Document KG7O7N3pmk6MJErNj47Lxb5x

Studies of airborne asbestos fiber concentrations associated with various operations of the drywall taping process have been undertaken in the province of Alberta. Canada. The results show that mixing, sanding and k veeping created high levels of airborne asbestos dust. The measured concentrations were frequently in excess occupational health standards. Sanding in particular was assessed the most hazardous operation. The results re discussed in light of present and proposed Occupational Health Standards, and in terms of its implications for other workers, household contacts, and consumer's risk. Measures to reduce and control the health hazards associated with the process are described. ( i I I ) f Occupational exposure to asbestos in the drywall taping process 1 I i DAVE X. VERMA* and CHARLES G. MIDOLETON8 ' 'Occupational Health Program. McMaster University. Hamilton. Ontario. Canada L8N 3Z5: 'Occupational Health & Safety Division. Alberta Worker's Health Safety Si Compensation. Edmonton. Albe Canada T5JC 2JS m Tl pa du ih< mt pa (re ret we wc ba rei & > introduction Occupational exposure to asbestos is associated with a risk, first study may not be indicative of typical occupational of asbescosis, mesothelioma, an excess risk of cancer of the exposure of the drywall taping process. lung and possible cancers at other sites.0'4* These asbestos related diseases have been found in mines and mills,151 in manufacturing industries,0' and in the use of asbestos products such as insulationin construction industries.|7>Thc magnitude of the occupational health problem associated asbestos exposure is enormous. The relative risk of f cancer among asbestos workers Has been, demonstrated from epidemiological studies to range between 1.4 and 3.3 for miners and millers, 1.0 to 13.7 for production and manufacturing industry workers and 5.1 to 8.3 for insulators.'4' The risk due to cigarette smoking and asbestos exposure has been recognized to be multiplicative rather than additive so that an asbestos worker who smokes has an extremely high risk of lung cancers. An asbestos worker who smokes has a 92 times greater risk than a worker who neither smokes nor works with asbestos.'5' Very little has been reported in the literature about the potential occupational health risk to drywall taping workers. A review of the literature revealed only two independent studies dealing with the occupational exposure t o asbestos in the taping process. In the first study results of thirty-nine air samples taken at the various operations of the process were discussed.'*1 Generally high (mean values of 2.6 Data is also lacking on the health status of (his group of workers exposed to asbestos. One published report of medical examinations conducted on a group of 69 tapers showed X-ray abnormalities characteristic of asbestos exposure in 37 out of 69 film's."" Two thirds of this group had an exposure of 10 years duration or longer, and 61 were smokers or ex-smokers. A recent clinical report'9' on the same group of drywall workers, but with an expanded cohort (I |4), showed radiological evidence for pulmonary asbestosis in 40.9% of the cases examined. This compares la 48.5% among insulators."" Consequently drywall tapef* appear to have similar exposure as insulators. In light ofthis it ^interesting to note that tapers in Alberta are not under medical surveillance whilst insulators, who are considered asbestos workers, are. To our knowledge this lack of medical surveillance for tapers as asbestos workers exists m other provinces of Canada and most parts of the U. S- Becausc of the above mentioned concerns we initiated.in 1975, an investigation in the province of Alberta of iht drywall taping process. This operation was known ,0 involve the use of an asbestos containing compotindSpccifically the aim ofthis study was to assess quantitative!} to 47.2 fibers/cc for specific operations) airborne asbestos the occupational exposure to asbestos in this group 0 levels were noted. This earlier report has recently been workers. Our findings are summarized in this report. published in an expanded version.'