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FILE NAME: Asbestos in Plastics (AIP) DATE: 2005 Oct DOC#: AIP003 DOCUMENT DESCRIPTION: Journal Article - Occupational Exposure to Airborne Asbestos from Phenolic Molding Material ~Bakelite~ During Sanding, Drilling, and Related Activities Journal o f Occupational and Environmental Hygiene 2- 497-507 ISSN; 1545-9624 print / 1545-9632 online Copyright 2005 JOEH, LLC DOI: 10.1080/15459620500274237 Occupational Exposure to Airborne Asbestos from Phenolic Molding Material (Bakelite) During Sanding, Drilling, and Related Activities Flonna Mowat,' Michael Bono,2 R.J. Lee,2Susan Tamburello,2 and Ian n is Paustenbach4 1Exponent, Menlo Park, California E xponent, Hudson, Ohio 3RJ Lee Group, Inc., Monroeville, Pennsylvania 4ChemRisk, San Francisco, California In this study, a historical phenolic (Bakelite) molding material, BMMA-5353, was tested to determine the airborne concentrations o fasbestosfibers released duringfour different activities (sawing, sanding, drilling, and cleanup o f dust generatedfrom these activities). Each activity was performed fo r 30 min, often in triplicate. The primary objectivefo r testing BMMA-5353 was to quantitatively determine the airborne concentration o fasbestosfibers, ifany, in the breathing zone o f workers. Uses o f this product typically did not include sawing or sanding, but it may have been drilled occasionally. For this compound was quite versatile and numerous uses were soon found for it, including production of automotive and electrical parts, abrasive wheels/sandpaper, appliances, and foundty molds. Phenolic resins have good chemical and thermal resistance, dielectric strength, and dimensional stability/1,4* 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 reason, only small quantities were sawed, sanded, and drilled in this simulation study. Personal (n = 40), area (n = 80), and background!clearance (n = 88) air samples were collected during each activity and analyzedfor totalfiber concentrations using phase contrast microscopy (PCM) and, fo r asbestos fiber counts, transmission electron microscopy (TEM). The raw PCM-total fiber concentrations were adjusted based on TEM analyses that reported the fraction o f asbestos fibers, to derive a PCM-asbestos concentration that would enable calculation o f an 8-hour time-weighted average (TWA). The estimated 8-hour TWAs ranged from 0.006 to 0.08 fibers per cubic centimeter using a variety o f worker exposure scenarios. Therefore, assuming an exposure scenario in which a worker usespower tools to cut and sandproducts moldedfrom BMMA5353 and similarproducts in the manner evaluated in this study, airborne asbestos concentrations should not exceed current or historical occupational exposure limits. commercial use longer than any other synthetic polymer with the exception of cellulose nitrate/1* 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/1,4,6* Fillers such as chrysotile asbestos were added to the plastic to improve its properties/6*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, east: 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 asbestos-containing products have led to a gradual decline in use of these fillers. However, due to the Keywords asbestos, Bakelite, industrial hygiene, occupational exposure, phenolic molding materials historical popularity ofBakelite 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 Address correspondence to: Fionna Mowat, F.xpnmit. 149 Commonwealth Drive, Menlo Park, CA 94025; e-mail: fmowat exponent.com. phenolic molding compounds; thus, this exposure simulation was undertaken to quantify these exposures and evaluate the airborne asbestos health hazard. I n 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.(1-3) The plastic resin When evaluating the possible health hazard associated with asbestos-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 known for decades/7and they were included in the regulations of the Occupational Safety and Health Administration (OSHA) at their inception/8Exposure 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/910In 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."^9 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 For this study, BMMA-5353 was manufactured in a pilot plant setting during February and March 2003 based on historical formulation information. The manufactured material is composed of a Novolac resin (a phenolic two-step resin) and contains 31% chrysotile asbestos (Jeffrey Mine 7RF-3) by weight. BMMA-5353 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 manufacturing this product, standard specifications for phe nolic molding compounds were followed (American Society for Testing and Materials [ASTM] D700-88)(U for a Type 13 material .