Document GmLVKLb87ewB0K049g8JqR91r

FILE NAME Plastics PLAS DATE 2005 Oct DOC PLAS001 DOCUMENT DESCRIPTION Journal Article - Occupational Exposure to Airborne Asbestos from Phenolic Molding Material Bakelite from Plastics File Journal of Occupational and Environmental Hygiene 2 497 507 ISSN 1545-9624 print/ 1545-9632 online Copyright '2005 JOEH LLC DOI 15459620500274237 Occupational Exposure to Airborne Asbestos from Phenolic Molding Material Bakelite During Sanding Drilling and Related Activities Fionna Mowat Michael Bono R.J. Lee Susan Tamburello and Dennis Paustenbach4 Exponent Menlo Park California 2Exponent Hudson Ohio 3RJ Lee Group Inc. Monroeville Pennsylvania Chem San Francisco California In this study a historical phenolic Bakelite molding material BMMA was tested to determine the airborne concentrations ofasbestosfibers released duringfour different activities sawing sanding drilling and cleanup of dust generatedfrom these activities Each activity was performed for 30 min often in triplicate The primary objectivefor testing BMMA was to quantitatively determine the airborne concentration ofasbestosfibers ifany in the breathing zone of workers Uses of this product typically did not include sawing or sanding but it may have been drilled occasionally For this reason only small quantities were sawed sanded and drilled in this simulation study Personal n = 40 area n = 80 and background = 88) air samples were collected during each activity and analyzedfor totalfiber concentrations using phase contrast microscopy PCM and for asbestos fiber counts transmission electron microscopy TEM The raw PCM fiber concentrations were adjusted based on TEM analyses that reported the fraction of asbestos fibers to derive a asbestos concentration that would enable calculation of an hour weighted average TWA The estimated hour TWAs ranged from 0.006 to 0.08 fibers per cubic centimeter using a variety ofworker exposure scenarios Therefore assuming an exposure scenario in which a worker uses power tools to cut and sandproducts moldedfrom BMMA- study 5353 and similarproducts the manner evaluated in this airborne asbestos concentrations should not exceed current or historical occupational exposure limits Keywords asbestos Bakelite industrial hygiene occupational exposure phenolic molding materials Address correspondence to Fionna Mowat Exponent 149 Commonwealth Drive Menlo Park CA 94025 mail fmowat exponent.com In the early 1900s Belgian chemist Leo Baekland discovered the method for combining phenol and formaldehyde to form the first synthetic thermosetting plastic which he named Bakelite The plastic resin compound was quite versatile and numerous uses were soon found for it including production of automotive and electrical parts abrasive sandpaper appliances and foundry molds Phenolic resins have good chemical and thermal resistance dielectric strength and dimensional stability Products made with these resins are inherently low in flamma- bility are creep resistant and have low moisture absorption Due to these characteristics phenolic resins have been in commercial use longer than any other synthetic polymer with the exception of cellulose nitrate Bakelite and other thermosetting resins were valued espe- cially for their thermal and electrical insulation properties and were used primarily in the electrical and electronics industries with other uses in appliances and the rubber industry Fillers such as chrysotile asbestos were added to the plastic to improve its properties Other fillers included wood flour walnut shells shredded paper mica and fibrous glass The abundant supply and low cost of asbestos combined with its fireproof nature chemical inertness ease of mixing and reinforcement properties led to its use in many applications Since the 1970s and 1980s however concerns about the health hazards posed by containing products have led to a gradual decline in use of these fillers However due to the historical popularity of Bakelite and other thermosetting resins sometimes these