Document oeedYodD50ZXXrk2VLqEeOqKE

FILE NAME: Union Carbide (UC) DATE: 1977 Aug 15 DOC#: UC078 DOCUMENT DESCRIPTION: Appendix to the Testimony Presented to the Commission by Harrison B. Rhodes RE Plan to Ban Certain Patching Compounds APPENDIX to the Testimony Presented to the Commission by Harrison B. Rhodes on August 15, 1977 Regarding 16 CFR Parts 1304 and 1305 RESPIRABLE FREE-FORM ASBESTOS Proposal to Ban Certain Patching Compounds and Artificial Emberizing Materials (Embers and Ash) Union Carbide Corporation Metals Division Niagara Falls, New York August 29, 1977 14302 aos BBffi m -- i SUMMARY AND CONCLUSIONS This report presents and compares all of the known data on asbestos dust exposure levels during commercial and consumer drywall installation operations. The following conclusions regarding consumer usage have been drawn from the data. -' : 1. Consumer exposure during drywall installation can reasonably be expected to be approximated by the range of 0.5-1.5 f/cc* during dust generation operations. 2. The corresponding 8-hour time-weighted average (TWA) exposures are only several tenths of a f/cc. 3. Residual household exposure after drywall installation is less than 0.01 f/cc which falls within the NIOSH description of ambient levels. * f/cc means asbestos fibers greater than five micrometers in length per cubic centimeter of air. TABLE OF CONTENTS Section INTRODUCTION ANALYTICAL METHODS AND LIMITATIONS PRESENTATION OF DATA Commercial Applications Rohl et al Rhodes and Ingalls Equitable Environmental Health and OSHA Compliance Data Consumer Applications. Union Carbide - Spackling andDrywall Replacement Union Carbide - LargeRoom DrywallInstallation DISCUSSION OF RESULTS Commercial Operations Consumer Operations CONCLUSIONS Page i T 1 2 2 3 5 7 8 9 10 11 1 ASBESTOS EXPOSURE IN DRYWALL INSTALLATION INTRODUCTION This document is the Appendix referred to by Dr. Harrison B. Rhodes in the testimony before the Consumer Products Safety Commission on August 15, 1977, in the matter of a "Proposal to Ban Certain Patching Compounds and Arti ficial Emberizing Materials (Embers and Ash)." It provides'the:technical support for Figures I and II that were presented to the Commissioners at that time. - 1- ANALYTICAL METHODS AND LIMITATIONS All of the exposure data to be presented will be in expressed terms of fibers/cubic centimeter longer than 5 micrometers as measured by the optical phase contrast procedures developed by NIOSH. This is done of necessity because the data were measured in these terms and most of the health data to which the results must be related are expressed in the same manner. , . The NIOSH procedure has a number of recognized problems which include: 1. The inability to distinguish asbestos fibers in an unambiguous manner from other non-asbestos particulate matter which meets the criteria for a fiber, i.e., a length greater than 5 micro meters and a 1ength-to-diameter ratio greater than 3. 2. Limitations on sample time due to the presence of other dust in the air which preclude collecting sufficient asbestos on the filter to meet the criteria for reliable counting. 3. A decrease in empirical precision as the airborne concentration to be measured decreases. All of these problems exist to varying degress in the data to be presented and will be referred to as data from different investigators are compared. It should also be pointed out that in several studies exposures from zero to several tenths of a fiber per cubic centimeter longer than five micrometers were found. Since these levels are in the same range and are compared to ambient background it is relevant to quote NIOSH on ambient levels to provide a proper frame of reference. Thus: "Only a few studies of ambient levels have been performed using phase contrast optical microscopy. These studies indi cate ambient levels to be generally less than 0.01 fibers >5 -j pm/cc, with some peak values as high as 0.03 fibers >5pm/cc." (Emphasis added.) PRESENTATION OF DATA The data to be presented are contained in five reports: 1. The tests conducted by Rohl et al 123 at one location in New York, Nv . This is the data cited by the petitioners. . 