Document b5ZeMddoD4aYrdaMVM6d7vpGZ

FILE NAME Brakes BRK DATE 2008 DOC BRK184 DOCUMENT DESCRIPTION Journal Article - Exposure to Chrysotile Associated with Working with Brake Pads and Shoes Ann Occup Hyg pp 1-17 'The Author 2008 Published by Oxford University Press on behalf of the British Occupational Hygiene Society doi 10 men028 Exposure to Chrysotile Asbestos Associated with Unpacking and Repacking Boxes of Automobile Brake Pads and Shoes MADL,, MURBACH,, K. L. L. SCOTTD. M. B. L. FINLEY,,and D. J. PAUSTENBACH,, K. A. FEHLING,, ChemRisk Inc. 25 Jessie Street Suite 1800 San Francisco CA 94105 USA 2ChemRisk Inc. Richmond Avenue Suite 350 Houston TX 77042 USA 10375 Received 15 November 2007 in final form 14 April 2008 Industrial hygiene surveys and epidemiologic studies of auto mechanics have shown that these workers are not at an increased risk of asbestos disease however concerns continue to be raised regarding asbestos exposure from containing brakes Handling new asbestos- containing brake components has recently been suggested as a potential source of asbestos exposure A simulation study involving the unpacking and repacking of 105 boxes of brakes for vehicles ca. 1946-80 including 62 boxes of brake pads and 43 boxes of brake shoes was con- ducted to examine how this activity might contribute to both short and h weighted average exposures to asbestos Breathing zone samples on the lapel of a volunteer worker n == 80 and area samples at bystander e.g. 1.5 m from worker n = 56 remote area n = 26 and ambient n = 10 locations collected during the unpacking and repacking of boxes of asbestos- containing brakes were analyzed by phase contrast microscopy and transmission electron microscopy Exposure to airborne asbestos was characterized for a variety of parameters in- cluding the number of boxes handled brake type i.e. pads versus shoes and the distance from the activity i.e. worker bystander and remote area This study also evaluated the fiber size and morphology distribution according to the International Organization for Standardization analytical method for asbestos It was observed that ) airborne asbestos concentrations in- creased with the number of boxes unpacked and repacked ii handling boxes of brake pads resulted in higher worker asbestos exposures compared to handling boxes of brake shoes iii cleanup and handling tasks produced less airborne asbestos than handling boxes of brakes and iv fiber size and morphology analysis showed that while the majority of fibers e.g. were free not associated with a cluster or matrix 30 were respirable and even fewer were of the size range 20 mlength considered to pose the greatest risk of asbestos disease It was found that average airborne chrysotile concentrations 30 min ranged from 0.086 to 0.368 and 0.021 to 0.126 f cc,,for a worker unpacking and repacking 4-20 boxes of asbestos brake pads and 4-20 boxes of brake shoes respectively Additionally average airborne exposures 30 min at bystander locations ranged from 0.004 to 0.035 and 0.002 to 0.011 f ccfl,, when 4-20 boxes of brake pads and 4-20 boxes of brake shoes were handled respectively These data show that a worker handling a relatively large number of boxes of brakes over short pe- riods of time will not be exposed to airborne asbestos in excess of its historical or current short- term occupational exposure limits Keywords asbestos automobile brakes exposure assessment INTRODUCTION Over the last 30 years significant attention has been paid to evaluating asbestos exposures and the poten- Author to whom correspondence should be addressed Tel 1-415-618-3200 fax 1-415-896-2444 mail amadl@chemrisk.com amadl@chemrisk.com tial risk of asbestos diseases among garage mechanics Paustenbach et al 2004 Such interest stems from decades use of chrysotile asbestos in automobile brake pads and shoes Chrysotile's su- perior characteristics as good tensile strength , durabilitydurabilty, flexibility such heatgood resistancetensile provided resistance the auto industry with a friction material that could 1 of 17 2 of 17 A. K. Madl et al withstand extreme temperatures pressure and stress Skinner et al 1988 Sheehy et al 1989 Paustenbach et al 2004 These characteristics were particularly necessary for safety as automobiles throughout the 20th century became larger heavier and better able to attain greater speeds Harper 1998 Despite the fact that numerous studies have shown that garage mechanics were historically exposed to airborne asbestos levels below contemporaneous and current occupational standards and are not at an increased risk of asbestos disease McDonald and McDonald 1980 Teta et al 1983 Spirtas et al 1985 Spirtas et al 1994 Woitowitz and Rodelsperger 1994 Teschke et al 1997 Agudo et al 2000 Wong 2001 Paustenbach et al 2003 Goodman et al 2004 Hessel et al 2004 Paustenbach et al 2004 concerns continue to be raised regarding the handling of containing brake components Handling new brake components is an aspect of brake repair work that has recently been suggested as a potential source of asbestos exposure and thus a hazard to individuals in work environments where these components are used Atkinson et al 2004 Handling new brake components is not limited to brake mechanics retail automobile parts store and distribution center personnel also face potential exposure to asbestos during the handling of boxes of asbestos brakes Fig ) Residual asbestos fibers might be present inside new brake box for example due to wear during product shipping or as a result of airborne fibers settling into the open box in the packaging facility These resid- ual fibers may become airborne when the brakes are re- moved from the box or repacked into the original box or another container Several studies have assessed airborne asbestos exposures to automobile and brake mechanics Paustenbach et al 2003 however it is not readily apparent that any of these studies included the handling of new brake components in their short or workday exposure estimates The purpose of the present evaluation was to characterize airborne asbestos exposures associated with typical tasks that might be performed by a mechanic in a repair shop a counter salesperson in a parts shop or a parts picker in an industrial warehouse in handling of boxes of new containing replacement brakes Given that replacement asbestos brakes are currently available from some parts suppliers the potential for handling asbestos brakes is not only a historical issue This study provides exposure information that improves the knowledge of the historic and current potential hazards associated with handling these products METHODS Testing was conducted in two phases Phase I 27 July 2004 focused on understanding and characterizing the plausible number of boxes that could be unpacked and repacked within a specific period of time as well as identifying optimal airflow rates and sample times Using the sampling parameters identified in the first phase Phase II 5 and 6 November 2005 testing was conducted to increase the sample size of a lower and upper bound handling sce- nario as well as to evaluate other related tasks i.e. cleanup and clothes handling that might be associated with asbestos exposure In both phases of testing breathing zone air samples were collected from the worker's lapel In addition area samples were collected at bystander 1.5 m from the main activity remote 7.6-9.1 m from the main activity and ambient outside testing facility locations