products are still present in older buildings in various industries There is a lack of information in the published literature regarding exposure levels associated with phenolic molding compounds thus this exposure simulation was undertaken to quantify these exposures and evaluate the airborne asbestos health hazard When evaluating the possible health hazard associated with containing materials ACM two categories of ACM are usually cited 1 those containing free fibers or that are friable and 2 those containing encapsulated fibers or are not friable The hazard potential for these two categories has been Journal of Occupational and Environmental Hygiene October 2005 497 known for decades and they were included in the regulations ofthe Occupational Safety and Health Administration OSHA at their inception Exposure to asbestos fibers occurs when workers handle and process raw asbestos fibers which can become airborne in their dry form or when someone works with friable products e.g. insulation In contrast ACMs with asbestos fibers that are encapsulated or bonded with other materials such as resins cement and other bonding agents limit the potential for airborne release The term encapsulated asbestos applies to fibers that are coated with a material or wetted with a binder resin or other medium thereby containing the asbestos fibers within a solid matrix and limiting their potential to become airborne e.g. asbestos in automotive brake pads vinyl composite floor tiles floor mastics roofing tars These fibers are considered to pose a negligible health hazard because of the inability of appreciable concentrations to become airborne and because the presence of the encapsulating medium inside and outside of the fiber may significantly reduce or eliminate its adverse effects In short due to the encapsulation of asbestos fibers in a solid matrix which serves to coat or saturate the fibers with a bonding agent only relatively low airborne concentrations of asbestos fibers are expected to be present during manipulation of most encapsulated products The low potential for release of fibers from these kinds of products is acknowledged in the federal regulations wherein OSHA in 1972 did not require asbestos caution labeling requirements for fibers that have been modified by a bonding agent coating binder or other material This labeling requirement still exists today as evidenced by the lack of warnings on most driveway sealants and roof coatings that contain asbestos In the present study we evaluated the potential for release of asbestos fibers from mechanical manipulation of BMMA5353 a phenolic molding compound that was manufactured by the Union Carbide Company from the late 1960s through 1974. Phenolic molding compounds were commonly used to manufacture parts for automotive purposes and in appliances These molded products were almost always manufactured for specific uses i.e. molded to the specific shape needed The primary objective for testing this phenolic molding compound was to quantitatively determine the airborne concentration of asbestos fibers if any that may be released to air during the cutting sanding and drilling that may have been associated with some uses in the field These airborne concentrations were then compared to current and historical workplace occupational exposure limits OELs MATERIALS AND METHODS Fo or this study BMMA was manufactured in a pilotplant setting during February and March 2003 based on historical formulation information The manufactured material is composed of a Novolac resin a phenolic step resin and contains 31 chrysotile asbestos Jeffrey Mine 7RF by weight BMMA is molded to provide a rigid product with a hard smooth surface with excellent dimensional stability and heat resistance fast cure and low mold shrinkage When medium manufacturing this product standard specifications for phe- nolic molding compounds were followed American Society for Testing and Materials ASTM D700-88 for a Type 13 material compounds containing mineral and other