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FILE NAME: Drywall Spackling Compounds (DWSC) DATE: 1975 Aug 15 DOC#: DWSC037 DOCUMENT DESCRIPTION: Journal Article - Exposure to Asbestos in the Use of Consumer Spackling, Patching, and Taping Compounds - Science Reprinted from 15 August 1975, Volume 189, pp. 551-553 Exposure to Asbestos in the Use of Consumer Spackling, Patching, and Taping Compounds A. N. Rohl, A. M. Langer, I. J. Selikoff and W. J. Nicholson Copyright 1975 by the American Association for the Advancement of Science Exposure to Asbestos in the Use of Consumer Spackling, Patching, and Taping Compounds Abstract. Analysis o f representative samples o f spackling, patching, andjointing com pounds, purchased at retail stores in the New York City area, has shown that some con tain asbestos minerals as well as other biologically active substances. Measurements sug gest that home repair work involving the use o f such materials may result in exposure to dust at concentrations sufficient to produce disease. Spackling and drywall taping com pounds consist of extremely fine-grained white powders or premixed pastes. Plaster of Paris is supposedly the major constitu ent, but other light-colored materials in cluding clays, micas, quartz, talc, and ground limestone, supplement or replace the plaster in many formulations. Chrysotile is added to some products, apparently because these minute fibers act as rein forcing agents. The presence of amphibole asbestos in some products results from its natural occurrence in talc, carbonates, and other rocks used as raw materials (/). Fifteen samples of consumer spackling and patching compounds were purchased at hardware stores in the New York City area, four in 1972 or earlier and the re mainder in January 1974. We analyzed the samples for mineral phases by polarized light microscopy, x-ray powder diffraction, and transmission electron microscopy, with particular attention to quantitative determination of asbestos minerals. The spackling and taping compounds consist mainly of particles smaller than 3 in average diameter or length (Fig. 1). Par ticles of this size are generally too small to Table 1. Mineral content of consumer spackling and patching compounds and industrial drywall taping compounds. Frequency of occurrence of mineral phases Mineral phase In 15 consumer spackling and patching compounds In 10 industrial drywall taping compounds Chrysotile T remolite Anthophyllite Tale Quartz Feldspar Pyrophyllite Mica Kaolinite Calcite Dolomite Piaster of Paris 3 (5-10%) 1 (4- 6%) 1 (10-12%) 2 9 (5-70%) 1 2 8 5 11 3 7 9 (5-12%) 1 (5- 7%) 2 6(10-30%) 9 7 4 4 6 be individually studied by polarized light microscopy, and identification is further confounded because these compounds commonly are mixtures of four or more different materials. The analytical use of the optical microscope with its limited res olution allows large numbers of fibers to go undetected. The asbestos minerals, in particular, are usually too fine-grained to identify. In such circumstances, x-ray pow der diffraction may be used to identify and quantify the individual crystalline phases present in the mixtures. In this investigation the amount of as bestos present in spackling compounds was determined by comparison with dilution standards (2). Binary systems of chrysotile, tremolite, and anthophyllite asbestos in plaster of Paris (C aS 0 4 '/2H20 ) were pre pared at varying dilutions on a weight-to- weight basis. Diagnostic reflections for each of the asbestos minerals were select ed. These reflections were step-scanned by x-ray diffraction at increments of 0.02 28, where 6 is the dispersion angle, over a goniometric interval sufficient to define a peak-to-background ratio for the diagnos tic reflections. A digital printout of elapsed time in a fixed-count determination was used to prepare precise positions and pro files of the diagnostic reflections. The area above background, determined with a compensating polar planimeter, was taken to be proportional to the concentration. Details of the method have been presented elsewhere (2). Samples of spackling and taping compounds were prepared, ana lyzed, and measured under the same condi tions as the dilution standards. Com parison of the results of known dilution standards with the samples permitted the amounts of asbestos to be estimated with approximately 20 percent reproducibility. The presence of certain minerals may in terfere with the detection or quantitation of chrysotile in spackling and taping com pounds. For example, chrysotile and kaolinite have similar crystal structures and consequently similar x-ray diffraction patterns (3). However, electron micros copy can be used to corroborate the re sults of x-ray diffraction and to directly estimate