Document bjE9DjZLgjpxaYDL6O6KeBLk

MONITORING FOR AIRBORNE ASBESTOS FIBERS: VINYL ASBESTOS FLOOR TILE Final Report December 1979 By: Richard Wilcort. Industrial Hygieniit James Warrick, Industrial Hygienist Prepared tor: Resilie-t Floor Covering Institute 1030 15th St. N.V,\ Suite 3E0 Washington. D.C. 20035 SRI Project 79ES Approved by: Sherry J. Hanen. Associate Director Center for Occupational and Environmental Safety and Health Ernest J. Moore, Vice President Baron A: B:ui.! Bulla (. o. Augu>l I I `' sri international SRI International is a problem-solving organization that provides consulting and research under contract for clients in business and government throughout the world. Since SRI was founded in 1946, the problems confronting our clients have so increased in complexity that few of them can be solved within the confines cf a single discipline. The organization is uniquely qualified to deal with such intricate problems. Professionals representing more than 100 ilisciplines comprise nearly two-thirds of the 3,000 staff members. SRI performs consulting and research for the public sector In such areas as urban management; healtn, education, and welfare; environmental management, and national security. In addition to broad-ranging activities for the U.S. and other national governments, SRI serves city, state, end county governments in the L'.S.., and also their international equivalents. Dne of the most attractive aspects of life at SRI for the staff is the opportunity to share in important work in the public interest. For private commercial and industrial clients, SRI engages in management consulting and corporate strategy determination; technoeconomic, market, and operational studies; new procuct, process, and equipment development; and the provision of information services. A significant percentage of SRI's professional staff nave had a number of years cf major responsibility ir. business prior to joining SRI. SRI is an -independent, nonprofit corporation, using revenues in excess of operating costs tc purchase aovancec scientific equipment and to enhance its ability to continue to provide the highest quality consulting anG research for its clients. SRI International has no shareholders and no encowcent. S?.I`s annual revenues for consulting and research contracts exceed S125 xJTlion. SRI's headquarters ere on a 70-acre site In tenlo Park, California, a suburban community about 20 miles south of the San Francisco International Airport and a few miles from the campus of Stanford University. . Other offices and laboratories are located in major centers in North America, Xurope, East Asia, and the Middle East. Baron & HuJJ Butler (_ ouni\ Aucum I. h;>r STATED NT OF OBJECTIVE The principal objective of this study was to monitor for airborne asbestos fibers, if any, during conditions of use, maintenance, installation and removal of vinyl asbestos floor tile and to determine their concentrations. Baron & Budd Butler Couniv 1II. III. 1Y. Y. Yl. VI1. Yl 11IX. X. TABLE O' CONTENTS Pace Introduction, VinylAsbestos Tile ......................................................... 1 Test Site Location.................................................................................. 2 Methodology................................................................................................... 7 Sunnary of Results....................................................................................6 Conclusions.......................................................................................................... 10 In-Use Tests, Site #2 .............................................................................. 11 Maintenance Tests, Site*2.........................................................................IS Complete Removal Tests,Site 3..................................................................22 Installation Tests.........................................................................................24 Attachments: A. NT OSH Analytical Method E. Representative Ambient Air Asbestos Concentrations in Cities Copyright 0 1979 by Resilient Floor Covering Institute Baron & BudJ Butler Couni\ August I. IW 2. INTRODUCTION Vinyl asbestos tiles are widely used In any homes and Institutional and commercial locations. Fibrous asbestos is used in the manufacture of vinyl asbestos floor tiles. The unique combination of resistance to physical and chemical deterioration and high tensile strength with flexibility are asbestos characteristics useful in the production and durability of the tile. It has been determined that the inhalation of airborne asbestos fibers over long periods of time may result in asbestosis or other serious illness. However, in vinyl asbestos floor tile, the asbestos is "locked-in" by polymeric binders of various types. SRI International was retained to measure the amount, if any, of airborne asbestos fibers associated with use, maintenance, installation and removal of vinyl asbestos floor tiles when RFC I recommended procedures ere followed, i.e., the operations are performed without sardine or sweepir.c an existinc floor. I Baron & Budd Butler Count) August I. 190" II. TEST SITE LOCATIONS Test Site #1. December 6, 1978. Installation was Bade in a node! of a new housing development In Northern Virginia. With the exception of some Interior finishing work, construction of the model home was essentially complete and The heme was being heated at the time of the test. Two types of vinyl asbestos tile were Installed: GAF "Taj Mahal* In a small utility room on the first floor, and GAF "Wood Block #1725" In the basement. In both areas, the vinyl asbestos tile was installed directly on concrete sub floors. Before the tile was installed, GAF *F3-5Q" asphalt cut-back adhesive was applied to the floor and allowed to dry. Some tiles were cut for edge and corner fitting. The utility room was approximately 15 square feet In area and the basement area was about 215 square feet. The time required for the basement tile-laying operation was about 2 hours, and approximately 20 minutes for the utility room. Figure 1 is a diagram of the site. Test Site *2. January 23-25, 1579, and January 29, 1979. This site, an office building called Hoffman #2 located in Alexandria, Va., was selected for in-use and maintenance tests. The building is approximately five years old and has a steel-reinforced concrete structure. The Internal structure of the building is essentially suspended ceilings, plasterboard walls, a-: vinyl asbestos floor tile. There is no sprayed-on fire-proofing in the building. With regard to the mechanical air movement in the building, 75t is recirculated and 25* is brought In as make-up air through the roof airhandling units. From the roof, the air is moved via metal ducts to individual heating and cooling units on the individual floors. Here the air Is passed through metal mesh filters before being sent to the Individual roems. The ductwork from the air-handlers to the rooms is partially lined with resin-impregnated mineral wool. A diagram of the site is shown in Figure 2. 2 Baron & Huj.j Butler Cnuni\ August I. |>()' This same site was also used on April 16, 1979, to further evaluate potential asbestos-fiber generation during buffing operations for longer periods of time than during the January 23-25, 1979, monitoring tests. Test Site #3. June 28, 1979. A private home In Newark, Delaware. Monitoring was <Jone for both removal and installation of vinyl asbestos tile. The existing GAF vinyl asbestos tile was removed in the laundry room, powder room, closet, and hallway. The sub-floor was concrete. After the removal operation, which took about 2 hours, Antico adhesive-backed "Sunbeam Duravinyl" vinyl asbestos tile was installed. The tiles were 12 inches square and 0.080 inches thick. This operation took approximately 4 hours. The relative room positions are shown in Figure 3. 3 Baron it BikU Bull er Couniv Aususl I. |W Sample XX-II Fiju'e 1 SITE PLAN-TESTSITE NO. 1 4 Baron & Budd Butler Count) August 1. 1997 XX-OOSO* XX-029 XX-019 XX-023 Storage SNACK SHOP XX-002 XX-022 XX017 Book Stall Counter JT c I 1 s AIR handling unit COeY RODV. 0 Pnition Storage Table Tiblt ---- Test xxon XX030 XX027 Background Ten XXCrtS C-1083 XX008 C-1D96 XX016 C-107B Figure 2. SITE PLAN-TEST SITE NO.2 5 Baron & BudJ Butler Count\ August I. iw Kitehtr. 6 Baron & BuJd Butler Couni\ August I. 194' III. METHODOLOGY 1. Use, Maintenance, Preparation, Installation and Removal The operations were done according to reconnended procedures.* 2. Determination of Airborne Asbestos Fibers The KIOSH method for determining asbestos fibers In the air was employed (see Attachment "A," KIOSH Method Ko. P4CAM 239, "Asbestos Fibers in Air1'). Kote: Personal and area samples were collected with a Mine Safety Appliance Company Model G portable sampling pump. High-volume samples were taken with a Gast punp. * Recommended procedures involve preparation, installation, and removal without sanding, use of equipment that would unduly shatter the tile instead of a flat-bladed wall scraper, or breaking the tile by hand before placing In a disposal bag. For the impact of deviation from reconnended procedures, see SRI International Report, "Comparison Testing, Monitoring for Airborne Asbestos Fibers: Vinyl Asbestos Floor Tile." (December, 1979) 7 Baron & Bud Butler Count Auaust I. 11,1 IV. SUWARY OF RESULTS The following Tables list the concentrations. If any, of airborne asbestos fibers measured at the various test sites during specified operations. NOTE: The OSKA Standard for a safe workplace allows a concentration of 2 fibers per cc of air on an 8-hour time-weighted-average {TWA). TWA exposures were calculated by assuming a full-days exposure to these conditions. Site No. and Descriptior 2 - Copy Center 2 - Snack Sncp Site No. and Descriotion 2 - Mopping 2 - Buffing Table No. 1 In-Use Text Table No. 2 Maintenance Asbestos Fibers/cc 0 0 8-Hr. TWA (Asbestos Fibers/cc) 0 0 B Baron & BuJJ Butler Count\ August I. 1W Site No. 1 3 Site No. 3 Table No. 3 Installation 8-Hr. TWA (Asbestos Fibers/cc) Han C-102 Han C-1062 0.0046 0.0092 Man JS Han TD 0.027 0.008 Table No. 4 Removal 8-Hr. TWA (Asbestos Fibers/cc) Han JS Han TD 0.006 0.015 9 Baron &. Budd Butler Count> Auaust I. 199" V. CONCLUSIONS 1. Use In use of vinyl asbestos floor tile there Is no exposure to airborne asbestos fibers. 