organic fillers formulated for resistant applications The characteristic properties of the formulated BMMA included specific gravity of 1.66 ASTM D700- 88 calls for specific gravity of 1.68 and notched impact of 0.3 foot pounds per inch We did not measure impact flexural or deflection strength of BMMA 5353 as described in ASTM D700-88 because insufficient material was formulated to cut out or machine shapes made from BMMA In addition the BMMA product specification does not provide guidelines for the molded material stating only that the granules used should have spiral flow and plasticity certain apparent density and sieve size distribution and specific appearance The plasticity of the product was determined by its ability to fill a specified mold and the granule sieve size distribution was within specified size limits to allow for full melting and formation of a uniform product Apparent density is related to the bulkiness of the material before molding and therefore does not affect performance however the final appearance of the product was within specifications so it was deemed that the density was within limits For this study BMMA was molded into test panels that were 10.2 cm long 15.2 cm wide and 0.6 cm high approximate total surface area of 342 cmeach to allow for manipulations of the compound to be conducted These manipulations included sawing sanding and drilling using power tools Following each procedure cleanup of dust generated from these activities was conducted as a separate test Testing Facility All tests of BMMA were carried out in an indoor test chamber that was 4.9 m long 4.9 m wide 2.4 m high 58 min Monroeville Pa Figure 1 A table was centered in the room as a work surface A single worker performed each test A efficiency particulate air HEPA filter operating at approximately 4.2 to 4.6 min was used creating an air exchange rate in the testing room of approximately four to five exchanges per hour Testing Procedures BMMA was tested to evaluate the potential release of asbestos fibers from the following activities sawing sanding drilling and cleanup of dust generated from these activities For purposes of this study the activities represent aggressive handling of the product thus simulating a worst scenario For each activity speed freestanding industrial equipment i.e. power tools was used to aggressively machine the BMMA panels 498 Journal of Occupational and Environmental Hygiene October 2005 _ aN NE corner ' e 6 feet Air Exchanger SE corner f 16 feet NW corner 6 feet e 6 feet | Air Intake | SW corner 16 feet >| @ Air Sampler | FIGURE 1. Schematic of testing facility Testing Protocol Four different activities were examined in the testing program ) band sawing of test panels 2 belt sanding of panels 3 press drilling of panels and 4 sweep cleanup of the work area The duration of the testing period was set based on the available quantity of the remanufactured testing material for completing four replicate tests 1 Band Sawing Test The sawing test used a Delta BS100 band saw 1/3 hp 1725 rpm Delta Woodworking Machinery Jackson Tenn to cut the test panels into strips No local exhaust ventilation was used during this test The saw blade had a width of 0.4 cm and six teeth to the inch During each min replicate of the sawing test a BMMA test panel was cut using the band saw which was placed on the table centered in the testing room Seven cuts were made on the test panel creating eight strips each 10.1 cm long 1.9 cm wide and 0.6 cm deep for a total of 71 linear centimeters per test Four replicates of the sawing test were performed The third replicate was aborted due to band saw failure during the test 2 Belt Sanding Test The sanding test used a Craftsman Model 351 belt sander 1.5 hp 3450 rpm Sears Hoffman Estates Ill to sand the edges of the test strips that remained from the sawing test The sandpaper used was 240 grit for 30 min per test Again no local exhaust ventilation was used during this test During each min replicate of the sanding test a worker beveled