2. A survey of a variety of sanding conditions made by Rhodes and Ingalls 3 and cited extensively by the .Asbestos Information Association/North America in their response to the petition. ` 1. Re-Examination and Update of Information on the Health Effects of Occupational Exposure to Asbestos. U.S. Dept, of H.E.W., December 1976, p. IV-18. 2. Rohl et al, Science, Volume 189, August 15, 1975, p. 552. 3. G.D.C.I. Drywall, January/February 1976. - 2- 3. Data from State and Federal OSHA compliance inspections com piled by Equitable Environmental Health Incorporated as part of a study of asbestos exposure in the construction industry. 4. A report submitted to the CPSC by Union Carbide Corporation on July 14, 1977, covering consumer exposure during a typical spackling and a moderate size drywall installation operation. 5. A study by Union Carbide of a consumer installation of a large room including the ceiling. The results of each investigation will be summarized in this section. Comparisons of the results of the several investigators will be made in the following section, "Discussion of Results". Commercial Applications Data of Rohl et al The data presented by the petitioners was that of Rohl, et al which is summarized in the'table below: AIRBORNE ASBESTOS FIBER CONCENTRATIONS SANDING, DRY-MIXING AND SWEEPIN?4 ' O p eratio n s P o tc -sa n d in g ( l to 1.5 m ) B a c k g ro u n d (2.5 m ). sa m e ro o m ' B a c k g ro u n d (7.5 m ). a d ja c e n t ro o m H a n d - v jn d i n g ( | to 1,5 m ) B a c k g ro u n d (2.5 m ), sam e rco m B ac k g ro u n d (4.5 m ). a d ja c e n t ro o m D iy m i. in j(l to 1.5 m ) B ack g ro u n d (3 to 6 m ), sam e room B ack g ro u n d (5 to 10 m ). a d jacen t room S w ee p in g floor (3 to 15 m ) 15 M in u tes a fte r sw eeping 35 M in u tes a fte r sw eeping H um ber o f sam ples 10 3 2 n 2 2 2 3 2 1 1 P eak fiber co n cen tratio n (fibers per m illiliter) M em 10.0 3 .6 4 .8 jj 2 .3 4 .3 4 7 .2 5.8 2 .6 R ange 1.2 t o 19 3 3.5 to 19.S 0.7 t o 8.8 1.3 to 16.9 2.1 to 2.5 1.5 t o 7.1 35.4 to 59.0 0 .5 to 13.1 2 . l t o 3.1 4 1 .4 2 6 .4 No details are provided on the nature of the operation sampled, i.e., whether it was run as a specific test or as the sampling of a routine commercial installation, the asbestos content of the mud, the number of men sanding in a room, the size of the room or rooms sanded, or the presence or lack of ventila tion. There is no way to evaluate the influence.of the specific test conditions on the results reported or to determine how they may relate to other commercial operations. The tests also appear to cover a total sanding time of no more ' than 15 minutes for pole sanding and about the same time for hand sanding. It can be questioned whether this is a representative sample of commercial operations. Regarding analytical methods, it was stated that the NIOSH procedure was used for optical measurements. The lack of any qualifying statement indi cates that all particles which met the length greater than 5 micrometers and 4. A. N. Rohl, A.M. Langer, I.J. Selikoff and W. J. Nicholson, Science, Volume 189, August 15, 1975, p. 552. - 3- L/D ratio greater than 3 were counted without any attempt to correct for non asbestos particulate as permitted under the "other information" provision in the method. It was also stated that for every fiber visible by light microscopy "... there were from 200 to almost 1000 that could be seen only at electron microscopic magnifications of X25,0Q0." * ^ No procedural details on the electron microscope method are provided nor are data presented