*1 In the second study, conducted on a similar sample size, much lower (mostly between 0.5 and 3.5 fibers/cc) exposure levels were reported."01 The latter authors inferred that the results of the the drywall taping process ^ In the construction of a commercial building. wallbo* opinions and suggestions contained in ihis repon are tfe private js <jf to* authors and are not to be construed as oHicie* or < anting the views ot Alberta Worker's Health Safety and are fixed to metal studs with screws, while in reside*1 houses the gypsum wallboards are nailed onto the *a0 g studs. The resulting joints, as well as screw and n "c'c jnsanon. indentations, are finished by taping. 190Q. Amria MwMl Aiwpltmi K1 Am. M. Hyt- Anon. ]. (41) > i i > i f I I I > iht S3 Th ap ca: art eit cai sai en- cai tot rut Th fre get e5f pr. Hr scf res t/is Th ma mo of cot *n on 0S& . jfcedry join* compound powder is normally contained m act bags- The bag ^ s**1 open by a knife and the powder aped into a container. Water is then added according to ^ uuflufacturer1* directions and the compound mixed by of a portable electric drill equipped with a mud and jjiat mixer. Some joint compound is sold as a paste purred to as "premix") and only a small amo unt of water is paired. The prepared mixture in its putty like form after rtjoog is referred to as mud. The time spent mixing in a sorting day is short. It usually takes 5 to 10 min. to mix a tatcb ind in most instances one to three batches are Bqoired daily. eftiat/prt IT* joint compound (mud) is placed on the bottom side ofa Hjet upc and is applied to cover the joints between the GysviD boards and allowed to dry. Subsequently, this compound is also applied on the front side of the tape and to ioe* rod nail indentations. A major portion (65-70%) of tbi working day is spent in this operation. U(Hjing Tbe (aiats and indentations are sanded between each implication of mud, with the major amount of sanding being arried out after the final coat. Three to four coats of mud ire usually applied. Sanding operations normally involve caber hand sanding or pole sanding. Hand sanding is timed out with a hand-held, abrasive paper, covered "odiag block. In pole sanding, the sanding block is at the *"1 o( a long pole. Generally speaking most of the sanding is out by pole sanding. We estimate that 25-30% of ^ lime is spent in this operation. t+ftptng md cleanup P* debris and the dust accumulated on the floor resulting Dtn fhe mixing, application and sanding operations is fc&eratty cleaned up by dry sweeping. In many instances,, **^ciaMy in cases of commercial building and large ^lcctt, this operation is carried out by general laborers. *eycr, it was generally found to be part of the work . `c f employees of small companies working on wtial construction projects. ^ co'nl>oxrti0n ofjoint compounds composition of joint compounds varies from e^*cuirer to manufacturer. During the study period of JOmt impounds were said to contain between 3 - 6% tysotile asbestos by weight. The remainder was Poscd of limestone or dolomite, talc, clay, mica, starch 95 the^0^6 ^ typical joint compound formulation, based information obtained from the manufacturers, was: ^icstone . . ............................................. 80 - 85% cu ^Ic, mica ............................................. 5-10% Asbe*{oc $ (as chrysotile) ................................. 3 - 6% r LUr[t*vgii_c*idje (,O^ rgani.c material) . Less than 1% 0 Tvinjri alcohol, Poly-vinyl starch, potassium ^tn-Pfyphosphate, ctc................................................ 2-3% u8hmost joint compounds at present contain 3 - 6% of asbestos (chrysotile). in the past they have contained much higher proportions of asbestos.''1 Three types of joint compounds are available: taping, topping, and all purpose, all of which contain asbestos. Taping joint compound is applied In one or two coats and is designed for strength. The topping or finishing variety is generally applied in the final coat and has better finishing qualities. The all purpose compound is a compromise formula that can he used for both taping and finishing purposes. Asbestos is used in these joint compounds because it serves several functions including controlling shrinkage and cracking when the mud dries, and providing good workability in troweling and sanding. materials and methods site description During 1975 to 1977 several work-sites were visited throughout the province and eight of them were evaluated by air