2. Maintenance In the maintenance of vinyl asbestos floor t\_le there is no exposure to airborne asbestos fibers. 7 Installation and Removal In the installation and removal of vinyl asbestos floor^tile, the results of these tests show that when recoonended procedures are used the exposure to airborne asbestos fibers is substantially below the allowed OSKA limit. * 10 Baron & Hu Builcr C'oun Auausi |. |u YI. IN-USE TESTS, SITE *2 Purpose: To monitor for airborne asbestos fibers during light and heavy pedestrian traffic (In-use) conditions of vinyl asbestos floor tile and to measure any Increased fiber concentrations above background levels. Discussion: At the time of the testing, the floors of the two areas sampled, a snack shop and a snail copy room, were in the unwaxed condition (wax had been stripped) and had received traffic in that condition. This was purposely done to simulate a very poor maintenance condition and/or a "worst-case'' situation. The analyses of both the background (collected after working hours) and In-use (collected during working hours) air samples did not show any asbestos fibers in heavily traveled areas. Sampling Procedure: Tne sampling protocol was designed to determine: 1. The background dust level in the building and outside air, with specific consideration to any ambient fibers. The sampling strategy for this Involved placement of sampling units both Inside and outside the building. The Inside units were placed at 1, 3, and 5 feet above the floor In both the snack shop and copy room, with single filters at other selected locations such as in the area of an air diffuser In these two areas. Outside samples were placed randomly. The multilevel sampling protocol could not be met in the snack shop so the following alternate sampling plan was used for this area: The dust level in the supply air entering the snack 11 Baron & Budd Butler Countv Aueust 1. IW shop was monitored by sampling air from the air-handling unit as it entered the duct leading to the air diffusers. An additional sample was collected In the hallway next to the snack shop. In both cases the ssnpling was performed several hours after the office wrk force had gone home. 2. The concentration of asbestos. If any, dispersed from the floor tile during light and heavy pedestrian traffic. In this case, the multilevel sampling outlined in 1, was used, except that tw such sampling units were placed In different locations of both the snack shop and copy room. Figure 2, page 5, shows the relative locations of the area-sar.plins units during the testing. Sampling Results: The results of the individual filter analyses are shown in Table No. 5. The types of fibers found in the samples collected were not asbestos but rather textile fibers that appeared to have been shredded off from larger textile fibers. The morphologic appearance of these fibers was quite different from asbestos. For illustrative purposes, in Figure 4, the first photomicrograph shows an asbestos sample that was prepared for the Proficiency and Accuracy Testing Program (sponsored by NIOSH) and shows fiber bundles of varying thicknesses. The second photomicrograph, not taken from these samples, shows two fibers which are examples of probable chrysotile asbestos. Characteristicallyin field samples of this type, the fiber bundles are much shorter than textile fibers. The third and final photonicrograph shows cotton fibers. This type shows typically twisted shapes. Additionally, the fiber diameter is substantially greater than that of asbestos, but is comparable to most other types of textile fibers, such as the types observed during this aspect of the sampling program. Figure 5, shows an electronmicrograph of chrystotlle asbestos. At this aagnification (40,000x), the appearance of these types of fibers is drastically different from the appearance of textile fibers, especially in the lack of twisting, much smaller fiber diameter (10 to 25 millimicrons), and the characteristic hollow core of the asbestos fibers. Consequently, we concluded that the fibers observed were textile fibers and not asbestos fibers. 12 Baron & Bud. Butler Count; August I. I 'to Table Ho. 5 In-Use Testing Results "Description Filter Air Yol. Time Fibers/ Total Asbestos** No. (liters) (min) so tr* Fibers/cc Fibers/cc BACKGROUND SAMPLES oooo oooooo Air Yent Hallway Copy Center Outside Outside Outside Copy Center 1 ft high 3 ft high 5 ft high Snack Shop C-I066 XX005 XJB XX102 XX031 XXOOS XX015 XXOOS XX016 C-1051 588 555 590 616 834 840 594 594 594 254 294 4.7 278 4.7 295 0 308 0 417 O 420 0 297 2.5 297 0 257 0 142 0 0.0067 0.007 0 0 0 0 0.0035 0 0 0 3H-USI SAMPLES oooooo ooo ooo Copy Center - Table 1 ft high XX027 833 419 4.4 0.0044 3 ft high XX030 63S 419 0 0 5 ft high XXOil 38 419 11.1 0.011 Copy Center - Middle Room 1 ft high C 1078 3 ft high C 10SS 5 ft high C 1083 22 411 22 - 411 22 411 2.3 4.5 4.6 0.0023 0.0046 0.0047 Snack Shop Bookcase - 1 ft XX017 250 130 0 0 Bookcase - 3 ft XX022 260 130 0 0 Bookcase - 5 ft XX002 260 130 2.5 0.0079 Storage Door - 1 ft XX023 266 133 4.5 0.0618 Storage Door - 3 ft XX019 266 133 2.4 0.0088 Storage Door - 5 ft XX029 266 133 0 0 Fibers/sq mm of filter surface area. **Analyst determined that none of the fibers were asbestos. 13 Baron A BuJ.I Bailor Count;. Auuust I. I Fx 4. FIBER FHOTOMICROGfUFHS Baron & BuJd Butler Couni> August I. IW F.fjft E ELECTRON MICROGRAPH. CHRYSOTILE ASBESTOS 15 Baron & Budd Butler Count> Aucust 1. IW Evaluation: The average background fiber count calculated on this floor of this building was 0.0025 fibers/cc of air (calculated from filters C-1066, XX005, XJB, XX015, XX008, XX016, and C-1051J as compared to the outside air fiber concentration of 0 (calculated frcm filters XX102, XX031, XX006). Comparing the average value of the background Indoor samples to the heavy and light pedestrian traffic areas, we found the following: the relative average concentrations for the copy room and snack shop were 0.0045 fibers/cc (calculated fron filters C-1078, C-1096, C-1083, XX027, XX030, XXOU) and .0056 fibers/cc (calculated from filters XX-002, XX-022, XX-017, XX-019, XX-023, XX-029), respectively. The finding that these concentrations are approximately 2 times the background concentrations is not surprising since the level of activity during a normal working day should increase the dust level over the background samples that were collected after vrking hours. Comparing the values found for the light and heavy pedestrian traffic areas, we found that the individual values in the snack shop are approximately 2 times those in the copy room, except for the 0 levels. This is due to the difference in the time of sampling and sample volune. The values found in the copy room are very consistent and represent 6-hour concentrations, while the snack shop samples could only be collected during the peak traffic time, from 10:52 a.m. to 1:05 p.m. These levels represent somewhat of a peak concentration for the day. Had the sampling been continued for the remainder of the day, the average concentration would probably have been lower by including the less dusty periods in the afternoon in-the total sampling time. Conclusion: Based on the absence of any detectable asbestos fibers during the pedestrian traffic tests, we conclude that, when properly maintained, the asbestos constituent of the floor tile does not pose a potential health risk to office employees or maintenance personnel. 16 Baron & Budd Butler Count\ AutttiNt I. lw~ The description of the fiber counts relating to textile fibers have been Included in this report for purposes of completeness and clarity. General Interest in a floor covering is greater In regard to use than to Installation since most persons' contact with a flooring is mainly through Its use over a 10-20 year period rather than through the occasional process of installation. 17 Baron & BuJJ Butler Counts August I. I oo' VI. HAIKTEHAKCE TESTS. SITE #2 Purpose: To monitor for airborne asbestos fibers during maintenance operations ef vinyl asbestos floor tile and to measure any increased fiber concentrations above background levels. Discussion: The actual sampling took place in a snack shop and in a copying room during prescribed routine maintenance. The wax was removed (stripped) and mo-wax maintenance procedures followed. This consisted of buffing the floor using a light misting of a mild cleaning solution, or of wet mopping. Sampling Procedure: The sampling protocol was designed to determine: 1. The background dust level in the building and outside air, with specific consideration to any ambient fibers. The sampling strategy for This involved placement of sampling units both inside and outside the building. The inside units were placed at 1, 3, and 5 feet above the floor in both the snack shop and copy room, with single filters at other selected locations such as in the area of the air diffuser in these two areas. Outside samples were placed randomly. The multilevel sampling protocol could not be met in the snack shop so the following alternate sampling plan was used for this area: the dust level in the supply air entering the snack shop was monitored by sampling air from the air-handling unit as it entered The duct leading to the air diffusers. An additional sample was collected In the hallway next to the snack shop. In both cases the sampling was performed several hours after the office work force had gone home. IB Baron & Bikid Butler Countv Ausust 1. IW7 2. The difference In the concentration of asbestos in the air during floor maintenance as compared to