(medium-specific-gravity compounds containing mineral and other organic fillers formulated for heat-resistant applications). The characteristic properties of the formulated BMMA-353 included specific gravity of 1.66 (ASTM D70088 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-5353. In addition, the BMMA-5353 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-5353 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 cm2 each) 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-5353 were carried out in an indoor test chamber that was 4.9 m long, 4.9 m wide, 2.4 m high (58 m3) in Monroeville, Pa. (Figure 1). A table was centered in the room as a work surface. A single worker performed each test. A high-efficiency particulate air (HEPA) filter operating at approximately 4.2 to 4.6 m3/min was used, creating an air exchange rate in the testing room of approximately four to five exchanges per hour. Testing Procedures BMMA-5353 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-case scenario. For each activity, high-speed, freestanding, industrial-grade equipment (i.e., power tools) was used to aggressively machine the BMMA-5353 panels. 498 Journal of Occupational and Environmental Hygiene October 2005 FIGURE 1. Schematic of testing facility Testing Protocol Four different activities were examined in the testing program: (1) 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 o f the testing period was set based on the available quantity ofthe 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, Term.) 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 30-min replicate of the sawing test, a BMMA-5353 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, 111.) 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 30-min replicate of the sanding test, a worker beveled the edges of the test strips using a bench-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 exhausl ventilation was used during this test. During each 30-min replicate of the drilling test, 0.32-cm 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-held brush was used to brush any surface debris from the band saw. A hand-held broom was then used to brush debris from the table surface and floor. For the sanding and drilling sweep cleanup tests, a hand-held 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. A ir Sampling During each 30-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 0.8-im (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 L/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 Area samples were collected on 0.45 fim (pore size), 25 mm diameter MCE filters. These samples were collected at a flow rate of approximately 2 to 5 L/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 col lected 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 fim pore 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 L/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 L/min. All personal, area, and background/clearance samples collected during testing were analyzed by phase contrast microscopy (PCM) to determine total fiber concentrations (asbestos and nonasbestos) using NIOSH Method 7400.(12) Samples were also analyzed by transmission electron mi croscopy (TEM) using NIOSH Method 7402^34 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 fim or greater in length, with an aspect ratio of at least 3:1, were counted. Standard quality assurance and quality control procedures were followed at all times. Calculation of PCM-Asbestos Concentrations In accordance with NIOSH Method 7402, the total fiber concentration obtained by PCM was converted to a PCMasbestos concentration using the asbestos-to-total-fiber ratio by TEM. The PCM-asbestos concentration represents the fraction of PCM total fibers estimated to be asbestos fibers. The PCM-asbestos concentrations were then used to calculate an 8-hour time-weighted average (TWA) in an attempt to estimate the airborne concentration during a typical workday. Calculations of 8-hour TWAs allowed for comparisons to the OSHA permissible exposure level (PEL). Calculation o f Estimated 8-Hour Time-Weighted Averages Typically, personal air samples are the best indicator of worker exposure. Eight-hour TWAs were calculated to (1) estimate potential exposure of workers conducting these activities for 0.5-hour, 1-hour, or 2-hour durations during the 8-hour workday, and (2) allow for direct comparison to current and historical occupational limits or guidelines. These 8-hour TWAs represent a worst-case analysis, because the 8hour TWA calculations include large amounts of machining, and because workers would not typically be engaged in aggressively machining BMMA-5353 products. The estimated 8-hour TWA was calculated using the following equation: where '= n -- the total number of activities evaluated in a particular scenario Ci = PCM-asbestos concentration measured during activity / (in fibers/mL, where activities include sawing, sanding, drilling, and cleanup of dust generated from these activities) tj = duration of activity i performed by a worker (in hours). When calculating the 8-hour TWA, the sum of all i, 