sampling. Work schedules and the time spent at various operations at worksites differed widely. In small companies, the owner often worked out of bis home and undertook all the work himself. Companies with larger workforces of 15-20 employees had individual workers performing specific tasks such as sanding on a-full-time basis. Following these initial surveys we conducted a more detailed study over a three-month period at a downtown site in Edmonton where a multi-storied hotel was under construction. This survey of a large commercial site was begun in January, 1978. - . Both the residential and commercial site studies concentrated on the evaluation of worker's exposure to airborne asbestos dust. The potentially hazardous effects of other components of dust such as nuisance particulates, crystalline silica, chemicals, etc., were not examined in the same detaiL It was felt that asbestos posed the most significant hazard and control measures applied for asbestos exposure would be equally effectiveagainst other hazardous particulates. methodology 1. Airborne asbestos dust samples were taken by using open-face filter cassettes, loaded with 37 mm 0.8 micron pore size Milfipore, Type AA membrane filters. Air was drawn through the filter papers by a portable pump at a flow rate of 2.0 liters) min. The sampling period was guided by two factors -- concentrations expected and duration of . operations. Most sampling assemblies were attached to the worker's lapels. To obtain area or location samples assemblies were attached (a portable stands. The pump was calibrated before each use by a soap bubble meter. The flow rate was checked frequently during sampling. 2. To determine the concentration of airborne asbestos, analysis of the samples was effected by the NIOSH reference Membrane filter method."" For consistency, most of the asbestos counting was done by one of us (C.M.) A very limited number of /*o 4/to 7SS TABLE I Summary of Airborne Asbestos Fiber Concentration* (in fiber* > 5 #i/ccj Encountered in the Drywail Taping Prudes* Operation** Number Sampling Time (Min) Samples Range Mesn Concentrations Range Mean Median Application* (2] . 10 39 - 65 54.4 0.4- 1.3 0.9 0.9 Mixing* (1} (Ory Powder) Mixing* [2) (Pre-mix) 3 10 - 12 10.6 9.0 - 12.4 11.2 12-2 7 4- 5 4.6 1.2 - 3.2 2.4 2.3 Mixing Areac (2) (Pre-mix) 7 3- 5 4.0 1.2- 2.7 2.0 2.0 Hand Sanding* 11) 22 io - ao 1S.0 2.1 24.2 11.5 11.5 Pole Sanding* (1) 20 10- 38 18.5 1.2 - 10.1 4.3 4.0 Pole Sanding* (2) Pole Sanding* (3) Sanding Areac (3) 32 4-21 13-9 1.2 - 10.0 4.6 3-8 52 4 - 38 15-7 1.2 - 10.1 4.9 3.8 10 10 - 58 22.0 0.3 - 7.0 3.2 2.3 |B from set 1) Sweeping* (1) 6 9 30 20.7 4.0 - 26.5 12.1 7.7 Sweeping* (2) 4 10 - 20 14.2 14.5-25.4 19.6 19.4 Sweeping* (3) 10 9 - 30 18-1 4.0 - 26.5 15-1 15.5 All operations (1) 59 9 - 80 17.5 0.3 - 26.5 8.0 5.9 AU operations {2.) 62 3-65 18.5 0.4 - 25.4 4.3 2.7 All operations (3| 121 3 80 18.0 0.3 - 26.5 6.1 3.7 `The numbers in parentheses refer to the following collection schedules; *' - (1) sir samples taken at several residential sites throughout the Province of Alberta during 1975-77; " (2} air samples taken at the Edmonton multi-storied hotel site during 1978; (3) air samples taken during 1975-1977 and 1970 combined. "Personal samples were collected. cArea samples were collected. samples (10) were either analyzed by X-ray diffraction or were subjected to scanning electron microscopy for asbestos fiber identification. 3. The data analysis involved the computation of simple descriptive statistics. results and discussions In Table I, the number of samples collected for various operations are given along with range and mean ofsampling time and range, mean and median of the observed fiber counts. The data obtained during 1975-77 are designated in this table as set (1) and those obtained in 1978 arc identified as set (2). This distinction between the two sets of data was made because, as already mentioned, set (1) was primarily from the residential taping operations and set (2) from large commercial building taping operations. However, since the joint compound used was similar and the exposure level comparable, to strengthen the data base they have been ombined as set (3). In addition, the Low Value (L), the *-ower Quartilc (IQ), the Median (M), the Upper Quartile (3Q)-and the High