on the actual size distribution, or the proportion of particles that were chrysotile and the proportion that were amphibole chips. It will only be noted here that the biological significance of particles that are so short that they can only be seen at magnifications of 25,000X is a very controversial subject at this time and is not directly relevant to the avail able commercial exposure data. Data of Rhodes and Ingalls Subsequent to the work of Rohl just cited, Rhodes and Ingalls^ conducted a study of asbestos dust levels during sanding at seven locations throughout the United Statps. This work was done at the invitation of the Gypsum Drywall Contraxtors International who assisted in the selection of jobsites to represent the range of sanding conditions normally encountered in industry. All samples were collected during routine commercial operations and in most cases the man doing the sanding was not aware of the details or purpose of the test. The results for these samples, plus a later test at Denver, CO, by the same investigators, are summarized in the following table. (Note that at one location, Minneapolis, MN, an "asbestos-free" mud was used.) 5. G.D.C.I. Drywall, January/February 1976. 4 imohm rsTcs n;r eoxctim n o is puamG s a s j INj o f t a p -j o i m c c x ?o :b Structure K w torli City, ht High rise apt. building. Windows open, light breeze. 13, 14, 15th Story. Humid -j$0ft.2 of floor area per apt. Ft. Lauderdale, FL Condominium apt. bldg. Windows in and goner* ally closed, little breeze. Hialeah, FL Condominium apt. bldg. Windows in and gener ally closed, little breeze. Sallas. TX Single level residen tial dwelling. >-2000 ft.2 floor area. Win dows in ar.d closed. Niagara Falls, NY Remedied office. W x l C W No ventilation. Detroit, MI Multilevel residential dwelling. ~ 3 C 0 0 ft.2 of floor area. No ventilation. Minneapolis, KN Two-level residential dwelling. -23C0 ft.2 of floor area. Moderate ventilation. Denver, CO Two-story medical bldg. Two-story hall, cany snail rooms. Rain, no ventilation. TJC Definition App. Tool Tvo# T ^ r- Hand Genera! Purpose, Pole & Reaoy-Mix Hand Ames General Purpose, Pole Ready-Mix Hand Ames Genera! Purpose, Pole Ready-Mix Ames General Purpose, Pole Ready-Mix Hand Genera! Purpose, Hand Reaay-Mix Ames Topping Compound,.Pole Dry Mix Ases Topsing Compound,, Pole D r y - Mix Asbestos Free Hand Ready-Mix to bury tape. Non asbestos ReadyMix Topping. Pole Sardine Definition Va 11 s Ceiling Description Str.p!e Definition Total Sample nre (Hrs.) No. Samples X X Finishing touch- 5 J 5 Personal up operation by ' 1 Area tapers. Scraping, sandirg (generally light) l filling. S P4 crew, 1 nan/roon. X X Steady sanding by 1.5 7 Persona! laborer. 10-15 7 Area r.inutes to complete 1 B.P.. apt., -'SCO ft.2 of floor area. X - Spot sanding bad 0.5 2 Personal areas. X Steady sanding by 1 2 Personal laborer. 15-20 1 Area minutes to do a 3-5 room apt. X X Steady sanding by 1 4 Persona! 2 laborers. 30 1 Area (after) r.inutes to do com plete house. X One man, heavy 0.6 3 Persona! sanding. X X Steady sanding by 4 8 Persona! laborer, ^ 4 hours 1 Area to complete. X X Steady, heavy sand- 4 6 Personal ing. 1 man -4 hours 3 Area X X One man, moderate 3 3 Personal sanding. -~30 mins. 2 Area Airborne Asbestos Fiber Concentration (r lers.'C C > V i ) fiance Aver*; lU o o 0.1-C.4 0.2 I .3-3.4 1.8 0,3-1.5 0.3 0.8-1.1 1.0 0.6-1.0 0.8 .6 0.6 0.6-1.8 1.1 0.1 0.1 2.3-3.6 2.5 .6-1.3 1 .0 0.5 o .s 0.2 0.2 0.1-0.4 .2 0.2 0.2 w <r O C3 o o o When the large differences between the two studies became apparent, filters from three locations were counted "blind" by two other laboratories. The results shown below demonstrate that the differences were not due to improper counting by the authors of the work. INTERLA30RAT0RY COMPARISON ASBESTOS FIBER COUNTS Sample Source Location I II * (Filter (Filter #2) Location