Document 4JaVzBk1Gvj1Rq3N3DRZwrbpQ

FILE NAME Packings and Gaskets PAG DATE 2006 DOC PAG044 DOCUMENT DESCRIPTION Journal Article - Assessment of Airborne Asbestos Exposure During the Servicing of Auto Gaskets i, ar ELSEVIER Available online at www.sciencedirect.com SCIENCE @DIR Regulatory Toxicology and Pharmacology 45 2006 214 222 Regulatory Toxicology and Pharmacology www.elsevier.com/locate/yrtph Assessment of airborne asbestos exposure during the servicing and handling of automobile containing gaskets Charles L. Blake a G. Scott Dotson b Raymond D. Harbison b * Bureau Veritas - Clayton Group Services Inc. Kennesaw GA 30144 USA b Department of Environmental and Occupational Health College of Public Health University of South Florida Tampa FL 33612 USA Received 3 April 2006 Available online 26 May 2006 Abstract Five test sessions were conducted to assess asbestos exposure during the removal or installation of containing gaskets on vehicles All testing took place within an operative automotive repair facility involving passenger cars and a pickup truck ranging in vintage from late 1960s through 1970s A professional mechanic performed all shop work including engine disassembly and reassembly gasket manipulation and parts cleaning Bulk sample analysis of removed gaskets through polarized light microscopy PLM revealed asbestos fiber concentrations ranging between 0 and 75 Personal and area air samples were collected and analyzed using National Institute of Occupational Safety Health NIOSH methods 7400 phase contrast microscopy PCM and 7402 transmission electron microscopy TEM Among all air samples collected approximately % 11 contained chrysotile fibers The mean PCM and phase contrast microscopy equivalent PCME h time weighted average TWA concentrations for these samples 0.0031 fibers centimeters cc and 0.0017 cc respectively Based on these findings automobile mechanics who worked with containing gaskets may have been exposed to concentrations of airborne asbestos concentrations approximately 100 times lower than the current Occupational Safety and Health Administration OSHA Permissible Exposure Limit PEL of 0.1 cc '2006 Elsevier Inc. All rights reserved Keywords Asbestos Automotive Gaskets Mechanics Occupational Exposure 1. Introduction containing materials ACMs have been used in automobile brakes gaskets clutches and some undercoating The presence of asbestos in the workplace and the potential for fibers to be liberated during the servicing of vehicles has given rise to allegations of increased rates of asbestos diseases among automotive mechanics Huncharek 1990 Lemen 2004 However epidemiological studies attempting to elucidate the risk of lung cancer and mesothelioma within automobile mechanics report no increased risk of asbestos diseases within the occupational cohort Agudo et 2000 Wong 2001 Goodman et al 2004 Hessel et al 2004 Laden et al 2004 . Corresponding author Present address 13201 Bruce B. Downs Blvd. Tampa FL 33612-3805 USA Fax +1 813 974 3637 mail address rharbiso@hsc.usf.edu R.D. Harbison 0273-2300 see front matter '2006 Elsevier Inc. All rights reserved j.yrtph.2006.04.007 Wong 2006 Despite these findings a debate continues about the deleterious effects of exposure to asbestos fibers in the automotive repair industry There is little exposure data characterizing the airborne asbestos fiber levels that workers may encounter while performing maintenance activities on the various containing parts found within automobiles Each component is an independent point source of asbestos exposure and may constitute a unique occupational hazard for mechanics Of the ACMs found in automobiles brakes and brake components have been the primary source of interest Several previously conducted exposure assessments report asbestos concentrations that do not exceed the current Occupational Safety and Health Administration's OSHA Permissible Exposure Limit PEL of 0.1 fibers per cubic centimeter cc OSHA 1997a Weir et 2001 Blake al 2003 Paustenbach et al 2003 2004 Other containing parts such as gaskets have not been studied in such detail C.L. Blake et al | Regulatory Toxicology and Pharmacology 45 2006 214 222 215 containing gaskets have historically been used in internal combustion engines as interfaces between solid components to prevent leakage The asbestos content of gasket material provides additional flexibility durability and resistance against thermal and chemical degradation During the servicing of vehicles containing these gaskets the potential release of asbestos fibers and subsequent worker exposures raise occupational health concerns Limited information is currently available that characterizes worker exposure to airborne asbestos fibers released dur- ing the servicing of vehicles assembled with asbestos taining gaskets A review of published literature identified three studies that examined the airborne fiber levels gener- ated during the handling and replacement of automotive gasket materials containing asbestos Yeung et al investigated chrysotile exposure in garage workers using various control methods during the servicing and replacement of friction materials and gaskets 1999 The average phase contrast microscopy PCM fiber concentrations for personal and area air samples associated with the cutting and stamping of compressed sheet automotive gaskets were below the analytical level of detection LOD of 0.05 cc Yeung et al 1999 Liukonen and Weir assessed asbestos concentrations during the dismantling and cleaning of a medium diesel engine containing asbestos gaskets 2005 Bulk sample analyses established the presence of asbestos fibers within 28 of the 33 removed gaskets in concentrations ranging from 15 to 70 Liukonen and Weir 2005 Airborne levels of asbestos fibers were reported to be approximately % of the OSHA PEL Liukonen and Weir 2005 Paustenbach et