Value (H) for the measured fiber concentration were evaluated. The results are depicted * Figure 1 and for the taping process as a whole, appear10 follow a log normal distribution. The results summarized in Table I and Figure I are conveniently discussed in detail in relation to each of four operations of the process: mixing, application- safldinf and cleanup. mixing Although the exposure duration ofthis operation was shortconcentrations as high as 12.4 fibers/cc were found in 0* limited number of samples (3) taken during mixing ofth* dry joint compound powder. Concentrations as highs* 59fibcis/cc havr been reported earlier.1*1 The mixing of the pre-mix compound on the other resulted in much lower exposure of only 1.2 to 3-2 fibers/cCConsidering the short duration of mixing and low expo*uf^ encountered, the use of pre-mix should not create significant hazard in this operation. | *Pf ; Du an< 1tak to lev m< op ea la i It } aik sa \ sa Ti a: d iF 3U Am. Ind. Myf. Assoc. J. (4 If CONCENTRATION Jf5be/ccJ Figure \ - Observed liber counts lor the various operations in the taping process. The numbers in parentheses (ordinate labelling) refer to the collection time and place as explained in footnote * of Table I. L. 1G. M. 3G and H represent Low value, the Lower Quanile. the Median, the Upper Quartile and the High value respectiveiy- ;pphcation, the compound is in the form of a paste Virtually ao dust should be generated. Air samples however, indicated concentrations ranging from 0.4 13 fibers/cc, Other studies1*'101 have not reponed fiber during this operation. The airborne fibers found were p*i likely the residual fibers that were generated in other ^rations, e.g. mixing or sanding that were carried out |*rtw. be seen from the data in Table I and Figure 1 that F"*6 asbestos fiber levels encountered during hand tanged from 2-1 to 24.2 ftbcrs/cc and during pole ,ng (which is the more prevalent means of sanding) from [.2 to 10.1 fibers/cc. There was good ent between the median concentrations encountered htpir'eSt-1a).nding in both the data for 1975-77 and for 1978 (see Our resu*ts which show high concentrations during V J*Vre gcnctal agreement with the results of one of ^ f Cr studies.*`',) Levels of 1.2 to 19.3 fibers/cc were b|<^.for P*e sanding (number of samples - 10) and 1.3 !|ji J:bers/cc during hand sanding (number of samples - 'CSe 2nd our own results are considerably higher to 3.5 fibers/cc, 29 samples composed of 24 lnls and 5 hand sandings) reported in the only u<Jy. 1 Although our results show hand sanding to *8her fiber concentrations than pole sanding, "dies have shown the opposite.***" The reason for this difference is not obvious but could be due to different work practices. No mechanical control measure c.g, local exhaust at the sandcr was employed. The only practical available measure is the use of appropriate respiratory protection. Unfortunately, the use of respirators by this group of workers was not widespread. sweeping and cleanup In cases where it was possible to obtain samples, concentrations of 4 to 26.5 ftbcrs/cc were measured. relation of findings to occupational health standards To facilitate the interpretation of exposure experienced by tapers, a brief discussion of the present and proposed occupational health standards follows. Our own results are subsequently discussed in the iight of these levels. The asbestos standards and recommendations in the U.S. and Canada arc constantly being revised. OSHA has a present standard ofan 8 hour time weighted average (TWA) of 2 fibers/cc that are greater than 5 microns tn length, with a ceiling of 10 fibcrs/cc and it has a proposal to reduce it to 0.5 fibers/cc as a TWA.|WI NIOSH has recommended the adoption of a TWA of 0-1 fibers/cc with a ceiling of 0.5 fibcrs/cc.|2! ACGIH -has also published in Us intended changes list of 1978 new TLV*s forvarious forms ofasbestos that range from 0.2 fiben/cc to 2 fibers/cc."31 In the Province of Alberta, the asbestos standard since 1975 has been a TWA of 2 fibers/cc with a ceiling of 10 2S7 fibcrs/cc. Some provinces (e.g. Alberta and Ontario) in Canada are considering adoption of asbestos standards .imilaT to those proposed by ACGIH in its intended changes list of 1978. To determine the time weighted average (TWA) concentrations to which tapers were exposed the following formula was employed: TWA = IGt, ' I t I Gt --------- IPit (=40) Where G is the exposure encountered at job i during the time (t,) employed at this operation. A typical taper's work week of 40 h could be broken down into the following exposures. (i) 2 h'(ti) during mixing with an exposure concentration of Ci (ii) 27 b (ti) during application with an exposure concentration of Cj (iii) 10 h (t?) during sanding with an exposure concentration of C.