the edges of the test strips using a mounted belt sander centered in the testing room Approximately 0.75 linear meters of material were beveled Four replicates were performed 3 Drilling Press Test The drilling test used a Craftsman Model 137 drill press 2340 rpm Sears to drill holes into the test strips No local exhaust ventilation was used during this test During each min replicate of the drilling test 0.32 holes were drilled into the test strips for a total of 32 holes Four replicates were performed for a total of 128 holes drilled 4 Sweep Cleanup Tests The sweep cleanup tests consisted of cleaning up the material generated during each of the prior three activities During the sweep cleanup test for sawing a small hand brush was used to brush any surface debris from the band saw A hand broom was then used to brush debris from the table surface and floor For the sanding and drilling sweep cleanup tests a hand broom was used All debris was swept into a dustpan and disposed of in a disposal container A total of nine replicates each 30 min in duration of the cleanup tests were performed Air Sampling During each min replicate of the four tests two personal air samples were collected from the worker's breathing zone by placing the sampling devices over the right and left shoulders The samples were collected on ...m pore size 25 mm diameter mixed cellulose ester MCE filters Zefon International St. Petersburg Fla Personal air samples were collected at a flow rate of approximately 1.7 min depending on the test type Four area air samples were also collected during each replicate at a distance of approximately 1.8 m from the center of the work surface and at a height of 1.5 m Journal of Occupational and Environmental Hygiene October 2005 499 Area samples were collected on 0.45 mpore size 25 mm diameter MCE filters These samples were collected at a flow rate of approximately 2 to 5 min depending on the test type Specific air sampling rates for each test and sample type area and personal were determined from a particulate loading study that was conducted prior to this study The goal of this study was to determine the appropriate flow rate to achieve the lowest limit of detection possible without collecting so much dust that the filter was overloaded which would prevent quantification of asbestos fibers Four background or four clearance air samples were collected in the testing room prior to and following each test These samples were collected as area samples using the four perimeter pumps located in the testing room Samples were collected on 0.8 ...mpore size 25 mm diameter MCE filters The background samples were collected prior to each of the sawing sanding or drilling tests to provide information on ambient concentrations of total and asbestos fibers in the air of the test room prior to the sweep cleanup tests Background samples were collected for at least 1 hour at a flow rate of 10 min Clearance samples were also collected following each sweep cleanup test These samples were generally collected for 2 hours at a flow rate of 10 min All personal area and background samples collected during testing were analyzed by phase contrast microscopy PCM to determine total fiber concentrations asbestos and nonasbestos using NIOSH Method 7400. Samples were also analyzed by transmission electron microscopy TEM using NIOSH Method 7402 to determine the fraction of airborne fibers that are asbestos Individual filters were obtained for the PCM and TEM analyses which were sampled separately As prescribed in NIOSH Methods 7400 and 7402 only fibers that were 5 ...mor greater in length with an aspect ratio of at least 3 were counted Standard quality assurance and quality control procedures were followed at all times Calculation of Asbestos Concentrations In accordance with NIOSH Method 7402 the total fiber concentration obtained by PCM was converted to a PCMasbestos concentration using the asbestos ratio by TEM The asbestos concentration represents the fraction of PCM total fibers estimated