al evaluated the exposure to asbestos during the removal of automotive exhaust systems containing asbestos gaskets 2005 Analysis of personal air samples were between 0.006 and 0.066 PCM cc Paustenbach al 2005 The fiber concentrations reported in these studies indicate that automotive mechanics are exposed to limited if any levels of airborne asbes- tos fibers The purpose of this study was to characterize airborne asbestos exposure during vehicle servicing and handling of containing gaskets Data were collected during normal operational conditions within an active automotive service facility to ensure a valid assessment of worker exposure during the disassembly and reassembly of automotive engines containing asbestos gaskets Personal and area air samples were analyzed for comparison against the OSHA PEL and with previous studies 2. Materials and methods 2.1 Test location and environmental setting This study was conducted in a fully equipped and functioning automobile service facility located in Detroit Michigan The specific workspace used for this testing was a bay automotive service garage with rollup doors on both ends of each bay Interior dimensions of the service garage measured 37.5 feet ft by 29 with exposed roof decking at 17.8 The general layout of this garage is shown in Fig 1. The north wall of this garage angled into a hallway that lead to offices and the main shops located to the north Barriers and isolation devices were not utilized to seal the test area from this section of the service facility due to its distance from the actual test area and to aid in maintaining standard environmental conditions Area samples were collected from midway between the two shop areas which showed an absence of airborne fiber migration from shop A warehouse used for storage purposes was located adjacent to the north wall of the garage Existing materials and equipment were left inside the automotive service facility and the connecting hallway during the testing This included but is not limited to parts bins used tires compressed gas bottles trash receptacles a tire inflation safety cage and two fully functional hydraulically operated automobile lifts Vehicles receiving service entered from the west side and exited from the east side or vice versa The ventilation system located within the two automotive service garage was shut down during the three days of testing Testing was performed in an unventilated facility to facilitate a worse case scenario Also the rollup vehicle doors remained closed during each test session The four rollup doors were opened between test sessions to remove airborne particles generated during the previous test sessions 2.2 Test vehicles Vintage vehicles utilized in this experiment were selected based on 1 the likelihood of encountering containing gaskets and 2 the availability of new replacement containing engine gaskets The tested vehicles included a 1974 Chevrolet Malibu 1978 Chevrolet pickup truck and a Ford 390 cubic inch V engine Table 1 contains a brief description of the vehicles and engines utilized in this study 2.3 Mechanic's activities equipment and tasks The professional automotive mechanic was Automobile Service Excellence ASE certified and was instructed to perform gasket removals or installations using his standard operating procedures SOP Thus he was allowed to select all tools and equipment to ensure limited interference with his job practices Tools utilized during this experiment included wrenches screwdrivers scrapers and hammers in addition to pneumatic powered ratchets for the removal of bolts and nuts The mechanic was directed to wear a normal work uniform to further ensure realism and avoid use of cumbersome or uncomfortable garments which would have interfered with his normal activities or work habitats Five individual test sessions were conducted to assess the levels of air- borne asbestos fiber generated during the servicing and handling of asbescontaining gaskets Three test sessions focused on the partial disassembly of engines and the removal of gasket remnants from engine receiving surfaces and loose parts The two remaining test sessions involved engine reassembly and included installation of new asbestos taining gaskets Table 2 summarizes the individual activities performed during testing During the gasket removal test sessions the mechanic first removed engine heads and manifolds components that covered or otherwise held the target gaskets Many of these gaskets came off intact leaving gasket residue on the metal mating surface Bulk samples of the removed gaskets were obtained for subsequent analysis The mechanic next scraped away gasket residue using a wide blade putty knife sometimes assisted with a rubber hammer Loose parts such as engine heads and manifolds were next immersed into a water bath cleaner a product of Safety Kleen and washed using an Arm and Hammer brand Aqua Works Cold Cleaning Solution before being burnished using a rotary in knot type wire end brush NAPA service tools Part Number N 2312. The end brush was powered by a hand held drill motor Ingersoll Rand model 7803R operated from 90 PSI line pressure To aid in the gasket and other residue removal process the mechanic sprayed the parts with a chlorine containing solvent dispersed from an aerosol spray can Aerosol Systems Inc. N T'M 3506. This solvent contained xylenes aliphatic petroleum distillates and acetone with a compressed carbon dioxide propellant When cleaning the surfaces of fixed transportable parts such as engine 216 C.L. Blake et al / Regulatory Toxicology and Pharmacology 45 2006 214 222 Warehouse Air Compressor _ fe Offices & Shops North Warehouse 3 Fi Roll up Doors mim f e Test Vehicle Engine e a, 8 1 Parts Cleaner 9 Ceiling Height 17'9 w - Roll up Doors x Lift 2 Work Bench 4 Outdoors Outdoors Fig 1. Automotive servicing facility