An analysis of workplace exposures to asbestos at three steel mills located in the United States (1972-1982)

Our plain-English summary of An analysis of workplace exposures to asbestos at three steel mills located in the United States (1972-1982), by D. Hollins, A. Burns, K. Unice, et al (Toxicology and Industrial Health, 2019).

The study

• Authors: D. Hollins, A. Burns, K. Unice, D.J. Paustenbach
• Journal: Toxicology and Industrial Health
• Published: 2019;35(11-12):726-737
• Type of article: Historical article
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The objective is to present historical asbestos airborne concentrations associated with activities involving presumably asbestos-containing materials in steel mills. A total of 138 historical industrial hygiene air samples collected in three US steel mills from 1972 to 1982 were analyzed. The majority of samples were collected during relining of open hearth furnaces, stoves, and blast furnaces by steel mill bricklayers and bricklayer helpers. Over 75% of the samples (n = 106) were collected for 50 min or less, four samples were collected for 227 to 306 min, and sample durations were not reported for the remaining 28 samples. Average airborne fiber concentrations measured during relining activities of open hearth furnaces, stoves, and blast furnaces were 0.21 f/cc, 0.72 f/cc and 0.13 f/cc phase-contrast microscopy (PCM), respectively. Measured airborne fiber concentrations of four time-weighted average (TWA) samples (>227 min) averaged 0.045 f/cc. Estimated 8-h TWAs concentrations averaged 0.34 f/cc for bricklayers and 0.2 f/cc bricklayer helpers. While 8-h TWA concentration estimates for monitored tasks/jobs may often have exceeded current Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits (PELs), they did not exceed relevant contemporaneous occupational exposure standards. This analysis provides a better understanding of historical airborne asbestos exposures that bricklayers and other tradesmen experienced during furnace and stove work in the US steel mills.

In plain English

This study compiled 138 personal air samples for asbestos taken at three large US steel mills between 1972 and 1982. Most were taken on bricklayers and bricklayer helpers relining furnaces and stoves. Samples were counted by phase-contrast microscopy, and the authors assumed all counted fibers were asbestos. Average concentrations were 0.21 f/cc during open hearth furnace relining, 0.72 f/cc during stove relining, and 0.13 f/cc in 15 samples linked to blast furnaces. The highest single sample was 3.2 f/cc. Four samples lasting 227 to 306 minutes averaged 0.045 f/cc. By combining shorter samples, the authors estimated upper-bound 8-hour averages of 0.34 f/cc for bricklayers and 0.2 f/cc for helpers, and lower-bound averages of 0.048 and 0.032 f/cc. The authors concluded that relining produced intermittent, short-term peak exposures. They said measured and estimated 8-hour averages may often have exceeded today's OSHA limit of 0.1 f/cc but not the 2 to 5 f/cc limits of the time. They noted that work-pattern information, bulk material testing and original microscopy reports were unavailable.

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: Retrospective analysis of historical industrial hygiene air sampling records
• Who was studied: Workers sampled at three large integrated US steel mills in Maryland, Alabama and Pennsylvania, 1972 to 1982. There were 138 personal samples, mostly on bricklayers and bricklayer helpers, plus a few on first helpers, process observers, first keeper helpers, an erector, a galvanizer, a painter and a turn foreman. Most of the data were provided to the authors in the context of litigation.
• Exposure: Airborne fibers counted by phase-contrast microscopy (PCM) during furnace and stove relining and a few other tasks, including handling Zonolite, asbestos rope and a Transite clamp pad. Fiber type was not identified; the authors assumed all counted fibers were asbestos.
• Main results:
  • Relining open hearth furnaces: mean 0.21 f/cc (102 samples).
  • Relining stoves: mean 0.72 f/cc (18 samples, average duration 17 minutes).
  • Blast furnaces: mean 0.13 f/cc (15 samples, which the tables assign to first keeper helpers).
  • Open hearth furnace relining by job: bricklayers averaged 0.28 f/cc and bricklayer helpers averaged 0.059 f/cc.
  • The three highest samples were 3.2, 2.7 and 2.0 f/cc, collected over 15 to 19 minutes on bricklayers or helpers relining furnaces or stoves.
  • All short-term samples were below the OSHA ceiling value of 10 f/cc in force at the time.
  • The four long samples (227 to 306 minutes) on bricklayers and helpers averaged 0.045 f/cc.
  • Estimated upper-bound 8-hour averages, which assume the sampled exposure lasted the whole workday: 0.34 f/cc for bricklayers (22 estimates from 81 samples) and 0.2 f/cc for bricklayer helpers (8 estimates from 28 samples).
  • Estimated lower-bound 8-hour averages, which assume exposure only during the sampled period: mean 0.048 f/cc for bricklayers (Table 5); the bricklayer helper lower bound was 0.032 f/cc.
  • A first helper and a process observer on the open hearth charging floor, while masons installed metal-clad bricks with asbestos spacers, averaged about 0.011 f/cc and 0.0037 f/cc respectively.
  • First keeper helper Zonolite tasks: mean exposures ranged from 0.0055 f/cc to 0.57 f/cc.
  • Samples on the galvanizer, painter and turn foreman were all below the limit of detection.
  • Of 21 area samples (1974 to 1981), 16 (76%) were below the limit of detection.
  • The authors stated that measured and estimated 8-hour averages may often have exceeded today's OSHA limit of 0.1 f/cc but did not exceed the contemporaneous standards of 2 to 5 f/cc.
• The authors' conclusion: The authors concluded that the data suggest furnace and stove relining resulted in relatively intermittent, short-term peak exposures to asbestos.
• Limitations the authors state:
  • Most samples covered only furnace and stove relining by bricklayers and helpers, at only three mills.
  • Little or no time-and-motion information was available, so typical full-shift exposures are uncertain.
  • The authors assumed all fibers counted by PCM were asbestos; some may not have been.
  • No bulk asbestos content or friability testing was found for the materials handled.
  • Respirator use during sampling was not recorded.
  • Original microscopy reports were not available to validate the data.
  • The calculated 8-hour averages likely overstate true full-shift exposures.
  • The sample size was limited, and the data may not represent other steel mills or time periods.

Topics

Medical terms in this study, explained in our Lexicon: Asbestos-Containing Material (ACM), Industrial Hygiene, Time-Weighted Average (TWA), OSHA, Permissible Exposure Limit (PEL), Occupational Exposure, Asbestos Exposure.

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