Figs 2 and 3 Protocol for this simulation study was approved by an accredited Institutional Review Board Essex Institutional Review Board Inc. Lebanon NJ USA Fig 1. Photo of brake replacement parts storage area in an automobile parts supply and repair shop It shows storage area of replacement brake parts in a vintage auto parts facility where the majority of boxes of brakes were purchased for the simulation study The volume of brakes that can be stored in a relatively small facility or operation can be substantial Description of site conditions The automobile repair shop where the study was conducted has been previously described in detail Paustenbach et al 2006 The shop which is located in Santa Rosa CA is a relatively large garage with an open floor plan 30.8 m wide by 14.5 m deep with a 4.6 m ceiling Fig 2 To prevent air measurements from being confounded by other Chrysotile Exposure from Boxes of Brakes a 4 -4 27 m- 5 service overhead doors || [i [ii s -427 -427 m Fem 27 m Peg 27 mm -427-427 -427 m Enclosed t Waiting Area 3 of 17 971 971 Garage ceiling height 4.67 m Bystander Bystander 122-152 a ue Bystander - "i+ Oo 40 m 09 Remote CA Area 09 os ome aon i ! 374 I 374 i { - 80 m Counter dimensions 36 47 x 95 1 ' i ' | Cot 84 Denotes ceiling heights between 2 13 and 2.44 meters Ambient Area Fig 2. Diagram of automotive repair shop and locations of area sampling stations repair activities in the shop no other automobile repair work was conducted during the study Additionally the shop was not ventilated with heating or air conditioning and all entry and service doors were closed during testing Description of boxes of brake pads and shoes A total of 105 boxes of brakes including 62 boxes of brake pads and 43 boxes of brake shoes were identified and purchased from vintage automotive parts suppliers and repair facilities primarily located in Arizona and California These brake boxes were not opened by investigators prior to testing so that the study's results would mimic a worker opening a new unused box of replacement brakes The investigators worked with personnel at the vintage automobile parts suppliers and repair facilities to identify boxes most likely to contain asbestos brake pads and shoes Fig 4 Based on the historical knowledge of the parts supplier the boxes were iden- tified with brand and year of the vehicle for which its replacement brakes were believed to contain asbestos In addition the boxes were inspected for information regarding the composition of the brakes e.g. asbestos warning labels Replacement brakes identified for the study were made for passenger vehicles and were manufactured prior to the mid 1970s by 15 different brake manufacturers Boxes of brakes were typically undisturbed for several years according to the parts suppliers and were in good structural condition Given the scarcity of unused vintage boxes of containing brakes the same boxes of brakes were used for both Phase I and II testing in the study After Phase I the boxes of brakes were shipped round to a location on the East Coast via ground transportation in order to simulate the dust generated from the rubbing of brake parts during shipment After shipment these boxes of brakes were not opened until Phase II of testing In addition boxes of brakes that were unpacked and repacked on the first day of Phase II testing were not used for the second day of sampling Each box then was unpacked and repacked only once during each phase of testing Description of work conditions and exposure scenarios The study was conducted in an automobile repair shop because it presented a more realistic environment in terms of conditions potentially experienced in a brake repair or auto parts shop This shop for example had a counter of a height 1.1 m that would typically be encountered in these kinds of settings e.g. closer to the breathing zone than a standard height table All handling work was performed by a single volunteer and was conducted in a manner consistent to that described by interviewed career automotive mechanics and parts suppliers These interviews revealed that in a parts supply or repair shop new replacement brakes would be removed from the box and compared to the old brake component to confirm that the correct part was indeed ordered In circumstances where the correct part was not 4 of 17 A. K. Madl et al Sampling Sequence of Testing I Event 1 Event 2 Ventilation Worker Right and lapel [ min | [ min | Right and left lapel | min | Bystander Remote area Four locations [ Two locations I min | min | Summary of Testing I Events Event No. Brake Type No. of Boxes Handled 15 min 30 min 1 Pad 2 wN Pad 4 6 wN Pad 8 43 Pad 12 23 43 Pad 16 6 Pad 20 36 7 Shoe 2 8 Shoe 4 6 g Shoe 8 10 Shoe 12 20 11 Shoe 17 Sampling Sequence of Testing II Event 1 Worker Right lapel | min | min Ventilation | Right and left lapel | 100 Bystander Four locations [ min | Background Background | Remote area Two locations | min | Summary of Testing II Events Event Brake Type -234 Shoe No. of Boxes Handled 15 min 30 min 4 4 -234 Shoo 16 16 -234 Pad 4 4 -234 Pad 16 16 5 Cleanup 6 Shoe 4 4 7 Shoe 16 16 8 Pad 4 4 9 Pad 16 16 10 Cleanup 11 Clothes handling Fig 3. Schematic of sampling regimen of airborne asbestos samples collected at various locations within the shop during the unpacking of boxes of brake pads and shoes identified this task would have to be duplicated Thus during the simulation study boxes of brakes were stored on a cart within reach of the worker new replacement brakes were opened compared to a demonstrative brake and then repacked in their original boxes Generally four brake shoes or brake pads were in each box however in some circumstances each brake shoe was packaged in separate boxes Airborne asbestos concentrations were character- ized for a worker handling between 2 and 20 boxes of brakes within a min time period or 6-36 boxes of brakes within a min time period Tables 1 and 2 In addition airborne asbestos concentrations were measured during cleanup of dust that accumulated on the counter and during the handling of clothes worn during the handling activities The handling task involved shaking and folding cloth coveralls worn by the volunteer during each day of testing to simulate the handling and laundering of potentially contaminated work clothes More specifically clean newly purchased cloth coveralls were worn during the entire duration of testing and were carefully removed by the worker as not to disturb the potentially adhered fibers Each coverall n = 3 was stored in separate plastic bags until the last day of testing when the handling task was conducted The simulated handling task involved repeatedly shaking folding and turning clothes inside out for ~ to 2 min for each pair of overalls Although no fibers or debris were visible Chrysotile Exposure from Boxes of Brakes 5 of 17 Fig 4. Photo of example brake shoes included in the exposure simulation study A blok relined shoes manufactured for Hudson 1953-54 IHC 1961-62 Jeep 1946-67 and Willys 1951-55 vehicles Warnings on this particular brake shoe box included Caution Contains asbestos fibers Avoid creating dust Breathing asbestos dust may cause serious bodily harm and Do not regrind these brake shoes on the coveralls after each day of testing some particles were observed in the air during the clotheshandling task Transmission electron microscopy TEM analysis of air samples was used to evaluate the proportion of airborne particles that were