Re-creation of historical chrysotile-containing joint compounds

Our plain-English summary of Re-creation of historical chrysotile-containing joint compounds, by G.P. Brorby, P.J. Sheehan, D.W. Berman, et al (Inhalation Toxicology, 2008).

The study

• Authors: G.P. Brorby, P.J. Sheehan, D.W. Berman, J.F. Greene, S.E. Holm
• Journal: Inhalation Toxicology
• Published: 2008;20(11):1043-53
• Type of article: Historical article
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Chrysotile-containing joint compound was commonly used in construction of residential and commercial buildings through the mid 1970s; however, these products have not been manufactured in the United States for more than 30 years. Little is known about actual human exposures to chrysotile fibers that may have resulted from use of chrysotile-containing joint compounds, because few exposure and no health-effects studies have been conducted specifically with these products. Because limited amounts of historical joint compounds are available (and the stability or representativeness of aged products is suspect), it is currently impossible to conduct meaningful studies to better understand the nature and magnitude of potential exposures to chrysotile that may have been associated with historical use of these products. Therefore, to support specific exposure and toxicology research activities, two types of chrysotile-containing joint compounds were produced according to original formulations from the late 1960s. To the extent possible, ingredients were the same as those used originally, with many obtained from the original suppliers. The chrysotile used historically in these products was primarily Grade 7RF9 from the Philip Carey mine. Because this mine is closed, a suitable alternate was identified by comparing the sizes and mineral composition of asbestos structures in a sample of what has been represented to be historical joint compound (all of which were chrysotile) to those in samples of three currently commercially available Grade 7 chrysotile products. The re-created materials generally conformed to original product specifications (e.g. viscosity, workability, crack resistance), indicating that these materials are sufficiently representative of the original products to support research activities.

In plain English

This was a laboratory study, not a study of people or health effects. The authors re-created two chrysotile-containing joint compounds from late-1960s Georgia-Pacific formulas: a dry joint system cement with about 5.5% chrysotile and a ready-mix whose dry filler contained about 4.5% chrysotile. The aim was to supply material for exposure and toxicology research. The original chrysotile, Grade 7RF9 from the closed Philip Carey mine in Quebec, was unavailable. The authors therefore used electron microscopy to compare a sample represented to be historical joint compound with three current Grade 7 chrysotile products. All structures seen were chrysotile. Johns Manville 7RF3 had the closest size distribution and was used, although the historical sample had a greater share of long, thin fibers than any of the three. Both re-created products generally met the original specifications, but tape bonding fell short in both. The authors concluded the materials were sufficiently representative to support research. They noted that the historical material appeared to interfere with filter preparation, causing some fiber loss, an effect still under evaluation. Georgia-Pacific, which has been in litigation over joint compound, primarily funded the work.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory re-creation of two historical joint compound products, with electron-microscope comparison of chrysotile fiber sizes and testing against original product specifications. The work was primarily funded by Georgia-Pacific, which the article states has been in litigation related to joint compound.
• Who was studied: No people were studied. Four materials were compared: a sample represented to be historical joint system cement and three commercially available Grade 7 chrysotile products (Johns Manville 7RF3, Johns Manville 7R05, Brazilian CB7RP). Each was analyzed in three replicates of about 450 structures, about 1,350 structures per material. The two re-created products were also tested.
• Exposure: Chrysotile in joint compound. The original formulas called for Grade 7RF9 chrysotile from the Philip Carey mine in Quebec. The re-created products used Johns Manville 7RF3 chrysotile from the Jeffrey Mine, Quebec: about 5.5% by weight of the dry joint system cement (1967 formula), and 4.5% by weight of the dry filler of the ready-mix (1969 formula). Table 2 lists that filler as 57% of the finished wet ready-mix.
• Main results:
  • All structures observed in the historical joint system cement and in the three Grade 7 chrysotile products were identified as chrysotile.
  • Of the three Grade 7 products, Johns Manville 7RF3 had the fiber size distribution most similar to the historical joint system cement.
  • The historical material contained a greater proportion of long, thin fibers and bundles than any of the three Grade 7 products.
  • In all four materials, most chrysotile structures were shorter than 5 µm, and relatively few were longer than 40 µm.
  • Results varied between replicate samples. The share of structures shorter than 5 µm ranged from about 50% to 80% for JM 7RF3, compared with about 92% to 93% for Brazilian CB7RP.
  • The authors described using JM 7RF3 as a conservative choice, tending toward maximizing potential health risks, because it contained the greatest fraction of the longest fibers among the materials tested.
  • The re-created joint system cement met the specifications for working consistency, alkalinity, working properties, crack resistance and color.
  • The re-created ready-mix met the specifications for working properties, color and viscosity, and essentially met those for working consistency and crack resistance. It needed about 60% water to dry ingredients, compared with a specified 53% to 56%.
  • For both products, tape bonding was better than current-day products but less than the product specification.
• The authors' conclusion: The authors concluded that the re-created materials generally conformed to the original product specifications and are sufficiently representative of the original products to support research activities.
• Limitations the authors state:
  • The historical material appeared to interfere with preparation of the polycarbonate filters used for analysis, so some fibers and other particles were lost. The authors said this was being evaluated further using mixed cellulose ester filters.
  • The substitute chrysotile (JM 7RF3) did not undergo the same mineralogical examination for amphibole that was reported for Carey Mine samples.
  • Some ingredients were substituted or left out because they were no longer available, and the batches were far smaller than the original production batches.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Joint Compound.

Related studies

• Potential artifacts associated with historical preparation of joint compound samples and reported airborne asbestos concentrations — G.P. Brorby, P.J. Sheehan, et al. (2011)
• More on the dynamics of dust generation: the effects of mixing and sanding chrysotile, calcium carbonate, and other components on the characteristics of joint-compound dusts — D.W. Berman, G.P. Brorby, et al. (2012)
• Chamber for testing asbestos-containing products: validation and testing of a re-created chrysotile-containing joint compound — P.J. Sheehan, G.P. Brorby, et al. (2011)
• Exposures from chrysotile-containing joint compound: evaluation of new model relating respirable dust to fiber concentrations — G.P. Brorby, P.J. Sheehan, et al. (2013)
• Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability — M.A. Atkinson, M. O'sullivan, et al. (2004)
• Re: Evaluation of the size and type of free particulates collected from unused asbestos-containing brake components as related to potential for respirability — D.J. Paustenbach, B.L. Finley, et al. (2006)

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