Authors: S. L. Mabila, K. Almberg, L. Friedman, N. Ndlovu, N. Vorajee, J. Murray, R. A. Cohen

Source: Am J Respir Crit Care Med 2017;195:A1747


Rationale: Emphysema rates have increased among South African miners who arrive at autopsy from 250 per 1,000 in 2010 to 355 per 1,000 individuals in 2013 as reported by the South African National Institute for Occupational Health (NIOH). In recent years, the workforce composition has changed in South Africa as more black miners have received long-term contracts and the mining industry has stabilized. In accordance to these changes in the mining industry, black race remains a significant determinant of increased disease burden. The main objective of the study was to determine the association between occupational exposures in mining and emphysema by race.Methods: We analyzed data from miners in the Pathology Automation (PATHAUT) database from 1975 to 2014. We examined the association between mine dust exposure, as measured by cumulative years of mining tenure, and emphysema presence and severity. We used logistic regression models to examine the relationship between mining tenure and both outcomes while controlling for age, tuberculosis, AIDS-related diseases, and year of death. Additionally, we controlled for smoking in a large sub-group of white miners with known smoking status since smoking status was not available for nearly all black miners.

Results: Our study included 64,766 South African Miners (black N = 43,030, white N = 21,736) from the PATHAUT database. Mean mining tenure was 24.9 years (STD = 12.0) among whites and 10.1 years (STD = 8.2) among blacks. Odds of emphysema presence and severity increased significantly for every 10 years of mining tenure among blacks (ORpresence = 1.17 95%CI 1.12 – 1.22; ORseverity = 1.16 95%CI 1.06 – 1.28), Among whites, we observed significantly increased odds of emphysema presence for every 10 years of mining tenure (OR = 1.07 95%CI 1.04 – 1.10), but no association between mining tenure and the severity of emphysema (OR = 1.01 95%CI 0.97-1.05). In the sub-group of white miners in whom we controlled for smoking status, we found an association between 10-year exposure and emphysema presence (OR = 1.14 95%CI 1.09 – 1.19), with a significant dose-response (p-trend = 0.0006), and emphysema severity (OR = 1.06 95%CI 1.00 – 1.10).

Conclusions: Analysis of data from PATHAUT lung autopsy material showed a significant relationship between occupational exposure and the presence and severity of emphysema. We also observed significantly higher odds of disease presence and severity among black miners compared to white miners.