Numerical values represent locations of area samples and correspond with Table 3 Table 1 Make and model of vehicles and engines Automobile 1974 Chevrolet Malibu 1978 Chevrolet Pickup Ford Thunderbird Description of engines Small Block Engine 350 Cubic Inch V line Engine 250 Cubic Inch 6 Cylinder 390 Cubic Inch V Loose Engine blocks the mechanic utilized scraping powered wire brushing and solvent spray however no aqueous wash occurred with the fixed parts This process continued until all gasket remnants were removed from the loose parts and engine blocks and subject parts were sufficiently clean to allow reassembly Reassembly of the engines and installation of new containing gaskets occurred in two test sessions The mechanic chose to initially apply an adhesive glue strip to previously cleaned receiving surfaces on the engine blocks This step ensured that the new gaskets would be securely held in place as the loose engine components were reattached New asbescontaining gaskets were laid on the engine receiving surfaces and the respective engine parts were lowered into place Finally bolts and other fasteners were tightened to specified torque limits The mechanic was responsible for cleaning the work area after each test session When conducting cleanups the mechanic utilized a hand held straw broom a push broom and a dust pan Debris on the work surfaces and floor was swept and disposed of into available trash containers Air sampling continued during this time period and ended after the mechanic was satisfied with the conditions of the garage and work area Table 2 Activities associated with the removal and replacement of asbestoscontaining gaskets Task Description Engine disassembly and removal of containing gaskets 1. Vehicle moved into service facility 2. Vehicle placed on rack 3. Engine partially disassembled 4. Gaskets removed 5. Engine receiving surfaces dry scrapped and brushed to remove gasket remnants 6. Loose engine components placed in water bath parts washed 7. Parts rotary brushed to remove gasket remnants Engine reassembly and installation of containing gaskets Cleanup of service facility 1. Placement of adhesive on engine receiving surfaces 2. Placement of gaskets into position 3. Placement of loose engine components 4. Tighten fasteners securing of loose parts to engine block 1. Sweeping of all debris into dust pan 2. Placement of debris into trash bin C.L. Blake et al | Regulatory Toxicology and Pharmacology 45 2006 214-222 217 2.4 Sampling and analysis of collected samples Personal and area air samples were collected to estimate airborne fiber exposure levels that mechanic and hypothetical bystanders would encounter during the previously described work activities The equipment utilized for collecting personal samples consisted of battery powered portable air pumps Ametek Model xl that drew air at metered flowrates nominally 2.0-2.4 liters per minute lpm through mm diameter cassettes mounted mixed cellulose ester MCE membrane filters The cassettes were placed within the mechanic's breathing zone The membrane filters placed atop the mechanics right shoulder were of 0.8 micron ...mpore size while those placed atop his left shoulder were of 0.45 ...mpore size Area air samples were collected using line operated vacuum pumps Gast Manufacturing Inc. at metered flowrates nominally 10 lpm These pumps drew air through 25 millimeter mm diameter cassettes mounted with 0.45 ...mpore size mixed cellulose ester MCE membrane filters The flowrates for all air sampling systems were measured and documented prior to and after completion of each test A primary standard airflow calibrator Bios International Model DC was used for these airflow measurements Nine area air samples = were collected during each test session at breathing zone heights ft above floor either being supported by portable stands the automobile lift or the test vehicles Area samples were located on either side of the test vehicles or engine at the four corners of the test garage on the work bench used for wire brush cleaning and down the connecting hallway These samples were placed at distances ranging from 0 to 50 from the test vehicle Table 3 also summaries the location of area samples during each test session Area samples locations are represented on Fig 1 Samples were analyzed using phase contrast microscopy PCM and transmission electron microscopy TEM PCM analysis followed the National Institute of Occupational Safety and Health NIOSH Method 7400 NIOSH 1994a This analytical method is unable to distinguish between fibers of asbestos and asbestos origins and provides an index of airborne fibers commonly used to estimate asbestos concentrations NIOSH 1994a The optical limitations of the phase contract microscope restrict its resolution capabilities to fibers wider than 0.25 micrometer um and longer than 5 ...min length Additionally fibers not exhibiting a three to one length to width ratio are excluded from the counting process Use of this method satisfies requirements of the OSHA standards for asbestos specific air sampling PCM analysis of air samples counts all resolvable fibrous structures including asbestos fibers that meet the dimensional criteria There exists the potential for such analysis to yield airborne fiber concentration data which exceed the actual airborne asbestos concentrations In settings such as automobile repair shops cellulose fibers long thin metal fragments from power brushing activities and synthetic and other fibers often appear in air samples taken during work of the type subject of this research For this reason additional analysis of air samples was done using TEM following NIOSH Method 7402 NIOSH 1994b This analytical method measures fibers longer than ...mand wider than 0.25 ...mand allows development of an asbestos fiber ratio This ratio is then multiplied by the