background concentrations of asbestos, if any, during operations such as damp mopping and floor stripping; personal sampling was performed in addition to area sampling. In all cases samples re collected for the naxlttun time allowed by the operation in order to collect a representative air sample. However, several of the sample vollines were very small (less than 50 liters) due to extrmely short operations. The Impact of the smaller sampling times will be discussed in the section on sampling results. Figure 2, page 5, shows the relative locations of the area sampling units during the testing. Sampling Results: The results of the individual filter analyses are shown In Table No. 6. Evaluation: The average textile fiber concentration found during the wet-stripping operation was O.C771 fibers/cc of air (calculated from filters XX-026, XX-0D1, XX-014- .XX-003, XX-025, and QTH-1). The average sample volume was 34.5 liters. Prior to this operation, a background sample (C-1051) was collected (264 liters) in the snack shop and showed no fibers when microscopically examined. This indicates that the operation may resuspend dust that has settled out during the several hours following the end of the office-employee work shift. Comparing the low value of the general area sample (QTH-1) collected during the wet stripping of the snack shop (0.0075 textile fibers/cc of air) with the results of the sampling of the worker performing the wet mopping (0.1351 textile fibers/cc - sample IXX-000), we see that the operation also tends to resuspend the dust in the worker's immediate area. However, the small sample volutes collected In the snack shop may have biased the results toward the high side because a particularly dusty spot on the floor was stripped during the sampling time; this might have averaged out somewhat in a longer operation, ie, in a larger sampling 19 Baron & Budd Butler Count) August 1. 1947 Table No. 6 Maintenance Description Filter Air Yol. Time Fibers/ Total Asbestos** No. (liters) (min) so mm* Fibers/cc Fibers/cc XX t c_> oooooo ooooooo BACKGROUND SAMPLES Air Yent hallway Copy Center Outside Outside Outside Snack Shop C1066 XX005 XJB XX102 XX031 XX005 C1051 588 556 590 616 834 840 264 294 4.7 278 4.7 295 0 308 0 417 0 420 0 142 0 0.0067 0.007 0 0 0 0 0 MAINTENANCE SAMPLES Mopping - Copy Center Buffing - Copy Center Mopping - Snack Shop Buffing - Snack Shop Buffing - Copy Center Buffing - Copy Center High-Volume Sample (Mopping) Floor Area XX 026 XXDOi XXOOO XX025 KGS-1 XX QTH-1 30 30 42 42 22 60 37 30 15 4.9 15 4.3 21 9.8 21 0 11 2.4 30 0 54 4.9 15 2.5 0.1351 0.1210 0.1949 0 0.0921 0 0.0075 0.6S2 *Fipers/sq mm of total filter surface area. **Analyst determined that none of the fibers were asbestos. 0 0 20 Baron & BuJd Butler C'oium August I. |vv~ volime. It is interesting to note that the personal sample from the buffer operator did not detect any textile fibers. Additionally, the writer was outside the snack shop during the wet mopping. While the results of the buffing operation recommended for a no-wax maintenance floor did not show any asbestos fibers, several factors prohibit drawing a firm conclusion on this aspect. The relative size of the operation tested was snail, requiring only 11 minutes to complete. The air sample size was also small (22 liters). The size was possibly too small for any asbestos fibers that may have been generated to have been picked up. Because of the small size of the sample collected during the buffing operation, a second sample (XX) was collected during a buffing operation at a later date. The duration of the second buffing was 30 minutes and a 60-liter sample was collected. Again, no asbestos fibers were found. An operation like the wet-stripping operation does tend to resuspend dust that has settled out of the air after working hours. This was shown by comparing filters XX-002 (0.007S textile fibers/cc) and XX-029 (0 fibers/cc), listed in Table S, page 13, both of which were taken during the day in the snack shop at the 5-foot level, with filter KGB-1 (0.0521 textile fibers/cc), the personal sample of the buffer operation. Conclusion: Based or, the absence of any detectable asbestos fibers during either the wet-stripping or buffing operations, we conclude that, when floor tile is properly maintained, its asbestos constituent does not pose a potential health risk to office employees or maintenance personnel. The data relative to textile fibers have been included in this report for purposes of completeness and clarity. Fibers were generated from maintenance, but they were all textile fibers. 21 Baron A: BudJ Bmicr Couni\ Aucusi 1. I1)''" VI11. COMPLETE REMOVAL TESTS. SITE 3 Purpose: To monitor for airborne asbestos fibers during the complete removal of vinyl asbestos floor tile. Discussion: The tests were done in the laundry room, powder room, closet, and hallway of a private home. Removal was accomplished by heating the tile with a cocnercial air blower. However, there was an unusually large amount of adhesive under the tile and the heating compounded the difficulty of removal. 3n main pedestrian traffic areas there was quite a bit of tile breakage and many small pieces were generated. In other areas, the tiles came up quite readily without excessive breaking. In the closet and bathroom areas, access for good leverage on the hand tools was difficult and the mechanics had to be very close in to do the work. Discarded tile was placed in trash bags for disposal. Sampling Procedure: A personal sampling pump was attached to the belt of each mechanic and a filter clipped to his collar. Four additional sampling pinps were placed to obtain area and background data. A background determination was also made the day prior to the test. A GCA Dust Monitor was used to measure total dust (by weight) in the area. This is a direct reading instrument; dust levels were below the detection level in 2 samples. A sketch of the work and indications of sample placement are presented in Figure 3, page 6. 22 Baron & BnJ.I Bullcr Cinini;Aucust 1. I1'1'" Sampling Results The results of fiber counting, other pertinent sampling data, and identifiers are listed in Table No. 7. Table No. 7 Description Filter Air Yol. Time Fibers/ Total Asbestos** 8-Hr. No. {liters! (min) sq. mm* Fibers/cc Fibers/cc TWA Background RFC1 #8 587 326 0 0 0 Background MWCO 700 594 297 10 0.014 0.001 Area-Breezeway HWCO 692 537 316 70 0.111 0.011 Area-La undry Room MWCO 686 739 389 140 0.161 0.016 Area-Powder Room MWCO 685 725 372 75 0.088 0.009 Mechanic JS MWCO 662 245 123 18 0.062 0.006 0.006 Mechanic TO MWCO 657 255 134 44 0.147 0.015 0.015 *Fibers/sq m of filter surface. Analyst estimated that lOi of the fibers were asbestos. Cor.clusic-: The number of asbestos fibers on the filters was very small, all well below 0.1 fibers/cc. Compared to the OSHA limit of 2.0 fibers/cc, the concentrations measured when recommended procedures were followed, 0.006 to 0.015 fibers/cc, are insignificant . 23 Baron dt BuJJ Butler Count) Auaust I. IW IX. INSTALLATION TESTS A. Site #3 Purpose: To monitor for airborne asbestos fibers during the installation of wl^yl asbestos floor tile. Discussion: The tests were done in the laundry room, powder room, closet, and hallway of a private hcne. The tiles were precoated with adhesive; Installation consisted of removing the release paper from the back and then pressing the tile firmly in place on the concrete slab floor. Where cutting cr trimming were required, it was done before the paper was removed. Sampling Procedure: A personal sampling pump was attached to the belt of each mechanic and a filter clipped to his collar. Four additional sampling purps were placed to obtain area and background data. A background determination was also made the day prior to the test. A GLA Dust tonitor was used to measure total dust (by weight) in the area. This Is a direct reading instrinent; dust levels were below the detection limit in 2 samples. A sketch of the work and indications of sample placement are presented in Figure 3, page 6. 24 Baron & BudJ Buller Conni' Aucust 1. IW Samplinc Results: The results of fiber counting, other pertinent sampling data, and Identifiers are listed in Table No. 8. Table No. 8 Description Filter Air Vol. Time Fibers/ Total Asbestos** 8-Hr No. (liters) (min) sq. mm* Flbers/cc Flbers/cc TWA Background RFC! #5 567 326 0 0 0 Background MWC3 700 59; 297 10 0.014 0.001 Area - Breezeway MWCO 652 537 316 70 0.0111 0.0011 Area - Laundry MWCO 6E 735 369 140 0.161 0.016 Area - Powder Room KWCD 655 725 372 75 0.086 0.009 Mechanic OS MWCO 652 ;e; 232 145 0.267 0.027 0.027 Mechanic TD MWCO 664 416 220 40 0.061 0.008 0.005 *Fibers/sq mm of filter surface area. Analyst estimated that lOt of the fibers were asbestos. 25 Baron & HuJJ Butler Coum-. Aiiuum I. low B SUe *1 Discussion: The tests were done in the basement and In a snail utility roan. The tile was installed directly on a concrete floor. The installation required about 2 hours for the basement and about 20 minutes for the utility room. Sampling Procedure: Two area samples were collected for background analysis -- one Inside the hcne and another outside. A personal sample was collected for each of the two mechanics Involved. In addition a high-volune sample was also collected. A sketch of the sampler placements is shown in Figure 1, page 4. Samplinc Results: The results of fiber counting and other identifiers are listed below In Table No. 9. The filters were heavily loaded with dust, making the fiber counting very difficult. 26 Baron & Budd Butler Comm Aliens! I. 104" Table No. 9 Description Filter Air Vol. Time Fibers/ Total Asbestos** 8-Hr. No. (liters) (min) so nr.