Tuberculosis, mining and silica

Correspondence to Professor Rodney I Ehrlich, Centre for Environmental and Occupational Health Research, School of Public Health and Family Medicine, University of Cape Town, Cape Town 7925, South Africa; rodney.ehrlich@uct.ac.za From the early years following its inception in 1886, South African gold mining was characterised by racial stratification and circular migrant labour from neighbouring colonies (later states), systems which underlay the labour and health profile of the industry for the next century.1 By the second decade of the twentieth century legal provisions were in place for regular physical and radiographical examination of new and returning miners for silicosis and tuberculosis. The decline in tuberculosis in the latest period 2010–2014 is plausibly attributed to the spread of antiretroviral treatment in both the mining industry and the state clinical facilities.8 However, as the gold mining industry is shedding jobs, a healthy worker effect may be contributing to the declining observed tuberculosis rates, with the corollary of ‘externalisation’ of continuing tuberculosis occurrence to the population of ex-miners.9 The devastating impact of HIV has, however, tended to overshadow the close association of tuberculosis and silica exposure, an association taken for granted in the first decades of the author proof twentieth century. Figure 1 of that article reveals that the mean duration of employment among black miners in this autopsy series doubled between 1975 and 2014. [...]the rising proportion of miners with silicosis detected at autopsy, a reflection of the increasing duration of exposure and therefore cumulative dust exposure, and the multiplicative interaction of silicosis with HIV, represent a second set of factors driving the tuberculosis epidemic in gold miners.