asbestos versus asbestos Cleanup of dust found on the countertop after testing was performed with dry and wet paper towels and wipes and was subsequently collected for bulk sample analysis via polarized light microscopy PLM The debris which had settled onto the countertop appeared to consist mostly of cardboard box fragments and debris The counter surface was cleaned for an approximate duration of 1-2 min Air samples collected during clothes handling and cleanup tasks followed the same protocol as that conducted for the handling tasks Fig 3 The number of boxes of brakes handled in this study is consistent with the number of brake repair jobs conducted in repair shops as reported in the literature For example a typical brake mechanic may conduct between 2 and 40 brake repair jobs per week Paustenbach et al 2003 and Hickish and Knight 1970 reported as many as 11 brake jobs being performed in 1 day at a repair shop Hickish and Knight 1970 Depending on the brand and the number of replacement brakes contained within each box potentially four times as many boxes of brakes could be handled because four brake pads or shoes are needed for a complete front or rear brake replacement The rate of handling boxes of brakes in a repair shop would certainly be limited by the pace of the brake repair work however a parts picker in an industrial warehouse would handle a far greater number of boxes than a worker in a repair shop While a worker may not handle 36 boxes of brakes within a min time period under normal conditions the study was designed to understand the range of airborne asbestos concentrations associated with a variety of conditions e.g. handling different number of boxes tasks and brake type In addition conducting the simulation study in such a manner allows one to estimate the contribution of handling a different number of boxes of brakes on a worker's short and h weighted average TWA exposure While some of the conditions in this study may represent more of a worst scenario e.g. low ventilation and high number of boxes being handled in a given time period the purpose of handling different number of boxes in our study was fold ) to understand how increasing the number of boxes being handled during a given time would influence the airborne asbestos and ii to assess the upper bound limits that a person could physically handle boxes of brakes in a given length of time Collection and analysis of airborne asbestos samples All airborne samples for asbestos were collected as previously described Paustenbach et al 2006 Airborne asbestos samples were collected using mixed cellulose ester filter membranes 25 mm 0.45 pore size Zefon International St Petersburg FL USA using either portable SKC Universal PCXR West Inc. Fullerton CA USA Gilian Gilair Ashtead Technology Rentals Hayward CA USA or volume Dawson 1300 sampling pumps Ashtead Technology Rentals Hayward CA USA Por- table 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 airflow rates between 3 and 10 LPM The sampling flow rates were calibrated with a Biosfi DryCal DCLite primary flow calibrator Bios International Corporation Butler NJ USA before and after sample collection Any discrepancies observed between start and stop airflow rates were within 15 All airborne asbestos samples were collected accordance with National Institute for Occupational Safety and Health NIOSH methods 7400 and 7402 National Institute for Occupational Safety and Health 1994a Field blanks were collected throughout each day of the sampling and were sent to the analytical laboratory for analysis along with the samples collected during the testing A total of 15 field blanks were collected and analyzed none of which showed any detectable asbestos fibers After collection all air samples were capped and sealed with tape and placed in sealable plastic bags inside cardboard boxes along with the corresponding custody sheets for overnight shipment to the analytical laboratory EMS Laboratories Inc Pasadena CA USA Background samples of airborne asbestos were collected within the shop each day before any asbestos sampling began in the simulation study Three Table 1. Worker airborne asbestos concentrations f ccc,,d,,uring unpacking and repacking of containing brake pads and shoes of No. of Chrysotile content PCM NIOSH 7400 method TEM NIOSH 7400 fiber parameters PCME NIOSH 17 boxes % by weight 7402 method Testing I worker Short sampling 15 min Pads 2 4 8 12 16 20 Average Range Average Range N NNR NND Average Range N NNR NND Average Range N 7432727210 41-45 0.100 0.092-0.108 2 0 0 0.072 0.013-0.131 2 0 0 0.058 0.008-0.108 2 7432727210 39-47 0.123 0.098 0.148 2 0 0 0.049 0.026-0.071 2 0 0 0.065 0.033-0.098 2 7432727210 20-43 0.330 0.260 0.399 2 0 0 0.494 0.694 2 0 0 0.330 0.260-0.399 2 7432727210 22-41 0.438 0.383-0.492 2 0 0 1.265 1.183-1.347 2 0 0 0.438 0.383-0.492 2 7432727210 24-42 0.657 0.477-0.836 2 0 0 1.762 1.744-1.779 2 0 0 0.657 0.477-0.836 2 7432727210 3-33 0.269 0.043-0.496 2 0 0 1.829 1.528-2.129 2 0 0 0.463 0.429-0.496 2 Shoes 22 7432727210 4 7432727210 * 7432727210 12 7432727210 25 34 Short sampling 30 min Pads 6 44 BaxBa 32 BaxBa 30 Shoes BaxBa 42 BaxBa 36 Testing II worker Short sampling 15 min Pads 4646 3633 4646 3633 Shoes 4646 3633 16 31 Cleanup Clothes handling Short sampling 30 min Pads +6 36 16 36 41-49 0.059 0.054-0.063 2 0 0 0.045 0.032-0.058 2 0 0 0.026 0.023-0.029 2 29-51 0.075 0.073-0.077 2 0 0 0.048 0.041-0.054 2 0 0 0.031 0.028-0.034 2 5-49 0.102 0.071 0.132 2 0 0 0.124 0.065-0.182 2 0 0 0.072 0.047-0.098 2 0.113 0.080-0.146 22 0 0 0.123 0.094 0.152 2 0.080 0.058-0.103 2 2202--4670 0 0 K. 0.150 0.145-0.154 22 0 0 0.282 0.262-0.302 2 0 0 0.120 0.119-0.122 2 Madl 39-47 0.111 0.073-0.148 2 0 0 0.133 0.132-0.133 220 020 0 0.108 0.070-0.145 2 et 20-43 0.374 0.358-0.389 2 0 0 0.453 0.416-0.489 220 00200 0 0.368 0.358-0.378 2 al 3-42 _ 02 0 _ 220 020 0 0 29-51 0.044 0.044 0.044 2 0 0 0.050 0.041-0.058 22 00200 0 0.028 0.027-0.029 2 5-60 0.064 0.060-0.067 2 0 0 0.089 0.066-0.112 20 20 0 0.051 0.046-0.055 2 24-49 0.193 0.072-0.320 8 0 0 0.369 0.080-0.826 4 0 0 0.171 0.058-0.294 4 5-60 0.559 0.062 1.190 8 0 0 1.423 1.000 2.502 4 0 0 0.541 0.057-1.190 4 22-45 0.060 0.033-0.077 8 0 0 0.071 0.119 4 0 0 0.030 0.024 4 3-47 0.167 0.053-0.261 8 0 0 0.328 0.121 0.600 8 0 ie) 0.126 0.036-0.193 8 0.017 0.008-0.029 8 0 0 0.012 0.001-0.040 8 0 3 0.004 0.002-0.006 5 0.037 0.030 0.047 4 0 0 0.009 0.003-0.020 4 0 1 0.011 0.007-0.015 3 24-49 0.104 0.068-0.140 0 ct) 0.187 0.089-0.284 2 0 0 0.086 0.049-0.122 2 5-60 0.297 0.276-0.318 2 0 0 0.750 0.619-0.882 20 20 0 0.284 0.252-0.315 Chrysotile Exposure from Boxes of Brakes 7 of 17 22 444 41 NIOSHmethod Range 0.21-0 0.9-162 0.1-07 0.15-280 0.2-03 0.17-0 0.12-0 Microspy PCME 7402 Average 0.021 0.126 0.032 0.157 0.012 0.046 0.012 Contrast Phase NND 0 0 0 0 0 0 PCME NNR 0 0 0000 limit parmetrs N 2 2 fiber 7400 Range 0.21-05 0.28-42 NIOSH TEM Average 0.038 0.328 NND 0 0 4 4 4 4 1 senitvy method the 7400 0.3-201 0.2-483 0.6-05 0.1-281 0.1-0 below NIOSH samples by 0.096 0.325 0.027 0.17 0.010 of outlined number ratio 0 0 0 0 0 NNR 0 0 NND aspect 00000 methods N 2 2 4 44 4I 3 method and 7400 Range 0.320.49 0.128-07 0.19-082 0.123-04 0.20.31 0.21-085 0.13-0.13 banlyytical lengthm NIOSH 5 PCM Average 0.040 0.167 0.04 0.180 0.028 0.059 0.013 readble not diametr Chrysotile parmetrs conte weight Range 2-45 3-47 24-49 5-60 2-45 3-47 osamfples7me4t0ho2d 0.25m b%y Average 31 36 36 35 31 number NIOSH | NNR the