* Fibers/cc Fibers/cc TWA Indoor Background C1069 876 438 111.7 0.104 0.0052 Outdoors XX-1 660 330 4.7 0.003 0.003 High-Yolline Sample XXII 1710 90 38.1 0.28 0.0014 Head Mechanic Cl 02 228 114 27 0.092 0.0046 0.0046 Assistant Mechanic C1062 226 113 52.3 0.184 0.0092 0.0092 *Fibers/sq nr of filter surface area. Analyst estimated that about 5* of the fibers were asbestos except for filter XX-1. Conclusion: The ninber of asbestos fibers on the filters was very small, all well below 0.1 fibers/cc. Compared to the OSHA limit of 2.0 fibers/cc, the concentrations measured when recommended procedures were followed, 0.004c {Table 9) to 0.027 {Table 6) fibers/cc, are insignificant. 27 Baron A: U Butler (.'o. Auau-i I i Baron iX. BudJ Boiler I'miii'} August 1. I'*''" ASBESTOS FIBERS IN AIR National Institute for Occupational Safety and Health Analytical Method Analyte: Matrix: Procedure: Date Issued: Date Revised: Asbestos fibers Air Filter collection, microscopic count 3/30/77 Method No.: PiCAM 239 Range: 0.1-60 fibers/cm* Precision (CVt): 0.24 to 0.3 S Classification: D (Operational) 1. 'Principle ol the Method 2.1 This method describes the equipment and procedures for collecting, mounting, end counting asbestos fibers on cellulose ester membrane filters in the evaluation of personal samples cl airborne asbestos fibers. The purpose of the method is to determine an employee's index of exposure to airborne asbestos fibers. The method is primarily a personal monitoring tech nique, but can be used for area monitoring. 2.2 The sample is collected by drawing sir through i membrsne filter by meins of a batterypowered persona! sampling pump. The filter is transformed from an opaque solid membrane to a transparent optically homogeneous gel. The fibers are sized and counted using a phasecontrast microscope at 400-450X magnification. 2.3 Definitions. Asbestos fiber, for counting purposes, means a particulate which has a physio.nt dimension longer than 5 micrometers and with a length to diameter ratio of 3 to 1 e: greater Asbestos includes chrysolite, eummingtonite-grunerite (amosite), crocidolite, fibrous tremo lit:, fibrous anthophyllite, ar.d fibrous aotir.olite. 2.4 Any laboratory attempting to use this procedure should have a: lens: one counter attend a training course conducted by an experienced, proficient laboratory. Novice, untutored counters, using only published instructions, can easily obtain counts of half those performed by experi enced, proficient counters, Large differences between laboratories can be caused by: 1) dif ferences in technique and observing ability among counters and 2) small, but significant, dif ferences between microscopes meeting the basic specifications of Section 6.2. The following procedures are recommended: 1.4.2 All mieroseopists who perform asbestos counting should meet together for an `asbestos counting workshop" at least quarterly. This is best accomplished with counters from several laboratories using their own microscopes. 1.4.2 Each microscopist should count the same series of slides and with the results being compared. 2.4.3 Differences between counters should be resolved with side-by-side counting of the fields by the different counters. 2.4.4 Individuals who arc found to be persistent outliers over several sessions should be cneouraged to seek other tasks in their respective laboratories. 239-1 Baron & BuJJ Butler Comm August I. IW 2. Range'and Sensitivity 2.1 The usable range is primarily a function of sample volume, microscope count field area, and background airborne particulates. The influence of these variables is discussed in 8.1.3. For a microscope count field area of 0.003 mm* (see Figure 1) and a pump Bow rate of 1.7 1pm, * the optimal fiber densities would be produced oyer the range of 0.4 fiber/ce* (8-hour sam ple) to about 60 fibers/cm1 (IS-misule simple). For a field area of 0.006 am* (see Figure 2) and a pump flow rate of 1.7 1pm, the optimal range is 0.2 fiber/cm* (8-hour sample) to about 30 fibers/cm1 (15-minute sample). Id each ease, the optimal detection limits are in versely proportional to pump tow rate. The upper detection limit can be extended by using sample times less than 15 minutes or rising lower flow rates. The lower detection limit ean be extended by increasing the Sow rale vp to about 2.5 1pm. Filter surface fiber densities less than optimal Cess than about 0.5 to 1.0 fiber per count field) are still adequate, but will lead to decreased precision for the t&e^iod (in creased coefficient of variation, ace Section 4). The minimum total fiber count in 100 fields considered adequate for reliable quantitation is 10 fibers. Thus, the lower limit of reliable quantitation is 0.1 fiber/em* (100,000 fibers/ n'). For this level, a flow rate of about 2.5 1pm is recommended. For a field area of 0.003 nr,:, the minimum sample time would be about 2 hours. For a field area of 0.006 mms, the minimum sample time would be about 1 hour. 2.2 This method considers only fibers with a length to diameter ratio of 3 to 1 or greater and a length greeter than 5 micrometers. 3. Interferences In an atmosphere known to contcir. asbestos, all particulates with a length to diameter ratio of 3 to 1 o: greater, and a length greater than 5 micrometers should, in the absence of ether information, be considered to be asbestos fibers ar.d counted as auch. 4. Precision end Accuracy 4.1 lr. the pcs', decade, there have appeared a number of articles examining sources of variation in the asbestos sampling and counting procedure. These include: Lynch et al. (11.1), Weidner and Ayer (11.2), Conway and Holland (11.3), Lcidcl and Busch (lt.4), Beckett and Attfield (11.5), and Rajhans and Bragg (11.6). The sources of variation will be discussed by stages in the membrane filter evaluation procedure. 4.2 Sources of Variation in the Sampling Process. These include variations in pump flow rate, proximity of the filter to the employee's body, and filter location (left to right) in the em ployee's breathing 2one. 4.2.1 Section 9.1 requires that the personal sampling pump be calibrated with sufficient accuracy such that the 955c confidence limits on the flow rate are m 105c. This is equivalent to a coefficient of variation (CV) of about S5w. However, this CV makes a negligible contribution to the total CV for the method due to the relatively large CV of the counting procedure. 4.2.2 Conway and Holland (11.3) concluded that positioning of the filter cassette on the wearer (regarding the angular portions of the filler and their proximity to the wearer) is not a significant facto? in determining the fiber distribution on filters. 4.2.3 Weidner and Ayer (11.2) concluded that there is no appreciable difference between aamplts collected on either the tight or left sides of a breathing ron: or between samples collected side-by-side, especially for samples with concentrations less than 2.5 fibers/cm\ 239-2 Baron & Ito.iJ Bailor (. oilin'Aiioum I. ! w`'~ 4.3 Sources ol Variation In the Counting Procedure 4.3.1 Rind cm variations exist in the fiber distribution on a filter wed;: (intra-wedge vari ability). The industrial hygiene literature bis teen considerable debate in the list 20 years concerning whether or not the distribution of mineral dust or asbestos fibers on a filter surface is adequately described by a Poisson distribution probability density function. Leidel and Busch (11.4) found excellent agreement between empirical error variance and theoretical variance calculated from the assumption of Poisson dis tributed true counts. They concluded that there was not excessive variation among count fields for a filter wedge and that clumping of fibers (son-random coalescence) did oot occur. 4.3.2 Variations exist in the fiber distribution on the total filter aurface (inter-wedge vari ability) due to the random or son-random distribution of fibers across the total sur face of the filter. This type of variation is easily confused with intra-wedge variations. The count procedure does sot require counting of multiple sectors or the filter. There may be significant differences between average counts for different wedges, or the fiber distribution variations for the total filler surface may be greater than the variations of the Poisson distribution. If either of these oeeur experimentally, one must tue the experimental variations to estimate the minimum precision of the count procedure. The minimum precision is governed by the variations of the fiber distribution cn the total surface of the filter. Conway ar.d Holland (11.3) concluded the distribution of fibers on filters is not uni form and the distribution of fiber counts is more disperse than Poisson. For their filters which had significant variations in fiber concentrations between sectors (as much as 50-60 7c of the total filter mean), they described the following relation for the standard deviation of the total number of fibers counted on a wedge (N) empirical s(N) = 1.6 (N)1'1 where N is about JCO. The Poisson standard deviation would be: Poisson e (N) ** (S)' Rajhans ar.d Bragc (13.6) in Series I of their study found significant variation between filter segments ar.d rejected the Poisson distribution for the total filter surface. However, in Series II of their study, utilizing various experimental modifications, they found no significant variation between filter segments and no reason to reject the assumption of Poisson distributed fiber counts. 4.3.3 Systematic variations due to differences between microscopes were studied by Leidel and Busch (11.4). In their study using five different brands of microscopes, they found no significant differences among four, but the fifth gave counts approximately 457c higher on the average than the other four. 4.3.4 Variations due to differences between counters should be examined at three levels: experienced counters occasionally counting, experienced counters routinely counting. and inexperienced (new- or untutored) counters. Leidel and Buseh (11.4) studied five experienced counters, with one counting only occasionally. There were no significant differences among three of the counters, but a fourth was 16% lower than the first three. The fifth, who occasionally counted, averaged 27% higher than the first three. Conway and Holland (11.3) studied thtee experienced counters and three inexperienced counters. They found statistically significant differences between the means of both the experienced and inexperienced counters that typically were in the range plus or minus 5 to 15 %. They concluded that experience as a fiber counter is not a significant parameter affecting intercounter variations. j j { j | | j | j ! 