Occupational Exposure To Asbestos In The Drywall Taping Process

Our plain-English summary of Occupational Exposure To Asbestos In The Drywall Taping Process, by D.K. Verma, C.G. Middleton (1980).

The study

• Authors: D.K. Verma, C.G. Middleton
• Published: American Industrial Hygiene Association Journal 41(4):264-269, April (1980)
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library, J-M no. 002060. The article is still under copyright, so we describe it here rather than post it.

In plain English

This study measured airborne asbestos during drywall taping in Alberta, Canada. The authors sampled air at eight work-sites from 1975 to 1977, mostly residential, and at a hotel under construction in Edmonton in 1978. During the study period, most joint compounds were said to contain 3 to 6% chrysotile asbestos by weight. Results were counted as fibers longer than 5 microns per cubic centimetre of air (fibers/cc). Levels reached 12.4 fibers/cc in 3 samples taken while mixing dry powder, compared with 1.2 to 3.2 when mixing pre-mixed paste. Application gave 0.4 to 1.3 fibers/cc, hand sanding 2.1 to 24.2, pole sanding 1.2 to 10.1, and sweeping 4 to 26.5. Estimated weekly averages were 4.5 fibers/cc for a taper using dry mix and hand sanding and 2.1 for one using pre-mix and pole sanding, against an Alberta limit of 2. The authors concluded tapers faced potentially hazardous asbestos levels, with sanding the most hazardous operation. They noted their time estimates were approximate, so no single average fits all tapers.

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: Workplace air sampling (exposure measurement) study using personal samplers on workers' lapels and area samplers on stands, analyzed by the NIOSH membrane filter method, with simple descriptive statistics
• Who was studied: Drywall tapers in Alberta, Canada: eight work-sites, mostly residential, sampled from 1975 to 1977, plus a three-month study begun in January 1978 at a multi-storied hotel under construction in downtown Edmonton
• Exposure: Asbestos-containing drywall joint compounds. During the study period, most were said to contain 3 to 6% chrysotile asbestos by weight. The work steps measured were mixing (dry powder or pre-mix paste), application, hand and pole sanding, and dry sweeping or cleanup. Fibers longer than 5 microns were counted.
• Main results:
  • Mixing dry joint compound powder: concentrations as high as 12.4 fibers/cc in a limited number of samples (3)
  • Mixing pre-mix compound: much lower exposure of 1.2 to 3.2 fibers/cc
  • Application: 0.4 to 1.3 fibers/cc. The authors considered these most likely residual fibers from earlier mixing or sanding.
  • Hand sanding: 2.1 to 24.2 fibers/cc
  • Pole sanding, the more common method: 1.2 to 10.1 fibers/cc
  • Sweeping and cleanup, where samples could be obtained: 4 to 26.5 fibers/cc
  • Calculated time-weighted averages for a typical 40-hour taper work week: 4.5 fibers/cc when dry mixing and hand sanding were used (case 1), and 2.1 fibers/cc when pre-mix and pole sanding were used (case 2)
  • The Alberta asbestos standard since 1975 was a time-weighted average of 2 fibers/cc with a ceiling of 10 fibers/cc. The authors stated the calculated averages were generally in excess of the present limit.
  • No mechanical control such as local exhaust was used at the sander, and respirator use by these workers was not widespread
• The authors' conclusion: The authors concluded that tapers were occupationally exposed to potentially hazardous asbestos dust concentrations, and that sanding was the most hazardous operation because concentrations were high and a large portion of time was spent on it. They also concluded that pre-mix compound was preferable to dry powder, and that asbestos-free compound was the only feasible method of total control.
• Limitations the authors state:
  • The time periods assigned to each operation in the time-weighted average calculation were only approximate and could vary significantly, so a single average for all drywall taping could not be accurately assessed
  • Other dust components, such as nuisance particulates, crystalline silica and chemicals, were not examined in the same detail as asbestos
  • The percentage of asbestos in the compounds may vary by manufacturer

Topics

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

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