acordancesamples boxesof to fiber No. 16 16 16 with of min TEM 100 number in using N conetraion Contiued sampling aplicable counted Long Equivalent 1. Shoes Pads Shoes Cleanup Not were Table _ Fibers samples were collected at the beginning of each day of Phase I and Phase II testing at an airflow rate of 10 LPM for 40 min Three consecutive ambient air samples were collected for 120 min each testing day with a sampling rate of 5-10 LPM outside the south wall of the shop away from automobile . traffic In Phase I testing two consecutive min n = 4 and one min n = 2 sample were collected at airflow rates of 8-10 LPM on both the right and left lapel of the worker during each event Fig 3 During Phase II testing two consecutive min n = 2 and min n = 2 samples on both the right and left lapel of the worker were collected at an airflow rate of 8-10 and 2-5 LPM respectively Fig 3 Bystander samples were collected at four locations 1.5 m from the handling activity at breathing zone height 1.5 m with sampling rates of 8-10 LPM for Phase I testing and 5-10 LPM for Phase II Fig 2 Remote area samples for airborne asbestos were also collected during handling work with an airflow rate of 8-10 LPM at breathing zone height 1.5 m at two locations near the center of the shop 7.6 to 9.1 m from the worker Fig 2 After each box handling clothes handling or cleanup event the shop doors were opened to ventilate the workspace and four background samples were then collected with an airflow rate of 9-10 LPM prior to the next testing event Fig ) Fibers were counted according to NIOSH methods 7400 and 7402 which define fibers as being > ...m in length and having at least a 3 aspect ratio and in the case of 7402 0.25 min diameter National Institute for Occupational Safety and Health 1994a All airborne asbestos samples were sent to an accredited laboratory EMS Laboratories Inc. for analysis by phase contrast microscopy PCM NIOSH method 7400 and TEM NIOSH method 7402 National Institute for Occupational Safety and Health 1994a For the analysis of air samples by TEM selected area electron diffraction and dispersive ray were used to assess the fiber type via the diffraction pattern and elemental profile of the asbestos fibers respectively National Institute for Occupational Safety and Health 1994b All sample analysis was performed by EMS Laboratories Inc. which is an accredited laboratory for asbestos analysis by the American Industrial Hygiene Association and the National Voluntary Laboratory Accreditation Program US Department of Commerce National Institute for Standards and Technology Gaithersburg MD USA This laboratory utilizes analysts trained according to NIOSH 582 and adheres to the quality assurance and quality control requirements set forth by Occupational Safety and Health Administration OSHA 29 CFR 1910.1001 Appendix A and the most current version of the NIOSH 7400 method Table 2. Area airborne asbestos concentrations f ccfld,,uring unpacking and repacking of containing brake pads and shoes testing I and II of No. of boxes Chrysotile Content % by weight PCM NIOSH 7400 method TEM NIOSH 7400 fiber parameters PCME NIOSH 7402 method Average Range Average Range N NNR NND Average Range N NNR NND Average Range N Bystander Short sampling 30 min Pads 76864658 76864658 76 864658 766864658 76 864658 Shoes 76864658 76864658 76 864658 20 Cleanup Clothes Handling Remote area Pads 4 6 16 20 36 Shoes 4 6 16 20 Cleanup Clothes handling . Background before testing Day 1 Day 2 Day 3 348883938 24-49 0.014 0.007-0.027 80 80 0 0.011 0.003-0.020 8 0 1 0.004 0.002 0.0097 0.020.097 348 83938 39-47 0.020 0.015-0.024 4 0 0 0.006 0.002-0.013 4 0 0 0.007 0.001-0.016 4 348883938 5-60 0.018 0.010-0.027 8 0 0 0.039 0.002 0.090 8 0 1 0.010 0.003-0.022 7 348883938 20-43 0.039 0.025-0.078 40 40 0 0.029 0.015-0.063 4 0 0 0.035 0.016-0.076 4 348883938 3-42 0.032 0.014 0.062 4 0 0 0.058 0.023-0.130 4 0 0 0.027 0.012-0.060 4 348883938 22-45 0.018 0.002-0.035 80 80 0 0.003 0.002 0.008 8 0 6 0.002 0.002 0.003 2 348883938 29-51 0.006 0.004-0.009 4 0 0 0.003 0.001-0.005 4 0 2 0.002 0.002-0.002 2 348 83938 3-47 0.022 0.001-0.059 12 0 1 0.019 0.003-0.074 12 0 2 0.011 0.003-0.038 9 348883938 5-60 0.017 0.002 0.030 4 0 0 0.019 0.001 0.052 4 0 1 0.011 0.006-0.020 3 K. 0.011 0.006-0.020 80 80 0 0.005 0.002-0.020 80 6 0.002 0.001-0.004 2 0.014 0.008-0.022 40 40 0 0.004 0.002-0.008 4 0 3 0.010 0.010-0.010 1 Madl 616223978 24-49 0.015 0.011-0.022 4 0 0 0.009 0.001-0.017 4 0 1 0.006 0.003-0.010 3 et 6162 3978 39-47 0.017 0.017 0.017 2 0 if) 0.033 0.014-0.052 20 0 0.017 0.017-0.017 2 al 616223978 5-60 0.011 0.008-0.016 400 400 400 0.015 0.009-0.024 4 0 0 0.005 0.003-0.007 4 616223978 20-43 0.016 0.012-0.019 20 20 0 0.012 0.004-0.020 20 0 0.008 0.006-0.010 2 616223978 3-42 0.005 0.003-0.006 20 20 0 0.014 0.013-0.015 2 0 0 0.005 0.003-0.006 2 6162 3978 22-45 0.016 0.010-0.024 4 0 0 0.002 0.001-0.002 4 0 3 0.001 0.001-0.001 1 42 29-51 0.008 0.007 0.008 20 20 0 0.001 0.001-0.001 2 0 1 0.001 0.001-0.001 1 6162 3978 3-47 0.007 0.003-0.011 4 0 0.003 0.002-0.006 4 0 i 0.001 0.001-0.002 3 616223978 5-60 0.008 0.007-0.009 200 200 200 0.001 0.001-0.001 20 2 _ 0 0.009 0.007 0.012 4 0 0 0.004 0.002 0.007 4 0 1 0.003 0.001-0.006 3 0.014 0.013-0.014 2010 2010 2010 0.002 0.002-0.003 2 0 1 0.002 0.002 1 0.001 0.018 0.001-0.002 0.012-0024 0.012-0024 30 30 200 0.001 20 20 200 0.002 0.001-0.001 0.002 0.002 3. 0 3 2 #0 2 0.009 0.003-0.017 300 300 300 0.002 0.002-0.002 0 3 | 0 0 _ ie) Table 2. Continued No. of boxes Chrysotile Content % by weight PCM NIOSH 7400 method TEM NIOSH 7400 fiber parameters PCME NIOSH 7402 method Average Range Average Range N NNR NND Average Range N NNR NND Average Range N Background between events Pads 4 848283978 24-49 0.006 0.002-0.010 80 80 0 0.003 0.002 0.008 8 0 6 0.002 0.002-0.002 2 6a 848283978 39-47 0.006 0.003-0.010 4 0 0 0.002 0.002 0.002 4 0 4 _ _ --- 16 848283978 5-60 0.007 0.004-0.009 80 80 0 0.004 0.002-0.015 8 0 4 0.004 0.001-0.008 4 20a 848283978 20-43 0.007 0.004-0.012 4 0 6 0.005 0.002-0.014 40 3 0.002 0.002 1 36" 848283978 3-42 0.005 0.004-0.006 4 0 0 0.001 0.001-0.002 4 0 4 --- _ Shoes Ambient 4 848283978 22-45 0.012 0.005-0.025 80 80 0 0.002 0.002-0.003 808 808 808 --- --- --- 6a 848283978 29-51 0.005 0.002 0.009 400 400 400 0.002 0.002 0.002 4 0 4 _ 16 20 848283978 36 3-47 0.007 0.004 80 80 0 0.002 0.002-0.003 5-60 ~ -0.005 0.003-0.007 4 0 0 0.002 0.001-0.003 00 0 7 40 3 0.001 0.003 0.001-0.001 1 0.003-0.003 1 Chrysotile Exposure Day 1 0.002 0.001-0.005 400 400 0.001 0.0004 404-- 404- 404-- 404-- 404-- 0 Day 2 0.001 0.0008-0.001 300 300 300 0.000 0.0003-0.0005 300 300 33 _ 0 Day 3 0.001 0.0004-0.0007 30 30 0 0.000 0.0003-0.0004 300 300 33 __ 0 from Boxes N,ot applicable N = number of samples NNR number of samples not readable by analytical methods ND number of samples below the sensitivity limit PCME Phase Contrast Microscopy Equivalent concentration in accordance to the NIOSH 7402 method Fibers were counted using TEM with fiber parameters 0.25 mdiameter > mlength and as3pect ratio outlined by NIOSH 7400 method of Brakes of 17 10 of 17 A. K. Madl et al Fiber size and morphology analysis Air samples were also analyzed according to the International Organization for Standardization ISO method for characterization of type size and morphology of fibers > ...min length International Organization for Standardization 1995 Asbestos fi- ber morphology was quantified by categorizing asbestos fibers of > ...