the asbestos content of materials, since each mineral type has a characteristic morphology and electron diffraction pat tern. The results of the analyses of 15 con sumer spackling and patching compounds are given in Table 1. Three of the samples were found to contain chrysotile asbestos, and two others contained tremolite and an thophyllite asbestos. Talc was a major con- Table 2. Asbestos fiber concentrations during use of taping compounds containing asbestos miner als. Multiplication of the number of fibers per milliliter by 106 gives the number of fibers per cubic meter of air, an amount which may be inhaled during 1 hour. An unstudied proportion of these fibers is retained and others are exhaled. Current (interim) regulations of the OSHA prohibit concentra tions of 5 fibers per milliliter or more, longer than 5 um, as a time-weighted average for workers. Concentrations above 2 fibers per milliliter will be illegal after 1976. Current regulations set a ceil ing concentration of 10 fibers, longer than 5 #im, per milliliter of air. Operations Number of samples Peak fiber concentration (fibers per milliliter) Mean Range Pole-sanding (1 to 1.5 m) Background (2.5 m), same room Background (7.5 m), adjacent room Hand-sanding (1 to 1.5 m) Background (2.5 m), same room Background (4.5 m), adjacent room Dry mixing (1 to 1.5 m) Background (3 to 6 m), same room Background (5 to 10 m), adjacent room Sweeping floor (3 to 15 m) 15 Minutes after sweeping 35 Minutes after sweeping 10 10.0 3 8.6 2 4.8 11 5.3 2 2.3 2 4.3 2 47.2 3 5.8 2 2.6 1 41.4 1 26.4 1.2 to 19.3 3.5 to 19.8 0.7 to 8.8 1.3 to 16.9 2.1 to 2.5 1.5 to 7.1 35.4 to 59.0 0.5 to 13.1 2.1 to 3.1 Fig. 1 Electron photomicrograph of a consumer spackling product. Large numbers of chrysotile fibers and fiber bundles are present. Granular particulates are clay, mica, and carbonate min erals. stituent in two samples and pyrophyllite in two. The crystal structure and physical properties of pryrophyllite are almost identical to those of talc; pyrophyllite may be considered the aluminum analog of talc. Its biological activity is presently un known. Quartz was a major constituent in seven of the samples, and it was present in two others in lesser concentrations. On the basis of the x-ray intensities of several ma jor quartz reflections, including those at 4.26, 3.34, and 1.817 A, the amount of quartz present is estimated to be greater than 10 percent in the seven samples. Opti cal and transmission electron microscopy have shown essentially all the quartz to be of respirable size (< 5 p,m). Both quartz and talc can produce pulmonary fibrosis (silicosis, talcosis) (4). One sample con sisted largely of quartz with lesser amounts of feldspar and anthophyllite. This may in dicate that the source material for this product was an anthophyllite schist. The combination of talc with some tremolite and quartz in another sample represents a common mineral association typical of commercial talc ore bodies. Both optical and electron microscopic analyses showed that the asbestos fibers present in the samples ranged in length from 0.25 to 8.0 ^m. Most were shorter than 5 /<m in length, which is respirable size, yet they were not generally detected by optical microscopy. The possibility of asbestos exposure dur ing home construction and repair is in dicated by the fact that drywall construc tion workers are exposed to significant concentrations of asbestos air con tamination. Mineralogical analyses of ten industrial drywall taping compounds show that nine contain chrysotile, in concentra tions ranging from 5 to 12 percent (by weight) (Table 1). We made measurements of peak as bestos air concentrations in the breathing zone of drywall construction workers, uti lizing the standard technique of the Na tional Institute for Occupational Safety and Health (NIOSH) for asbestos sam pling and analysis (phase-contrast optical microscopy at x 430) (5). These air sam ples were also analyzed by transmission electron microscopy. Air samples were taken at various building jobs and job sites and included such operations as handsanding, pole-sanding, mixing of dry spackle with water, and sweeping after completion of such operations. Personal air samples were also taken in adjacent areas; such air samples, taken in the breathing zones of the operators, consti tute measurements of their exposure to dust. Table 2 shows that airborne concentra tions of 5 fibers per milliliter of air or more, longer than 5 /an, are common dur ing the use of drywall taping compounds containing asbestos. This exceeds the inter im legal standard excursion set by the Oc cupational Safety and Health Administra tion (OSHA) of the U.S. Department of Labor. The OSHA standard calls for an 8hour time-weighted average. The discon