Document GB2rK4rpv0xY1jzw4XQ6eX5m

FILE NAME Brakes BRK DATE 2008 Feb DOC BRK176 DOCUMENT DESCRIPTION Accepted Article - Study of Chrysotile Concentrations Associated with Working with Clutch Discs Accepted Manuscript em aa Box A Study of Airborne Chrysotile Concentrations Associated with Handling Un- packing and Repacking Boxes of Automobile Clutch Discs George C.T. Jiang Amy K. Madl Kelsey J. Ingmundson Dana M. Murbach Kurt A. Fehling Dennis J. Paustenbach Brent L. Finley PII DOI Reference To appear in S0273-2300 0039-1 j.yrtph.2008.02.009 YRTPH 2124 Regulatory Toxicology and Pharmacology Received Date Revised Date Accepted Date 30 November 2007 19 February 2008 22 February 2008 Regulatory Toxicology and Pharmacology Regulatory Journal Toutlogy Toutolgy internatinat mlagy of ScienceDirect Please cite this article as Jiang G.C.T. Madl A.K. Ingmundson K.J. Murbach D.M. Fehling K.A. Paustenbach D.J. Finley B.L. A Study of Airborne Chrysotile Concentrations Associated with Handling Unpacking and Repacking Boxes of Automobile Clutch Discs Regulatory Toxicology and Pharmacology 2008 doi 10.1016 j.yrtph.2008.02.009 This is a PDF file of an unedited manuscript that has been accepted for publication As a service to our customers we are providing this early version of the manuscript The manuscript will undergo copyediting typesetting and review of the resulting proof before it is published in its final form Please note that during the production process errors may be discovered which could affect the content and all legal disclaimers that apply to the journal pertain A Study of Airborne Chrysotile Concentrations Associated with Handling Unpacking and Repacking Boxes of Automobile Clutch Discs George C.T. Jiang 1 Amy K. Madl ' Kelsey J. Ingmundson ,,Dana M. Murbach ' Kurt A. Fehling , Dennis J. Paustenbach 1 and Brent L. Finley ' ChemRisk 25 Jessie Street Suite 1800 San Francisco CA 94105 * Corresponding Author Brent L. Finley ChemRisk Inc. 25 Jessie Street Suite 1800 San Francisco CA 94105 Phone 415 896-2400 Fax 415 896-2444 Email bfinley@chemrisk.com Keywords Asbestos Automobile Clutches Chrysotile Exposure Assessment For Submission to Regulatory Toxicology and Pharmacology Running Title Clutch Study 0.001 cc and 0.004 -0.002 cc when 1 or 2 boxes of clutches were handled respectively Estimated hr TWA asbestos exposures for a worker handling 1 or 2 boxes of clutches over a workday ranged from 0.002 to 0.006 cc The min PCM adjusted average airborne asbestos concentration for a worker continuously stacking unopened boxes of clutches was 0.212 = 0.014 cc the hr TWA was 0.013 cc Additionally min PCM adjusted average airborne asbestos concentrations following cleanup and clothing handling were 0.002 -0.001 cc and 0.002 + 0.002 cc respectively both resulting in estimated hr TWA asbestos exposures of 0.0001 cc The results of this study indicate that the handling unpacking and repacking of clutches and the subsequent cleanup and clothes handling by a worker within a short period or over the entire workday result in exposures below the historical and current short and hr occupational exposure limits for asbestos INTRODUCTION The purpose of an automotive manual clutch is to allow for alternate connection and separation of the engine to the transmission shaft that drives the wheels Similar to automotive brake pads and linings clutch disc faces frequently contain friction materials that come in contact with rotating metallic surfaces Over time the friction materials on the clutch will wear and the clutch disc must eventually be replaced or the clutch will begin to slip Manual clutches typically require repair or replacement every 50,000 to 100,000 miles Figure 1 illustrates the location of a clutch and a away schematic drawing of a clutch disc Chrysotile asbestos was a primary component of the friction material in manual automobile and truck clutch discs from the early 1900s to the 1980s The chrysotile fibers if present which comprised approximately 30-60 of the original clutch disc facing material offered superior frictional characteristics such as good tensile strength durability flexibility and heat resistance Paustenbach et al 2004 Sheehy et al 1989 Skinner et al 1988 By the mid1980's several acceptable substitutes for chrysotile asbestos were identified and the manufacture and use of containing manual clutches was gradually discontinued in the United States Paustenbach et al 2004 Paustenbach et al 2003 During manual clutch installation and repair asbestos fibers might become airborne if clutch wear debris is present Clutch wear debris is formed when the friction material degrades due to the heat and pressure generated when the clutch surface is in contact with the flywheel and pressure plate It has been known for several decades that similar to brake wear debris the levels of chrysotile asbestos in clutch wear debris are very low if any are detected Boelter et al 2007 Kauppinen and Korhonen 1987 Lynch 1968 R J. Lee Group 2004 Yeung et al 1999 Specifically in 1968 Lynch reported no detectable fibers in clutch wear debris following normal 3 driving conditions Lynch 1968 Other reported measurements of asbestos in clutch wear debris are < % Boelter et al 2007 and detect to 0.4 R.J. Lee Group 2004 This is consistent with the fact that airborne concentrations of asbestos during clutch repair are also quite low Numerous studies have shown that the weighted average TWA airborne asbestos levels during installation of containing manual clutches on automobiles and heavy equipment are consistently below the current OSHA hour permissible exposure limit PEL of 0.1 cc Boelter et al , 2007 R.J. Lee Group 2004 Yeung et al 1999 Workers who handle unpack and repack boxes of new clutches could also theoretically experience some degree of exposure to asbestos Such workers would include the mechanics themselves bystanders pickers and other staff at a distribution center or an auto parts store Theoretically residual asbestos fibers could be present inside a new clutch box possibly as wear during product shipping or as a result of airborne fibers settling into the open box in the manufacturing or packaging facility These residual fibers could become airborne when the boxes are handled or the clutches are removed from the box and installed or when