to be asbestos fibers The asbestos concentrations were then used to calculate an hour weighted average TWA in an attempt to estimate the airborne concentration during a typical workday Calculations of hour TWAs allowed for comparisons to the OSHA permissible exposure level PEL Calculation of Estimated Hour Weighted Averages Typically personal air samples are the best indicator of worker exposure Eight TWAs were calculated to 1 estimate potential exposure of workers conducting these activities for hour hour or hour durations during the hour workday and 2 allow for direct comparison to current and historical occupational limits or guidelines These hour TWAS represent a worst analysis because the 8hour TWA calculations include large amounts of machining and because workers would not typically be engaged in aggressively machining BMMA products The estimated hour TWA was calculated using the following equation (ci ) > 1 where = n - the total number of activities evaluated in a particular scenario c = asbestos concentration measured during activity i in fibers where activities include sawing sanding drilling and cleanup of dust generated from these activities t~fl = duration of activity i performed by a worker in hours When calculating the hour TWA the sum of all t must equal 8 hours Given the fact that products are generally molded to fit and require little or no lengthy manipulation it was assumed that a worker would perform any of the activities sawing sanding drilling or sweep cleanup for no more than 0.5 1 or 2 hours within an hour day RESULTS he weight of the test panels was measured before and The weight test panels the casound of material that was removed during each activity Table I Based on the machining manipulations conducted in this test between 1.4 and 3.4 of the material was removed some of which TABLE I. Weight Changes for BMMA Test Material Pre- and Manipulation Difference Test Band sawingA Belt sanding Press drilling Weight g Weight Replicate Start End g a 160.1 154.7 5.4 b 164.6 159.4 5.2 157.6 152.2 5.4 a 154.7 152.5 2.2 b 159.4 156.1 3.3 166.3 160.7 5.6 d 152.2 148.1 4.1 a 152.5 150.4 2.1 b 156.1 153.8 2.3 c 160.7 156.0 4.7 d 148.1 145.4 2.7 Percent of Original Weight 3.4 3.2 3.4 1.4 2.1 3.4 2.7 1.4 1.5 2.9 1.8 Only three replicates were conducted of the sawing test because one test was aborted due to band saw failure 500 Journal of Occupational and Environmental Hygiene October 2005 became airborne Although this is a relatively limited amount of material on a weight loss basis the manipulations conducted were considered to be aggressive Exposure levels obtained from the testing are thought to be representative of a worstcase scenario because products were generally molded to fit precluding the need for cutting and machining Thus if cutting or machining occurred it was a rare event Fiber release results are reported as raw values as opposed to hour TWAS with average values calculated using the full detection limit for samples reported as below the detection limit Average values presented in the tables were calculated using both the full detection limit and half of the detection limit for samples reported as below the detection limit The average results discussed in the text use the full detection limit because this measure is more conservative and use of the full detection limit did not markedly change the averages the sawing sanding drilling and sweep cleaning tests are presented in Tables II and III Using TEM analyses asbestos fibers were detected in all 6 of the personal samples and in all 12 of the area samples collected during the sawing test They were also detected in all 8 of the personal samples and in all 16 of the area samples collected during the sanding test During the drilling test measurable concentrations were noted in only 1 of the 8 personal samples and in only 2 of the 16 area samples collected during the test Finally during the sweep cleanup test asbestos was detected in 10 of the 18 personal samples and in 22 of the 36 area