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 dimen- sions of the cluster or matrix structure as well as those of the individual fibers themselves were re- corded Asbestos fibers were characterized by their morphology as well as their size in order to evaluate the potentially respirable proportion of airborne fibers Long thin fibers can penetrate the deep lung Once in the lung those fibers that can be fully engulfed by macrophages can be removed Fibers 5...min length are cleared easily by the lung and present little risk to exposed groups Agency for Toxic Substances and Disease Registry 2001 2003 The US Environmental Protection Agency US EPA US Environmental Protection Agency 2003 determined that length of the fiber has little impact on the respirability up to a length of 20 ...mbut that the deposition of longer fibers is inversely related to the length of longer fibers While fibers up to 3.5 ...min diameter have been detected in the lungs of asbestos workers fibers of this dimension may represent the very upper bound limit of respirability Gross et al 1971 Morgan and Holmes 1980 Timbrell 1980 1982 A number of studies have shown that nearly all fibers deposited in the pulmonary region of the lung are thinner than 0.7 m Harris and Timbrell 1975 Sussman et al 1991a Strom and Yu 1994 Yu et al 1995 Respirable fibers free and bundles were therefore designated as those with diameter of /0. 7 ...mThe deposition of fibers contained within clusters or matrices was as- sumed to be based on the dimensions of the overall cluster or matrix structure Depending on the size and shape of these structures the fiber cluster or matrix may act aerodynamically more as a particle rather than a fiber Respirability of fiber clusters or matrices was therefore evaluated in two ways as re- respirable spirable fiber of diameter 0.7 ...mor as a particle with diameter 10 ...m Collection and analysis of bulk asbestos samples Brake material filings and dust from the counter after the handling activities were collected for bulk sample analysis for asbestos Brake material from brake pads and shoes were manually filed on a separate day and location from the simulation study Both brake filings and countertop debris were collected in separate sterilized sealed plastic bags and sent to EMS Laboratories Inc. for analysis by PLM according to NIOSH method 9002 National Institute for Occupational Safety and Health 1994b Air exchange measurements using tracer gas Sulfur hexafluoride SF was used as a tracer gas to estimate the air exchange rate within the garage as previously described Paustenbach et al 2006 Measurements of the gas were taken according to American Society for Testing and Materials method E741-00 American Society for Testing and Materials International 2001 A steady concentration of 1 ppm for SF6 Aldrich St Louis MO USA was targeted for the tracer gas analysis After steady state was reached SF6 measurements were taken in 30 intervals with a MIRAN SapphIReXL Analyzer Electron Corporation Hayward CA USA for 1 h The air exchange in the garage was calculated using the concentration decay optional regression test method of plotting the natural logarithm of SF6 concentration over time American Society for Testing and Materials International 2001 Data and statistical analyses Descriptive statistics were calculated for both PCM and TEM airborne fiber concentration meas- urements Analytical sensitivity limits also referred to as limits of detection were estimated based on the presumption that one fiber could be counted within 100 microscopic fields for a given volume of air sampled Results below the analytical sensitivity limit were entered using a value equal to half the sensitivity limit PCM measurements were adjusted for asbestos fiber content according to NIOSH method 7402 which specifies multiplying the ratio of asbestos fibers to total fibers observed in the TEM analysis by the PCM fiber concentration National Institute for Occupational Safety and Health 1994c The ratios of asbestos to total fibers asbestos and asbestos fibers were based on TEM fiber counts from the same filters the PCM fiber counts were obtained In this study the PCM measurements adjusted by the ratio of asbestos versus total fibers were referred to as phase contrast microscopy equivalent PCME airborne asbestos concentrations 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 to total fibers observed by TEM In circumstan- ces where PCM measurements were above the sensitivity limit but asbestos fibers were not detectable by TEM a PCME asbestos concentration was not calculated In addition to using TEM for NIOSH Chrysotile Exposure from Boxes of Brakes ooff 17 7202 and ISO TEM was also used to measure an asbestos fiber concentration using the same fiber parameters utilized by NIOSH 7400 All statistical analyses were performed using Microsoft Excel Correlation coefficients r were used to assess the association between the number of boxes of brakes handled and airborne asbestos concentrations RESULTS Air exchange measurements using SF6 as a tracer gas showed rates of 0.83 air exchanges per hour on 27 July 2004 during Phase I testing and 0.39 and 0.66 air exchanges per hour on 5 and 6 November 2005 during Phase II testing These low exchange rates were expected considering that no active ventilation system was present in the building and all windows were kept closed These air exchange rates were consistent with those reported previously for this building by Paustenbach et al 2006 and are low compared to what would be expected in most auto repair facilities four to six air exchanges per hour American Society of Heating Refrigerating and Air Conditioning Engineers Inc. 1991 Paustenbach et al 2006 Asbestos bulk sample analyses Detailed information regarding the number of boxes of brakes the type of brakes and the average chrysotile composition of the brakes used in each sampling event is provided in Tables 1 and 2. Bulk sample analysis revealed that the average chrysotile asbestos content in the brake pads and shoes ranged from 27 to 45 for the various simulation events in Phase I testing and ranged from 31 to 36 for events in Phase II testing Individual measurements of chrysotile asbestos in brake pads and shoes ranged from 3 to 60 PLM analysis did not indicate the presence of amphibole asbestos fibers in any of the brake pads or shoes Bulk sample analysis of the dust that accumulated on the countertop during the unpacking and repacking of boxes of brakes indicated average chrysotile asbestos concentrations ranging from 2 to % Airborne asbestos exposures The number and types of asbestos samples collected during each handling scenario as well as the airborne asbestos concentrations as determined by PCM and TEM are presented in Tables 1 and 2. A total of 214 air samples were collected for different scenarios associated with the unpacking and repacking of boxes of brake pads and shoes including 80 personal samples fifty 15 min ten 30 min and sixteen 100 min 56 bystander samples 8 indoor background samples prior to any testing 26 remote area samples 52 indoor background samples between testing events and 10 outdoor ambient samples Of the samples collected only two personal lapel samples could not be analyzed due to particulate interferences and excessive loading Comparisons of right and left lapel samples showed no difference and because they were viewed as replicate samples the right and left lapel samples were averaged for each