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 8-hour day. RESULTS The weight of the test panels was measured before and after manipulation to determine the amount 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-5353 Test Material Pre- and Post-Manipulation Difference Weight (g) Percent of --------------- Original Test Replicate Start End (g) Weight Band sawing'4 a b c Belt sanding a b c d Press drilling a b c d 160.1 154.7 5.4 3.4 164.6 159.4 5.2 3.2 157.6 152.2 5.4 3.4 154.7 152.5 2.2 1.4 159.4 156.1 3.3 2.1 166.3 160.7 .5.6 3.4 152.2 148.1 4.1 2.7 152.5 150.4 2.1 1.4 156.1 153.8 2.3 1.5 160.7 156.0 4.7 2.9 148.1 145.4 2.7 1.8 AOnly three replicates were conducted ofthe 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 8-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 one-half o f 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. Total Fibers The detection limits for total airborne fibers using the PCM method ranged from 0.041 to 0.053 fibers per cubic centimeter (f/cc) for the personal samples, from 0.016 to 0.045 f/cc for the area samples, and from 0.002 to 0.009 f/cc for the background/clearance samples. This range in detection limits is due to variation in the air volumes sampled during the different tests. Because the area and background/clearance 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 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 HI), and in 31 of the 88 background/clearance samples (Table Iff). The results for the personal and area air samples collected during the sawing, sanding, drilling, and sweep cleaning tests are summarized in Tables H and III. The average total airborne fiber concentrations for the personal and area air samples collected during the sawing tests were 0.13 f/cc (<0.05-0.23) and 0.10 f/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 f/cc (personal, <0.05-- 0.09 f/cc; area, <0.05-0.09 f/cc). The average total airborne fiber concentrations for the personal and area air samples collected during the drilling tests were 0.05 f/cc (<0.04-0.07 f/cc) and 0.02 f/cc (<0.02-0.02 f/cc), respectively. Finally, the average total fiber concentrations for the personal and area air samples collected during the sweep cleanup tests were 0.07 f/cc (<0.05-0.18 f/cc) and 0.03 f/cc (<0.02-0.08 f/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 Iff), and in 18 of the 88 background/clearance samples (Table HI). The results for the personal and area air samples collected during the sawing, sanding, drilling, and sweep cleaning tests are presented in Tables II and m. 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 PCM-asbestos concentrations ranged from <0.01 to 0.21 f/cc for the personal samples (Table II), from <0.0003 to 0.32 f/cc for the area samples (Table HI), and from <0.0004 to 0.005 f/cc for the background/clearance samples (Table HI). For the personal samples, the average PCMasbestos concentrations for the sawing, sanding, drilling, and sweepcleanuptestswereO.il f/cc (<0.04-0.21 f/cc), 0.04 f/cc (<0.02-0.05 f/cc), <0.01 f/cc, and 0.02 f/cc (<0.01-0.08 f/cc), respectively (Table II). For the area samples, 1he average PCMasbestos concentrations for the sawing, sanding, drilling, and sweep cleanup tests were 0.08 f/cc (<0.03-0.32 f/cc), 0.04 f/cc (<0.03-0.08 f/cc), 0.01 f/cc (<0.003-0.2 f/cc), and 0.01 f/cc (<0.003-0.03 f/cc), respectively (Table III). The average PCM-asbestos concentrations for the background/clearance samples associated with the sawing, sanding, drilling, and sweep cleanup tests were 0.001, <0.001, <0.001, and 0.002 f/cc, respectively (Table Iff). 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 f/cc (Table Iff). Most samples were detected at concentrations <0.001 f/cc. The average total fiber concentrations for the background and clearance air samples collected during the sawing, sanding, drilling, and sweep cleanup tests were 0.004 f/cc, 0.002 f/cc, 0.003 f/cc, and 0.005 f/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 f/cc). The average PCM-asbestos concentrations for the background and clearance air samples collected during the sawing, sanding, drilling, and sweep cleanup tests were 0.001 f/cc, <0.001 f/cc, <0.001 f/cc, and 0.002 f/cc, respectively. Estimated 8-Hour TWA Concentrations Using the PCM-asbestos concentration from the personal air samples, an upper-bound 8-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 esti mated 8-hour TWAs were derived using maximum and average PCM-asbestos concentrations for personal and background samples for each test activity. Assuming a worst-case 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 TABLE H. ,, ,, .. ............. im - - . - ' ' I A ir S a m p jg s q ummarV i U te, Concentration -- -0 In (I h <i)j04 0 c ' t\ ; b r <-orw O (! 01 0 0 n n il1 n <-n m b C <o:04 R d 8.0? 