Effects of commodity on the risk of emphysema in South African miners

Our plain-English summary of Effects of commodity on the risk of emphysema in South African miners, by S.L. Mabila, K.S. Almberg, L. Friedman, et al (International Archives of Occupational and Environmental Health, 2020).

The study

• Authors: S.L. Mabila, K.S. Almberg, L. Friedman, R.A. Cohen, N. Ndlovu, N. Vorajee, J. Murray
• Journal: International Archives of Occupational and Environmental Health
• Published: 2020;93(3):315-323
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Purpose: To examine associations between mine commodity such as coal, platinum, or diamonds and emphysema among South African miners at autopsy.

Methods: We examined the association between mine commodity and emphysema using the Pathology Automation (PATHAUT) database, 1975-2014. Exposure was characterized as longest tenure in each commodity. We constructed separate multivariable logistic regression models for black and white miners. Smoking was assessed in a sub-analysis of white miners.

Results: Among black miners, coal mining was significantly associated with increased odds of emphysema [OR = 2.39 (95% CI 1.86, 3.07)] when compared to gold mining. Asbestos was also associated with significantly increased odds of emphysema among black miners [OR = 1.47 (95% CI 1.01, 2.12)]. No associations between commodity and emphysema were observed among white miners. Cumulative years of exposure and age at death were significant predictors for emphysema for both black and white miners. Smoking was a significant predictor of emphysema in the sub-analysis of white miners with smoking information, but no effect of commodity was observed.

Conclusions: We observed a significant association between coal mining and emphysema among black miners. Adverse health effects of coal mining are evidenced by more than twofold increase in emphysema among black coal miners compared to gold miners. This suggests that South African Coal miners are exposed to high dust concentrations or more damaging components compared to other commodities, resulting in elevated risk of emphysema.

In plain English

This registry-based retrospective cohort study used a South African autopsy database (PATHAUT) to ask whether the type of mineral mined was linked to emphysema found at autopsy. It included 42,609 black and 20,720 white miners autopsied between 1975 and 2014. Each miner was assigned the commodity they worked in longest. Gold mining was the comparison group, and black and white miners were analyzed separately. A case meant moderate or marked emphysema. After adjustment for tenure, age at death, year of death, active TB and HIV, black coal miners had higher odds of emphysema than black gold miners (OR 2.39, 95% CI 1.86 to 3.07), as did black asbestos miners (OR 1.47, 95% CI 1.01 to 2.12). Among white miners, no commodity showed a significant positive association, and asbestos mining was linked to lower odds (OR 0.72, 95% CI 0.54 to 0.97). Among white miners with smoking information, current and former smokers had higher odds than never smokers. The authors concluded that coal mining was significantly associated with emphysema among black miners. They noted that the study had no dust exposure measurements.

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: Registry-based retrospective cohort study of autopsy records (PATHAUT database), analyzed with logistic regression separately for black and white miners
• Who was studied: Of 110,167 South African miners autopsied at NIOH in Johannesburg from 1975 to 2014, 42,609 black and 20,720 white miners remained after exclusions for missing data
• Exposure: Mining commodity in which the miner worked longest: gold (reference), coal, platinum, asbestos, iron, diamond, copper, or other. Cumulative tenure was used as a stand-in for dust exposure. The article does not name an asbestos fiber type.
• Main results:
  • Black miners, fully adjusted model: coal mining was associated with higher odds of moderate or marked emphysema than gold mining (OR = 2.39, 95% CI 1.86, 3.07)
  • Black miners, fully adjusted model: asbestos mining was associated with higher odds of emphysema than gold mining (OR = 1.47, 95% CI 1.01, 2.12)
  • White miners, fully adjusted model: asbestos mining was associated with lower odds of emphysema than gold mining (OR = 0.72, 95% CI 0.54, 0.97). No commodity showed a significant positive association.
  • Overall prevalence of moderate or marked emphysema was 1.2% among black miners and 15.9% among white miners
  • Sub-analysis of white miners with smoking information (n = 8297): no significant associations between commodity and emphysema after adjusting for smoking and other factors
  • In that white-miner smoking sub-analysis, current smokers had 5.5 (95% CI 4.46, 6.90) times and former smokers 3.97 (95% CI 3.17, 4.98) times the odds of emphysema compared with never smokers
  • In a sensitivity analysis of miners who worked in only one commodity, with at least 5 years of tenure, results were similar. Age at death and cumulative tenure remained significant predictors in both black and white miners.
• The authors' conclusion: The authors concluded that coal mining was significantly associated with emphysema among black miners. They suggested that historically high-exposure jobs held by black miners may explain why the asbestos association was seen only among black asbestos miners.
• Limitations the authors state:
  • There were no exposure measurements; commodity and tenure were used as stand-ins for exposure
  • Autopsy participation was voluntary, which could bias prevalence estimates
  • Emphysema diagnosis was based largely on non-inflated lungs, which could cause misclassification
  • There was limited information on former occupation, biomass fuel use and tobacco smoking. Smoking status was not available for black miners.
  • The analysis did not distinguish open-pit from underground mining
  • Large numbers of miners with missing tenure or commodity were excluded

Topics

Medical terms in this study, explained in our Lexicon: Emphysema, Autopsy, Pathology.

Related studies

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• Risk of mesothelioma from exposure to crocidolite asbestos: a 1995 update of a South African mortality study — D. Kielkowski, G. Nelson, et al. (2000)
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