simulation event Table 3 summarizes the total number of samples collected and the mean and range of PCM and TEM analytical sensitivity limits for each type of sample While PCM TEM and PCME airborne fiber concentrations are summa- rized in Tables 1 and 2 only PCME asbestos concen- trations are discussed in the text A number of observations can be derived from the study results First airborne asbestos concentrations generally increased with the number of boxes handled Figs 5 and 6 This relationship was linear Figs 5 and 6 with a strong positive correlation between the mean min worker asbestos concentration and the number of boxes handled for both pads and Table 3. Estimated analytical sensitivity limits f ccc ,,f,,or asbestos for each type of sample collected during various box handling activities testing I and II PCM NIOSH 7400 method TEM NIOSH 7400 fiber parameters N Average Range N Worker min 54 0.003 0.002-0.004 54 Worker min 10 0.001 0.001-0.001 10 Worker min 17 0.002 0.001-0.003 17 Bystander 68 Background between testing events 56 0.002 0.002 0.001-0.003 68 0.001-0.003 56 Background before testing 8 0.001 0.001-0.002 8 Remote area 32 0.001 0.001-0.002 32 Ambient 10 0.001 0.0003 10 Average 0.008 0.003 0.004 0.003 0.004 0.002 0.003 0.001 Range 0.001-0.024 0.001-0.005 0.002-0.007 0.002-0.005 0.003-0.005 0.001-0.004 0.001-0.021 0.001-0.002 N number of samples Fibers were counted using TEM with fiber parameters 0.25 NIOSH 7400 method mdiameter 5 mlength and 23 aspect ratio outlined by 12 of 17 A. K. Madl et al 10.0 cc seen Pads @ Pads / 1.6 Concentration Shoes Concentration Concentration 1.2 Concentration Concentration Concetraion Asbestos Asbestos 0.8 Asbestos Asbestos Average 0.4 AverageAverage { Average 2 4 an nnenememenn enn nn mene tenn OSHA min Ceiling Limit 1972-1986 $ t a a 6 8 10 12 14 16 18 20 Numob f e Boxr es Bars represent the range of minimum and maximum values Fig 5. Airborne asbestos concentrations min PCME for worker handling different numbers of boxes of brake pads and shoes Concentration Concentration Concentration Concentration Concentration Concentration cc cc Asbestos Asbestos Average Average Average Average 1.0 pw 0.8 4] 0.6 4 0.4 4 0.2 5 0.0 ee a eee e ee ee ee Worker - Pads OSHA min Excursion Limit present - BystandPeadrs - WorkSe hor es Bystander - Shoes t }$ ~ & _2_, $ a, i : + 2 4 6 8 10 12 14 16 18 20 Number of Boxes Bars represent the range of minimum and maximum values Fig 6. Comparison of airborne asbestos concentrations min PCME for worker and bystander samples during the handling of different numbers of boxes of brake pads and shoes shoes brake pads r = 0.91 and brake shoes r = 0.98 For worker samples collected over a min time period a strong association existed between the number of boxes of brake pads and the airborne asbestos concentrations r = 0.99 but not with the number of boxes of brake shoes r = 0.61 This trend was more apparent in the personal samples than in the area samples collected at bystander locations Table 1 Fig 6 The number of boxes handled appeared to be associated with increasing bystander PCME concentrations for brake shoes as well as brake pads No such trend was observed at remote area locations 25-30 ft from handling activity Second the type of brake material in each box influenced airborne asbestos concentrations Al- though the brake pad and shoe asbestos content was similar it was consistently observed that handling brake pad boxes resulted in higher airborne asbestos concentrations within the breathing zone of the worker than handling brake shoe boxes Specifi- cally it was observed that boxes of brake pads produced two to seven times higher airborne asbestos concentrations PCME in a 15- or min time period for the worker compared to the concentrations created by boxes of brake shoes Table 1 Figs 5 and 6 Third airborne asbestos concentrations in the worker's breathing zone were greater than those observed at the bystander locations Table 2 Fig 6 and airborne asbestos concentrations at bystander locations were higher than those observed at remote area locations For example average min samples collected on the lapel of the worker ranged from 0.086 to 0.368 f ccfl,,PCME for handling 4-20 boxes of brake pads and 0.021 to 0.126 f cc1 PCME for the same number of boxes of brake shoes Table 2 Fig 4 At the bystander sampling locations for the same number of boxes of brakes average PCME airborne asbestos concentrations were ob- served at 0.004-0.035 f cc for brake pads and 0.002 0.011f ccfl,,for brake shoes No difference Chrysotile Exposure from Boxes of Brakes 13 of 17 was apparent between bystander brake pads average 0.004 f cc,,brake shoes average 0.002 f ccfla,,nd remote brake pads average 0.006 f cc and brake shoes average 0.001 f cc areas when only four boxes of brakes pads were handled Higher airborne asbestos concentrations however were observed at bystander brake pads average 0.010 f cc,,andcc,,andbrake shoes 0.011 f cc,,locations compared to remote area brake pads average 0.005 f ccfland brake shoes average 0.001 f cc locations when 16 boxes of brakes were unpacked and repacked Although re- mote area airborne asbestos concentrations were higher during the handling of brake pad boxes compared to brake shoes the samples collected in the remote area locations were not greatly influenced by the various handling tasks Comparisons demon- strated similar airborne asbestos concentrations f cc,,and cleanup average 0.003 f ccflc,,oncentra- tions measured during handling activities Fifth background airborne asbestos concentra- tions measured between testing events compared to those measured prior to the study showed that results from each testing event were independent Background measurements collected prior to any testing did not show any detectable asbestos fibers by TEM Of the 52 background samples collected in between handling testing events only nine showed a measurable concentrations of asbestos The sam- ples in which asbestos fibers were detected resulted in average PCME airborne asbestos concentrations ranging from 0.001 to 0.004 f ccflG,,iven that asbestos measurements between testing events were low or below the sensitivity limit e.g. 83 were 0.001 0.008 f cc concentrations of asbestos from one for the remote area samples range of averages 0.001-0.017 f cc ) collected during the box- handling tasks when compared to the background samples range of averages 0.001-0.004 f ccc,,ol- lected in between the testing events While it is not surprising that the airborne asbestos measurements from the worker's lapel were greater than those observed at bystander sample locations it is worth noting that asbestos concentrations decreased quickly and significantly in the breathing zone of the worker after handling activities ceased Most boxes of brakes all but two brake shoe boxes in Phase II testing were handled within the first 15 min Therefore the second min sample represents the concentration of airborne asbestos that remains in the air after handling activities cease Comparison of the first and second min samples showed a decrease in airborne asbestos concentra- testing event did not impact the results of successive testing events Ambient contributions to background asbestos concentrations were also characterized Although av- erage PCM airborne fiber concentrations for ambient air samples ranged from 0.001 to 0.002 f cc,,cc,, no as- bestos fibers were detected by TEM The observed PCM concentrations were