clutches are repacked into the original box or another container To date there are no studies that describe airborne asbestos concentrations associated with clutch or box handling or cleanup activities We recently completed a study involving boxes of containing brake pads and discs Madl et al 2007 In that study we measured worker and bystander airborne asbestos levels during the unpacking and repacking of containing brake pads and brake shoes The results indicated that 1 airborne asbestos concentrations increased with the number of boxes unpacked and repacked 2 handling brake pads resulted in higher asbestos concentrations than handling brake shoes and ) amphibole fibers were not detectable in bulk samples of the brake pads and shoes In this analysis we employ a similar research protocol to characterize potential worker and bystander exposures to asbestos during the handling unpacking and repacking of asbestoscontaining clutch discs Short and hour TWA concentrations were measured and calculated under a variety of worker scenarios In addition we evaluated 1 potential asbestos exposures associated with clean and clothes handling activities and 2 size and morphology of airborne asbestos fibers The resulting data are compared to historical and current OSHA short and term asbestos standards and cumulative chrysotile exposures experienced by other cohorts These comparisons are used to determine whether and to what degree handling packing and packing containing clutch discs might contribute to asbestos pulmonary diseases METHODS The protocol for the study was approved by Copernicus Group IRB Research Triangle Park NC an accredited Institutional Review Board IRB Description ofBoxes of Clutch Discs A total of 27 boxes of clutch discs were obtained from an automotive parts warehouse The clutches were made prior to the 1980s for passenger vehicles and were therefore expected to contain chrysotile asbestos The boxes had typically been stock and undisturbed for several years and were in good structural condition in the original packaging The boxes were not taped together and did not appear to have been opened prior to the study The boxes were not opened prior to sampling to ensure that the results would be consistent with a worker opening a new unused box of replacement clutches Each box contained one clutch disc The brands on the boxes of the clutches were used to identify the individual clutches Table II Figure 2A illustrates the worker with a stack of clutch boxes and Figure 2B illustrates close photographs of representative brands of clutch discs and their respective boxes Description ofStudy Setting The automobile repair shop where the study was conducted has been previously described in detail in Paustenbach et al 2006 Paustenbach et al 2006 The shop which is located in Santa Rosa CA is a garage with an open floor plan with dimensions of approximately 101 ft wide by 48 ft deep with a 15 ceiling Figure 3A To prevent air sampling measurements from being confounded by other repair activities in the shop no other automobile repair work was conducted on the testing days of this study Additionally the shop was not ventilated with heating or air conditioning To simulate low ventilation conditions all entry and service doors were closed during the testing Temperature and weather conditions were noted each day of the testing Description ofExposure Scenarios The different tasks evaluated over the three days of study are summarized in Table I On January 20 2007 discrete airborne asbestos measurements were obtained during the following tasks ) continuous repetitive stacking and handling 27 unopened boxes of clutches one event 2 unpacking and repacking 1 box 4 events 3 unpacking and repacking 1 box with overhead disc manipulation and dry cloth wipe 2 events or spray clean wipe 2 events 4 counter cleanup one event On January 21 2007 the tasks were ) unpacking and repacking 1 box 4 events 2 unpacking and repacking 2 boxes with overhead manipulation 2 events and 3 counter cleanup one event On January 27 2007 the tasks were ) unpacking and repacking I 6 box 4 events 2 unpacking and repacking 2 boxes with overhead manipulation 2 events 3 counter cleanup one event and 4 clothes handling one event All handling work was performed by a single individual The box and clutch handling activities were designed to be consistent with those described by career automotive mechanics and parts suppliers The handling unpacking and repacking of boxes of clutches was conducted at a 3.5 ft high counter open to the automotive repair section of the shop Figure 3A The counter was wiped thoroughly before each sampling event with a commercial cleaner and a rag Boxes of clutches were stored on the counter within reach of the worker The handling activity consisted of opening the box comparing the new replacement clutch to a demonstrative clutch and then repacking the clutch in the original box This entire process required approximately 15-30 seconds In some cases the individual also cleaned the disc with a dry cloth or spray cleaner 30 seconds and held the disc overhead 10-15 seconds before returning the clutch to the box Each box was unpacked and repacked only once The repetitive box stacking task was conducted for the entire 30 minute period Counter cleanup events occurred at the end of the day for approximately 1 minute and were performed using paper towels and wet wipes The handling task approximately 45 seconds in length involved shaking and folding 3 different pairs of overalls a fresh pair was worn by the individual during each day of testing to simulate a person handling and laundering potentially contaminated work clothes The overalls from the first 2 days were kept in a sealed bag until testing Collection and Analysis ofAirborne Asbestos Samples Airborne asbestos samples were collected in a manner consistent as previously described Paustenbach et al 2006 Briefly samples were collected using mixed cellulose ester MCE filter membranes 25 mm 0.45 ...mpore size Zefon International St. Petersburg FL USA using either portable SKC Universal PCXR West Inc. Fullerton CA. USA or Gilian Gilair pumps Sensidyne Inc. Clearwater FL USA or Dawson 1300 volume sampling pumps Ashtead Technology Rentals Hayward CA USA The sampling pumps were noted with a Bios DryCal DCLite