0 d <0.04 1 Maximum 0,07 Average'-1 O.US Average 0.03 Sweep cleanup Sawing a 0.10 1 Sawing a 0.06 4 Sawing b <0.05 1 SMitfg b <0.05 0 km m 4 -M i Mgi I 4 is <0.04 0 Sanding b 0,04 1 Sanding c 0.18 3 Sanding c 0.11 0 Drilling a 0.05 0 Drilling a 0.06 0 Drilling b 0.07 0 Drilling b <0.05 2 Drilling c 0.07 0.5 Drilling c 0.09 2 Drilling d 0.06 0 Drilling d <0.05 0 Maximum 0.18 Average0 0.07 Average 0.06 tj <0.0 i 2 0 sU.il l 3 0.25 <0,01 0.01 ^0 01 <0.01 5 0.17 0.02 3.5 0.53 0.03 1 0.50 <0.02 1 0.00 <0.01 0 1.00 <0.05 2 0.67 <0.03 1 0.00 <0.01 3 0.25 0.01 4 0.43 0.08 2 0.00 <0.01 4 0.00 <0.01 6 0.00 <0.01 6 0.00 <0.01 5 0.29 <0.01 1 0.33 0.02 3 0.40 0.04 1.5 0.00 <0.01 0 0.00 <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/F) by TEM. BTotal fiber concentrations by PCM were converted to PCM-asbestos concentrations using the fiber ratio reported from TEM analyses in accordance with NIOSH Method 7402.'I3> c Replicate 3 of the band sawing test was aborted due to band saw failure. Average calculated using the values shown (full detection limit for nondetect samples). EAverage calculated using half the detection limit for nondetect samples. 502 Journal of Occupational and Environmental Hygiene October 2005 t a p i p in. Summar , nf Results for Araa Air Sam ples. Test Band sawingc Background/ clearance0 Background/ clearance8 Belt sanding Background/ clearance0 Background/ Replicate a a a a b b b b c c c c Maximum Average0 Average8 PCM Total Concentration (f/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 0.35 0.10 0.09 0.004 0.004 a a a a b b b b c c c c d d d d Maximum Average0 Average8 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 0.002 Asbestos Fibers 22.5 12 13.5 IO 8 23 12.5 8 10 2 12 1 5.5 28.5 30 12 9 15 D 24.5 4 8 10 4 7 4.5 9 16 Precslesadrrainllcien8g a 00..0022 1 0 a <0.02 0 a < 0.02 0 a < 0.02 0 b <0.02 0 b < 0.02 0 b < 0.02 0 bc <<00..0022 00 0 c c < 0.02 0 c < 0.02 0 d 0.02 1 d 0.02 0 d 0.02 0 d 0.02 TEM Data Nonasbestos Fibers 4 4.5 0 6 3 ot A 1 1 i 2 4 11 5 2 2 10 6 5 1 0.5 10 0 4 2.5 1 10.5 0 0 0 1 1 1 2 0.5 0 0 2 1 1 0.5 0 0 Ratio4 (f/F) 0.85 0.73 1.00 0.75 U . /J 0.92 0.86 0.67 0.91 0.67 0.80 0.33 PCM-Asbestos Concentration (f/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 0.07 0.001 0.001 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 1 0.02 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 0 < 0.003 0.667 0.01 0 < 0.003 0 < 0.003 (Continued on next page) 503 October 2005 journal of Occupational and Environmental Hygiene 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 Maximum Average Average a a a a b b b b a a a a b b b b c c c c a a a a b b b b c c c c d d d d Maximum Average Average PCM Total Concentration (f/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 _______________ TEMData Asbestos Fibers Nonasbestos Fibers 1 1 1.5 2 3 3 5 3 0 4 3 2.5 1 2.5 3 2.5 2 3 0 1 3 1.5 0 2 9 5 2 3 3 2 0 1 3 5 0 5.5 0 3.5 3 9 0 0 2 3 0 0.5 0 0.5 1 4 0 3.5 2 3 1 3 0 2 1 1 2 3 1 2 0 0.5 1 0.5 0 0 0 0 Ratio'4 (f/F) 0 50 0 4^ n so 0 63 000 0 55 0 29 0 55 040 000 0.67 000 0.64 0.40 060 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 PCM-Asbestos Concentration (f/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. ARatio of asbestos fibers to total fibers (f/F) by TEM. Total fiber concentrations by PCM were converted to PCM-asbestos concentrations using the fiber ratio reported from TEM analyses in accordance with NIOSH Method 7402.(l2) c Replicate 3 o f the band sawing test was aborted due to band saw failure. 0 Average calculated using the values shown (full detection limit for nondetect samples). EAverage calculated using half the detection limit for nondetect samples. 504 Journal of Occupational and Environmental Hygiene October 2005 TABLE IV. Estimated 8-Hour Time-Weighted Average Concentrations Scenario Average PCM-Asbestos Concentration (f/mL)4 Sawing Sanding Drilling Sweep Cleanup 8-Hour TWA Concentration8 (f/mL) Maximum PCM-Asbestos Concentration (f/mL)'4 Sawing Sanding Drilling Sweep Cleanup 8-Hour TWA Concentration8 (f/mL) A 0.11 0.04 <0.01 0.02 B 0.11 NA NA 0.02 C NA 0.04 NA 0.02 D NA 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 8-hour time-weighted average concentrations were calculated assuming various scenarios o f work activity: A -For an 8-hour workday: 2 hours sanding, 2 hours sawing, 2 hours drilling, 1.5 hours sweep cleaning (remainder at background concentration). B-For an 8-hour workday: 2 hours sawing, 1.0 hours sweep cleaning (remainder at background concentration). C-For an 8-hour workday: 2 hours sanding, 1.0 hours sweep cleaning (remainder at background concentration). D -For an 8-hour workday: 2 hours drilling, 1.0 hours sweep cleaning (remainder at background concentration). PCM = phase contrast microscopy; TWA = time-weighted average; NA = not used in calculation of 8-hour TWA. ''Total fiber concentrations by PCM were converted to PCM-asbestos concentrations using the fiber ratio reported from transmission electron microscopy analyses in accordance with NIOSH Method 7402.<I3) B8-hour TWA concentrations were calculated using the equation presented in the text 505