slightly less than the ambient air concentrations reported by Paustenbach et al 2006 and in general were consistent with background concentrations reported by the Agency for Toxic Substances and Disease Registry and US EPA for typical US cities Agency for Toxic Substances and Disease Registry 2001 US Environmental Protection Agency 2003 Paustenbach et al 2006 Airborne asbestos TWA exposures tions for the handling of brake pad boxes but not for brake shoe boxes Specifically average airborne asbestos concentrations decreased from 0.356 to 0.021 f cc after unpacking and repacking of brake pads ceased and concentrations decreased from 0.030 to 0.013 f cc after unpacking and repacking of brake shoe boxes ceased Fourth personal airborne asbestos concentrations during handling tasks were higher than those measured during cleanup and handling tasks Cleanup of dust which had accumulated on the work countertop and handling of clothes which had been worn while boxes were unpacked and repacked showed airborne asbestos concentrations of 0.004 and 0.011 f cc for the worker and 0.002 and 0.010 f cc for the bystander locations respectively Comparisons showed that worker exposures result- ing from handling activities average 0.011 f cccc,,w,,ere similar to measurements collected during cleanup average 0.004 f cc ,,both activities were comparable to bystander handling average 0.010 f cc,,and cleanup average 0.002 f ccfl,, and remote area handling average 0.002 Measurements collected during handling handling and cleanup events were used to estimate h TWA exposures for a worker handling 4 16 and 40 boxes of brakes in a workday In Phase II testing term samples were collected in consecutive min intervals which encompassed the testing event 30 min ventilation period 30 min and background characterization 30 min Air concentrations during the cessation of these tasks were assumed to be equivalent to remote area asbestos concentrations collected during testing events Based on the min samples collected during the handling activities h TWA asbestos exposures for workers handling 4 16 or 40 boxes of brakes over a workday were estimated to be below the current OSHA PEL for asbestos Eight TWAs for workers handling 4 or 16 boxes of containing brakes ranged from 0.002 to 0.021 f cca,,pproximately quarter to hundredths below the OSHA PEL of 0.1 f cc for asbestos Eight TWA worker exposures handling up to 40 boxes of brakes in a workday was 0.063 f ce nearly one- half of the current OSHA PEL 14 of 17 A. K. Madl et al Fiber size and morphology Fiber size and morphology were assessed in the personal worker samples collected during boxhandling cleanup and handling activities from Phase II testing Results showed that 50-59 of the fibers counted for the different activities were free fibers or bundles 9-33 were fiber clusters and 16-31 were associated with a matrix Table 4 Assuming though that only fibers 0.7 um in diameter can reach the deep lungs then only 30 of the total fibers were respirable considering the fiber size and morphology characteristics It was also observed that % specifically 0-7 of the total fibers counted within this size range were respirable and had a fiber length 20 ...mIf the criterion for respi- rability was extended to 3 ...min diameter 33-56 of the asbestos fibers free or bundles would therefore be considered respirable The majority of fibers associated with a cluster or a matrix were too large to be considered as respirable fibers whereas 0-27 could be classified as respirable particles DISCUSSION This study was conducted to assess possible exposures to airborne asbestos during unpacking and repacking of boxes of containing brake pads and shoes for vehicles ca. 1946-80 as well as to understand potential asbestos exposures associated with other related activities such as cleanup and clothes handling In addition to those already dis- cussed there are a few other observations that can be made from this simulation study Not surprisingly for example we observed that there were physical limitations to the number of boxes that could be han- dled within a certain time period We found that handling 16 to 20 boxes in 15 or 30 min represented a maximum physical limit It was interesting to observe higher airborne asbestos concentrations associated with the handling of brake pad boxes compared to brake shoe boxes Due to the curvature of the brake shoe and the fact that these parts were often packed tightly it is possible that the boxes of brake shoes produced less airborne asbestos because there was less of an opportunity for the brake parts to rub against one another during shipment In addition it is noteworthy that the shipment of the boxes prior to the commencement of Phase II testing appeared to produce dust to such an extent that the airborne asbestos concentrations mea- sured in Phase II were similar to those produced from comparable events in Phase I. The difference in air exchange rates between days of testing also did not appear to have an effect on worker or bystander exposures thus emphasizing that activities have the greatest impact on exposures in the near field The handling and cleaning of contaminated work clothing worn in some occupational environments have been suggested as a possible source of paraoccupational or home chemical exposure Studies that have reported exposure through this possible secondary exposure pathway include industries where beryllium lead or even asbestos e.g. insulation workers exposures in the workplace were excessive For example Eisenbud et al 1949 found mean Table 4. Size and morphology distribution of fibers detected in personal workers samples collected during various box handling activities Fiber structure classification N Total Percent fibers % classified as fiber or particle with dimensions fibers % 0.7 ...mwidth < ...mwidth 10 ...mwidth > ...,, 20 ...m length length > ...m length 20 ...m length > ...m length 20 ...m length handling activities Total fibers 1128 _ _ _ Free bundle 667 59.1 35.1 4.7 55.9 8.6 _ Fiber clusters 109 9.7 0.0 0.0 2.0 0.8 7.0 2.7 Matrix disperse 352 31.2 0.7 0.0 4.6 0.8 23.4 4.2 Cleanup activities Total fibers 15 - _ _ _ 8821 9811 Free bundle 8 53.3 33.3 6.7 53.3 8821 9811 Fiber clusters Matrix disperse handling activities Total fibers Free bundle Fiber clusters 4 26.7 3 20.0 6 3 50.0 2 33.3 0.0 0.0 _ 33.3 0.0 0.0 0.0 0.0 0.0 6.7 8821 0.0 8821 coe 1888 33.3 1888 0.0 1888 26.7 20.0 0.0 9811 9811 1188 1188 1188 Matrix disperse 1 16.7 0.0 0.0 0.0 1888 16.7 0.0 Chrysotile Exposure from Boxes of Brakes 15 of 17 -3 air concentrations of 500 ...gberyllium m when the clothing of beryllium manufacturing workers was shaken out Piacitelli et al 1997 found elevated lead concentrations in the vehicles and homes of exposed construction workers Some persons who live in the homes of workers exposed to free asbestos fibers developed asbestos disease Lieben and Pistawka 1967 Anderson et al 1976 Li et al 1978 Anderson et al 1979 Epler et al 1980 McDonald and McDonald 1980 Joubert et al 1991 Magnani et al 1993 Generally workers in asbestos manufacturing mining and shipyard industries are exposed to very high airborne concen- trations of asbestos and come in direct contact with large amounts of bulk asbestos and in the majority of cases amphibole asbestos The home exposure of other household members called secondary exposure or occupational exposure is thought to occur as a result of bringing very dusty work clothing into the