airborne fiber concentration generated using the PCM analysis yielding an asbestos fiber count known as phase contrast microscopy equivalent PCME This asbestos fiber count may be used for comparison against occupational exposure limits OEL such as the OSHA PEL or NIOSH recommended exposure limits REL Table 3 Location of area samples within service facility Sample No. Location 1 Southeast corner SE corner 22 feet SE of vehicle 2 Southwest corner SW corner 19 feet SW of vehicle 3 Northwest corner NW corner 15 feet NW of vehicle 4 Northeast corner NE corner feet NE of vehicle 5 Intermediate hallway 30 feet NE of vehicle 6 Distant hallway 50 NE of vehicle 7 Driver's side fender 89 Passenger's side fender 89 Work bench 9 feet S of vehicle Asbestos contents of gaskets were determined by polarized light microscopy PLM using the United States Environmental Protection Agency USEPA Method 116 Perkins and Harvey 1993 PLM is capable of identifying the individual components of a sample and estimating their relative concentration within the sample's matrix Additionally the specificity of the method allows for the differentiation between serpentine and amphibole asbestos fibers 2.5 Statistical analysis Descriptive statistics have been provided for personal and area samples collected during the five test sessions Several of the samples collected n = 15 were reported at the LOD for PCM These unreported values are unusable for statistical analysis and must be addressed to limit censorship of the data The LOD for NIOSH Method 7400 is determined based on the number of optical fields and fibers counted and the volume of sampled air and represents a dynamic value for each individual sample For the purpose of statistical analysis samples reported at the LOD have been counted as the full value This method of analysis will skew the data towards an exaggerated mean fiber concentration and provide a more conservative or worse scenario estimate of the airborne asbestos levels generated during this test The Hour Time Weighted Average HR TWA for the individual samples and mean concentrations have been calculated based on the computation formula prescribed by OSHA Occupational Safety and Health Administration 1997b Values of 0 cc were applied in the equation for the time period for which no work or sampling was performed All reported values have been calculated by this method unless otherwise noted 3. Results 3.1 Individual test sessions A summary of the area airborne fiber levels generated during the removal and installment of containing gaskets is presented in Table 4. During the three sessions associated with the disassembly of the test engines the length of the tests ranged from 132 to 157min Installation of replacement gaskets in the Ford engine and Chevrolet Malibu required 122 and 150 min respectively Approximately 23 = 10 of the area samples were below the analytical LOD for PCM The highest HR TWA fiber concentration was 0.0079 cc and occurred during the removal of gaskets from the Chevrolet Malibu The relationship of the individual area air samples to the OSHA PEL is illustrated in Fig 2. All area samples = 43 were approximately 100 times lower than the current PEL of 0.1 cc Among the nine area sampling locations only slight variations in the fiber concentrations were observed throughout the automotive service facility during the removal and replacement of containing gaskets The highest fiber concentrations observed during the removal of gaskets from the three test vehicles did not occur in the immediate test area Background levels of fibers ranged from HR TWA of 0.0005-0.001c5cf A summary of the mean fiber levels rela- tive to sampling location is provided in Table 5 3.2 Personal samples Table 6 provides a descriptive summary of the personal samples Results from personal samples are 218 C.L. Blake et al / Regulatory Toxicology and Pharmacology 45 2006 214-222 Table 4 PCM fiber concentrations for the individual test sessions Test Vehicle Session description 1 Chevrolet Malibu Engine disassembly gaskets removed 2 Chevrolet Malibu Engine reassembly gaskets installed 3 Chevrolet Pickup Truck Engine disassembly gaskets removed 4 Ford 390 Engine Engine disassembly gaskets removed 5 Ford 390 Engine Engine reassembly gaskets installed * PCM phase contrast microscopy b HR TWA eight hour time weighted average cf cc fibers per cubic centimeter d Indicates test with one sample overloaded Sample No. gd gd 9 9 9 Duration min 151 157 132 122 150 Mean PCMa Concentration HR TWAb cc ' 0.002 0.0015 0.0002 0.0009 0.0006 Range 0.0017-0.0026 0.0012-0.0017 0.0002-0.0003 0.0007-0.0011 0.0003-0.0009 ) cc cc f 0.1- Concentration Concentration Concentration Concentration 0.01 Concentration Concentration Concentration 0.001 Concentration @ PCM HRTWA 0.0001 coat Samples Fig 2. Distribution of area samples Table 5 Average area air fiber concentrations relative to location of the samples to the automobiles Task Location Gasket removal Bench Driver side Passenger side Northeast corner Northwest corner Southeast corner Southwest corner Distant hallway Intermediate hallway Gasket installment Bench Driver side Passenger side Northeast corner Northwest corner Southeast corner Southwest corner Distant hallway Intermediate hallway a PCM phase contrast microscopy b cc fibers per cubic centimeter ' HR TWA average eight hour time weighted * Indicates location with one or more samples reported below the LOD a Mean PCM cc 0.0069 0.0028 0.0049d 0.0035 0.0061 0.0062 0.0078 0.0049 0.0051" 0.0021d 0.0023d 0.0078d 0.0019d 0.0036d 0.003d 0.0023d 0.0015d 0.0015d Mean PCM HR TWA cc 0.0019 0.0005 0.0013 0.001 0.002 0.0018 0.0022 0.0013 0.0015 0.0036 0.0007 0.0024 0.0006 0.0011 0.0009 0.0007 0.0005 0.0005 presented as HR TWA PCM and PCME fiber concentrations for comparison purposes against the OSHA PEL The PCM HR TWA fiber