Mining Migrant Worker Recruitment Policy and the Production of a Silicosis Epidemic in Late 20th-Century Southern Africa

Objectives: Between the 1980s and 2000s, an epidemic of silicosis was identified in migrant black goldminers, many from neighbouring countries, on the South African gold mines. This studies aimed to use the newly available employment database of a large goldmining company to demonstrate how a sustained rise in employment duration in a new cohort of black migrant workers resulted from changes in recruitment policy, and the implications for current surveillance and redress of silicosis. Methods: Contract data of 300,774 workers from the employment database of a multi-mine goldmining company were analysed for 1973-2018. Piecewise logistic regression was applied to determine trends in cumulative employment, including South African versus cross-border miners. The proportions with cumulative employment >10, 15 or 20 years, typical thresholds for chronic silicosis, were also calculated. Results: Five calendar phases were identified between 1973 and 2018. During the second phase, 1985-2013, mean cumulative employment rose five-fold, from four to 20 years. Cumulative employment continued to rise, although more slowly, before peaking in 2014 and falling thereafter. Over most of the 1973-2018 period, cross-border miners had greater cumulative employment than South African miners. Overall, the proportion of miners exiting with >15 years, rose from 5% in 1988 to 75% in 2018. The record of changes in labour recruitment in the 1970s is consistent with the emergence of this epidemic, with no corresponding evidence of a sustained rise in dust concentrations. Conclusions: These new data support the hypothesis of a silicosis epidemic driven by increasing cumulative dust exposure in a new cohort of circular migrant workers from the 1970s. They inform current programmes to examine and compensate this neglected population for silicosis and related disease, while highlighting the lack of information on cumulative employment and silicosis among migrant miners in previous decades. The findings also have relevance to the plight of such migrant workers in hazardous occupations globally.