A review of mortality associated with elongate mineral particle (EMP) exposure in occupational epidemiology studies of gold, talc, and taconite mining

Our plain-English summary of A review of mortality associated with elongate mineral particle (EMP) exposure in occupational epidemiology studies of gold, talc, and taconite mining, by J.H. Mandel, B.H. Alexander, G. Ramachandran (American Journal of Industrial Medicine, 2016).

The study

• Authors: J.H. Mandel, B.H. Alexander, G. Ramachandran
• Journal: American Journal of Industrial Medicine
• Published: 2016;59(12):1047-1060
• Type of article: Review
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Mining of gold, taconite, and talc may involve exposure to elongate mineral particles (EMP). The involved EMPs are typically non-asbestiform, include dimensions that regulatory definitions exclude, and have been less studied.

Methods: A review of the literature was undertaken for this exposure and occupational epidemiological studies that occur in gold, talc, and taconite mining.

Results: Quantitative EMP exposure information in these industries is incomplete. However, there are consistent findings of pneumoconiosis in each of these types of mining. A recent case-control study suggests a possible association between this exposure and mesothelioma. Lung cancer is inconsistently reported in these industries and is an unlikely outcome of non-asbestiform EMP exposure. There is evidence of cardiovascular mortality excess across all of these types of mining.

Conclusions: Non-malignant respiratory disease and cardiovascular mortality have been consistently increased in these industries. Further investigation, including additional insights for the role of non-asbestiform EMP, is warranted. Am. J. Ind. Med. 59:1047-1060, 2016. © 2016 Wiley Periodicals, Inc.

© 2016 Wiley Periodicals, Inc.

In plain English

This was a literature review. The authors searched mainly PubMed for studies of gold, talc and taconite (iron ore) workers possibly exposed to non-asbestiform elongate mineral particles (EMP). These were mostly cummingtonite-grunerite (gold, taconite) or tremolite and anthophyllite (talc). They identified 14 mortality, three cross-sectional, four case-control and eight exposure assessment studies. Non-malignant respiratory disease was the most consistent finding: deaths were significantly raised in four of six talc cohorts, though the largest taconite study found no increase in respiratory disease deaths (SMR 0.94, 95% CI 0.86 to 1.02). Lung cancer findings were inconsistent. In a taconite lung cancer case-control study (1,706 cases, 3,381 controls), the odds ratio for cumulative EMP exposure was 0.94 (95% CI 0.89 to 1.01). In a taconite mesothelioma case-control study (80 cases, 315 controls), risk rose with years employed (1.03 per year, 95% CI 1.0 to 1.06). Its link with cumulative EMP exposure was imprecise: rate ratio 1.10 per (EMP/cc)-year (95% CI 0.97 to 1.24). Several studies suggested excess cardiovascular deaths. The authors found the EMP type behind the mesothelioma finding uncertain and urged further investigation.