samples The asbestos concentrations ranged from 0.01 to 0.21 cc for the personal samples Table II from 0.0003 to 0.32 cc for the area samples Table III and from 0.0004 to 0.005 cc for the background samples Table III For the personal samples the average PCMasbestos concentrations for the sawing sanding drilling and Total Fibers The detection limits for total airborne fibers using the PCM method ranged from 0.041 to 0.053 fibers per cubic centimeter cc for the personal samples from 0.016 to 0.045 cc for the area samples and from 0.002 to 0.009 cc for the backclearance samples This range in detection limits is due to variation in the air volumes sampled during the different tests Because the area and background samples were collected at a higher flow rate than the personal samples a larger volume of air was sampled and a lower detection limit could be achieved Total fibers which are composed of sweep cleanup tests were 0.11 0.11 cc 0.04 0.2c 1 c 0.04 cc 0.02-0.05 cc 0.01 cc and 0.02 cc ( 0.01 0.0c 8 c respectively Table II For the area samples the average PCMasbestos concentrations for the sawing sanding drilling and sweep cleanup tests were 0.08 cc 0.03-0.32 cc 0.04 cc 0.03-0.08 cc 0.01 cc 0.003-0.2 cc and 0.01 cc 0.003-0.03 cc respectively Table III The average asbestos concentrations for the background samples associated with the sawing sanding drilling and sweep cleanup tests were 0.001 0.001 0.001 and 0.002 cc respectively Table III asbestos fibers other noncountable asbestos fibers and other nonasbestos fibers such as cotton fibers from the worker's clothing were present at detectable concentrations in 22 of the 40 personal samples Table II in 48 of the 80 area samples Table III and in 31 of the 88 background samples Background and Clearance Samples For PCM analyses total fibers were detected in 31 of the 88 background and clearance samples with concentrations ranging from 0.002 to 0.01 cc Table III Most samples were detected at concentrations 0.001 cc The average Table III The results for the personal and area air samples collected during the sawing sanding drilling and sweep cleaning tests are summarized in Tables II and III The average total airborne fiber concentrations for the personal and area air samples collected during the sawing tests were 0.13 cc 0.05 0.23 and 0.10 cc 0.04-0.35 respectively For the sanding test the average total fiber concentrations for the personal and area air samples were both 0.06 cc personal 0.05 0.09 cc area 0.05 0.0c 9 c The average total airborne fiber concentrations for the personal and area air samples total fiber concentrations for the background and clearance air samples collected during the sawing sanding drilling and sweep cleanup tests were 0.004 cc 0.002 cc 0.003 cc and 0.005 cc respectively Using TEM analyses asbestos fibers were detected in 8 of the 88 background and clearance samples but were detected at very low concentrations usually 0.001 cc The average asbestos concentrations for the background and clearance air samples collected during the sawing sanding drilling and sweep cleanup tests were 0.001 cc 0.001 cc 0.001 cc and 0.002 cc respectively collected during the drilling tests were 0.05 cc 0.04-0.07 cc and 0.02 cc 0.02-0.02 cc respectively Finally the average total fiber concentrations for the personal and area air samples collected during the sweep cleanup tests were 0.07 cc 0.05 0.1c8 c and 0.03 cc 0.02-0.08 cc respectively Asbestos Fibers Asbestos fibers were detected in 25 of the 40 personal samples Table II in 52 of the 80 area samples Table III and in 18 of the 88 background samples Table III The results for the personal and area air samples collected during Estimated Hour TWA Concentrations Using the asbestos concentration from the personal air samples an bound hour TWA air concentration was calculated based on hypothetical exposure scenarios For calculation purposes it was assumed that a worker might perform any of the activities for 0.5 1 or 2 hours The estimated hour TWAs were derived using