High exposure to cobalt and other metals in mineworkers and malachite workers in Katanga, D.R. Congo

Introduction
Southern Katanga is part of the African Copperbelt. Mining and artisanal exploitation of copper and cobalt ores are widespread, with thousands of “diggers” working in poorly regulated and dangerous working conditions.

Methods
We obtained spot samples of urine from three convenience samples of workers: 15 male miners (mean age 30.4 y) upon their return from work in a copper-cobalt mine, 26 informal diggers [7 men (31.4 y), 12 women (38.2 y), 7 children (12.7 y)] during their work on mine tailings and 18 artisanal workers processing malachite (54.5 y). The urinary concentrations of metals (and metalloids) were analyzed by ICP-MS.

Results
Median urinary concentrations (µg/g creatinine) of selected metals are shown in the table
Manganese Cobalt Arsenic Uranium
Mineworkers 2.79 214.5 26.5 0.040
Diggers (children) 1.56 40.2 20.6 0.156
Diggers (adults) 1.17 26.2 13.9 0.059
Malachite workers 23.08 40.1 12.0 0.044

Discussion
The observed values are generally much higher than those found in the general population of Southern Katanga, even among people living close to mines or smelting plants (Banza et al. Environ Res 2009), and they also exceed occupational exposure limits (e.g. the ACGIH-BEI for Co is 15 µg/l). This cross-sectional study shows a high to very high occupational exposure to various metals among workers, including children, engaged in mining or processing copper or cobalt ores in Katanga. The health significance of this high exposure remains to be established, but adequate prevention of excessive exposures should be implemented.