239-3 ar-Aix.' Baron & BuJd Butler Countv August I. IW Rajhcns and Brigs (H.6) found bo significant differences among means of five experi enced counters in Series I of their study. But in their carefully controlled Scries II, an analysis of variance showed significant variations between counters that were plus or minus I to 155e. 4.3.5 Variations between laboratories are most likely due to systematic biases and are aot a aignificant additional source of random variations. Any additional variations are most likely due to differences in counting technique. Beckett and Airfield (11.5) cbaerved that standard counters improved greatly after personal instruction; also new counters, after instruction, tended to overcompecsite and get exceedingly high counts. Additionally, they found that counts from an experienced laboratory that had not had contact with other laboratories performing the same analysis were as far from the standard values as were the counts by new counters. -4.4 Sources of variations between samples taken at different times on one employee during one work shift can affect the exposure estimate for that employee. These are primarily due to a) differences in exposure concentrations during the day. b) differences in location of the employee within the plant, and c) differences in work operation performed by the employee during the day. These sources of variation can be controlled by proper choice of sampling strategy. Refer to Leidel and Busch (11.7) and Leidel, Busch, and Lynch (11.8) for an extended discussion of sampling strategies. Interday temporal variations can affect the ex posure estimates obtained on different days. Refer Us Leidel, Busch, and Crouse (11.9) for a discussion of this type of variation. 4.5 Until recently, the total coefficient of variation (CVT) for the sampling and counting proce dure was best estimated from the work of Conway ar.d Holland (11.3). The conclusions cf their study included: 45.1 The precision of their procedure for filters re1-, containing an abundance of fine fibers can be estimated by a coefficient of variation of 16.25c. This value includes variation among counters and observed interaction effects. 4.5.2 The accuracy of the procedure for similar filters may b: estimated for a 100-fiber count by a coefficient cf variation cf 2145c. This assumes that the contribution of the overall variance from the nonuniform fiber distribution is additive. 4.5.3 A high percentage cf very fin: fibers on the filter can significantly .affect the standard deviation and confider.ee limits for counts by different counters. After combining variations in fiber concentrations over the entire filter with those for difleren: counters, it was concluded: a. For filters with a low concentration of fine fibers, the coefficient of variation is estimated at 219c and tbc 957c confidence interval is m 435c. b. For filters with a high concentration of fir.: fibers, the coefficient of variation is estimated at 255c and the 955c confidence interval is sc 505r. Lynch, Kronoveter, and Leidel (11.1) hast also reported on variations of the method. Their intralaboratory study utilized the data from a large number of dust counts made by different methods by experienced counters over a period of years in an epidemiologic study of the asbestos products industry. They concluded that the standard deviation of counts of fibers longer than 5 micrometers on membrane filters could be estimated from the relation e * (K)'' Titus for counts of about 100 fibers, the coefficient of variation could be estimated at about 15.2 7c and the 95 5f confidence limits at m 30.45c. These values are lower than the values reported by Conway and Holland (11.3). Recently, the Johns-Manvillc Corporation conducted an in-house investigation of the asbestos conn: method (11.10). The study data contained total fiber counts for over 103 Tihcrs with each Alter counted by two to five counters. Frost the Johro-Minville * data, NIOSH calculated over 100 estimates of the count CV for the method (11.11). The NIOSH CV estimates Included random intrafilter variations and iniercounter variations, but did not include random pump flow rate variations. It was found that the count coefficient of variation (all random variations except for pump varialioos) . was a function of the total fiber count. NIOSH then included a CV ef 0.05 for ran dom pump variations (see Section 9.1) in the CV-estimator aquation.to obtain a CVf-estimator. The CV^-estimator line is plotted on Figure 3 for total fiber counts in the range 10 to 100 fibers. Or the following equation can be toed: CV, - Iantilogi#(--0.215 - 0.203 (Jog,.FB)) + 0.0025)* where FB is total fiber count as discussed in Section 10. Figure 3 demonstrates that for a total fiber count ef 100, the best CVT is attainable with the appropriate sampling times given in 8.1.3 and the count ndes in 83.9. When making decisions regarding compliance with the OSHA asbestos exposure standards in 29 CFR 1910.1001, the statistical procedures given in Leidel ct al. (11.11) should be followed. The procedures arc based on statistical theory and assumptions given in References 11.12, 11.13. Because of the possibility of systematic biases due to differences between microscopes, counters, and laboratories as discussed above, it is strongly recommended that any laboratory counting asbestos should participate in an interlaboratory quality centre! program that includes the counting of standard reference fillers. These standard filters are available from NIOSH through the Proficiency Analytical Testing (PAT) Pro gram. The PAT Program is used by the American Industrial Hygiene Association (A1HA) as part of its Laboratory Accreditation Program. Each laboratory's quality control program must include protocols for routinely adjusting and calibrating sampling and counting equipment plus training and evaluation programs for counters.' 5. Advnntrges and Disadvantages c! the Method 5.1 The method is intended to give an index cf employe: exposure to airborne asbestos fibers of specified dimensional characteristics. 5.2 It is not meant to count cl) asbestos fibers in al! size ranges or to differentiate asbestos from other fibrous particulates. . Apparatus .1 Sampling Equipment The persona! sampling equipment train consists of 1) personal aampling pump, 2) tubing. 3) clothing spring clip, 4) tubir.g-to-field monitor metal adaptor, and 5) field monitor (filter and holder). 6.1.1 Personal Sampling Pump. The pump must be capable of sampling at 1.0 to 23 liters per minute (1pm) against a flow resistance of 73 inches ef water (1.4 cm Hg) for 8 continuous hours on a fully charged battery. 6.1.2 Tubing. Laboratory tubing such as rubber or plastic with 6-mm bore and about 103 cm length. 6.1.3 Clothing Spring Clip. The clip attaches the rubber tubing to the lapel or shirt of the individual being monitored. 6.1.4 Tubing-to-ficUI Monitor Adaptor. A short mctnl adaptor with ridges on one end to grip the inside cf the tubing. The other end L designed fur a pressure fit into the field monitor. 6.1.5 Field Monitor (Miter and Holder). The only field monitor currently considered acceptable by NIOSH is manufactured by the Milliporc Corporation. The unit con- 239-5 Baron & BuJd Butler C cnimx Auttust I. Iv>(~ situ el 1) a three section styrene plistie east designated Millipore Aerosol Monitor Case, 2) * 37*mm diameter plain white cellulose ester membrane fitter designated Millipore AA (pore si of 0.8 micrometer), 3) a support pad, and 4) two plastic sealing eaps. If a large number of samples are to be taken, h may be less expensive io reuse the plastic cases. Crest care must be taken in the cleaning and reassembly process. The outside mating surfaces of the field monitors may be covered with a "shrink-fir' band to provide proper sealing and a writing surfaee for filter identifies* tion. 6.2 Optical Equipment and Microscope Features 6.2.1 Microscope body with binocular head. 2.2 10X Huygenian eyepieces are recommended. Other eyepieces can be substituted if necessary. Wide field eyepieces can be used; however, wide field eyepieces may yield a count field area less than 0.003 mm* with the Porton retiele. This b not always desirable from the standpoint of obtaining optimum sampling times (see Sec* lion 8.1.3). If wide field eyepieces are used, h is preferable to use the Patterson Globe ted Circle reticle to obtain a larger count field area. 6.2.3 Koehler illumination (preferably built-in with provisions for adjusting light intensity). 6.2.4 A Porton reticle is recommended. Others sueh as the Patterson Globe ar.d Circle can be substituted. 6.2.5 Mechanical stage. 6.2.6 Phase-Contrast condenser with a numerical aperture (N.A.) equal to or greater than the N.A. of the objective. 6.2.7 40-45X phase contrast achromatic objective (N.A. 0.65 to 0.75). 6.2.8 Phase-rir.g centering telescope or Bertrand lens. 6.2.9 Gieen or b'.u-. filter, if recommended by microscope manufacturer. 6.2.10 St2g: nicjome'.e: with 0.01 mm subdivisions. 6.2.11 For general guidance on phase contrast microscopy, consult Needham (11.12), Clark (11.15) ar.d MeCrc.ne (11.14). t ... 6.3 Filter Mounting Equipmtnl. Experience has shown that certain equipment is useful for efficient sample mounting. The following items are recommended for extracting and mounting a portion of the filter for counting. 6.3.1 Mierosccp: slides. 2.5 by 7.5 cm glass slides are most commonly used. Sample number, data, initials, etc., can be conveniently written on a frosted end slide. 