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: Literature review of occupational exposure assessment and epidemiology studies (cohort, case-control and cross-sectional; proportionate mortality studies excluded)
• Who was studied: Published studies of Homestake gold miners in South Dakota, taconite miners in northeastern Minnesota, and talc workers in the United States and Europe: 14 mortality, 3 cross-sectional morbidity, 4 case-control and 8 exposure assessment studies
• Exposure: Non-asbestiform amphibole elongate mineral particles, including cleavage fragments. Gold and taconite workers were described as exposed mainly to cummingtonite-grunerite. Talc workers were exposed to tremolite and anthophyllite or actinolite. Crystalline silica and respirable dust were also present in many of these settings.
• Main results:
  • In talc worker cohorts, death rates from non-malignant respiratory disease (NMRD) were statistically significantly raised in four of six cohorts. Two smaller cohorts showed lower than expected SMRs.
  • In the largest taconite mortality study (Allen et al., 2014), work in taconite was not associated with increased mortality from respiratory disease (SMR 0.94, 95% CI 0.86 to 1.02)
  • In the most recent and largest Homestake gold miner cohort (Steenland study), the SMR for lung cancer was 1.13 (95% CI 0.94 to 1.36)
  • In the largest taconite mortality study (Allen et al., 2014; 31,067 workers), SMRs were 1.16 (95% CI 1.09 to 1.24) for respiratory cancer, 2.77 (95% CI 1.87 to 3.96) for mesothelioma and 1.81 (95% CI 1.39 to 2.33) for hypertensive heart disease
  • In a taconite lung cancer case-control study (1,706 cases, 3,381 controls; no smoking data), the odds ratio per unit cumulative EMP exposure was 0.94 (95% CI 0.89 to 1.01)
  • In a taconite mesothelioma case-control study (80 cases, 315 controls), the rate ratio was 1.03 per year employed (95% CI 1.0 to 1.06). It was 1.10 for each (EMP/cc)-year of cumulative EMP exposure (95% CI 0.97 to 1.24).
  • In that mesothelioma study, workers above the mean cumulative EMP exposure had twice the risk of those below it
  • In that mesothelioma study, the highest rate ratio was among workers in the western Mesabi Range, where amphibole EMP exposures were not found
  • A taconite cancer incidence study reported a mesothelioma SIR of 2.4 (95% CI 1.8 to 3.2) and a lung cancer SIR of 1.3 (95% CI 1.2 to 1.3). After a bias analysis for smoking, the lung cancer SIR was 1.1 (95% CI 1.0 to 1.3).
  • In a New York talc cohort (Honda), the lung cancer SMR was 2.32 (95% CI 1.57 to 3.29). However, risk did not rise with cumulative exposure: the relative risk in the highest tertile was 0.5 (95% CI 0.2 to 1.3).
  • Cardiovascular findings: taconite workers had an SMR of 1.10 (95% CI 1.06 to 1.14) for heart disease, and the gold miner update had an SMR of 1.19 (95% CI 1.02 to 1.38) for circulatory disease. In an Italian talc cohort the cardiovascular SMR was decreased (0.77, 95% CI 0.62 to 0.95).
  • In cross-sectional studies of taconite workers, pleural abnormalities were found in 16% and parenchymal abnormalities in 5%. Pleural findings were more frequent with more than 35 years of employment (RR 1.84, 95% CI 1.11 to 3.07).
• The authors' conclusion: The authors concluded that studies of these mining industries most consistently showed increased NMRD. Where exposure assessment was more rigorous, lung cancer was not associated with this exposure. Mesothelioma was increased in a recent taconite case-control study, but the type of EMP exposure involved was uncertain. Whether the suggested excess of cardiovascular disease reflects particle exposure or lifestyle factors was unresolved.
• Limitations the authors state:
  • In most of the reviewed mortality studies, exposure was judged by job rather than by personal EMP measurements, which may reduce accuracy and precision
  • Many reviewed studies were small, did not control for smoking, and did not account for co-exposure to silica and respirable dust
  • NMRD is a mixed category open to disease misclassification, and differences in how often it is listed on death certificates could bias SMRs upwards
  • Phase contrast microscopy, used to count EMP in the mesothelioma study, cannot tell asbestiform from non-asbestiform EMP

Topics

The National Library of Medicine indexes this study under subjects our site covers: Talc and vermiculite.

Medical terms in this study, explained in our Lexicon: elongate mineral particles (EMPs), Epidemiology, Talc, Taconite, Non-Asbestiform, Pneumoconiosis, Case-Control Study, Mesothelioma.

Related studies

• The relationship between various exposure metrics for elongate mineral particles (EMP) in the taconite mining and processing industry — J. Hwang, G. Ramachandran, et al. (2014)
• Comprehensive assessment of exposures to elongate mineral particles in the taconite mining industry — J. Hwang, G. Ramachandran, et al. (2013)
• A comparison of asbestos fiber potency and elongate mineral particle (EMP) potency for mesothelioma in humans — D.H. Garabrant, S.T. Pastula (2018)
• Occupational exposures and lung cancer risk among Minnesota taconite mining workers — E.M. Allen, B.H. Alexander, et al. (2015)
• Mortality experience among Minnesota taconite mining industry workers — E.M. Allen, B.H. Alexander, et al. (2014)
• Respiratory effects of exposure to dust in taconite mining and processing — T.C. Clark, V.A. Harrington, et al. (1980)

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