II 1 (Filter # D (Filter #2) LocatUion III (Filter (Filter 51) #2) Airborne Asbestos Fiber Concentration _____ (Fibers/cc longer than Sum) By UCC By Lab A B.y Lab B 0.4 0.3 * 0.2 0.4 0.0 0.2 1.5 1.0 1.6 1.3 1.0 0.6 0.6 0.0 0.9 0.4 0.2 0.2 - 5- _ The concentrations just described were obtained during the actual sanding operation. In virtually all cases, even the commercial operators do not sand for a full shift so that the 8-hour time-weighted average will be considerably less than the exposure while dust is being generated. Values for the sanding conditions in the 8-hour time-weighted average in this study are shown in the table below. Note that the highest TWA value obtained was 0.9 f/cc. , , SUMMARY OF AIRBORNE ASBESTOS FIBER CONCENTRATIONS DURING DRYWALL SANDING Location New York City, NY Hialeah, FL Ft. Lauderdale, FL (Hand) Detroit, MI Dallas, TX Ft. Lauderdale, FL (Pole) Niagara Falls, NY Ceiling Exposure (Fibers/cc >5ym) 0.4 1.0 1.1 1.3 1.8 ' 3.4 3.6 Exposure Tima During Sanding (Hours) 8.0 4.0 1.0 8.0 0.5 3.3 0.6 Estimated 8-Hour TWA Exposure (Fibers/cc >5:Jm) 0.3 0.4 0.1 0.9 0.1 0.6 0.2 Equitable Environmental Health and OSHA Compliance Data There is another source of exposure data which is particularly relevant, that obtained by OSHA compliance inspectors. The Asbestos Informa tion Association/North America has engaged a contractor, Equitable Environmental Health, Inc. to study asbestos exposure in the construction industry. As part of this project they obtained a fairly substantial body of data from several State and Federal compliance offices. The OSHA results for the sanding opera tion plus data from a test that was run directly by EEH are summarized in the following table: - 6- AIRBORKE ASBESTOS FIBER CONCENTRATIONS DURING SAN31HG OF TAPE-JOINT COMPOUNDS^) icaticn Structure TJC Definition App. Tool Tvoe DATA FROH OSHA COMPLIANCE INSPECTIONS^) A - - Ready-mix Pole F * * Pole H ** " --------------- - DATA FROH EQUITABLE ENVIRONMFNTAI HEALTH. INC. Sardine Defiririon ' X X - - " - - - Apparently 3 men sanding. - - - Sanole Definition total Time iJ,rs i !.o, Samples Ai room e Asbestos fiber C: ncer:r-tiof (Fibs' s/;c >:,,) Rd.-.ce A.ere ;: 0.5-2 0.7 1.2 8 Personal 4 Area 1 Personal 9 Personal 3 Personal 1.5-5.0 1.0-10.C) 0.1 0.3-1.5 Q.2-0. -- --------- -- -- -- . ,<2) i:w 0.1 0.7 U .T CO One story annex to existing building. * Non-asbestos Pole - X for tape, fin Heavy sanding. 0.5 1 Personal 0.2 C .2 ished with One man on stilts. 2 Area 0.1 0.1 asbestos- containing. M * Non-asbestos Pole - X " throughout. 0.5 1 Personal 0.1 C 1 1 Area 0.1 QA 1- Supplied to Equitable Environmental Health, Inc not identified. as part of a study of asbestos exposure in the construction industry. Specific loc. ions 2. Includes all particles L/D >3 L>5W is available. Estimated by TEH proceeding to be about 50-701 chrysotile plus amphibole. Ho split on relative ar.o<-r.Ls Although sample collection details are limited for the OSHA data, it should be noted that at location A it appears that a three man crew was sanding together and moving from room to room. It was reported that the optical fiber counts included all particles which met the criteria, but a representative sample v/as analyzed by TEM procedures and the particulates in this size range counted optically were 50-80% chrysotile and tremolite. No breakdown of the relative amounts of the two was available. A figure of 70% was used to correct the data for asbestos content for graphical presentation in Figure 1. It should also be noted that the area sample in this study that showed 10 f/cc was collected directly below the place where a ceiling was being sanded while receiving c heavy stream of dust. In addition to this sanding data, EEH was able to obtain OSHA results for the wet-out of dry-mix TJC and for a similar material, spray texture paints. Data for cleanup after