6.3.2 Cover Slips. Cover slips are a necessary pan of the slide mount and optical system. The shape should be appropriate for the sire of the filter wedge. The appropriate cover alip depends upon the objective to be used. Ordinarily, objectives are optically corTccicd for a #l'/i (0.17 millimeter) thickness cover slip. Improper cover glass thickness will detract from the final image quality. 6.3.3 Scalpel. A scalpel is needed to cut out a portion of the filter to be examined. A num ber-ten curved blade scalpel is recommended. 6.3.4 Tweezers. A pair of fine-tipped tweeters is used to temove the membrane filter slice from the field monitor and place it upon the slide. 6.35 Lens Tissue. To insure cleanliness, & lint-fret tissue b tceommendcd. This tissue should also be used for wiping mounting tools nnd for cleaning slides and cover slips. 6.3.6 Glass Rod. A fire-polished glass rod may be used to spread the mounting solution or. the slide. 239-6 r I | ! , j I j , ' ! : j '| .i |j |j .j i > j' . 1j ; j[ : j: Baron & Budd But/cr Count\ August I. lw 6.3.7 Wheaton Btilsam Bottle. This special (Jus container has a glass top which prevents contamination of the mounting solution. A glass rod is deluded for dispensing the solution. 7. Reagertts Chemicals should be reagent grade, free from particles and color, conforming to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where sueh specifi cations are available. 7.1 Dimethyl phthalate 12. Diethyl oxalate Avoid getting the mounting solution on the shin. Wash shin promptly with soap and water if shin contact occurs. 2. Procedure 2.1 Sampling 2.1.1 General Information Guidelines for the monitoring of employee exposures to industrial atmospheres are given in Reference 11.8. The Federal requirements for monitoring employee expo sure to sirborne asbestos are found in 29 CFR 1910.1001. E.1.2 Mounting the Sampling Pump on the Worher Fasten the sampling pump to the worker's belt and fasten the field monitor to the lapel or shin front (as close to the breathing zone as is practical). Remove the top cover of the plastic monitor, then invert the monitor mahing certain ihe exposed flier is facing downward. Turn the pump on and adjust to the calibrated flow rate (1.0 to 2.5 1pm). Record the following information in a logbooh. 1. Filter number 2. Pump star: time end d2te 3. Flow rate A. Subjects name and job title - 5. Type of operation or process 6. Ventilation controls and is the worker wearing a respirator approved for asbestos? The pump should b: checked periodically during the sampling period for proper oper ation and flow rate. 8.1.3 Optimum Sempling Times The requirement for the minimum count of 100 fibers or 20 fields in S.3.9 was determined to be the best compromise to achieve adequate precision for the airborne fiber estimate and reasonable counting times. An optimum fiber density of about 1 to 5 fibers per microscope count field is recommended. To estimate appropriate sampling times foT feasible counting and optimal counting, one must consider the following constraints: 1. microscope count field area (generally 0.003 to 0.006 mm?) 2. pump flow rate (typically 2.5 1pm maximum) 3. average airborne fiber concentrations 4. counting rule range of 20 to 100 fields 5. adequate fiber density to obtain a minimum count of 10 fibers in 100 fields, which is the least total fiber count that yields an aeceptable count precision 6. background airborne particulate levels that can reduce the count precision due to an obscuring of fibers on the filter surface 239-7 Baron &. Budd Butler Count) Auaust I. 140" Tin preceding constraints were conjidered in drawing Frures 1 and 2. Thn: figures were developed from the following relationship: sampling time (FB/FL) (ECA/MFA) (FR) (AC) 0000) minutes where: FB/FL - 1 lo 5 fibers/field CA effective collecting area of filters (855 mm* for 37-mm fiiltcr with effec tive diameter of 33 mm) MFA " microscope field area (generally 0.003 lo 0.006 mm*) FR Pump flow nte (generally 1.0 lo 1L5 1pm) AC Air concentration of fibers in fiben/on*. Figure 1 (microscope field area 0.003 mm*) and Figure 2 (microscope field area 0.006 mm*) show optimum and feasible aampling times for a pump flow nte of 1.7 1pm. Each individual responsible for sampling asbestos should prepare a similar chart for his particular pump flow rate and microscope field area before sampling is per* formed to aid in estimating proper sampling times. On Figures 1 and 2. the areas with solid shading lines are generally the optimum conditions for counting. The broken shading lines are for conditions very close to optimal. However, feasible counting conditions may extend down to about 0.1 fiber/field and and above 5 fibers/field. Recommended aampling times are most strongly influenced by background airborne paniculate levels, once all the other constraints have been estimated. For heavy paniculate levels, it may be necessary to limit each filter to about 60 to ISO minutes sampling duration. Each individual responsible fe: sampling ahculd work closely with the microscopist to attain as high as possible filter surface fiber densities (up to about 5 fibers/field), while avoiding filter surface background particular levels that create very difficult or impossible counting conditions. If cr.e hav very little idea of airborne fiber and particulate levels, the best procedure is to take several long samples (as cr.e S-hour or two consecutive 4-hour samples) if. con juration with several shon samples (as four consecutive 2-hour c: eight consecutive 1-hou: samples). If the longer samples prove very difficult to count, the microscopist will have the shorter samples to fali back on. From. Figures 1 and 2, it car. be seen that there are certain aampling times which will yield optimum fiber densities on the filler for almost all airborne fiber concen trations from 1 to 10 fibers/cmh Tr.tse optimum times have been calculated and are presented in Figure 4. Note that the optimum times given by Figure 4 are approxi mate and can be varied by as much as d: 25Sc. The nomogram is intended as a guide to be used where no prior knowledge of the air concentration is available. 8.1.4 End of Sampling Period Remove the field monitor, replace the plastic top cover and the small end caps, and - store the monitor. Always shut off the pump when changing monitors to avoid contaminating or damaging the pump. Record the pump shutoff time and flow rate in the logbook. 8.1.5 Blanks With each hatch (25 to 50 filters) of samples sen* for analysis, submit two unopened field monitors which have been subjected to the same treatment as the samples except that they were not exposed to the sampling environment. Lnbcl these as blanks. If the blanks yield fiber counts greater than 5-fibers/100 fields, then the entire sam pling procedure should h: examined carefully for the cause of contamination. The 23V-X Baron & Budd Butler County Aueust 1. 1W mounting wluiica of Section 1.2.1 should also be eaumioed for contamination and/cr crystal growth. 8.1.6 Shipping The field monitor; in which the samples are collected should be shipped in a rigid ' container with sufficient packing materia! to prevent crushing. 8.1.7 Numbers of Samples When sampling for the Federal ceiling standard of 10 fibers (>5>*m)/cm\ (29 CFR 1910.1003(b) (3), effective July 7, 1972], only one simple (15 minutes maximum duration) is necessary, theoretically. However, seven! samples should be taken during expected periods of peak air concentrations to allow for detection of gross sam pling or counting errors. When sampling for determination of noneomplianee with the Federal 8-hour TWA standard of 2 fibers (>5>tm)/cm\ (29 CFR 1910.1001(b) (2)], one should contin uously simple as large a portion of the work day as is feasible for airborne concen trations of about 2 to 10 fibcrs/cm*. However, for a lower airborne concentration such as 0.5 fiber/cm\ one sample might require 4 to 8 hours sampling time is order to get the proper filter fiber density (Section 8.1.3). For tljis situation, the 8-hcur TWA exposure would be determined from one 8-hour or two 4-hour samples as ap propriate. 8.2 Semple Preparation 8.2.1 Preparation of Mounting Solution A very important par. cf the sample evaluation is the mounting process. This proc ess involves a special mounting medium of prescribed viscosity. The proper viscosity is important in order to expedite filter dissolving and still minimise panicle migration. After the sample has beer, mounted, an elapsed time of approximately sixty minutes is needed before the sample is ready for evaluation. Combine the dimethyl phthalate and diethyl oxalate ir. a on* to one ratio by volume and pour into a Wheaton balsam bottle. Add approximately 0.05 (= 0.0D5) grams cf new membrane filter per milliliter of solution to reaeh the necessary viscosity. The mixture must be stirred periodically until the filters have dissolved and a homogeneous mixture is formed. The normal shelf life cf the mounting solution is about three months. Twenty milliliters of mounting solution will prepare approximately 303 samples. 8.2.2 Sample Mounting Cleanliness is important! A dirty working area may result in sample contamination and erroneous counts. The following steps should be followed when mounting a sample. 1. Clean the slides and cover slips with lens tissue. Lay each slide down on a clear, surface with the frosted end up. It is a good practice to rest one edge of the cover slip on the slide and the other edge on the working surface. By doing this, you keep the bottom surface (the one which contacts the filter) from becoming contaminated. 2. Wipe all the mounting tools dean with lens tisstje and place them on a clean surface (such as lens tissue). A1J tools should be wiped clean prior to mounting each sample. 3. Using the glass rod supplied with the Wheaton balsam bottle, apply a drop of mounting solution onto the center of the slide. It may be necessary to adjust the quantity of solution so that after the eover slip has been placed on top. the solu tion extends only slightly beyond the filter boundary. If the quantity is greater than this, particle migration may occur. 