primary flow calibrator Bios International Corporation Butler NJ USA before and after sample collection Portable SKC or Gilair pumps were used to collect asbestos samples at 2 liters per minute LPM whereas volume pumps were used to collect samples at air flow rates between 3 - 10 LPM Collection of all airborne asbestos samples was consistent with NIOSH Methods 7400 and 7402 NIOSH 1994a NIOSH 1994c During each individual event personal air samples were collected on the left and right lapels of the worker Specifically worker lapel samples were collected in both minute n 2 consecutive samples on both the right and left lapel 8 - 10 LPM respectively and minute n one sample on both the left and right lapel 3 - 6 LPM respectively time segments In addition during each event 30 minute area samples were collected at two bystander locations 5 feet from the main activity 8 - 10 LPM and a remote location over 50 feet from the main activity 10 LPM at breathing zone height 5 feet Figure 3A To assess background conditions inside the facility prior to testing three consecutive minute samples were collected at the beginning of each day of testing at both bystander locations Three consecutive 120minute ambient air samples were also collected each day of testing with a sampling rate of 10 LPM outside the south wall of the shop away from automobile traffic All event sampling was completed with the entry and service doors of the repair shop closed After each box handling clothes handling or counter cleanup event the doors of the shop were opened to out the workspace A summary of the airborne asbestos sampling events collected per exposure scenario is shown in Figure 3B Fibers were counted according to the NIOSH Methods 7400 and 7402 which define fibers as being greater than 5 ...min length and 0.25 ...min diameter and having at least a 3-1 aspect ratio NIOSH 1994a NIOSH 1994c All airborne asbestos samples were sent to an American Industrial Hygiene Association accredited laboratory EMS Laboratories Pasadena CA for analysis of asbestos by Phase Contrast Microscopy PCM NIOSH Method 7400 and Transmission Electron Microscopy TEM NIOSH Method 7402 NIOSH 1994a NIOSH 1994c Air samples were also analyzed according to the International Organization for Standardization ISO method for characterization of fiber type size and morphology offibers greater than 5 ...min length ISO 1995 Fiber Size and Morphology Analysis Because OSHA specifies PCM analysis with or without TEM analysis for the evaluation of occupational exposures to airborne asbestos most workplace measurements of asbestos utilize the NIOSH Method 7400. However the NIOSH Method 7400 PCM analysis does not differentiate asbestos fibers from other structurally similar asbestos fibers therefore OSHA has indicated that TEM analysis NIOSH Method 7402 can be used to quantify the ratio of asbestos fibers to total fibers which is then applied to the PCM fiber concentration result OSHA 1994 To assess occupational exposure to asbestos one can compare either the PCM result or the PCM adjusted result to the OSHA PEL While the NIOSH methods 7400 and 7402 cannot be used to assess the fiber size length and width of any given fiber the ISO Standard method is a refined technique using TEM that permits characterization of both fiber size and type and it can differentiate between free fibers and fibers associated with a matrix ISO 1995 Using the ISO 10312 methodology asbestos 9 fiber morphology in the personal air samples was quantified by categorizing asbestos fibers greater than 5 ...min length as free fibers free fiber bundles fiber clusters or matrix fibers including matrix fibers bundles and dispersed arrangements In those instances where asbestos fibers were associated with a cluster or matrix the dimensions of the cluster or matrix structure as well as those of the individual fibers within the cluster or matrix were recorded The ISO methodology was also used to assess the presence of amphibole fibers in the personal air samples A number of studies have shown that fibers that are deposited in the pulmonary region of the lung are thinner than 0.7 ...mand virtually all are thinner than 1 ...mHarris and Timbrell 1975 Strom and Yu 1994 Sussman et al 1991a Sussman et al 1991b Yu et al 1995 Therefore for the purposes of this analysis respirable fibers free and bundles were designated as those with width of 0.7 ...mor less Collection and Analysis of Bulk Asbestos Samples Filings of the clutch lining material from each box and the dust that accumulated on the counter during the box handling activities were collected for bulk sample analysis for asbestos in a plastic bag which was then sealed and sent for analysis Both types of bulk material were analyzed by EMS Laboratories Pasadena CA using Ray Diffraction XRD according to NIOSH Method 9000 NIOSH 1994d and Polarized Light Microscopy PLM according to NIOSH Method 9002 NIOSH 1994b XRD analysis was used to determine the % composition by weight of the bulk samples that were comprised of asbestos while the PLM analyses were used to assess the presence of chrysotile or amphibole asbestos fibers The limit of detection LOD for PLM analysis was % 10 Air Exchange Measurements Using Tracer Gas Sulfur hexafluoride SF6 was used as a tracer gas to estimate the air exchange rate within the garage as previously described by Paustenbach and coworkers Paustenbach et al 2006 In summary measurements of the gas were taken according to ASTM Method E741-00 ASTM International 2001 A steady concentration of 1 ppm for SF6 Aldrich St. Louis MO was targeted for the tracer gas analysis Based on the estimated volume of the repair shop three Tedlar bags Fisher Scientific Hampton NH were filled with SF6 outside of the garage to prevent leakage into the shop The bags were then released in the garage with all doors closed Fans on either end of the garage were used to facilitate dispersion of the gas After steady was reached SF6 measurements were taken in sec intervals with a MIRAN SapphIRe Analyzer Electron Corporation Hayward CA for approximately 1 hr The air exchange was calculated by the following equation A In C2 In C 11 1 The air exchange in the garage was calculated using the concentration decay optional regression test method by plotting the natural logarithm of SF6 concentration