Discussion paper: asbestos fiber exposures in a hard rock gold mine

Our plain-English summary of Discussion paper: asbestos fiber exposures in a hard rock gold mine, by J.M. Dement, R.D. Zumwalde, K.M. Wallingford (Annals of the New York Academy of Sciences, 1976).

The study

• Authors: J.M. Dement, R.D. Zumwalde, K.M. Wallingford
• Journal: Annals of the New York Academy of Sciences
• Published: 1976;271:345-52
• Cited by: 10 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 005488).

Summary of the article

This discussion paper described the laboratory analyses NIOSH used to characterize airborne fiber exposures in a hard rock gold mine in Lead, South Dakota. A companion mortality study by Gillam et al. had reported increased respiratory disease among the mine's workers. In 1974, the U.S. Bureau of Mines' Mining Enforcement and Safety Administration (MESA) collected about 200 air samples. Phase-contrast optical microscopy gave an average of 0.25 fibers longer than 5 µm per cm³, with a highest single value of 2.8 fibers/cm³, but the fibers were not identified. NIOSH selected the 25 underground personal samples with the highest fiber counts and analyzed them by transmission/scanning electron microscopy with electron diffraction and energy-dispersive x-ray analysis. About 250 fiber analyses were done, and 2111 fibers were counted and sized. Of the airborne fibers, 80-90% showed an amphibole diffraction pattern. Of these amphiboles, 60-70% had compositions identical to fibrous grunerite (amosite), 1-2% were cummingtonite and 10-15% were hornblende. Mean concentrations were 0.36 fibers/cm³ longer than 5 µm and 4.82 total fibers/cm³. Median fiber diameter was 0.13 µm and median length 1.1 µm, and 94% of fibers were shorter than 5 µm. The authors concluded that the 1976 OSHA standard of 2.0 fibers/cm³ may not protect against asbestos-induced respiratory cancer. They also concluded that fibers shorter than 5 µm need more attention and better sampling methods, and that noncommercial asbestos present as a contaminant can cause disease.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This paper by NIOSH, a US government agency, analyzed air samples from a hard rock gold mine in Lead, South Dakota. In 1974, a federal mine safety agency (MESA) took about 200 air samples. By optical (phase-contrast) microscopy these averaged 0.25 fibers longer than 5 µm per cubic centimeter, with a highest single value of 2.8. The authors examined the 25 underground personal samples with the highest counts by electron microscopy, which can identify fiber types. Of the airborne fibers, 80-90% were amphiboles. Of these, 60-70% matched fibrous grunerite (amosite), 1-2% cummingtonite and 10-15% hornblende. About 20% could not be classified. Averaged over 22 samples, electron microscopy found 0.36 fibers longer than 5 µm per cubic centimeter and 4.82 fibers of all lengths; of 2,111 fibers sized, 94% were shorter than 5 µm. The miners' increased respiratory disease risks came from a separate mortality study by Gillam and colleagues. Drawing on that study, the authors concluded that the 1976 OSHA standard of 2.0 fibers longer than 5 µm per cubic centimeter may not adequately protect against asbestos-induced respiratory cancer.

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 exposure study: electron microscopy analysis (fiber identification, counting and sizing) of workplace air samples collected in an earlier government survey. It is not itself a health study.
• Who was studied: Air samples from a hard rock gold mine in Lead, South Dakota. About 200 samples were taken by MESA in a 1974 industrial hygiene survey. The 25 underground personal samples with the highest fiber counts were chosen for detailed analysis. Concentration averages in Table 2 are based on 22 samples, and 2111 fibers were counted and sized.
• Exposure: Airborne fibers in the mine's work atmosphere, mainly amphiboles: fibrous grunerite (amosite), plus fibrous cummingtonite and common hornblende.
• Main results:
  • MESA's earlier phase-contrast (optical) counts of the roughly 200 samples averaged 0.25 fibers longer than 5 µm per cubic centimeter of air. The highest single concentration was 2.8 fibers per cubic centimeter. No fiber identification was done in that survey.
  • 80-90% of the airborne fibers showed an amphibole diffraction pattern. Of these amphiboles, 60-70% had a chemical composition identical to fibrous grunerite (amosite), 1-2% were fibrous cummingtonite, and 10-15% had the composition of common hornblende.
  • About 20% of the airborne fibers could not be classified. The authors noted that many of these also had a chemical composition identical to amosite.
  • By electron microscopy, averaged over 22 samples, the mean concentration was 0.36 fibers longer than 5 µm per cubic centimeter. The mean total fiber concentration (all lengths) was 4.82 fibers per cubic centimeter. Table 2 gives ranges of 0.07-1.29 for fibers longer than 5 µm and 0.66-11.79 for total fibers.
  • Among the 2111 fibers counted and sized, median fiber diameter was 0.13 µm and median length 1.1 µm. 94% of the fibers were shorter than 5 µm.
• The authors' conclusion: The authors concluded that amosite fibers of short length were present at concentrations far below the 1976 OSHA standard. They based their health conclusions on combining these results with a separate mortality study (Gillam et al.) and other conference data. On that basis they concluded that the OSHA 1976 standard of 2.0 fibers longer than 5 µm per cubic centimeter may not be adequate to protect against asbestos-induced respiratory cancer. They also concluded that fibers shorter than 5 µm need greater attention in setting standards, and that noncommercial asbestos fibers present as contaminants are capable of producing disease.
• Limitations the authors state:
  • About one fifth of the airborne fibers could not be identified by diffraction because they were too thick or too thin.
  • The authors stated that phase-contrast optical counts, which count only fibers longer than 5 µm and miss very thin fibers, are at best a crude measure of true total fiber exposure.

Topics

Medical terms in this study, explained in our Lexicon: NIOSH, U.S. Bureau of Mines, Personal Breathing Zone Sample, Scanning Electron Microscopy (SEM), Amphibole Group, Grunerite, Amosite, Hornblende.

Related studies

• Mortality patterns among hard rock gold miners exposed to an asbestiform mineral — J.D. Gillam, J.M. Dement, et al. (1976)
• Some investigations into the nature and cause of massive fibrosis (MF) in the lungs of South African gold, coal, and asbestos mine workers — M.C. Leibowitz, B. Goldstein (1987)
• A review of mortality associated with elongate mineral particle (EMP) exposure in occupational epidemiology studies of gold, talc, and taconite mining — J.H. Mandel, B.H. Alexander, et al. (2016)
• Lung mineral fibers of former miners and millers from Thetford-Mines and asbestos regions: a comparative study of fiber concentration and dimension — A. Nayebzadeh, A. Dufresne, et al. (2001)
• Asbestos-related pleural disease in Western Australian gold-miners — Y.C. Lee, N.H. De Klerk, et al. (1999)
• The distribution and characteristics of asbestos fibers in the lungs of Finnish anthophyllite mine-workers — A. Morgan, A. Holmes (1984)

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