239-9 /t Baron A. Hu..\J Butler (. , .., Auuu.r | i 4. Using another glass rod, spread the mounting media faro a triangular shape. The size of this triangle should coincide with tlie dimension of the filter wedge. 5. Separate the middle and bottom sections of the field monitor case to expose the filter. Cut a triangular wedge from the center to the edge of the filter using the scalpel.* The size of the wedge should approximate one-eighth of the filter surface. The filter can be very carefully removed from the cassette for cutting, but this should only be done with great care.. 6. Grasp the filter wedge with the tweezers on the perimeter of the filter which was clamped between the monitor case sections. Do so: touch the filter with your fingers. Place the wedge, sample side op, upon the mounting medium. 7. Pick up a clean cover slip with tweezers and carefully place it on the filter wedge. Once this contact has been made, do not reposition (hr cover slip. S. Label the slide with the sample number and current date before proceeding to the next filter. On the bottom (backside) of the slide, trace the perimeter of the filter wedge with a felt tip marking pen. This will enable the counter, after the filter has become transparent, to stcy within the filter perimeter when counting. 9. The sample should become transparent within fifteen minutes. If the filter appears cloudy, it may be necessary to press very lightly cr. the cover slip. This is rarely accessary; however, counting should no: be started until an hour after the mount ing. This allows the microscopic texture of the filter to become invisible to micro scope viewing. 3D. Disrzrd the sample mount after two days if it has not been counted. Crystals appearing similar to asbestos fibers may begin to grow at the mounting media/air interfaces. They seldom, present ar.y problems if the slide is examined before two days. In any case, stay away from the filter's edges when counting and sizing. 3 Courting of Fibers 2.3.1 Pia: e the slid: or. the me chzr.i czl stage c f the micrcsccpr and position the center of the wedge und :: th: obj: :ti\e ler.s and f ecus upon th: sample Star. cour. ting from enr end of the wedge and P-0 ress along a radial lin: to the ether end (count in eith:*r direction from peri rr.::er to wedge tip). Random fields are selected , without look ing into th : eyepieces by slightly ad van.ring the si de in one direction with the mechanical stage control. 233 It is essential to continually scan over a range of focal planes (generally the upper 10 to 15 micrometers of the filter surface) with the fine focus control during each field count. This is especially necessary for asbestos fibers due to their impaction into the filter matrix. 233 On most airborne samples, asbestos fibers will generally have fiber diameters less than one micrometer. Therefore, it is necessary to look carefully to: faint fiber images. 23.4 Regularly check phase ring alignment. 233 When an agglomerate (mass of material) covers a significant portion of the field of view (approx 1/6 or greater) rejeet the field and select another. (Do not include it in the number of fields counted.) However, report the fact as it mzy have meaning * on other data collection. 23.6 Bundles of fibers arc counted as one fiber unless both ends of the fiber can be dearly resolved. 23.7 Count only fibers with a length to width ratio greater than or equal to 3:1. 23.5 Count only fibers greater than 5 micrometers in length. (Be as accurate as possible in accepting fibers near this length.) Measure curved fibers along the curve to esti mate the total length. 235-10 i >I :I ,,I lI l 1I ii i i ! : i !i ! *i ii t i !l ! u I I: ., i! i; i: . i. i? .. i . I:; Baron & BuJd Butler Comm Aucust I. IvV F.3.9 Count as many field; at necessary (o yield a toUl count of at leas: IOO fiber;. Ex. eeptions: a) count a: least 20 field; even if you count store than 100 fibers, and b) step at 100 held; even If you haven't reached 100 fiber;. .3.10 For fiber; that cross either one or two tides of the counting field, the following pro cedure is used to obtain a representative count. COUNT any fiber greater than 5 micrometers in length, that lies entirely within the counting area. COUNT as **k5 fiber" any fiber with only one end lying within the counting area. DO NOT COUNT any fiber crossing any two tides. Reject and do not count all other fibers. Refer to Figures 5 through 10. Note that the fibers in Figures S through 10 are not representative of the appearance of most as bestos fibers. Most fibers have a very faint image. 9. Calibration and Standards 9.1 Sampling Train Calibration The accurate calibration of the sampling pump it essentia! to the correct calculation of the air volume sampled. The frequency of calibration b dependent on the use, care, and hand ling to which the pump is subjected. Pumps must be recalibrated if they have just been repaired, misused, or received from the manufacturer. If the pump receives hard usage, more frequent calibration may be necessary. Ordinarily, pumps should be calibrated in the labora tory both before they are used in the field and after they have been used to collect a large `number of field samples. The accuracy of calibration is dependent upon the type of instrument used as a reference. The choice of a calibration instrument will depend largely on where the calibration is petformed. For laboratory testing, a 1-liter buret used as a soap bubble flow meter or wet-test meter is recommended. Other standard calibrating instruments, such as a spirometer, Mar riott's bottle, or dry gas meter can be used. The calibration should be of sufficient precision that the 95 Te confidence limits cn the flow rate are m 10% (95 5e of the flow rates will fall within ce 10% of the calibrated value). Instructions for calibration with the seep bubble flow meter follow. The sampling train used (pump, hose, filter cassette) in the pump calibration should be the same as the on: used in the field. 9.3.1 Check the voltage of the pump battery with a voltmeter both with the pump off and while it is operating to assure.adequate voltage for calibration. If necessary. chcrg: "! the batter)- to manufacturer's specifications. ' 9.1.2 Fill a beaker with 10 ml of soap solution. 9.1.3 Connect the filter cassette inlet to the top of the buret with a length of hose. 9.1.* Turn the pump on and moisten the inside of the soap bubble meter by immersing the , open end of the burr, into the soap solution and drawing bubbles up the inside of the buret. Perform this task until the bubbles are able to travel the entire length of the buret without breaking. 9.1.5 Adjust the pump rotameter to provide a flow between 1.5 to 2.5 ]pm. 9.1.6 With a water manometer, check that the pressure drop across the filter is less than 13 inches of water (about 1 inch of mercury). 9.1.7 Start a seep bubble up the buret and measure the time it takes for the bubble to travel a minimum volume of 1 liter. 9.1.8 Repeat the procedure in 9.1.7 at least three times, average the results, and calculate the calibrated flow rate by dividing the volume traveled by the soap bubble by the elapsed lime. If thu range between the highest and lowest of the three flow rotes is greater then about 0.33 ipm, then the calibration should be repeated sinee it is likely that the precision is not adequate. 239-11 Baron & Budd Butler Count) August I. 1W" 9.1.9 Data required for the calibration include the volume measured, elapsed time, pressure drop, air temperature, atmospheric pressure (or elevation), pump serial number, date, and name of person performing the calibration. 9.1.10 Correetioas to the flow rate for pumps with rotameters may be necessary if the pres sure (elevation) or temperature where the samples are collected (actual flow rate) differs significantly from that adhere the calibration was performed (indicated flow rate). Actual flow rates at time of sampling may be calculated for a linear scale rotameter by using the following correction formula: BA /^ y p*,i * T M1>) where both pressure (?) and temperature (T) are is absolute sails such as: psia " psig + 14.7 deg Rankin " deg Fahrenheit + 460 deg Kelvin deg Celsius + 273 9.2 Microscope Setup 9.2.1 Portcn Reticle and the Counting Field The asbestos fiber ecun: procedure consists of comparing fiber length to the diam eters of calibrated circles of a Porton reticle, and counting all fibers greater then - 5 micrometers in length lying within a given counting field area. The Porton reticle is a glass pf2tr inscribed with a series of circles and rectangles. The left half of the reticle is divided into six rectangles constituting the counting field. The counting field is illustrated in Figures 5 through 10. 9.2.2 Placemen: in Eyepiece The Porter, reticle is placed inside the Huygenian eyepieee where it rests cn the fieldlimiting diaphragm If other types of eyepieces ire used, it may be necessary to insert a counting collar for retaining the reticle. The reticle should always be kept clean, since dirt or. the reticle is in focus and could complicate the counting and siring process. 9.2.3 Stage Micrometer The Porton reticle cannot be used for counting until it has been properly calibrated with a stage micrometer. Most stage micrometer scales are approximately two millimeters long and are divided into units of one-hundredth of a millimeter (ter. micrometers). 9.2.4 Microscope Adjustment When adjusting the microseope, follow the manufacturer's instructions while observing the following guidelines. 3. The light source imege must be in fo:u> and centered on the condenser iris or annular diaphragm. 2. The particulate material to be examined must be in focus. 3. The illuminator field iris must be in focus, centered on the sample, and opened only lo the point where the field of view is illuminated. 