over time ASTM International 2001 Data and Statistical Analyses Descriptive statistics were calculated for both PCM and TEM measurements of airborne fiber concentrations Analytical sensitivity limits were estimated based on the presumption that 1 fiber could be counted within 100 microscopic fields and the volume of air sampled NIOSH 1994a NIOSH 1994c Results below the analytical sensitivity limit LOD were inputed using a value equal to half the sensitivity limit PCM measurements were adjusted adjusted for asbestos fiber content according to the method outlined in NIOSH Method 7402 which specifies multiplying 11 the ratio of asbestos fibers to total fibers observed in the TEM analysis by the PCM fiber concentration NIOSH 1994c The ratios of asbestos to total fibers asbestos and asbestos fibers were based on TEM fiber counts for the same filters from which the PCM fiber counts were obtained The PCM measurements adjusted by the ratio of asbestos versus total fibers were referred to as PCM adjusted PCMadj airborne asbestos concentrations in this study In cases where the PCM result was below the analytical sensitivity limit but asbestos fibers were detected in the corresponding TEM measurement a value of half the PCM analytical sensitivity limit was substituted and multiplied by the ratio of asbestos fibers fibers observed by TEM In circumstances where PCM measurements were above the sensitivity limit LOD but asbestos fibers were not detectable by TEM a adjusted asbestos concentration was not calculated All of the reported measurements for the various activities are the actual measured values and have not been adjusted for contributions from background or ambient sources minute TWA and hr TWA airborne asbestos concentrations were calculated from the consecutive min samples collected on the right and left lapel of the worker using the following equations respectively C * 30 min 2 C * 480 min 3 where C is the average airborne concentration cc for the left and right lapel collected for each of the sampling segments and , is the duration of the task For the hr TWA calculation the mean of all the measured background values was assumed to be present for the remaining 7.5 hours of the workday The min concentrations were compared to the historical OSHA 15- min ceiling limit of 10 cc 1972 1986 and the calculated min TWA concentrations were compared to the current OSHA min excursion limit of 1 cc 1988 - present Eight TWA airborne asbestos concentrations were compared to the current OSHA PEL of 0.1 cc RESULTS Air exchange on the days of testing measured with SF6 tracer gas indicated rates of 0.4 air exchanges per hour on January 20 2007 2.0 air exchanges per hour on January 21 2007 and 0.3 air exchanges per hour on January 27 2007. These air exchange rates are similar to those reported previously for this building by Paustenbach et al 2006 and are low compared to the rates expected in most auto repair facilities ASHRAE 1991 Paustenbach et al 2006 This is not surprising given that no active ventilation system was present in the building and all doors and windows were kept closed during sampling Asbestos Bulk Sample Analyses The chrysotile content of each clutch is summarized in Table II Bulk sample analysis via ray diffraction XRD indicated that all of the clutches contained asbestos and the mean chrysotile asbestos content was 33.7 -2.0 with a range of 20 - 52 PLM analysis LOD % did not indicate the presence of amphibole asbestos fibers in any of the clutches Bulk sample analysis XRD of dust which had accumulated on the countertop during the unpacking and repacking of boxes of clutches indicated an average chrysotile asbestos concentration of 6.8 - 2.2 and range of 1 - 14 Table III Airborne Asbestos Sample Analyses Table IV presents the mean minimum and maximum airborne PCM TEM and PCMadj 13 data for the different activities and sampling periods Average sensitivity limits for airborne asbestos samples ranged between 0.0004 and 0.0042 cc for PCM and 0.003 and 0.009 cc for TEM data not shown As summarized in Table IV the mean of the " minute PCMadj values for unpacking a single box were very similar in all handling scenarios 0.051 cc with no manipulation 0.050 cc with dry wipe and overhead handling 0.046 cc with spray clean wipe and overhead handling As is also summarized in Table IV for each of these activities the means of the 2nd minute PCMadj values were far lower means of 0.002 0.005 and 0 001 cc respectively than the 1st minute means The mean of the 1st minute asbestos concentrations associated with unpacking two boxes 0.196 cc was higher than the 2nd means measured with one box however the concentrations measured during the 2nd minutes were far lower mean of 0.001 cc and similar to the values measured with one box The relatively higher personal measurements during the 1st minute sample 2 boxes were not evident at the bystander and remote locations Table IV Repetitive stacking and handling of 27 unopened boxes generated the highest mean concentrations in this study 1st- and 2nd minute PCMadj means of 0.231 and 0.194 cc respectively Again however airborne concentrations of asbestos above background were not present at the bystander or remote locations Table IV The trends observed in the 60 minute samples were generally consistent with those discussed above Table IV Cleanup and clothes handling activities did not generate significant concentrations of airborne asbestos maximum PCMadj value of 0.006 cc on personal lapel samples no measurable asbestos fibers at remote or bystander locations Samples collected at the bystander locations 5 feet away from the box activities were less than 0.02 cc regardless of activity 14 while all of the samples collected at the remote location contained zero PCMadj values Similarly all background PCMadj samples collected between testing events and ambient measurements were calculated to be 0.000 cc Table IV As can be seen in Table IV every individual 15 minute sample was less than the historical OSHA short term min ceiling limit of 10 cc 1972-1986 1972-1986 1972-1986 As shown in Figure 5 the calculated minute TWAs for all activities were less than the current present short term minute OSHA standard of 1 cc As shown in Figure 6 the calculated hr TWAs for all activities were far below the current