concentrations ranged from 0.001 to 0.0079 cc Only 3 of the 10 personal sam- _ ples were identified through TEM to contain chrysotile fibers Additionally % = 5 of these samples were _below the LOD The highest PCME fiber concentration _ _was 0.0044 cc C.L. Blake et al | Regulatory Toxicology and Pharmacology 45 2006) 214 222 219 Table 6 Personal samples Test session I 1 2 2 3 3 4 4 5 5 Description Engine disassembly gaskets Chevrolet Malibu Engine disassembly gaskets Chevrolet Malibu Engine reassembly gaskets Chevrolet Malibu Engine reassembly gaskets Chevrolet Malibu Engine disassembly gaskets Chevrolet Truck Engine disassembly gaskets Chevrolet Truck Engine disassembly gaskets removed 390 Engine Engine disassembly gaskets removed 390 Engine Engine reassembly gaskets installed 390 Engine Engine reassembly gaskets installed 390 Engine Location Left shoulder Right shoulder Left shoulder Right shoulder Left shoulder Right shoulder Left shoulder Right shoulder Left shoulder Right shoulder Time min 141 140 156 155 124 60 119 119 151 151 Volume L 320 348 345 371 242 131 285 262 335 371 PCMC cc 0.023 0.027 0.0058 0.005h 0.012 0.01 0.007 0.01 0.0032 0.005 PCM HR TWA cc 0.0068 0.0079 0.0019 0.0016 0.0031 0.0013 0.0017 0.0025 0.0010 0.0016 Asbestos fiber ratiof 0.381 0.556 0 0 0 0 0 0.333 0 0 PCMEB HR TWA cc 0.0026 0.0044 0 0 0 0 0 0.0018 0 0 a Min minutes b L liters PCM phase contrast microscopy d cc fibers per cubic centimeter * HR TWA eight hour time weighted average f Asbestos fiber ratio is defined as the number of asbestos fibers detected via transmission electron microscopy TEM divided by the total number of all fibers detected via TEM 8 PCME phase contrast microscopy equivalent h Indicates samples below the LOD 3.3 Samples identified to contain asbestos Approximately % 11 of all samples were determined through TEM analysis to contain chrysotile fibers A summary of the individual air samples is presented in Table 7. The majority of the air samples determined to contain asbestos fibers were collected during the removal of gaskets from the 1974 Chevrolet Malibu Asbestos fibers were not detected in samples associated with the installation of new containing gaskets in the Malibu or the Ford engine Table 8 provides descriptive statistics for these samples The average HR TWA PCM and PCME Table 7 Samples containing asbestos fibers Description Location Time min Volume L PCMC HR TWAd cc Asbestos fiber ratiof PCME HR TWA cc Gaskets removed Chevy Malibu Gaskets installed Chevrolet Malibu Gaskets removed Chevy Malibu Gaskets removed Chevy Malibu Gaskets removed Chevy Malibu Gaskets removed Chevy Malibu Gaskets removed Chevy Malibu Gaskets removed Chevy Malibu Gaskets removed Chevy Malibu Gaskets removed Ford Engine Gaskets removed Ford Engine Personal right Area southeast corner Area southwest corner Area northeast corner Area northwest corner Area driver side Area bench Area hall intermediate Personal left Personal right Area southwest corner 140 151 151 148 151 151 148 148 141 119 120 348 1498 1505 1471 1144 1495 1463 1048 320 262 1017 0.0079 0.0026 0.0031 0.0014 0.0026 0.0009 0.0029 0.0026 0.0068 0.0025 0.13 0.556 0.4 0.833 0.757 0.487 0.762 0.596 0.622 0.381 0.333 0.7 0.0044 0.0010 0.0026 0.0011 0.0013 0.0007 0.0017 0.0017 0.0026 0.0008 0.0009 a Min minutes b L liters PCM phase contrast microscopy d cc fibers per cubic centimeter * HR TWA eight hour time weighted average f Asbestos fiber ratio is defined as the number of asbestos fibers detected via transmission electron microscopy TEM divided by the total number of all fibers detected via TEM * PCME phase contrast microscopy equivalent 220 C.L. Blake et al | Regulatory Toxicology and Pharmacology 45 2006 214 222 Table 8 PCM and PCME fiber concentrations for samples containing asbestos Sample type No. of samples PCMmean concentration cc Personal 3 Area 8 All 11 0.0018 0.0022 0.0031 a PCM phase contrast microscopy b cc fibers per cubic centimeter ' SD standard deviation d PCME phase contrast microscopy equivalent SD 0.0011 0.0008 0.0022 Table 9 Asbestos and asbestos components of removed gaskets Gasket description Asbestos content 390 Ford exhaust manifold gasket 390 Ford intake manifold gasket 390 Ford head gasket 1978 Chevy head gasket Thermostat gasket 1978 Chevrolet carburetor space Exhaust donut 350 Chevrolet V intake gasket 350 Chevrolet V carburetor gasket 70 Chrysotile % Chrysotile 70 Chrysotile 70 Chrysotile ND % Chrysotile ND 75 Chrysotile ND ND none detected Range 0.0007-0.0044 0.0009-0.0031 0.0009-0.0079 PCMEd Mean concentration cc 0.0026 0.0014 0.0017 SD 0.0018 0.0006 0.0011 Range 0.0008 0.0044 0.0007-0.0026 0.0007-0.0043 asbestos fibrous materials Cellulose fiber Fibrous glass Cellulose fiber Cellulose fiber Cellulose fiber Cellulose fiber Cellulose fiber No fibers detected Cellulose fiber Cellulose fiber fibrous glass fibrous materials grease metallic sheet grease Metallic sheet grease Metallic sheet grease metallic sheet paint Binder mastic paint Binder mastic Binder metallic rust grease metallic sheet grease concentrations were 0.0022 fibers and 0.0017 fibers respectively It should be noted no amphibole fibers were identified within any sample 3.4 Bulk sample analysis Bulk sample analysis of the removed gaskets was performed to provide evidence of the presence of asbestos fibers in the gaskets and the workplace A total of nine gaskets were removed from the three test engines and analyzed via polarized light microscopy PLM The results and the descriptions of the gaskets can be found in Table 9 Asbestos concentrations ranged from 0 to 75 of the gasket matrices with five of the gaskets identified to contain more than 70 asbestos Amphibole asbestos fibers were not identified in any of the samples but chrysotile fibers were present in six of the removed gaskets asbestos fibrous materials including cellulose