowledge be noticeable increases from such asbestos in ambient air there could sources in high braking areas such as toll booths of Jaffrey 1990 found that analysis by transmission electron microscopy air samples collected adjacent tboratkreas fafndiccluatrcehaess rfervoemalevdehitchautlaarsbtreasftfoisc fibers were being released from numbers of asbestos fibers including some long His study showed quantifiable in contrast with the findings of Jacko et al 1973 fibers > ...mAdditionally of air samples during brake repair and samples of are findings in analysis Rohl and Langer Rohl et al 1976 These worn brake drums as reported by investigators reported that unaltered chrysotile was observed It was sug- gested from this study that fiber concentrations frequently in excess of reg- ulated limits were common p 110 in brake lining maintenance thus em- phasizing the potential of exposure to after asbestos from such products of Limited information exists as to exposures during either replacement Ficate the used facility huasdedwtoorkreedfaibn- asbestos clutch components or in operations where the processes are clutches A patient evaluated in our such a refabrication facility and had been diagnosed with disease The tissue and sputum analysis revealed asbestos bodies Clutches were provided that were repotrhteedhiasstosriimciallardattoato honseexrpeopsauirreedainndthceomfapcairlietdy This present study ecxhaarmaictneerdistics of material obtained from the clutch faces twhiethmocrhaprhaocltoergiisctailcs of the asbestos fibers found in the worker's lung CLINICAL BACKGROUND man whose admission record indicated The patient was a year of breath and persistent cough The he had complained of both shortness diffuse interstitial fibrosis at the lung bases as clinical evaluation revealed also was found to have scarring The patient well as bilateral apical pleural function revealed coarse rales on clinical examination and pulmonary The individ- lung disease severe restrictive and reduced diffusion capacity for 35-40 ual had smoked one to one and a half packs of cigarettes per day a years and history of working in a facility that reprocessed clutches His the use of drilling connectors as necessary for role in the process included There was no other separation of the components for further processing bron- known occupational history of exposure to asbestos A optic choscopy was performed and btohediweasshTihnegsdwie agrneosfiosunadt ttohicsonatdamiinssaippornecwiaas - ble numbers of ferruginous with an underlying complication of determined as eosinophilic pneumonia induced fibrosis ASBESTOS IN FRICTION MATERIALS 641 The patient became more dyspneic and suffered from weight loss In a subsequent admission a large mass was detected in the right hilar area by computerized tomography which also confirmed severe interstitial fibrosis Figure ) A computerized tomography biopsy was used to deter- mine the mass was a small undifferentiated carcinoma Formalin fixed tissue was collected at the time of autopsy and used for determination of asbestos burden by light and electron microscopy METHOD Two bags containing used clutches similar to those used for refrabication were received Eight random clutches were selected and external debris was carefully removed from their surface The exposed face from each of the clutches was washed with a measured flow 100 ...lof distilled water The rinse along with the suspended particles was collected and placed in a vial The rinses were pooled and increased to a volume of 10 ml The sample was gently swirled to resuspend the particulates and allowed to settle for one minute One half of the volume was filtered through a mm 0.2 pore polycarbonate Nuclepore filter The particulates were coated with evaporated carbon and the filter matrix was FIGURE 1. Computerized tomography CT scan of the chest This slice shows a large right hilar mass bronchus black arrow Dense consolidation is noted just lateral to the enveloping the right mainstem Severe interstitial changes are seen bilaterally right hilar mass compatible with obstructive pneumonitis consistent with the diagnosis of asbestosis white arrow 642 J. L. LEVIN ET AL removed with chloroform The carbon replicas mounted on mesh grids were examined at magnifications of up to 50,000x in a JEOL 1200EX analytical transmission electron microscope which was equipped with an ^ DAXDX Prime ray dispersive analysis system Tissue Preparation Formalin lung tissue was submitted for analysis to determine the of asbestos There were 18 sites sampled and a digest pool was presence made that contained 0.3814 g dry weight The pool was carried through a modified bleach digestion procedure Williams et al 1982 and aliquots were collected on filters For light microscopy analysis fourth of a mixed cellulose ester filter 0.22 pores that contained 0.0346 g dry weight was mounted on a glass slide and cleared by exposure