sanding and texturing operations were also available and are summarized in the following table: - 7- Location B C E G H AIRBORNE FIBER CONCENTRATIONS FROM OSHA COMPLIANCE INSPECTIONS 0 ) OURING WET-OUT OF DRY PRQOUCT ANO CLEANUP AFTER SPRAYING OR SANDING Product Identification All purpose TJC Spray Texture'(21' Spray T e x t u r e ^ TJC TOC (Morter) Operation Wet-out at M N M Samp!e Ceiling Time Concentration (Min.) F-ibers/cc >5y 10 5.4 10 4.4 20 4.9 2 4.0 - 2.7 0 TOC TJC H TJC Sweeping 15 2.7 M , 15 2.5 M M 15 2.0 30 0.9 SweepingM and Scraping 1155 01..65 II 15 1.6 Sweeping 0.6 1. Supplied to Equitable Environmental Health, Inc. as part of a study of asbestos exposure in the construction industry. Specific locations not identified. 2. Spray texture compounds are generally similar in composition to dry-mix tape-joint compounds with texturing material added. Consumer Applications . Union Carbide Corporation - Spackling and Drywall Replacement On July 14, 1977, Union Carbide Corporation submitted a report to the Consumer Product Safety Commission covering asbestos exposures in a home during spackling and the installation of about 12 feet of drywall by a con sumer. Since a copy of the report is available to the commission only the key points need to be included here. To quote from the Summary and Conclusions "Residual asbestos exposure in a two-story residential structure that resulted from two prior consumer uses of asbestos-containing tape-joint compound was measured. Asbestos . exposure during and after a consumer spackling and drywall renovation job was also measured. This job consisted of exten sive spackling in one room and removal and replacement of approx imately three 4' x 8' panels of drywall. - 8- Samples were collected on Millipore filters and counted by optical phase-contrast microscopy in accordance with the March 30, 1977, edition of the NI0SH-0SHA method (P & CAM 239). The absence of significant numbers of short and/or narrow fibers not visible optically in the samples was verified by scanning electron microscope techniques at magnifications of 1 ,500X and to a limited extent at 15,C00X. - The results showed that residual asbestos exposure was somewhat less than 0.01 fibers/cc >5p and was not changed appreciably by the present test. It is questionable whether this is really different from the natural background. The combined spackling and drywall renovation operation tested gave a maximum, one-day time-weighted average operator exposure of about 0.3 fibers/cc longer than 5y and a maximum ceiling exposure (10 minutes) of 0.5 fibers/cc >5p. Considering the size of the area renovated, these values are consistent with \alues of 1 - 4 fibers/cc >5y that have been reported for commercial sanding operations where entire series of rooms (including the ceilings) are sanded in sequence.''' Union Carbide Corporation - Large Room Drywall Installation Union Carbide Corporation has also conducted a study of asbestos . exposure during the installation of drywall by a consumer in a large room. A complete report is included with this presentation to the Commission so only the Summary and Conclusions will be presented here. "Asbestos exposure during and after consumer installation of drywall for the finishing of a 12' x 24' basement recreation room was measured. Nineteen panels of wall board, each 4' x 8', were required to cover three walls and the ceiling of this room. About 80 pounds of ready-mix taping compound containing 1.75% by weight asbestos as manufactured and 2.6% by weight when dry was used. Personal and area samples were collected throughout the installation using 0.8p porosity Millipore filter and pre-calibrated MSA pumps. The filters were mounted and counted by optical phase contrast microscopy in accordance with the latest, March 30, 1977, draft of the NI0SH method (P & CAM 239). The maximum ceiling