maximum and average asbestos concentrations for personal and background samples for each test activity Assuming a worst scenario where a worker conducts all the activities evaluated in this study for 2 hours each Journal of Occupational and Environmental Hygiene October 2005 501 TABLETABLE II. PersonalPersonal of Results of Summary PCM Total Personal Concentration Concentration Test Replicate Replicate mL sawing a Band sawing a Air SamSamplpes les Asbestos Fibers 18.5 13 21 b 11.5 b 28.5 28 C Belt sanding MAavexriamgeuDm Average a a 8 : i ty Nu Nu 8 13 15 4 Operating drill 8 STOC TEM Data NonasbestosNonasbestos Fibers 225225225225- 3.5 2 11 m m mr^/z mr^/z mr^/z 6747 6747 RatioRa"tio" 0.87 0.81 0.92 0.92 0.89 00..9933 0.71 0.73 0.77 0.0.8923 0.92 3) 8 Asbestos Concentration mL 0.04 0.09 0.11 0.18 0.21 0.21 0.13 0.11 0.03 0.03 0.03 0.03 0.05 28:02 00..0044 0.04 0.03 0,01 000 5 0 P " " -0.65 h 0 0.04 " c10 nid 10 i 2004 = 2004 e , Toad 0.01 0 0 a ah = n = 2001 { - ve 0:04 q UTO 8.87 0 d 0.04 1 Maximum 0.07 Average 0.05 Average 0.03 Sweep cleanup 0.06 Sawing a 0.10 1 Sawing Sawing a 4 Sawing Sawing b 0.05 1 Sawing Sawing b 0.05 0 # 0.65 i Sanding a 0.06 4 Sanding ^' 0.04 0 Sanding b 0.04 1 Sanding c 0.18 3 Sanding c 0.11 OOOON Drilling a 0.05 OOOON Drilling a 0.06 OOOON Dalling b 0.07 OOOON Drilling b 0.05 OOOON Drilling OOOD 0.07 0.5 Drilling OOOD 0.09 NOO Drilling OOOD 0.06 NOO Drilling OOOD 0.05 0 Maximum 0.18 AverageD 0.07 Average 0.06 = WN2 WN2 WN2 5 3.5 --N --N --N --N 3 tntoon tntoon tntoon tntoon tntoon tntoon 1 m 1.5 0 i 0.25 0.25 0.17 0.53 0.50 0.00 1.00 0.67 0.00 0.25 0.43 0.00 0.00 0.00 0.00 0.29 0.33 0.40 0.00 0.00 0.01 < 0.01 0.01 0.001.01 0.01 0.02 0.03 0.002.02 0.01 0.05 0.03 0.01 0.01 0.08 0.01 0.01 0.01 0.01 0.01 0.02 0.04 0.01 0.01 0.08 0.02 0.02 Note PCM - phase contrast microscopy TEM = transmission electron microscopy Ratio of asbestos fibers to total fibers F by TEM 8 Total fiber concentrations by PCM were converted to asbestos concentrations using the fiber ratio reported from TEM analyses in accordance with NIOSH Method 7402. Replicate 3 of the band sawing test was aborted due to band saw failure D Average calculated using the values shown full detection limit for nondetect samples * Average calculated using half the detection limit for nondetect samples 502 Journal of Occupational and Environmental Hygiene October 2005 TABLE III of Results for Area Air Summary PCM Total Test sawing Band sawing Replicate a a a b b b b c c c Concentration mL 0.04 0.04 0.04 0.04 0.08 0.08 0.07 0.05 0.35 0.17 0.12 0.09 Samples TEM Data Ratio Ratio* Asbestos Fibers Nonasbestos Fibers 4 F 0.85 22.5 0.73 4.5 23883220022- 1.00 JobmnNT 13.5 23883220022- 0.75 JobmnNT 0.73 JobmnNT 23832022388322002212.5 2383202- 0.92 JobmnNT 0.86 JobmnNT 0.67 JobmnNT 0.91 -- 23883220022- 0.67 -- 2383202- 0.80 32 23883220022- 0.33 32 2383202- Asbestos Concentration mL 0.04 0.03 0.04 0.03 0.06 0.08 0.06 0.03 0.32 0.11 0.10 0.03 0.32 0.08 Background Maximum Average Average 0.35 0.10 0.09 0.004 0.07 0.001 0.001 clearance Background clearance Belt sanding Background 21 a a a b b b b c c c c d d d d Maximum AverageD Average 0.004 0.07 0.07 0.06 0.09 0.05 0.05 0.05 0.05 0.06 0.07 0.08 0.05 0.05 0.05 0.08 0.05 0.09 0.06 0.05 0.002 5.5 28.5 30 12 9 15 5 24.5 4 8 10 4 7 4.5 9 16 4152 06511 4152 0654152 0654152 065415220654152 0654152 065- 41520650.5 10 0 4 2.5 1 10.5 0.58 0.72 0.86 0.86 0.82 0.60 0.46 0.83 0.80 0.94 0.50 1.00 0.64 0.64 0.90 0.60 0.04 0.05 0.05 0.08 0.04 0.03 0.02 0.04 0.05 0.07 0.04 0.05 0.03 0.03 0.07 0.03 0.08 0.04 0.04 0.001 0.001 clearance Background 0.002 clearance i 0.02 Press drilling a 0.02 0 a 0 0.02 a 0 0.02 a 0 0.02 b 0 0.02 b 0 0.02 b 0 0.02 0 0 0 0.02 0 0.02 0 0 0.02 OOOO 0 0.02 OOOO 0 0.02 OOOO 1 0.02 OOOO 0 0.02 d 0 d 0.02 0 0 0 1 1 1 2 0.5 0 0 2 1 1 0.5 0 0 0.02 1 0 0.003 0 0.003 0 0.003 0 0.004 0 0.004 0 0.004 0 0.004 0 0.004 0 0.004 0 0.004 0 0.004 ooooo 0.003 0.667 ooooo 0.01 0.003 0 0.003 Continued on next page ) 503 Journal of Occupational and Environmental