to an ace- the tone The transparent wedge of the filter was then scanned for vapor of ferruginous bodies by light microscopy AO Microstar light presence body which consisted of an elon- microscope at 4 wit0 h 0 cox loArfeerdruogfitneonusbeaded surface features and a clear gated structure fibrous core was considered to be an asbestos body for electron microscopy analysis representing 0.0069 g The preparation polycarbonate 0.2 pores filter dry weight was collected on a mm removed of the coated filter were cut and the filter matrix was extraction replica Strips to chloroform which produced a carbon by exposure All fibers with an aspect ratio > containing the entrapped particulates in the ana- and equal to or longer than 0.5 ...mwere evaluated at 20,000 and a scan was carried out at low magnifica- lytical electron microscope tion 1200 for the presence of ferruginous bodies RESULTS The clutches showed considerable physical wear Figure 2 There were fibers and some bundles found in the collected sample of the abundant classified as bundles fibrils or clutch washings These particulates could be of the abundance of clusters of chrysotile asbestos Figure 3 Confirmation is that there chrysotile structures which were roepaedniliyngfrFeeidguvriea a4geTnhtleereriwnesr ee % of the were up to 1000 fibers per grid which had a diameter greater than 0.25 fibrous particulates in one samplingbetween 0.24 and 0.11 ...min diameter ...mFive percent of the fibers were Most of these were typically less than in diameter while 93 were 0.1 m from 0.04 to 0.08 ...m chrysotile diameters ranging single fibrils with less than 8 in length while Regarding length 90 of the structures were ...m asbestos fibers were larger 75 were less than 5 ...mLess than % of the 60 and than 20 The shortest fibril was 2 mwhile the longest was ...m had a diam...etmer of only 0.06 ...mThe serpentine asbestos components of the ASBESTOS IN FRICTION MATERIALS 643 FIGURE 2. Illustration of the conditions of typical clutches that were scheduled for refabrication surface of the material shows conspicuous wear The FIGURE 3. Material collected from the surface of the used clutches contained various types of chrysotile structures Magnification 12,000 644 J. L. LEVIN ET AL well as a cluster of material which contains the FIGURE 4. This figure shows both individuals fibrils as individuals fibrils as well as multiple fibrils Magnification 10,000 greater classifiable as chrysotile by the typical scroll appear- particulates were readily 5 and as further confirmed by the ele- ance at higher magnification Figure dispersive analysis Figure 6 as well as mental composition by ray energy selected diffraction There were crystalline composition confirmed by that could be detected no indications of fiber degradation or conversion numbers of as- Tissue analysis confirmed the presence of appreciable These entities represented a gram of dry tissue fibers that had been bestos bodies 3810 per of the longer population > ...mof asbestos macro- portion inhaled and eventually coated through interactions with pulmonary not Several of the bodies were obviously formed on bundles an phages such core material Dodson et al 1982 unusual finding chaorfacttheericzoirnegs by analytical transmission electron microsof more complex 1983 The analysis whether of several fibrils or copy confirmed the cores There were occasional composition to be chrysotile asbestos Figure 7 commonly encountered fibrils however the most of the fibril An example bundles of chrysotile finding was chrysotile in the form of an individual fiber count features was demonstrated in a continuous compositional where 30 of the fibers were chryso- by transmission electron microscopy and an average diameter of 0.063 tile with an average length of 12.95 ...m aluminum ferrosili- There was one anthophyllite fiber one magnesium The uncoated ...m and one titanium fiber also found in the count area 2 cate fiber burden in the tissue was determined to be than of chrysotile fibrils combined with bundles per gram ee million chrysotile structures dry tissue ASBESTOS IN FRICTION MATERIALS 645 FIGURE 5. This higher magnification view of the chrysotile chrysotile components clearly shows the tubular con figuration consistent with the morphology of chrysotile Magnification 100,000 DISCUSSION The sample of the loose surface material from the used clutch faces contained a large number of bundles fibers and fibrils These structures were identified by ultrastructural morphology ray dispersive analysis and selected diffraction as chrysotile asbestos There were no discernable changes in the fibers or any indication of transitional forms to another mineralogical form There were abundant individual fibrils as well as bundles of fibers that were in the respirable range Timbrell 1965 These included both short < ...mand longer fibers The majority of the freed fibers were less than 