hour OSHA PEL of 0.1 cc Fiber Size and Morphology Fiber size and morphology were assessed for personal worker samples collected during box handling cleanup and clothes handling activities For the purposes of this analysis the limit of detection of fiber length was 5 ...mWhen all the data are considered in aggregate all activities combined the results indicate that 57 of the fibers counted were free fibers or bundles 19 were fiber clusters and 24 were associated with a matrix Table V Approximately third 29 of the free bundles were of a respirable width less than 0.7 ...mVery few % of the bundles longer than 20 ...mwere less than 0.7 ...min width It should also be noted that % of the respirable fibers fibers of widths less than 0.7 ...m were actually bound in a matrix Using a respirable particle definition of < 10 ...min diameter yielded similar values for the clusters and matrix fibers None of the personal air samples contained detectable amphibole fibers 15 DISCUSSION The results of this study indicate a number of activity patterns and data trends that should permit an accurate evaluation of potential asbestos exposures associated with a variety of clutchhandling scenarios First unpacking and repacking unused containing manual clutches results in brief peak asbestos levels that rapidly return to concentrations at or near background levels As a result asbestos levels associated with unpacking one or two boxes did not exceed any of the historical or current short- or term occupational standards Table IV and Figures 2 and 3 Cleaning the clutch face with a dry wipe or spray cleaner did not influence the airborne asbestos levels Figure 4 Airborne concentrations at bystander locations 5 feet from the work activities were even lower and often indistinguishable from background Given the fact that garage mechanics rarely conducted more than one clutch change a week Cohen and Van Orden 2008 Kauppinen and Korhonen 1987 Yeung et al 1999 it can be concluded that clutch box handling did not result in exceedances of workplace standards for garage mechanics or workers at any point in time Interestingly the results of the stacking activity suggest that handling numerous unopened boxes in a short amount of time can result in higher asbestos levels than actually opening the boxes and handling the clutch In this study 27 unopened boxes were repetitively unstacked and otherwise moved about on the work counter throughout the first and second 15 minute periods approximately 4 cycles of unstacking during each 15 minute period The bystander but not remote concentrations were also elevated relative to all other activities The box stacking activity constituted the first sampling event on the first day and therefore the results are not due to suspension of residual fibers from previous activities Hence the results indicate that repetitive handling of numerous unopened boxes as might be conducted 16 by a distribution warehouse parts picker or occasionally by an auto parts dealer or counterman could result in higher short exposures than might be experienced by a mechanic who would would typically open one or two boxes a week at most Nonetheless the 15 minute samples were all below the historical 15 minute STEL 10 cc Table IV Figure 4 the calculated minute TWAs were all below the current OSHA 30 minute STEL of 1 cc Figure 5 and the calculated hour TWAS assuming background exposure levels for the remainder of the day were also below the current hour PEL 0.1 cc Figure 6 Personal airborne samples collected during counter cleanup and clothes handling were all low and often detectable suggesting that these activities would contribute little if any to the total asbestos exposure experienced by a mechanic parts picker or auto parts dealer The data also suggest that take home exposures as might be experienced by a person laundering the clothes of the worker would be minimal It is interesting to note that the personal TEM results were higher than the personal PCM results for all activities except cleanup and clothes handling which indicates that asbestos fibers from the cleanup activities and clothing contributed to the PCM values This is consistent with the findings of Weir et al in which airborne asbestos levels were measured during the agitation of a brake mechanic's clothing to determine the quantity of fibers remaining on the clothing Weir et al 2001 The majority of fibers were not asbestos fibers but other benign fiber types such as cotton fibers the small amount that was asbestiform was composed of chrysotile fibers Weir et al 2001 Similarly analysis of the counter top bulk samples collected at the end of each day indicated a chrysotile content of 6.8 2.2 This is much lower than the chrysotile content of the original clutch material 33 % - 2.0 suggesting the presence of asbestos material in the dust that accumulated on the counter possibly from the box itself It is also worth noting that the PCM results of the 17 bystander and remote samples were consistently higher than TEM results again indicating the presence of a significant number of asbestos fibers at these locations The low airborne asbestos levels measured in this study are consistent with recent studies of clutch handling and repair activities Yeung et al 1999 reported no detectable airborne asbestos at a detection limit of 0.05 cc PCM during a single clutch repair in an Australian passenger car service garage Yeung et al 1999 RJ Lee 2004 measured airborne asbestos concentrations PCM during clutch servicing activities that included opening of the bell housing removing the clutch plate and scraping debris from inside the housing R.J. Lee Group 2004 All hour TWAs were below the current hour OSHA PEL of 0.10 cc the highest reported concentration was 0.0363 cc and in fact most samples did not contain any detectable asbestos fibers R.J. Lee Group 2004 Boelter et al 2007 reported hr TWAs ranging from 0.007 to 0.013 cc during specific repair from heavy equipment Boelter et al 2007 In many instances the previous studies also involved brake servicing activities which may have influenced the airborne asbestos fiber concentrations Hence even if it was assumed that all of the asbestos measured in those studies was derived solely from clutches i.e. brakes and gaskets made no contribution the results