Hygiene October 2005 TABLE III Summary of Results for Area Air Samples Continued PCM Total TEM Data Test Background clearance Background clearance Sweep cleanup Sawing Sawing Sawing Sawing Sawing Sawing Sawing Sawing Sanding Sanding Sanding Sanding Sanding Sanding Sanding Sanding Sanding Sanding Sanding Sanding Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Drilling Background clearance Background clearance Replicate Replicate Maximum AverageD Average a a a a b b b b a a a a b b b b C a a a a b b b b c c c c d d d d Maximum AverageD Average Concentration mL 0.02 0.02 0.02 0.003 0.003 0.04 0.02 0.03 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.08 0.06 0.05 0.06 0.05 0.03 0.03 0.02 0.04 0.04 0.04 0.03 0.03 0.05 0.07 0.07 0.02 0.03 0.02 0.02 0.08 0.03 0.03 0.005 0.003 Asbestos Fibers Nonasbestos Fibers 1 1.5 mnom mnom mnom 3 MNOoanmo mo20-2 MNOMoanmo om20-02MNOMoanmo om20-02MNOoanmo mo20-2 MNOMoanmo om20-02MNOMoanmoom20-02MNOoanmo mo20-2 MNOoanmo mo20-2 MNOMoanmo om20-02MNOoanmo mo20-2 MNOMoanmo om20-02MNOMoanmo om20-02MNOoanmo mo20-2 MNOMoanmo om20-02MNOMoanmoom20-02MNOMoanmo om20-02MNOMoanmo om20-02MNOoanmom20-2 MNOMoanmo om20-02MNOMoanmoom20-021 0 1 2 1 0 1 0 0 1 2 3 3 4 2.5 2.5 2.5 3 1 1.5 2032-5naomi 2032-5naomi 2032-5naomi 2032-5naomi 2032-5naomi 2032-5naomi 5.5 3.5 2032-5naomi 2032-5naomi 2032-5naomi NWwwDooW 0.5 NWwwDooW NWwwDooW NWw Do W NWw Do W NWw Do W 1 0000NW 0000NW 0.5 0000NW 0000NW 0000NW Ratio4 F 0.50 0.43 0.50 0.63 0.00 0.55 0.29 0.55 0.40 0.00 0.67 0.00 0.64 0.40 0.60 0.00 0.38 0.00 0.00 0.25 0.00 0.40 0.00 0.00 0.20 0.00 0.40 0.25 0.00 0.50 0.40 0.33 0.00 0.67 0.00 0.00 Asbestos ConcentrationB mL 0.02 0.01 0.01 0.001 0.001 0.02 0.01 0.01 0.01 0.003 0.01 0.01 0.01 0.01 0.004 0.02 0.004 0.01 0.01 0.01 0.003 0.03 0.004 0.004 0.01 0.004 0.01 0.004 0.004 0.01 0.004 0.02 0.01 0.004 0.03 0.03 0.02 0.004 0.02 0.004 0.004 0.03 0.01 0.01 0.002 0.001 Notes Background samples were collected between the sawing sanding and drilling tests and the sweep cleanup tests clearance samples were collected before the sawing sanding and drilling tests PCM = phase contrast microscopy TEM = transmission elctron microscopy Ratio of asbestos fibers to total fibers F by TEM B Total fiber concentrations by PCM were converted to asbestos concentrations using the fiber ratio reported from TEM analyses in accordance with NIOSH Method 7402. Replicate 3 of the band sawing test was aborted due to band saw failure D Average calculated using the values shown full detection limit for nondetect samples E Average calculated using half the detection limit for nondetect samples 504 Journal of Occupational and Environmental Hygiene October 2005 TABLE IV Estimated Hour Weighted Average Concentrations Scenario Average Asbestos Concentration mL Sawing Sanding Drilling Sweep Cleanup Maximum Asbestos Concentration Hour TWA mL Concentrationfi mL Sawing Sanding Drilling Sweep Cleanup Hour TWA Concentration mL A 0.11 0.04 0.01 0.02 B 0.11 NA NA 0.02 C NA 0.04 NA 0.02 NA 0.01 0.02 0.06 0.03 0.03 0.006 0.21 0.05 0.21 NA NA 0.05 NA NA 0.01 NA NA 0.01 0.08 0.08 0.08 0.06 0.08 0.06 0.08 0.01 Notes The hour weighted average concentrations were calculated assuming various scenarios of work activity For an hour workday 2 hours sanding 2 hours sawing 2 hours drilling 1.5 hours sweep cleaning remainder at background concentration For an hour workday 2 hours sawing 1.0 hours sweep cleaning remainder at background concentration For an hour workday 2 hours sanding 1.0 hours sweep cleaning remainder at background concentration For an hour workday 2 hours drilling 1.0 hours sweep cleaning remainder at background concentration PCM = phase contrast microscopy TWA = weighted average NA = not used in calculation of hour TWA Total fiber concentrations by PCM were converted to asbestos concentrations using the fiber ratio reported from transmission electron microscopy analyses in accordance with NIOSH Method 7402. hour TWA concentrations were calculated using the equation presented in the text 505