exposure for any of the operators was 1.3 f/cc which occurred during cleanup after sanding. Eight hour time-weighted average operator exposures ranged from 0.1 to 0.2 f/cc with an overall average of 0.2 f/cc. General area exposure levels did not exceed 0.1 f/cc on an 8-hour ` time-weighted average basis in the work area (cellar) or 0.02 f/cc in the living room. A general house survey on the day after the job was completed showed that all values were well below 0.01 f/cc and had not been changed appreciably by the present installation. It is questionable whether this is different from the ambient background." - 9- DISCUSSION OF RESULTS Commercial Operations . The airborne asbestos fiber concentrations obtained in the operator's breathing zone during sanding for all of the references cited are shown graph ically in Figure 1. Similarly, the data for the wet-out of, dry.powder and for cleanup after drywall installation operations are shown in Figure 2. , Examination of Figure 1 shows that the commercial data from the OSHA compliance samples, from EEH, and from Union Carbide generally fall in the same range of several tenths to about four f/cc whereas the data of Rohl et al appear to be substantially different and much higher. As noted previously, the Rohl article does not provide sufficient information to relate the condi tions used to those of the other studies but the following points based on extensive experience in this application are offered as a possible explanation: 1. It is well known that short samples give erratic results. This is in large part due to the combined effects of non uniformities in the airborne concentration being sampled and in the deposition of fibers on the filter. The Rohl data which appear to be 1-1.5 minute samples are an excellent illustration of this, i.e., 10 pole-sanding samples ranged from 1.2 to 19.3 f/cc and 11 hand-sanding samples showed 3.5 to 19.8 f/cc. With this kind of variability it is most useful to look at the mean values of 5.3 and 10 f/cc for hand and pole sanding respectively. 2. There is little doubt that the Rohl data include an unknown fraction of particles which are neither chrysotile nor amphibole. If the 20 to 50% figure found by one of the OSHA laboratories using TEM techniques is applied the mean values decrease to the range of 2.7-5 f/cc for a 50% correction and 4-8 fibers/cc for a 20% reduction. Any remaining differences, which are now not large, could be due to the sanding proce dures, and the configuration and ventilation of the rooms where the tests were conducted. _ The commercial wet-out and cleanup data in Figure 2 show even wider differences between the Rohl study and the OSHA compliance data. There is insufficient information to even suggest the reason for such differences, but it is believed that the OSHA data from a total of 8 locations can be taken as the most representative of regular commercial use. - It can be concluded from the data presented that operator airborne asbestos exposure during regular commercial drywall operations varies widely but generally falls within the range of several tenths to about four f/cc. ' Since the dust generating operations normally occupy only a moderate portion of the working day, the corresponding 8-hour time-weighted average exposures will generally be less than 1 f/cc and usually substantially less than this figure. - 10- Consumer Operations The data for the two consumer installations given on the Figures shows that the large, full-room job gave higher levels than the replacement of one wall. In both cases the exposures during the dust generating operations fell in the lower end of the commercial range, i.e., several tenths to less than 1.5 f/cc. , . # There was an apparent misunderstanding at the hearing of the descrip tion of the counting procedure which we used to obtain these results. It should be reiterated and emphasized that: 1. The procedure used conforms to the NIOSH requirements. 