would still clearly indicate that clutch repair does not result in asbestos levels in excess of workplace standards The airborne asbestos concentrations measured in this study are likely biased high for most settings First the data were collected under conditions of very little ventilation Second the boxes and the clutches used in this study were at least 30 years old and therefore the data are probably conservative for potential exposures that occurred when relatively new clutch boxes were handled or opened Third while it is reasonable to expect that a mechanic or parts picker would open and possibly repack clutch boxes on a fairly consistent basis it is unlikely that an 18 auto parts counterman would actually repetitively shuffle and stack 27 clutch boxes on a counter in a minute period The same individual conducted all of the tasks in this analysis and therefore the influence of worker variability is unknown Given the fairly simplistic nature of the tasks conducted in this study e.g. repacking or shuffling clutch boxes the influence of worker variability should be minimal Future studies evaluating more complex tasks e.g. performing a complete clutch change should address this potential variability factor The clutches used in this study contained 33.3 -2.0 chrysotile asbestos by weight as determined by ray diffraction Although chrysotile fibers were used to manufacture asbestoscontaining automotive friction products such as brakes and manual clutches it has been known for some time that certain chrysotile mines contained trace amounts of tremolite a noncommercial amphibole fiber Accordingly it is theoretically possible that small amounts of tremolite may have been present in some containing friction products at different points in time However the weight of evidence is largely negative in this respect For example Sheehy et al 1989 found that fibers in 40 vehicles with asbestos brake shoes contained mostly chrysotile fibers and that fibers in the wheel drum bulk samples represented less than % of the brake dust and were generally 60-100 chrysotile Sheehy et al 1989 Weir et al demonstrated that an overwhelming majority of samples from dust collected from the brake drum where air was not used to blow out the drum contained fibrous material cotton and that most fibers were attached to phenolic residue deposits Weir et al 2001 Weir et al further demonstrated that fibrous containing material determined to be chrysotile by morphology could be removed from brake pads by grinding or drilling processes but they remained bound to the matrix of the underlying material Weir and Meraz 2001 Blake et al 19 determined that air samples contained only chrysotile asbestos and an absence of other types of asbestos following brake changes in 4 different vehicles Blake et al 2003 In a recent study we found that 121 containing brakes had no detectable amphibole fibers polarized light microscopy analysis with a limit of detection of % Madl et al 2007 Similarly in the current study we found that none of the 24 containing clutches contained amphibole fibers polarized light microscopy analysis with a limit of detection of % It has been understood since the 1970's that the producing potential of an inhaled fiber is governed in part by the fiber dimension Stanton and Wrench 1972 Stanton et al 1972 Recent government expert panel evaluations have concluded that asbestos fibers < 5 ...min length ATSDR or up to 20 ...min length EPA probably do not contribute to disease ATSDR 2001 USEPA 2003 Fiber widths of > 0.7 ...mare rarely found in the lung Stanton et al 1972 Sussman et al 1991a Sussman et al 1991b Timbrell 1980 Timbrell 1982 and for the purposes of this analysis 0.7 ...mis assumed to represent the upper bound of a respirable width Hence fibers of > 5 ...mand > 20 ...min length both with respirable widths < 0.7 ...mare of particular interest in this study The fiber size and morphology analyses of the air samples demonstrated that only 29 of the airborne free fibers > 5 ...min length were of a respirable width 0.7 um Very few % of the free fibers > 20 ...min length were of a respirable width Table V It is worth noting that a significant fraction of the respirable OSHA fibers 0.7 um width 5 um in length measured in this study were present either in clusters % or were bound in a matrix 17 The current understanding of lung deposition characteristics of fibers is based primarily on free fibrous structures the behavior of more complex fibrous structures such as those attached to a matrix or resin is less clear Gross et al 1971 Harris and Timbrell 1977 ISO 1995 Morgan and Holmes 1980 OSHA 1994 Strom and Yu 1994 Sussman et al 20 1991a Sussman et al 1991b Timbrell 1980 Timbrell 1982 Yu et al 1995 Presumably at least some of these fibers would not be respirable due to a large aerodynamic diameter of the cluster or matrix and would not biologically active due to their encapsulation in a solid matrix The PCM analytical methods typically used to monitor asbestos concentrations in the workplace cannot distinguish between free fibers vs. fiber clusters vs. matrix fibers and therefore these results suggest that the PCMadj values reported in this paper are likely to overestimate actual respirable concentrations of OSHA fibers associated with different clutch handling activities Since the late 1960's numerous industrial hygiene studies involving service and repair of containing brakes have consistently found that the airborne asbestos levels were below contemporaneous and current occupational standards Agudo et al 2000 Goodman et al 2004 Hessel et al 2004 McDonald and McDonald 1980 Paustenbach et al 2004 Paustenbach et al 2003 Spirtas et al 1994 Spirtas et al 1985 Teschke et al 1997 Teta et al 1983 Woitowitz and Rodelsperger 1994 Wong 2001 We recently developed estimates of cumulative asbestos exposures for brake mechanics based on industrial hygiene data and assumptions regarding the number of brake jobs a career mechanic might perform Finley et al 2007 We reported that the median and bound cumulative exposures for U.S. automobile and light truck brake mechanics who worked prior to the installation of control technologies i.e. before the 1970's were 0.41 and 2.79 years respectively Finley et al 2007 Similarly estimates of lifetime cumulative asbestos