* (iv) 1 h (t) during cleaning with an exposure concentration of C* The calculated TWA values differ greatly depending upon the type of operations used in the above formula. Let us consider two situations: case (I) where mixing was done by employing' dry mixing and sanding effected by hand tnding- Case (2) where a pre-mix compound was employed and che finishing achieved b pole sanding. Using the median values given in Table 1 and Figure 1 of 12.2 fibers/cc, 2.3 fibers/cc, 11.5 fibers/cc, 3.8 fibers/cc, 0.9 fibers/cc and 15.5 fibers/cc for dry mixing, mixing pre-mix, hand sanding, pole sanding, application and sweeping respectively, the calculated TWA values are 4.5 fibers/cc for case (!) and 2.1 fibcrs/cc for case (2). It is clear that the TWA values calculated in the above manner arc generally in excess of the present occupational limit and are far in excess of the newly proposed criteria. Such assessments for the taping process may not be very adequate in all cases since various factors affect the final result. These include: (1) Time periods allocated to various operations arc only approximates and may vary significantly. (II) Operations may be performed solely by one individual (e.g. a person doing sanding full-time which was the case in some instances). (III) Dry-joint compound produces a much higher dust concentration than pre-mix compound during mixing. (IV) The percentage of asbestos found in the compounds may vary depending upon the manufacturers. (V) Some operations (c.g. cleaning and sweeping) may not be performed by all tapers. Because of these limitations a single TWA value for all drywall taping processes, cannot be accurately assessed. Zt Consequently, it is our opinion that the exposure data most meaningful when expressed, as in Table I and Figure t as the concentrations encountered in specific operations (mixing, application, sanding and cleanup) of the tap,n? process from which the TWA for any situation could be derived. In the U.S. the Consumer Product Safety Commission (CPSC) in 1978 banned the sale of asbestos containini compounds to the consumer, on the grounds of possible asbestos related health risks/1*"'*1 This ban, however. do not apply to the products made for commercial and industrial use where most of the occupational exposuret& tapers occurs. In Canada, the Department ofConsumer and Corporate Affairs of the Federal Government currently has under consideration a similar ban/16'17' This Canadian proposal differs from the U.S. Consumer Product Safm Commission's in that it may apply to products made both for consumer and industrial/commcrcial markets. conclusions and recommendations We believe that our results constitute a realistic and comprehensive assessment of typical exposure experienced by tapers. The data should be useful in planning.suitabk health protection programs and in the assessment of past exposure for such purposes as adjudication at compensation claims, and design of epidemiological studies. The essentials of our findings may be summarized as follows: (1) The tapers are'occupationally exposed to potentially hazardous asbestos dust concentrations in their work. The asbestos hazard can be eliminated by the use of asbestos free joint compound. Although asbestos free joint compound is available and most manufacturers arc actively working towards the reduction and/or elimination r asbestos in their material, most of the tapm? compounds used still contain asbestos. The use oi asbestos free compound is the only feasible method of total control ofasbestos exposure and is therefore strongly recommended. However, a person engaged in mixing, sanding, and sweeping, of asbe* containing compound should wear an apProv4 respiratory protective device. (2) The use of pre-mix compound is preferable over dr> powder joint compound, because it eliminates hig exposure