home which was usually contaminated due to daily contact to bulk or raw asbestos Although all exposures associated with handling work clothes worn during handling activities were extremely low it was felt that this issue deserved greater characterization as it has implications for both historical and current asbestos exposures of a group of individuals not previously studied While we were interested in exposures distant by- stander and remote from the primary activity it was not intended as a part of the sample design to charac- terize exposures associated with settled asbestos on work surfaces but rather associated with the box- handling activity itself The fact that asbestos was found in the settled dust on the countertop as a result of handling boxes of brakes however illustrates how such work might contribute to the presence of asbestos on nearby work surfaces It should be noted that the dust which settled on the counter surface was present only in the immediate vicinity to the boxhandling activities and consisted of % asbestos as compared to 30 in the original brake material If the settled dust was not properly cleaned after work activities theoretically there could be a potential for dispersal to locations distant from the original work activity In regards to results associated with the handling activities it is likely that closing up the facility resulted in higher worker and bystander exposures than if the facility was fully ventilated It is also possible that some fibers remain in the air after the work activities ceased However our results show that airborne fibers detected in the 15 min following the cessation of handling activities were significantly reduced compared to those generated during the handling activities and approached background concentrations as measured in between the testing events It has been well established that the precision of airborne fiber concentrations by counting fibers on a membrane filters is dependent on the fiber density and proportion of filter surface area e.g. microscope fields examined with statistical uncertainties generally being inversely proportional to the fiber density Ogden 1982 Johnston et al 1982 Cherrie et al 1986 Lange et al 1996 Some researchers have suggested that the variations of low asbestos count data are attributed to a psychological incentive for analysts to search harder for fibers on density samples Cherrie et al 1986 It has been reported that the accuracy is not greatly improved for counts beyond 50 fibers and thus has been recommended that at least 50 fibers be counted and the number of fields be only limited where the airborne fiber concentrations are so low that the accuracy is no longer important Ogden 1982 These concepts have been incorporated into the current NIOSH method for asbestos National Institute for Occupational Safety and Health 1994a where 100 fibers or 100 micro- scope fields whichever criterion is met first are counted For the majority of the worker samples collected in this simulation study 50 fibers were counted within the prescribed 100 microscope fields whereas far fewer fibers 10-20 fibers were ob- served in samples collected in bystander or remote area locations The confidence limits would as a result be expected to be narrower for personal compared to those for area airborne asbestos concentrations This trend has been supported in the literature by comparisons of personal and area asbes- tos fiber concentrations measured during asbestos in- sulation tile and transite abatement operations which showed that airborne asbestos concentrations were not normally distributed and area measurements were more variable compared to personal fiber measurements Lange et al 1996 In our study however the range or variability of asbestos fiber concentrations within a given event and location e.g. worker and bystander appeared relatively narrow with the exception of handling 16 boxes of brake pads Fig 5 The range of asbestos concentrations across scenarios e.g. brake type worker versus bystander also appeared relatively constant Possible reasons for this limited variability within or across events or sample locations potentially include i the controlled repetitive conditions under which the simulated tasks were performed ii similarity of airborne concentrations across similar spatial distances e.g. right and left lapel and concentric area samples and iii consistent sample analysis under one laboratory and by similarly trained and certified microscopists Despite these observations asbestos counts at low concentrations are generally not normally distributed and variance usually depends on the airborne concentration precluding the use of statistical comparisons that rely on normality and symmetrical distributions With this in mind data were presented in 16 of 17 A. K. Madl et al a descriptive manner and statistical comparisons were not attempted The data collected in this simulation study are believed to capture the plausible range of handling scenarios i.e. number of boxes type of brakes and distance from activity for a brake mechanic auto parts supplier or warehouse parts picker in addition to evaluating potential exposure associated with handling work clothes or performing clean activities In summary the short airborne asbestos con- centrations measured for both a worker unpacking and repacking of boxes of containing brakes as well as a bystander working in the vicinity of such activity were below both the current OSHA excursion limit for asbestos and all previous US occupational asbestos standards The industrial hygiene data presented here should therefore prove useful for retrospective and current exposure assess- ments of individuals and hazard assessments of work activities which involve the handling of asbestoscontaining brakes in a variety of workplace settings FUNDING Ford Motor Company Chrysler LLC and General Motors Corporation Acknowledgements --Ford Motor Company Chrysler LLC and General Motors Corporation have been involved in litigation related to the possible exposure of brake mechanics to asbestos The funding organizations have not reviewed any part of this manuscript prior to its publication Some of the authors have served as expert witnesses in litigation regarding the potential asbestos health hazards to mechanics historically involved in automobile work REFERENCES Agency for Toxic Substances and Disease Registry 2001 Toxicological profile for asbestos Atlanta GA US Department of Health and Human Services DHHS Public Health Service Agency for Toxic Substances and Disease Registry ATSDR Agency for Toxic Substances and Disease Registry 2003 Toxicological profile for asbestos Atlanta GA US Department of Health and Human Services DHHS Public Health Service Agency for Toxic Substances and Disease Registry ATSDR Agudo A Gonz^lezCA Bleda MJ et al 2000 Occupation and risk of malignant pleural mesothelioma A control study in spain Am J Ind Med 37 157 68 American Society for Testing and Materials International 2001 Standard test method for determining air change in single zone by means of a tracer gas dilution West Conshohocken PA American Society for Testing and Materials ASTM E741-00 American Society of Heating Refrigerating and Air Conditioning Engineers Inc. 1991 Heating ventilation and airconditioning applications Pound Edition Atlanta GA American Society of Heating Refrigerating and AirConditioning Engineers Inc. 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