exposuress associated with clutch box handling can be developed for a variety of individual work scenarios using the data presented in this paper the product of the hr TWA of a task and the number of years performing the task For example based on the hr TWA estimate of 0.0016 cc for opening one clutch box Figure 6 a year career mechanic who performs one clutch change per week would experience a cumulative chrysotile asbestos dose of 0.065 years as a result of taking the clutch out of the box 0.0016 cc x 40 years A counterman unpacking 10 boxes a week for 20 years would have a cumulative exposure of 0.62 years hr TWA estimate of 0.0062 cc for unpacking 2 boxes x 5 x 20 years while a parts picker stacking and shuffling 200 boxes per week for 5 years would have a cumulative exposure of 0.066 years hr TWA estimate of 0.0133 cc for stacking boxes x 5 years In all cases background values were used for the exposure periods These exposures and generally any plausible exposures associated solely with clutch box handling are similar to or less than the aforementioned estimated exposures for mechanics conducting brake repair Finley et al 2007 Because it has been established that garage mechanics conducting brake repair are not an increased risk of developing asbestos diseases Finley et al 2007 it can be inferred that the cumulative asbestos doses associated with clutch box handling do not pose a health risk Also any estimated exposures from clutch box handling would be far below the cumulative effect exposures that have been reported for chrysotile cohorts 25-1,000 years for lung cancer Albin et al 1990 Berry and Newhouse 1983 Brown et al 1994 Hughes et al . 1987 Lacquet et al 1980 Liddell and Armstrong 2002 McDonald et al 1983a McDonald et al 1983b McDonald et al 1984 McDonald et al 1993 Neuberger and Kundi 1993 Peto et al 1985 Pierce et al 2007 Piolatto et al 1990 and 15-500 years mesothelioma Albin et al 1990 Lacquet et al 1980 McDonald et al 1984 Pierce et al 2007 Piolatto et al 1990 In short our findings suggest that individuals opening repacking or otherwise handling clutch boxes are not at an increased risk of asbestos disease Bystander or home exposures would be even lower and would also pose no health risk 22 In conclusion we have assessed airborne asbestos concentrations associated with several automotive clutch disc handling exposure scenarios not previously characterized in the literature A broad range of both typical and worst clutch box handling scenarios was studied in addition to evaluating potential exposure associated with handling work clothes or performing clean activities following these scenarios While this study characterizes potential exposures associated with handling boxes of clutches a scenario not previously assessed in the historical exposure studies of automobile mechanics the results of this study should not be extrapolated beyond what was tested In summary the short and hr TWA airborne asbestos concentrations measured and calculated for a mechanic or bystander unpacking and repacking boxes of containing clutches were below the current OSHA excursion limit and PEL for asbestos as well as below all previous U.S occupational standards for asbestos ACKNOWLEDGEMENTS This research was supported by funding from Warner Corporation who have been involved in litigation related to the possible exposure of clutch mechanics and handlers and their family members to asbestos Some of the authors have served as expert witnesses in litigation regarding the potential asbestos health hazards to mechanics and friction product handlers historically involved in automobile work 23 LIST OF TABLES AND FIGURES Table I. Summary of clutch handling and associated activities performed throughout the simulation study Table II Chrysotile content of the 24 clutch linings used in the simulation study Table III Chrysotile content of the counter dust from the simulation study Table IV Summary of airborne asbestos concentrations cc during different handling scenarios Table V. Size and morphology distribution of fibers detected in personal worker samples collected during various clutch handling and associated activities Figure 1. Schematic drawing of a clutch and its location Figure 2. A Photograph of the stack of clutch boxes B A close view of a clutch and its clutch box Figure 3. A Diagram of automotive repair shop and locations of area sampling stations B Schematic of sampling scheme for airborne asbestos sampling collected during each clutch handling associated event Figure 4. adjusted airborne asbestos concentrations for the worker during different clutch handling associated scenarios Figure 5 min TWA airborne asbestos concentrations for the worker during different clutch handling associated scenarios Figure 6. Estimated hr TWA airborne asbestos concentrations for the worker during different clutch handling scenarios 24 REFERENCES Agudo A. et al 2000. Occupation and risk of malignant pleural mesothelioma A casecontrol study in Spain Am J Ind Med 37 157-168 Albin M. et al 1990. Mortality and cancer morbidity in cohorts of asbestos cement workers and referents Br J Ind Med 47 602-10 , ASHRAE Heating Ventilation and conditioning Applications American Society of Heating Refrigerating and Conditioning Engineers Inc. 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Deposition of refractory ceramic fibers RCF from the rat lung development of a model Environ Res 65 243-253 29 Jiang et al A Study of Airborne Chrysotile Concentrations Associated with Handling Unpacking and Repacking Boxes of Automobile Clutch Discs Table | Summary of clutch handling and associated activities performed throughout the simulation study Activities Stack boxes Day 1 1 R 1 box 4 R 1 box DW OH 2 R 1 box SC OH 2 R 2 boxes OH --- Clean counter 1 Clothes handling R - Repack Day 2 Day 3 111 4 12 4 --- 12 --- 12 2 - 1 on 1 DW - Dry Wipe Activity replicates 1 12 2 2 4 3 1 SC - Spray cleaner # personal worker samples 4 48 8 8 16 12 4 OH - Handle overhead Jiang et al A Study of Airborne Chrysotile Concentrations Associated with Handling Unpacking and Repacking Boxes of Automobile Clutch Discs Table II Chrysotile content of the 24 clutch linings used in the simulation study Brand Brand 1 Brand 2 Brand 3 Brand 4 Brand 5 Brand 6 Brand 7 Brand 8 Brand 9 Brand 10 Brand 