8 um which is consistent with data from air samples in many occupational exposure settings The process for removal of the loose material utilized a gentle rinse with water Given the potential C 70 40 10 ul 80 sal 3.50 Fe Fe ri m rn Fe La hte 5.607 adel 77 FIGURE 6. ray dispersive pattern from the retrieved material indicated elemental composition and peak ratios consistent with chrysotile asbestos 646 J. L. LEVIN ET AL FIGURE 7. This higher magnification view of the core material of a ferruginous body shows both the multiple components of chrysotile that make up the core material and the tubular array consistent with chrysotile Magnification 40,000 for chrysotile to separate under trauma it is reasonable that a physical dis- turbance of the surfaces of the clutches would create even larger numbers of respirable size fibers as the aggregates break into smaller units These findings are in contrast with those suggesting that asbestos and friction products are pulverized and trapped in the housing or converted to a nonasbestos mineral during use Jacko et al 1973 Williams et al 1982 The lung tissue from the worker contained both short fibers of chrysotile population and longer fibers including the cores of the ferruginous body Thereis considerable contrast between the ferruginous bodyburden in this individual's lung 3810 per graom f dry tissue and that constitutingthe bur- den of the general population of nonoccupationally exposed individuals livingin East Texas Our studies indicate thatin this group the ferruginous body burden ranges from 0 to 200 ferruginous per gram of dry lung tissue Dodson et al 1983 1999 The finding of 2 million chrysotile structures per gram of dry tissue also contrasts with our findings findings regarding asbestos burden in nonoccupationally _. exposedindividuals from the East Texas region In a studyof 33 such indi- chrysotile fibers for the 14 positive individuals consisted of 68,000 fibers per gram dry lung whereas the averagefor all 33 individuals was 29,000 fibers pergram of dry weight of luntitgssiuessue Dodsonet al 1999 ASBESTOS IN FRICTION MATERIALS 647 The numbers of uncoated chrysotile fibers are of even greater relevance given the impact that clearance can take place from time of first exposure to that of death It is recognized that chrysotile being a curved fiber is less respirable when compared to a comparable amphibole fiber Furthermore it has been reported that chrysotile more readily inhaled in a short form clears more rapidly from the lung than amphiboles Hammar & Dod- son 1994 An expected difference in this case report was in the limited numbers of bundles found within the tissue samples as compared with the clutch washings While this could be explained by the limitations of res- pirability as based on theoretical diameter there were adequate numbers of such bundles in the workplace that some bypassed entrapment in the upper airways and were found in the parenchyma a The study shows striking similarity between chrysotile structures ob- tained from the faces of clutches that were similar to those being repaired by the worker and the chrysotile population found in the lung tissue These data suggest that work with such friction materials in the after phase may result in appreciable exposure to asbestos dust sufficient to cause clinical disease of the type seen in this case including interstitial fibrosis and lung cancer REFERENCES Dodson R. F. O'Sullivan M. F. Williams M. G. and Hurst G. 1982. Analysis of cores of ferrugi- nous bodies from former asbestos workers Environ Res 171 178 Dodson R. F. Williams M. G. and Hurst G. A. 1983. Method for removing the ferruginous coating from asbestos bodies J. Toxicol Environ Health 959 966 Dodson R. F. Williams G. Huang J. and Bruce J. R. 1999. Tissue burden of asbestos in nonoccupa- tionally exposed individuals from East Texas Am J. Ind Med 281 286 Hammar S. P. and Dodson R. F. 1994. Asbestos In Pulmonary pathology vol 2 eds D H. Dail and S. P. Hammar pp 901-983 New York Springer Jacko M. G. DuCharme R T. and Somers J. H. 1973. Brake and clutch emissions generated during vehicle operation New York Society of Automotive Engineers Jaffrey S. A. M. T. 1990. Environmental asbestos fibre release from brake and clutch linings of vehicular traffic Ann Occup Hyg 529 534 Landrigan P. J. and Kazemi H. 1991 The third wave of asbestos disease Exposure to asbestos in place Ann NY Acad Sci 643 Rohl A. N Langer A. Wolff M S. and Weisman I. 1976. Asbestos exposure during maintenance and repair Environ Res 110-128 Timbrell V. 1965. The inhalation of fibrous dusts Ann NY Acad Sci 255 273 brake lining Williams M. G. Dodson R. F. Corn C. and Hurst G. A. 1982. A procedure for the isolation of amosite asbestos and ferruginous bodies from lung tissue and sputum J. Toxicol Environ Healtn 627-638 Williams R. L. and Muhlbaier J. L. 1982. Asbestos brake emissions Environ Res 70 82