Mortality patterns among hard rock gold miners exposed to an asbestiform mineral

Our plain-English summary of Mortality patterns among hard rock gold miners exposed to an asbestiform mineral, by J.D. Gillam, J.M. Dement, R.A. Lemen, et al (Annals of the New York Academy of Sciences, 1976).

The study

• Authors: J.D. Gillam, J.M. Dement, R.A. Lemen, J.K. Wagoner, V.E. Archer, H.P. Blejer
• Journal: Annals of the New York Academy of Sciences
• Published: 1976;271:336-44
• Cited by: 38 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. 002283).

Summary of the article

This study examined whether exposure to cummingtonite-grunerite, an amphibole mineral, was linked to excess mortality among hard rock gold miners in Lead, South Dakota. The cohort comprised 440 white men examined in a 1960 U.S. Public Health Service silicosis survey who had at least 60 months of underground mining at the mine and had never mined underground elsewhere. They were followed from April 1960 to December 31, 1973, with none lost to follow-up. Observed deaths were compared with those expected from South Dakota white male rates. There were 71 deaths against 52.9 expected. Respiratory cancer deaths numbered 10 against 2.7 expected, eight of them bronchogenic carcinomas. Nonmalignant respiratory deaths numbered 8 against 3.2 expected, and this excess appeared 20 or more years after first underground work. Surveys found free silica exposures below the OSHA standard, no detectable radon daughters, and trace arsenic, chromium and nickel. In 1974 about 200 personal samples averaged 0.25 fibers longer than 5 µm per cm3 by phase-contrast microscopy. Electron microscopy of selected samples showed that 80-90% of airborne fibers were fibrous amphiboles, mostly fibrous grunerite (amosite), and that about 94% were shorter than 5 µm. The authors attributed the respiratory cancer excess to asbestos, alone or with cigarette smoking. They attributed the nonmalignant excess to asbestos, possibly with free silica. They called for reevaluation of asbestos standards and sampling methods.

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 NIOSH study followed 440 white men who had worked at least five years underground at a hard rock gold mine in Lead, South Dakota, and had never mined underground elsewhere. Their deaths from April 1960 to the end of 1973 were compared with the numbers expected from death rates for South Dakota white men. There were 71 deaths against 52.9 expected. Deaths from respiratory cancer (10 observed vs 2.7 expected) and from non-cancer respiratory disease (8 vs 3.2) were significantly raised. Eight of the ten respiratory cancers were bronchogenic carcinomas. Air sampling in 1974 found that 80-90% of airborne fibers were amphiboles, mostly fibrous grunerite (amosite). By optical microscopy the average was 0.25 fibers longer than 5 micrometers per cubic centimeter. About 94% of fibers seen by electron microscopy were shorter than 5 micrometers. Free silica exposures were below the OSHA standard. The authors concluded that the excess respiratory cancer can be attributed to asbestos, alone or combined with cigarette smoke. They attributed the excess non-cancer respiratory disease to asbestos, with a possible added role for free silica.

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: Two-phase retrospective cohort mortality study with an industrial hygiene study, carried out by NIOSH; deaths compared with expected numbers based on the general white male population of South Dakota
• Who was studied: 440 white (Caucasian) male miners at a hard rock gold mine in Lead, South Dakota, examined in 1960 by the U.S. Public Health Service during a silicosis survey. All had at least 60 months of underground mining there by 1960 and had never mined underground elsewhere. They were followed from April 1960 to December 31, 1973, and the authors report that none were lost to follow-up.
• Exposure: Underground dust from ore of the cummingtonite-grunerite amphibole series. In 1974 electron microscopy, 80-90% of airborne fibers were fibrous amphiboles, and 60-70% of these were fibrous grunerite (amosite); smaller shares were fibrous hornblende and fibrous cummingtonite. Miners were also exposed to free silica. Arsenic, chromium and nickel were found only at trace or very low levels, and radon daughters were not detected.
• Main results:
  • All causes, whole cohort: 71 deaths observed vs 52.9 expected (p less than 0.05)
  • Respiratory cancer, whole cohort: 10 observed vs 2.7 expected (p less than 0.01)
  • Non-cancer respiratory disease, whole cohort: 8 observed vs 3.2 expected (p less than 0.05)
  • A significant excess of 'other accidental deaths' was also found (8 observed vs 2.7 expected in Table 1, p less than 0.05)
  • 20 or more years after starting underground work: non-cancer respiratory disease 8 observed vs 2.56 expected (p less than 0.01), and pneumoconiotic disease 5 observed vs 1.57 expected (p less than 0.05). No such excess was seen in the first 19 years.
  • Respiratory cancer by time since starting underground work: 3 observed vs 0.56 expected (p less than 0.05) at less than 20 years, and 7 observed vs 2.18 expected (p less than 0.01) at 20 or more years
  • Of the 10 respiratory cancer deaths, 8 were primary bronchogenic carcinomas, 1 was a carcinoma of the maxillary sinus, and 1 was a mediastinal carcinoma (otherwise unspecified)
  • Of the 9 deaths in the 'all other causes' category, 3 (33%) had pneumoconiotic disease mentioned on the death certificate
  • In about 200 full-shift samples taken in 1974 and counted by optical (phase-contrast) microscopy, the average was 0.25 fibers longer than 5 micrometers per cubic centimeter, and the highest single concentration was 2.8 fibers per cubic centimeter
  • By transmission electron microscopy of the highest-concentration samples, total fibers averaged 4.82 fibers per cubic centimeter and fibers longer than 5 micrometers averaged 0.36 per cubic centimeter. Median fiber length was 1.1 micrometers, and about 94% of fibers were shorter than 5 micrometers.
  • Free silica exposures measured in 1960 were well below the then-applicable OSHA standard
• The authors' conclusion: The authors concluded that the excess of respiratory cancer can be attributed to asbestos, alone or together with cigarette smoke. They ascribed the excess of non-cancer respiratory disease to asbestos, with a possible additive role from low exposures to free silica dust. They called for reevaluation of the OSHA standard of 2 fibers longer than 5 micrometers per cubic centimeter and of the health effects of fibers shorter than 5 micrometers.

Topics

Medical terms in this study, explained in our Lexicon: Asbestiform, Cummingtonite-Grunerite, Amphibole Group, Silicosis, Bronchogenic Carcinoma, OSHA, Personal Breathing Zone Sample, Grunerite.

Related studies

• Discussion paper: asbestos fiber exposures in a hard rock gold mine — J.M. Dement, R.D. Zumwalde, et al. (1976)
• 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)
• 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)
• Mortality of former crocidolite (blue asbestos) miners and millers at Wittenoom — A.W. Musk, N.H. de Klerk, et al. (2008)
• Asbestos-related pleural disease in Western Australian gold-miners — Y.C. Lee, N.H. De Klerk, et al. (1999)
• Cohort study of mortality of vermiculite miners exposed to tremolite — J.C. McDonald, A.D. McDonald, et al. (1986)

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