11 Brand 12 Brand 13 Brand 14 Brand 15 Brand 16 Brand 17 Brand 18 Brand 19 Brand 20 Brand 21 Brand 22 Brand 23 Brand 24 XRD Result Chrysotile % 27 29 39 52 48 48 23 43 44 39 26 35 43 28 33 27 33 20 25 21 20 47 28 31 PLM Result Amphibole % ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND ND Note ND - detectable XRD - ray diffraction PLM - Polarized light microscopy detectable samples entered as haltf he limit of detection or sensitivity limit Limit of detection = % Jiang et al A Study of Airborne Chrysotile Concentrations Associated with Handling Unpacking and Repacking Boxes of Automobile Clutch Discs Table III Chrysotile content of the counter dust from the simulation study XRD Result PLM Result Sample ID All boxes Counter 012007 Counter 012107 Counter 012107 Counter 012707 Counter 012707 Sample Counter Dust Counter Dust Counter Dust Counter Dust Counter Dust Counter Dust Chrysotile % 2 5 5 1 14 9 Amphibole % ND ND ND ND ND ND Note ND - detectable XRD - ray diffraction PLM - Polarized light microscopy Nondetectable samples entered as half the limit of detection or sensitivity limit LOD = % Jiang et al A Study of Airborne Chrysotile Concentrations Associated with Handling Unpacking and Repacking Boxes of Automobile Clutch Discs Table IV Summary of airborne asbestos concentrations cc during different handling scenarios PCM TEM PCMadj Location Task Worker 1st min One box One box DW OH One box SC OH Two boxes Stacking boxes Cleanup __Clothes handling Worker One box 2nd 15 min One box DW OH One box SC OH Two boxes Stacking boxes Worker 60 min Cleanup Clothes handling _ One box One box DW OH One box SC OH Two boxes Bystander Stacking boxes | One box One box DW OH One box SC OH Two boxes Stacking boxes ____ Remote area Cleanup Clothes handling One box One box DW OH One box SC OH Two boxes Stacking boxes Cleanup Lo. Background Ambient Clothes handling : Replicates N 12 24 2 4 2 4 4 8 1 2 3 6 12 12 24 22 4 2 4 4 8 1 2 3 6 1 2 12 24 22 4 22 4 4 8 12 12 24 2224 4 2224 4 2224 8 1 2 312 6 312 2 12 12 2 2 2 2 4 4 1 1 3 3 1 1 3 9 3 9 Mean 057 058 0.055 209 0.294 0.012 110 0.011 0014 0007 0013 0.230 0010 0047 0.021 0035 0017 0.061 0.172 0010 0011 009 009 0030 0006 0010 0.008 0005 0005 003 0008 0.006 0 009 0.007 0.001 Min 0.006 0.035 0.034 0.110 278 0 006 0 090 005 0.008 0005 0 008 0 207 0.004 0.039 0 007 019 0.007 0 027 0118 0.04 0.004 0005 0005 0.06 0.006 0.002 0.027 001 0.006 0003 0.001 0003 0003 0.01 0.001 0.08 0.008 0004 0004 0.009 0.02 0.002 0.000 0.000 Max 0 138 0.120 0073 0370 0.310 021 130 0.019 019 0010 024 0 253 0018 0 054 0041 0046 0026 0 097 0 225 0 032 0019 0015 0019 0032 0032 0015 0013 0 022 008 0.007 0.007 0.006 0.006 0.008 0.008 010 0.009 0014 0.001 ND N Mean Min Max ND Nz Mean i) 24 132 010 0 400 Oo 24 0051 0 4 0.115 0.060 0 200 a) 4 050 0 4 0.078 0060 0060 0.100 ) 4 0046 0 8 02 06 0 2 |. 0 24 ) 4 0 4 0 8 0413 600 0.006 0006 0.006 010 0011 0.005 0 100 0.500 0.004 0.004 004 0.003 0.003 0.0 5 0.005 0004 0004 0.04 0.004 0700 0700 0 700 0.008 0.008 0.007 020 020 0030 0030 010 fe) 8 Oo | 2 50 | 6 50 2 17 71 24 Oo |} 4 75 4 75 |, 8 0.196 231 002 0.003 0002 005 0001 0.001 9) 2 450 0 400 500 0 194 0 6 0.005 0.004 0.007 67 | 6 002 | ) 2 0.004 0.004 0.005 100 2 000 0 24 025 0.003 0 090 24 24 0014 ) 4 0035 0.030 0 050 4 4 0016 o 4 0017 o 8 = 121 02 250 0 24 0003 0.006 0.006 0.050 0.200 0002 0002 0.030 0 300 300 0.006 2 4 0013 12 8 25 54 24 054 149 0001 0 |: 4 0 4 |o || 826N o | 826N 0 | 826N oO 826N 0 12 0 224 0.004 0.003 0.007 0.02 0.002 0002 0002 0.02 0.002 0010 0004 0.020 0.007 0.002 0004 0004 0 002 0 009 0.004 0004 0.004 0.004 004 0004 0004 0.007 0.004 0.004 0.004 50 4 = 50 4 38 8 9) 2 83 |; 6 100 2 92 | 12 100 2 0004 0.001 004 0010 000 000 000 000 rc) 224 0, 224 ft) 1 |) 3 91 || |) 9 0 9 0.004 004 0 004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.004 0.04 0.004 004 0.004 0.004 0.004 0.007 0.004 0.004 0.004 0004 0007 0007 100 2 100 4 100 1 100 |3 100 | 1 100 89 | 9 000 0000 000 000 0000 0000 0000 0.000 Min 0.04 0.004 0.027 0034 0034 0 102 0.217 0.000 0.000 0.000 0.003 0.000 0 000 0 180 0.000 0.000 0000 0.03 0.003 0.002 0.024 0.097 0.000 0.000 0000 0.000 0.03 0.003 0.00 0.000 0.000 0.00 0.000 0.000 0.000 0 000 0.00 0.000 0000 0000 0.00 0.000 0000 0000 0 000 Max 138 0.109 0 063 0 366 0.245 0.006 0.006 0 005 0.008 0.008 0.005 0.007 0.007 0 207 0006 0006 0 000 031 0034 0034 0.022 0.091 200 0.008 0015 0.003 0019 0016 0.00 0.000 0.00 0.000 0.03 0.003 0 000 0 000 000 0.000 0.000 0.000 _ 0.000 0.00 0.000 0000 0000 Jiang et al A Study of Airborne Chrysotile Concentrations Table V Size and morphology distribution of fibers detected in personal worker samples collected during various clutch handling and associated activities Fiber Structure Classification Total Fibers Free Bundle Fiber Clusters Matrix Disperse Percent Fibers % Classified as Fiber or Particle with Dimensions of Respirable Fiber Respirable Particle 0.7 ...mwidth < ...mwidth 10 ...mwidth N Total Fibers % > mlength 20 ...mlength 5 ...mlength 20 ...mlength 5 ...mlength 20 ...mlength 1424 --- o- --- 113 wee ~- - 816 57 29 % 41 % ao ~- 267 19 11 % 15 % 15 % 341 24 17 % 21 % 21 % Figure 1 Transmission _ Pressure Plate Flywheel Engine Figure 2A Figure 2B General MotorsMotors wa diene WARNERWARNER Saray a fFe Figure 3A re 1 Mo Ht aT a a atk 14% a 2H Enclosed Waiting Area ligh espe ench Garage CD 4 e ce Garage ligh ench 2 Poi, ol a7 - = Hae Samal hn! Jj Pr sy 17 17 eas it ter Tonensienr + 120 245.425 245.425 245.425 be P M - file be Figure 3B Worker -< | i min min min Bystander Remote min min Figure 4 1.2 - fcc 1.0 0.8 Concetrai 0.6 Fiber 0.4 Asbeto 0.2 0.2 0.2 Averag 0.0 30mn Lima LimaLimLaima presentprespernetsentpresnt ) Worker Worker Worker Worker ! Worke SI LWLWLW \ ee 7, 2 07 : . oe , - oS ~, ad we ase -* 2, - ra . : the wh ca of - we nm ' 172 1712 he ... ~ M 1 . : . - , ... ... Figure 5 1.20 1.201.20 cc 1.00 OSHA 30 min Excursion Limit Concetrai 60 i Fiber Asbeto Average 0.002 0002 0.002 T One box 12)) One DWV OH One Box SC OH boxes = Stacking boxes () Cleanup NF3 Clothes handing N Figure 6 cc Concetrai 006 Fiber 00-2 4 Asbeto Average he. H bee pont tt t ao viaie _ 2001 2001 201 ~ ohio oe we . ' r - Pree gids bo te Fox S te owe Low Fox The 1, rhon ra . tt # ' soe * - wey Pao ee begs no oa ' b it a f ote prays wae Nde -,! . amin ' 5 a ~ yt se 7 i Re .