fiber and fibrous glass were present in all gaskets except the donut gasket removed from the Chevrolet Malibu 4. Discussion Previous assessments of asbestos exposure during the servicing of containing materials in the automotive repair industry predominantly report fiber levels at or below the current OSHA PEL Yeung al 1999 Weir al 2001 Blake al 2003 Paustenbach et al 2003 2004 2005 Liukonen and Weir 2005 Yeung et al evaluated the concentrations of chrysotile fibers mechanic were exposed during the maintenance of vehicles assembled with containing brakes and gaskets 1999 Nine auto- motive service facilities were utilized in this assessment and a total of 68 air samples were collected Yeung et al 1999 Transmission electron microscopy TEM analysis of the samples revealed a range of 0.01-0.07 chrysotile fibers per cubic centimeter Yeung et al 1999 The authors note that the majority of particulates identified in the air samples were foresterite a asbestiform silicate mineral produced when chrysotile fibers are exposed to high temperatures Yeung al 1999 Weir al conducted an exposure assessment aimed at determining the airborne asbestos concentrations and total particulate matter associated with the replacement of brake drums and the arc grinding of asbestos brake pads Weir et al 2001 The majority of samples contained fibrous material with little if any asbestos or asbestos fibers being detected Weir et al 2001 The highest PCM TWA observed in area samples was 0.02 cc Weir et al 2001 Blake et al characterized the airborne asbestos fibers generated during the maintenance of containing brakes Blake et al 2003 Six independent test sessions were conducted in which one of the following tasks were performed 1 the repair and replacement of brake shoes 2 filing of new replacement containing shoes for installation purposes 3 sanding of new shoes to remove the outermost wear surfaces or 4 arc grinding of new shoes to match companion brake drum's circumstance Blake et al 2003 The HR TWA PCM fibers concentrations reported for the personal air samples collected during the six test sessions ranged from 0.008 to 0.0937 cc Blake et al 2003 Ten previously published asbestos monitoring studies were identified and assembled to characterize retrospective asbestos exposures for brake mechanics under various working conditions Paustenbach et al 2003 A total of 162 HR time weighted average TWA asbestos concen- C.L. Blake et al / Regulatory Toxicology and Pharmacology 45 2006 214 222 221 trations from the late 1960s to 2003 where identified from the 10 original studies Airborne asbestos levels were evaluated and compared based on the location and time period of sampling servicing methodology and type of vehicle receiving brake maintenance Paustenbach et al 2003 Analysis of a subset of 141 samples collected during the servicing of light trucks and automobiles between 1968 and 1996 reported an average TWA of 0.05 cc with a range of 0.004-0.28 cc with the overall HR TWA for all identified air samples n 162 being 0.04 Paustenbach et al 2003 The airborne asbestos levels detected during our assess- ment in most cases are lower than the concentrations observed in the previously discussed studies and present additional evidence against excessive exposure to airborne asbestos fibers associated with the maintenance of vehicles assembled with parts containing asbestos using standard workplace practices Additionally the current investigation provides support to epidemiological studies that have reported no association between the servicing and handling of containing materials and increased rates of mesothelioma and lung cancer among automotive mechanics Agudo et al 2000 Wong 2001 Goodman et al 2004 Hessel et al 2004 Laden et al 2004 Wong 2006 The findings of this study are consistent with previous exposure assessments and workplace simulations and add evidence to the position that asbestos exposure among mechanics does not increase the risk of developing pulmonary cancer Approximately % of all samples collected during the five test sessions were identified to contain asbestos through TEM No amphibole fibers were found in any sample and chrysotile fibers were detected only in samples associated with the removal of gaskets from the Chevrolet Malibu and Ford engine Six gaskets were removed from the two engines with asbestos concentra- tions determined via PLM to range from 0 to 75 Several of these gaskets were extracted intact with small amounts of residue remaining on metal mating surfaces Torn gaskets and remnants found on the surfaces of the engine components can be attributed to heat produced by the normal operations of internal combustion engines Thermal stress is capable of degrading the gasket matrices over time and results in the baking of gaskets onto engine mating surfaces No asbestos fibers were found in the samples collected during the installation of new asbestos gaskets Replacement gaskets have no discernible ability to release fibers when installed using standard operating procedures due to the gasket being precut and sprayed with adhesive sealant Criticism of the use of phase contrast microscopy and transmission electron microscopy focuses on the exclusion of short ...m long and long but thin 0.25 ...m wide asbestos fibers Atkinson et al 2004 Lemen 2004 Those who oppose the use of NIOSH Methods 7400 and 7402 state that the elimination of short and thin structures from the data set underestimates the risk that exposed workers encounter Recent committee findings released by the Agency for Toxic Substances and Disease Registry ATSDR report limited or no human cancer risk from fibers fitting the previous descriptions ATSDR 2003 Research has demonstrated that the pathogenesis of asbesrelated diseases is directly influenced by the physical dimensions of asbestos fibers Stanton al 1981 The length