tinuous nature of these operations suggests that the 8-hour sampling is inappropriate in that peak exposures in the present in stance, under a range of application and cleanup operations, greatly exceed the maximum allowable excursions of 10 fi bers per milliliter for a 15-minute interval. These concentrations, determined by the NIOSH method, are only suggestive of the total asbestos exposure. Comparison of optical microscopic and electron micro scopic analyses of asbestos fiber counts of identical samples showed that, for every fi ber visible by light microscopy ( x400 mag nification), there were from 200 to almost 1000 that could be seen only at electron microscopic magnifications of x25,000. The background measurements in Table 2 suggest that in home repair work in volving sanding of spackling compounds, members of the entire household or other occupants of a building may inhale as bestos fibers. This could occur during mix ing, sanding, or cleaning up of debris. Dur ing mixing of drywall taping compounds, spackle is gradually poured from a bag into a bucket of water and the mixture is stirred until the desired consistency is at tained. Fiber counts measured during mix ing were found to be from 7 to 12 times greater than the current occupational standard. Detectable fiber concentrations were found in adjacent rooms during mixing, and fibers were still suspended in the room air at least 15 minutes after mix ing had ceased. Personal air samples were taken after sanding was completed. The floors of the rooms and halls were swept with a hand broom, which raised a cloud of dust. Fiber counts could not be made on floor sweeping samples because the filters were too heavily laden to count. Samples were taken after 15 minutes had elapsed, and, in one case, 15 m away in another room. Measurements showed that signifi cant concentrations of asbestos remained suspended and could pervade living quar ters for a considerable duration of time af ter sweeping had ceased. In summary, our analysis of 15 repre sentative samples of consumer spackling, patching, and taping compounds has shown that five contained appreciable amounts of chrysotile or other asbestos minerals. Many contained substantial amounts of quartz, talc, and other miner als with disease potential. Optical micro scopic analysis of personal air samples ob tained during the use of asbestos-contain ing compounds showed concentrations frequently in excess of the current oc cupational standard of 5 fibers per mil liliter, longer than 5 /im. Use of these ma terials in home repair work (for example, mixing, sanding, and cleanup) may expose the user (and other members of the house hold) to significant concentrations of as bestos. Even more important, none of the 25 in dustrial and consumer spackling and tap ing compounds examined had warning la bels or indication that they might contain toxic or hazardous materials. It is, there fore, recommended that potentially toxic or hazardous materials be eliminated from consumer spackling, taping, and wall patching compounds as soon as feasible. As an interim measure, labels should be re quired on such products stating their con tent and providing instructions for the use of appropriate respirator protection and for safe cleanup procedures, including the disposal of waste materials. A. N. R ohl A. M . Langer I. J. S elik o ff W . J. N ich o lso n Environmental Sciences Laboratory, Mount Sinai School o f Medicine, City University o f New York,- New York 0029 References and Notes 1. M. Ross, W. L. Smith, W. Ashton, Am. Mineral. 53, 751 (1968); W. A. Deer, R. A. Howie, J. Zussman, Rock Forming Minerals (Wiley, New York, 1962), vol. 2, pp. 223-262; H. S. Yoder, Am. J. Sci., Bowen volume (1952), p. 569. 2. A. N. Rohl and A. M. Langer, Environ. Health Perspect. 9,95 (Dec. 1974). 3. G. W. Brindley, in X-ray Identification and Crystal Structures o f Clay Minerals, G. W. Brindley, Ed. (Mineralgica! Society, London, 1951), pp. 32-75. 4. For example, see: M. Kleinfeld, J. Messite, A. M. Langer, Environ. Res. 6, 132 (1973); M. Kleinfeld, J. Messite, O. Kooyman, M. Zaki, Arch. Environ. Health 14,663 (1967); W. G. B. Graham and E. A. Gaensler, Med. Thorac 22,590 (1965). 5. S. G. Bayer, T. A. Brown, R. D. Zumwalde (Docu ment TR-84, U.S. Department of Health, Educa tion, and Welfare, Public Health Service, National Institute for Occupational Safety and Health, Cin cinnati, Ohio, 1975). 6. Supported by National Institute of Environmental Health Sciences (N1EHS) Center grant ES 00928 and by New York City Health Research Council grant U-2331. One of us (A.M.L.) wishes to ac knowledge support under a Career Scientist Award from the NIEHS (grant ES 44812). We thank K. Martin, R. Klimentidis, and P. Formby for technical assistance. 7 March 1975