during mixing. It is recommended that ^ amount of joint compound used should be 1 minimum necessary for the job. (3) Sanding is the most hazardous operation at l^j. taping process because the concentraunS . asbestos encountered are high and a large portion iota! time is spent in this operation. To reduce exposure various control measures should ^ considered, including the effective use ofte*P'rl,J and rotation of workers. (4) The short term hazard associated with sweeps cleanup operations could be reduced by cmpl an industrial type vacuum cleaner. If a brootf , Am* tnd. Hyg. Assoc. J. (Al) AO* & be employed, a dust suppressant compound should be used. . (5) Tapers who work with asbestos containing compound should be included in the medical surveillance program, for asbestos workers. Additional epidemiological studies of this group of workers arc also recommended. Furthermore, tapers should be familiarized with the potential health hazards, especially the greatly elevated lung cancer risks for asbestos workers who smoke. (61 The unnecessary exposure of tradesmen not directly involved in taping, can be avoided by proper job scheduling and-restricting, the entry to exposure areas. Contamination of the homeienvironmentcan be minimized by careful handling of workclothes and good'personal hygiene. | idenowtedgement ' Ik authors wish to thank Mr. David E. Gibson, Director, I Occupational Hygiene Branch, Alberta .Worker's Health | Safety & Compensation for his help and encouragement J bring the study. Thanks are also due to Mr. Gerry Vindcrlich. of Alpine Drywall Company and to those ijvall Upcrs who-participated in the study. We are grateful to Mr. Jim Julian, Dr. David Muir and Ct. Evert Niebocr of McMaster University for their help in preparation of this report. j l- Nitiomi Institute tor Occupational Safety and Haaith: ' Criteria tar a Recommended Standard . . . Occupational } ^oosure to Asbestos. U. S. DHEW. Cincinnati (1972). | ^ Actional Institute for Occupational Safety and Haaith: ^^sed Recommended Asbestos Standard. U.S. DHEW. \ Cincinnati 11976). 3. Selikoft. 1. J-. E- C. Hammond and J. Churg: Asbestos Exposure. Smoking and Neoplasia. J. Am. Med-'-Assoc.: 204:104-110 (1968). 4. Becktake, M. R.: Asbestos Relaxed Diseases of the Lung and j; Other Organs: Their Epidemiology and Implications; for f-: Clinical Practices. Am. Rev. Resp. Dis. I ?4;187-227 (1976). 5. McDonald. J. C-, M. R. Becklake. G. W. Gibba^A. D.^ - McDonald and C. E. Hoaaher The Health of Chrysodla: Asbestos Mine and Milt Workers. Arch. Env. HAattii. 25:61 - 68(19741. .i 6.. Knox.-J. F.. S* Holmes, R. Dolland I. D. Hill: MortalityFrom V Lung Cancers and Other Causes Among Workers in an Asbestos Textile Factory.Sr. J. tnd. Med. 25:293-303(1 968). 7. Selikoff. I- J-: Asbestos Disease in the United States (1918- . 1975). Rev. Jr: Mai. Resp. Suppl. 1 au Tome 4:7-24 (1 976). 3. RohL A. N.. A- M. Langer, ).. J., Selikoff arid - W- J-0 Nicholson:: Exposure to Asbestos in the Use of Consumer Spackling. Patching and Taping Compounds. :Science,- /89:56l-553(1975)_ , ' .-.V 9.. FischbemV A., A. N. Rohl. A. M. Langer and I. J.'Selikoff: Drywall Construction and Asbestos Exposure. Am. InttHyg. - Assoc.. JE;ijf0i4C2-A07 (1979). ' . " S;: 10- Rhode*. H: 8. and B. L- Ingalls: Asbestos and Silica Oust in the Drywall Industry. Part 1 and Pan 2. G.D.CJ. (Gypsum . Drywall Contractors International) Drywall. 21:6-8 (1975).; 22:1-6(1976). 11. Anon.: Asbestos Risk Exists From Use of Taping Compound. ' InsulationHyg. progress Rep. 7:2-4(1975). 12. National- Inatitma for Occupational Safety ancfTlealth: Sampling and Evaluating Airborne Asbestos Dust. U. S. DHEW. Cincinnati (1974). ' 13. (TLV*): ThresholdLimit Values for Chemical Substances and PhysicalAgents in ihe Workroom Environment with Intended Changes tor 1979. ACGJH. Cincinnati (1978). 14. Ray, D. R.: Personal Communication. Consumer Product Safety Commission. Washington. DC 20207 (December, 1978). 15. U. S. Federal Register: 42:63354-63365 (December. 1977). 16. Brownstein. M.: Personal Communication. Consumer and Corporate Affairs, Gov't of Canada. Ottawa. Canada (May, 1979). 17. Consumer and Corporate Affairs Canada. Product Safety Branch: Trade Communique `Asbestos Containing Products. Issue No. 1. (April. 1979). J fyw* Attoeubcn JOURNAL Mi) 4/8D Z69