and width of fibers determine their ability to be deposited within the lungs and subsequently affect the onset of malignant and malignant diseases Lippmann 1990 ATSDR 2003 Fibers longer than 10...mare not easily phagocytized and tend to remain in the lower respiratory tract or penetrate the pleural membrane Hume and Rimstidt 1992 Shorter fibers including the fiber populations < ...min length and 0.25 ...min width excluded from consideration by NIOSH Methods 7400 and 7402 are arguably of less significance in terms of the development of asbestosrelated cancers In addition the debate regarding dimension based fiber exclusion distracts attention from the real benefit these methods offer NIOSH Methods 7400/7402 data can be directly compared against established health risk dat- abases No such databases exist for the asbestos structure data for short < ...mlong and long but thin 0.25 ...m wide asbestos fibers Despite the limitations associated with these NIOSH Methods 7400 and 7402 the advantages of their use exceed their disadvantages Use of the water bath cleaner may have had some asbestos fiber suppression effect Despite the argument that the wetting of loose parts may potentially prevent the liberation of fibers during the cleaning process and subsequently reduce the concentration of airborne asbestos fibers the water bath cleaner is commonly used in the automotive repair industry and conforms to the study design's aim of applying actual work practices Additionally the water wash periods were brief and power wire brushing was performed without aqueous wash on the engine blocks For these reasons the fiber suppression effect attributed to the use of the water bath cleaner was minimal NIOSH Method 7400 recommends fiber loading concen- trations at or above 100 fibers mmto avoid inac- curacies during the counting process 1994a In situations such as the current study where airborne fibers concentrations remain extremely low or below the analytical level of detection compliance with the recommendation is difficult Several methods have been suggested to offset the effects of low fiber densities including decreasing the surface area of the filter or increasing the sampling flowrates Cherrie et al 1986 During the current study the range of applied flowrates varied from 2 to 101pm The fiber concentrations determined through PCM and TEM analysis for air samples collected at the different flowrates did not noticeably differ and indicate the absence of airborne fibers both asbestos and asbestos within the automotive repair facility The potential error associated with low fiber densities has been demonstrated to result in high fiber counts and frequently yield overestimated airborne fiber concentrations Cherrie et al 1986 C.L. Blake et al | Regulatory Toxicology and Pharmacology 45 2006 214 222 221 trations from the late 1960s to 2003 where identified from the 10 original studies Airborne asbestos levels were evaluated and compared based on the location and time period of sampling servicing methodology and type of vehicle receiving brake maintenance Paustenbach al 2003 Analysis of a subset of 141 samples collected during the servicing of light trucks and automobiles between 1968 and 1996 reported an average TWA of 0.05 cc with a range of 0.004-0.28 cc with the overall HR TWA for all identified air samples = 162 being 0.04f cc Paustenbach et al 2003 The airborne asbestos levels detected during our assess- ment in most cases are lower than the concentrations observed in the previously discussed studies and present additional evidence against excessive exposure to airborne asbestos fibers associated with the maintenance of vehicles assembled with parts containing asbestos using standard workplace practices Additionally the current investigation provides support to epidemiological studies that have reported no association between the servicing and handling of containing materials and increased rates of mesothelioma and lung cancer among automotive mechanics Agudo et al 2000 Wong 2001 Goodman et al 2004 Hessel et al 2004 Laden et al 2004 Wong 2006 The findings of this study are consistent with previous exposure assessments and workplace simulations and add evidence to the position that asbestos exposure among mechanics does not increase the risk of developing pulmonary cancer Approximately % of all samples collected during the five test sessions were identified to contain asbestos through TEM No amphibole fibers were found in any sample and chrysotile fibers were detected only in samples associated with the removal of gaskets from the Chevrolet Malibu and Ford engine Six gaskets were removed from the two engines with asbestos concentra- tions determined via PLM to range from 0 to 75 Several of these gaskets were extracted intact with small amounts of residue remaining on metal mating surfaces Torn gaskets and remnants found on the surfaces of the engine components can be attributed to heat produced by the normal operations of internal combustion engines Thermal stress is capable of degrading the gasket matrices over time and results in the baking of gaskets onto engine mating surfaces No asbestos fibers were found in the samples collected during the installation of new asbestos gaskets Replacement gaskets have no discernible ability to release fibers when installed using standard operating procedures due to the gasket being precut and sprayed with adhesive sealant Criticism of the use of phase contrast microscopy and transmission electron microscopy focuses on the exclusion of short ... ...mm long and long but thin 0.25...mwide asbestos fibers Atkinson et al 2004 Lemen 2004 Those who oppose the use of NIOSH Methods 7400 and 7402 state that the elimination of short and thin structures from the data set underestimates the risk that exposed workers encounter Recent committee