2. It is biased to provide a high count for both chrysotile and amphibole while not including such things as fiberglass, mica chips, clay particles, and similar materials which occur in varying amounts in many industrial samples. Al 1 doubts about the identity of any particle found are resolved in favor of .including it as asbestos. 3. All concentrations reported on the Figures or in the discussion were based on the total of chrysotile plus amphibole, not chrysotile alone. As a further check twelve of the samples, five from the small job and 7 from the large, were submitted to two independent laboratories for "blind" counting checks. The results are summarized below: Sample Designation M-22 M-24 M-26 M-3Q N-79 Count by uccO) 0.5 0.2 0.2 0.3 0.1 Airborne Fiber Concentration ______ (Fiber/cc >5y)_______ Count by NGC 0.6 0.06 0.4 0.4 0.08 Count by McCrone 0.2 0.1 1.0 1.2 0.3 B-10 B-14 B--18 N-10 N-75 N-76 P-60 0.02 1.3 0.8 1.2 0.7 0.9 0.9 0.004 0.5 0.4 1.1 0.4 0.7 0.5 0.003 0.2 0.4 0.5 0.8 0.7 0.2 (1) Total of chrysotile and possible amphibole. - 11- The highest count found for any of the samples is still 1.3 f/cc. There is some notable scatter but considering the low asbestos level and the extremely difficult nature of the samples, the general agreement is reasonably good. It should be pointed out that UCC had the high reading on seven samples, McCrone in four, and NGC in one. UCC was also second high on three other samples. Since the overall conclusions are directed towards the highest numbers found in either test they are not affected by the variability shown. All of the counts so far discussed were ceiling exposures that occurred during the dust generating operations. It is necessary to estimate 8-hour time-weighted average exposures in order to relate to health data. There was some question raised at the hearing as to whether the proper pro cedure was used for this calculation. In OSHA compliance activities when a man works in an asbestoscontaining area for part of a day and in an area where there is no exposure for the remainder of the day, his TWA is calculated to include his entire shift, i.e., the part with no exposure is weighted at zero. This method was used in the small-job consumer study dated July 12, 1977. It should be pointed out, however, that, the calculation basis was clearly stated and data were provided to allow calculation for the operator remaining in the house for the rest of the day. Regardless of the approach selected the results do not alter the conclusion that the highest TWA reported was 0.3 f/cc. CONCLUSIONS are: The principle conclusions that can be drawn from the data presented 1. Consumer exposure during drywall installation can reasonably be expected to be approximated by the range of 0.5-1.5 f/cc during dust generation operations. 2. The corresponding 8-hour time-weighted average exposures are only several tenths of a f/cc. 3. Residual household exposure after drywall installation is less than 0.01 f/cc which falls within the NIOSH description of ambient levels. - % AIRBORNE ASBESTOS FIBER CONCENTRATION DURING SANDING (F1bers/cc longer than 5 micrometers) w ro u r\> u tn Gn CD O O AIRBORNE ASBESTOS CONCENTRATIONS TYPE: HANO OR POLE NO. OF SAMPLES TAKEl NUMBER OF SAMPLES AIRBORNE ASBESTOS CONCENTRATION (F ib e r s / c c lo n g e r than 5 m icrom eters) 1jj& 'i VL m2 2> OSH COMPl.IANCE INSPEC TIONS CONSUM ER'I- 5 lbs. .. . 1 1 m2 > 8WSS 1 ROHL ET AL 1 1 70 rZ~ 1 >5 Minu tes af ter sv.eeping , I 15 Minut ;s aft ;r swe :ping. rn r>* o<> 1 z> > n 3SQ O:z mTO i "< "O . 3 r- i>r> zIA z> zo mo z cr> i 1 SPACKLING PLUS 3 PANE -S JRY J A U oo Z 1. 1 1 1 t -- c 3: 1 19 PAN ELS DRYWALL (INCL. CEILI NG) 7m0 \ 1 SWFFPING ANO CLEANUP WET-OUT OF DRY MATERIALS I . * > ~0 5* TO IA > DURING WET-OUT OF DRY MATERIALS