4. The phase rings (annular diaphragm and phase-shifting elements) must be con centric. $2JS Porton Reticle Calibration Procedure Each eycpieec-objeciivc-rcliele combination on the microscope must be calibrated. Should any of th: three be changed (disassembly, replacement, loom adjustment, etc.), the combination must be recalibrated. Calibration may change if intcrpupillary dis- tance is changed. For proper calibration, the following procedure should be followed closely. With a 10X objeetive in place, place the stage micrometer on the mechanical stage, focus the millimeter scale, and center the image. Change to the 40-45X objec tive and adjust the first millimeter scale division to coincide with the kft boundary of - the Porton rectangle. Measure the distance between the left and extreme right bound aries of the Porton rectangle, estimating any portion of the final division. This meas urement represents 200 L units. The reetangle is 100 L units on the short vertical dimension. The calculated "L" is inserted into the formula D Lf2x)1'5 where *N" is the circle number {indicated on the reticle) and "D"* is the clrele diameter. Since the circle diameters vary logarithmically, every ether circle doubles in diameter. For example, circle number three is twice the diameter of number one; number four is twice the diameter of number two. When the circle sizes have been determined, the count ing field area which consists of the left six smaller rectangles can be calculated from the relation 10,000 L*. This completes the reticle calibration for this specific objective-eyepiece-retiele combination. Example for Porton Reticle The following calibration was obtained for a pair of 10X Huygenian eyepieces and a 43X objeetive: 200 L = 0.3 -4E mm = 1*8 micrometers 100 L 0.074 mm *= 74 micrometers One D-unit * 0.74 micrometers Thus Circle #1 h2s a diameter D = LP'T'5 * 0.74 C1)1'1 - 0.74 (1.414) = 1.05 micrometers. Then our circle diameter calibration table lool'.s like: Diameter of Circle #1 *= 1.05 micrometer* *2 = 1.4S #3 2.0? #4 = 2.95 *5 = 4.19 #6 = 5.92 Field area = (10,000) (L*) = (100 L) (100 L) - (0.074) (0.074) 0.0055 nr.! Thus fibers with a length greater than a distance halfway between the diameters of the #5 and #6 circles would be counted. If a Patterson Globe and Circle reticle is sued, a different calculation procedure is required. The circle diameters are related as follows. The #25 circle diameter is (0.1) (reticle length). The circle diameters are proportional to the ratio of their numbers. Thus the #20 circle diameter is (20/25) or 0.S times the #25 circle diameter. 30. Calculations 10.1 The average airborne asbestos fiber concentration estimated by the filter sample may be calculated from the following formula: , _ KFB/FI.) - (BFB/BFU) (ECA) (1000) (FR) (T) (MFA) .239-13 K`v.13.-e j i i Baron <fc Budd Butler Count) August 1. 1497 where: AC Airborne fiber concentriiion in (fibers > 5 *m)/em\ BFB m Tot! number of fiber* counted in the BFL field* of the blink or control filters in fiber* > 5 *m. BFL Totil number of fields counted on the blink or control filters. CA Effective collecting irei of filter (855 mm* for a 37-mm filter with cfieetive di ameter of 33 mm). FR m Pump flow rite in liters/min Opm). FB Toul number of fibers counted in the FL field* in fibers > 5 ^m. FL Total number of fields counted on the filter. MFA m Microscope count field area in mm* (generally 0.003 to 0.006). T Sample collection time in minutes. 302 Recount criteria. It is very desirable for a counter to conduct a "blind recount'* for about I in every 10 filter wedges (slides) counted. Alternatively, a second counter could perform the blind recount. In training sessions for nonce counter*, the trainee should conduct a blind . recount for filter wedge* counted by an experienced, proficient counter. In all eases, we will observe difference* between the fir*t and second counts of the sane filter wedge. Most of these differences will be due to chance alone, that is, due to the random variability (precision) of the count method. Statistical recount criteria enable us to decide whether observed dif ferences can reasonably be explained due to ehanee alone or are probably due to telematic differences between counters or microscopes or due to some other biasing factor. The following recount criterion is for a pair of counts that estimate some airborne fiber con centration (AC) in fib:rs/cr.:\ The criterion is given at the type-1 error level. That is, there is a 57c maximum risk that we will reject a pair of count* for the reason that one might be biased, when the large observed difference is really due to chance. Reject a pair of count* because one might be biased if: (AC, - AC,) exceeds 2.7/(AC)[CVlb) where: AC, = lower estimated airborne fiber concentration AC- *= higher estimated airborne fiber concentration AC average of the two airborne concentration estimelcs CVja = average CV fo' the two concentration estimates which are a function of the total fiber count (FB) in each cast. Use the relation in Section 4 or Figure 3. For r. pair of counts on the same filter, reject the pair because one might be biased if: (FB, - FB,) exceeds 2.77(FB)(CVTj where: FB4 * lower fiber count on the filter (total fibers) FB.. *= higher fiber count on the filter (total fiber*) FB average of the two totnl fiber counts CVri: CVT for the value FB. Use the relation in Section 4 or Figure 3. L Jleltrences JJ.l Lynch. J. 71., K. J. Kronovuter, and N. A. Lcidul, "Validity of the Poi**on Distribution in Dust Counting", unpub!i*hcd. 33.2 Wcitlner, R. B. and H. E Ayer, "Du*: Exposure in Asbestos Processing*", Transactions of the 239-14 I I j1 4: ;i , ti iI 1! : .` t * ` [i ; *V ilt1 lI i 1j I * ,' >. i' ii j.i i, -l 1 Baron iV BuUJ Butler Count'Auuu>t 1. i'1'' American Conference of Governmental Industrial Hygienists, May 1972, pp. 103-221, San Francisco, California. 11.3 Conway, R. E. and W. D. Holland, "Statistical Evaluation of she Procedure for Counting Asbestos Fibers on Membrane Fibers", LFE Corporation, Richmond, California. Prepared for the Asbestos on Membrane Assoc/North America, Hew York, 1973. 31.4 Leidel, N. A. and K. A. Busch, "An Evaluation of Phase Contrast Microscopes for Asbestos Counting", presented at the 1974 American Industrial Hygiene Conference, Miami Beach, Florida, May 18, 1974, unpublished. lli Beckett, S. T. and M. D. Attficld, Tnter-Libcratory Comparison of the Counting of Asbestos Fibers Sampled on Membrane Fillers", Ann Oceup Hyg 17:85*96, 1974. 11.6 Rajhans, G. S. and G. M. Brag:. "A Statistical Analysis of Asbestos Fiber Counting fa the Laboratory and Industrial Environment", Am Ind Hyg Assoc J 36(32):909*915. 1975. 11.7 Leidel, N. A. and K. A. Busch, "Statistical Methods for the Determination of Honcompli* ance with Occupational Health Standards", NIOSH Technical Publication 75*159, 1975. 11.5 Leidel, K. A., K. A. Busch, and J. R. Lynch, "Occupational Exposure Sampling Strategy Manual", KIOSH Technical Publication 77*173, 1977. 11.9 Leidel, N. A., K. A. Busch, ar.d W. E. Crouse, "Exposure Measurement Action Level and Occupational Environmental Variability", NIOSH Technical Publication 76-131, 1975. 31.10 Comments of the Johns-Manville Corporation with Respect to the Notice of Proposed Rule making: Occupational Exposure to Asbestos, Federal Register, October 9, 1975. Submitted to the public record a: the U. S. Department of Labor, Occupational Safety and Health Ad ministration, April 1976: 31.11 Leidel. N. A.. S. G. Bayer. R. D. Zumwalde, and K. A. Busch. USPHS/NIOSH Membrane Filter Method for Evaluating Airborne Asbestos Fibers, to be published by NIOSH in 1577. 31.12 Needham, G. H., The Practical Use of the Microscope, Charles C. Thomas Publishing Corporation, Springfield, Illinois, 1958. 31.13 Clark, G. L., The Encyclopedia cf Microscopy, Rheinhold Publishing Corporation, New York, 1561. 11.34 McCrene. W. C. and J. G. Drily. I. The Particle Atlas, Edition Two, Ann Arbcr Science Publishers, Inc., Ann Arbcr, Michigan, 1573. 239*15 Baron & Budd Butler Counts August I. I oo' M V C .N / O t. M L)C .IU > M-< U t-L M lM | M it t ti i <1 I 11 . 1 1. s : l ; i; ir !i 11 1 1: t; i- < CURZ X. Optimum Samplir Times (or Airborne asbestos where microscopic field area 0.003 sum* 239-1C . I: ii : i! . Baron & BnJJ Butler Couniv Aumtst 1. luu? Br"n * t- 0.40 8 oo 8 L i / / too o o o6 /O'NOUVIHtA JO 1K3S0UJ300 "IVlOl 239-1B ow> oe u. i z 3 O o c VJ o oI o rj Lb J~c o o n c9 *5 'C E s 5 u c => 15 C ii iI I* II i ! ;! I ; `<t l I ;I : !! i Baron & Bull'd Butler C oum\ August I. |w~ FIGURE 4. Noninfi.im of optimum unmpfin^ lim n for nlrbomt mbnfo flb m In toner nfr.illoiw of 1 lo 10 fib m /c m ' ,M3\u ` trt 01313 330DS0U01H - V w' ^ 'y ^ ^ y" lititl|iiil.iil!ntili.iilinilj IM t [ i I l> i I 1 l t 111 t 1 E/ Orj w oE. E Ld s E CJ UJ --1 roo> o 6 I-' sm tN o +i a. 5 < X tiJ < o < UJ c: T" t--i--j--i--tt--i" : I-1 i t--]--r--1--i--r i i i i i j--i--j j j j to rsj Mjnutuj`awn ONndWVS/WnWIldO r Jll n CSI \j i--i--r *n *31VH M013 dwnd- UJ 239-19 Baron HnJd Butler C.hiiv. Auausi I. I-I'/' IJCURE 5 'I i: ( i 1 I3CURE 9 239-20 1I iI >4 Baron &. BndJ Butler Count;. August I. loo' LIST OF FIGURES (5 through 10) FI CURE 5- DO NOT COUNT. Fiber crosses to; cad bottom tides. FICURE 6. COUNT. Oae fiber. FIGURE 7. .COUNT. One-half fiber. Fiber crosses left side cad oae ead lies within count am. FIGURE 8. COUNT. One-haU fiber. Fiber crosses bottom tide cad eae cad lies within count area. FIGURE 9. DO NOT COUNT. Fiber crosses two sides. FIGURE 30. DO NOT COUNT'. Fiber crosses two sides (bottom left comer). COUNT. One-half fiber. Fiber crosses bottom tide tad oae cad lies within count cm. COUNT. One fiber (top xi^ht corner). 239-21 Baron & BudJ Butler Counn Ausust 1. W ATTACHMENT B REPRESENTATIVE WE1ENT-AIR ASBESTOS CONCENTRATIONS Baron & BuJJ Butler Count' August I. 144" Representative Ambient-Air Asbestos Concentrations Location New York Washington Hi ami Cl eve!and Denver San Francisco Spokane Fibers/cc 0 0.0022 0.0027 0.0067 0.0041 0.003S 0.01S4 Baron & Budd Butler Counn \ August I. |w~