findings released by the Agency for Toxic Substances and Disease Registry ATSDR report limited or no human cancer risk from fibers fitting the previous descriptions ATSDR 2003 Research has demonstrated that the pathogenesis of asbesrelated diseases is directly influenced by the physical dimensions of asbestos fibers Stanton et al 1981 The length and width of fibers determine their ability to be deposited within the lungs and subsequently affect the onset of malignant and malignant diseases Lippmann 1990 ATSDR 2003 Fibers longer than 10...mare not easily phagocytized and tend to remain in the lower respiratory tract or penetrate the pleural membrane Hume and Rimstidt 1992 Shorter fibers including the fiber populations < ...min length and 0.25 ...min width excluded from consideration by NIOSH Methods 7400 and 7402 are arguably of less significance in terms of the development of asbestosrelated cancers In addition the debate regarding dimension based fiber exclusion distracts attention from the real benefit these methods offer NIOSH Methods 7400/7402 data can be directly compared against established health risk dat- abases No such databases exist for the asbestos structure data for short 5...mlong and long but thin 0.25 ...m wide asbestos fibers Despite the limitations associated with these NIOSH Methods 7400 and 7402 the advantages of their use exceed their disadvantages Use of the water bath cleaner may have had some asbestos fiber suppression effect Despite the argument that the wetting of loose parts may potentially prevent the liberation of fibers during the cleaning process and subsequently reduce the concentration of airborne asbestos fibers the water bath cleaner is commonly used in the automotive repair industry and conforms to the study design's aim of applying actual work practices Additionally the water wash periods were brief and power wire brushing was performed without aqueous wash on the engine blocks For these reasons the fiber suppression effect attributed to the use of the water bath cleaner was minimal NIOSH Method 7400 recommends fiber loading concen- trations at or above 100 fibers mmto avoid inac- curacies during the counting process 1994a In situations such as the current study where airborne fibers concentrations remain extremely low or below the analytical level of detection compliance with the recommendation is difficult Several methods have been suggested to offset the effects of low fiber densities including decreasing the surface area of the filter or increasing the sampling flowrates Cherrie et al 1986 During the current study the range of applied flowrates varied from 2 to 101pm The fiber concentrations determined through PCM and TEM analysis for air samples collected at the different flowrates did not noticeably differ and indicate the absence of airborne fibers both asbestos and asbestos within the automotive repair facility The potential error associated with low fiber densities has been demonstrated to result in high fiber counts and frequently yield overestimated airborne fiber concentrations Cherrie et al 1986 222 C.L. Blake et al / Regulatory Toxicology and Pharmacology 45 2006 214 222 5. Conclusion The airborne asbestos concentrations observed during the removal and replacement of containing automotive gaskets remained well below the occupational exposure limit currently enforced by OSHA The average PCM fiber concentrations for all air samples n = 53 and samples identified through TEM to contain asbestos fiber = 11 were 0.0015 and 0.0031 cc respectively In conclusion the findings of the current study indicate that 1. The use of standard workplace practices produces limited fiber release during the handling and removal of containing gaskets and workers receive only a minimal exposure under these conditions 2. 2. Airborne asbestos levels observed in exposure assess- ments are predominantly lower than the OSHA PEL and support the claim of no relationship between employment in the automotive repair industry and increased rates of cancers Yeung et al 1999 Weir et al 2001 Blake et al 2003 Paustenbach et al 2003 Paustenbach et al 2004 Paustenbach et al 2005 Liukonen and Weir 2005 The fiber levels reported in the current study are in most cases lower than the concentrations observed in previously reported studies References Agency for Toxic Substances and Disease Registry 2003. Report on the Expert Panel on Health Effects of Asbestos and Synthetic Vitreous Fibers The Influence of Fiber Length http://www.atsdr.cdc.gov/ asbestostoc.html Accessed December 15 2005 Agudo A. Gonzalez C.A. Bleda M.J. Ramirez J. Hernandez S. Lopez F. Calleja A. Panades R. Turuguet D. Escolar A. Beltran M. 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Asbestos exposure from gaskets during disassembly of a medium duty diesel engine Regulatory Toxicology and Pharmacology 41 113 121 National Institute of Occupational Safety and Health 1994a Asbestos and other fibers by PCM NIOSH Manual of Analytical Methods Method 7400 Issue 2 15 August 1994. http://www.cdc.gov/niosh/ method Accessed March 12 2006 National Institute of Occupational Safety and Health 1994b Asbestos and other fibers by TEM NIOSH Manual of Analytical Methods Method 7400 Issue 2 15 August 1994. http://www.cdc.gov/niosh/ method Accessed March 12 2006 Occupational Safety and Health Administration 1997a Limits for Air Contaminants Code of Federal Regulation 29 CFR 1910.1000 Table http://www.osha.gov/pls/oshaweb/owadisp.show_document http://www.osha.gov/pls/oshaweb/owadisp.show_document STANDARDS Accessed March 12 2006 Occupational Safety and Health Administration 1997b Air Contami- nants Code of Federal Regulation 29 CFR 1910.1000 http www.osha.gov/pls/osha disp.show_document STANDARDS = 9991 Accessed March 12 2006 p_table Paustenbach D.J. 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