Potential artifacts associated with historical preparation of joint compound samples and reported airborne asbestos concentrations

Our plain-English summary of Potential artifacts associated with historical preparation of joint compound samples and reported airborne asbestos concentrations, by G.P. Brorby, P.J. Sheehan, D.W. Berman, et al (Journal of Occupational and Environmental Hygiene, 2011).

The study

• Authors: G.P. Brorby, P.J. Sheehan, D.W. Berman, K.T. Bogen, S.E. Holm
• Journal: Journal of Occupational and Environmental Hygiene
• Published: 2011;8(5):271-8
• Cited by: 6 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Airborne samples collected in the 1970s for drywall workers using asbestos-containing joint compounds were likely prepared and analyzed according to National Institute of Occupational Safety and Health Method P&CAM 239, the historical precursor to current Method 7400. Experimentation with a re-created, chrysotile-containing, carbonate-based joint compound suggested that analysis following sample preparation by the historical vs. current method produces different fiber counts, likely because of an interaction between the different clearing and mounting chemicals used and the carbonate-based joint compound matrix. Differences were also observed during analysis using Method 7402, depending on whether acetic acid/dimethylformamide or acetone was used during preparation to collapse the filter. Specifically, air samples of sanded chrysotile-containing joint compound prepared by the historical method yielded fiber counts significantly greater (average of 1.7-fold, 95% confidence interval: 1.5- to 2.0-fold) than those obtained by the current method. In addition, air samples prepared by Method 7402 using acetic acid/dimethylformamide yielded fiber counts that were greater (2.8-fold, 95% confidence interval: 2.5- to 3.2-fold) than those prepared by this method using acetone. These results indicated (1) there is an interaction between Method P&CAM 239 preparation chemicals and the carbonate-based joint compound matrix that reveals fibers that were previously bound in the matrix, and (2) the same appeared to be true for Method 7402 preparation chemicals acetic acid/dimethylformamide. This difference in fiber counts is the opposite of what has been reported historically for samples of relatively pure chrysotile dusts prepared using the same chemicals. This preparation artifact should be considered when interpreting historical air samples for drywall workers prepared by Method P&CAM 239.

Copyright © 2011 JOEH, LLC

In plain English

This laboratory study tested whether filter-preparation chemicals change asbestos fiber counts in joint compound dust. The authors re-created a chrysotile-containing, carbonate-based joint compound from a late 1960s formulation, sanded it, and collected dust on six pilot-study and 32 full-study filters. Filter pieces were prepared with chemicals from the historical NIOSH method P&CAM 239 or the current Method 7400. Other pieces received an acetone/refractive-index fluid or two electron-microscope (TEM) preparations. Filters prepared the historical way gave on average 1.7 times as many fibers as current-method filters (95% confidence interval 1.5 to 2.0). The refractive-index fluid gave results similar to the current method. For TEM, acetic acid/dimethylformamide gave 2.8 times as many fibers as acetone (95% confidence interval 2.5 to 3.2), excluding one filter. The authors concluded that this artifact should be considered when interpreting 1970s air samples for drywall workers, likely prepared by P&CAM 239. They said these workers' concentrations may be overstated relative to workers using asbestos materials unaffected by the preparation chemicals. They noted more research is needed on whether the effect extends beyond carbonate-based joint compound.

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 experiment in two parts (pilot study and full study) comparing filter-preparation chemicals. It tested the authors' hypothesis that some preparation chemicals interact with the carbonate-based joint compound matrix.
• Who was studied: No people were studied. The samples were filters of dust from re-created joint compound: 6 filters in the pilot study and 32 filters in the full study. The full-study filters were 16 from elutriator tubes and 16 from cyclones or cassettes. All were prepared and analyzed by an AIHA-accredited laboratory.
• Exposure: Dust from sanding (and, in the full study, sweeping) a re-created chrysotile-containing, carbonate-based ready-mix joint compound applied to drywall. The filters were prepared with four sets of chemicals: dimethyl phthalate/diethyl oxalate (P&CAM 239), acetone/triacetin (Method 7400), acetone/refractive-index fluid, and, for TEM under Method 7402, acetic acid/dimethylformamide or acetone.
• Main results:
  • With pilot and full-study data combined, filters prepared by the historical P&CAM 239 chemicals gave fiber counts on average 1.7 times those prepared by the current Method 7400 chemicals (95% CI 1.5 to 2.0). The difference was statistically significant (p less than 0.0003).
  • Taken separately, the P&CAM 239 versus Method 7400 ratio was 1.9 (95% CI 1.6 to 2.2) in the pilot study of six filters and 1.7 (95% CI 1.4 to 2.1) in the full study of 32 filters.
  • In the pilot study, the acetone/refractive-index fluid preparation and the current acetone/triacetin preparation gave similar counts (average ratio 0.97).
  • For TEM analysis, grids prepared with acetic acid/dimethylformamide gave fiber counts on average 2.8 times those prepared with acetone alone (95% CI 2.5 to 3.2).
  • In the pilot study micrographs, starburst-shaped structures appeared in about 60% of micrographs of samples prepared with P&CAM 239 chemicals and in none prepared with the other two methods. The authors suggested these structures may be associated with the proposed reaction.
• The authors' conclusion: The authors concluded that 1970s air samples for drywall workers using asbestos-containing joint compound were likely prepared by P&CAM 239, and that this preparation artifact should be considered when interpreting those data. In their view, concentrations may be overstated for these workers relative to workers using asbestos materials unaffected by the preparation chemicals.
• Limitations the authors state:
  • The authors stated that additional research would be needed to know whether the effect extends beyond carbonate-based joint compound.
  • Data for one filter (Filter 16) prepared with acetic acid/dimethylformamide were excluded from the TEM comparison because they showed significant extra-Poisson variability, for reasons the authors did not know.

Topics

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

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

Related studies

• 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)
• Re-creation of historical chrysotile-containing joint compounds — G.P. Brorby, P.J. Sheehan, et al. (2008)
• 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)
• 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)
• Simulation tests to assess occupational exposure to airborne asbestos from artificially weathered asphalt-based roofing products — P. Sheehan, F. Mowat, et al. (2010)
• Mesothelioma associated with use of drywall joint compound: a case series and review of literature — J. Dahlgren, T. Peckham (2012)

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