A systematic review of respirable dust and respirable crystalline silica dust concentrations in copper mines: guiding Zambia’s development of an airborne dust monitoring programme

Abstract

Background: Workers in copper mines are exposed to respirable dust (RD) and respirable crystalline silica (RCS), which could lead to the development of silicosis. With the expected increase in copper production in the next two decades due to the world's green energy pathway, the number of miners exposed to RCS and incidents of exposure exceeding the recommended occupational exposure and other limits may increase. However, data for RD and RCS concentrations in the copper mining industry are limited. Objective: The objectives of this study were to assess the current state of knowledge about exposure to RD and RCS in copper mines, and to provide recommendations for the development of an airborne dust monitoring programme in Zambia. Methods: A systematic literature review was conducted, using the PRISMA methodology. The following online databases were searched for relevant research articles about RD and RCS in copper mines: Clarivate's Web of Science, Google Scholar, PubMed, Science Direct, EBSCO Host, and Scopus, using keywords and phrases with boolean operators. Articles were eligible for inclusion regardless of the sampling method used to measure airborne RD and/or RCS (personal exposure or area monitoring), were published in the period 1970-2023, and met the quality requirements. Results: After full-text screening, nine out of 6 710 potential articles remained. We found that area and personal RD and RCS data in copper mines are not widely documented in the open-access online literature. For personal RCS data, exposure exceeded the occupational exposure or other recognised limits in most sites; the highest personal RCS exposures occurred in sections of the mine where ore was crushed and transported. For mines that only conducted area monitoring of RD, the airborne dust concentrations that were potentially available for personal exposure were relatively low, compared to the RD exposure limit of 3 mg/m3 . Overexposure to RCS occurred even though personal exposure to RD complied with applicable limits in most cases. Conclusion: We found evidence of personal overexposure to RCS in copper mines, globally. Assessment of RD concentrations alone (even when exposure is under control) is not adequate to protect workers against overexposure to RCS. Zambia needs to develop an RCS monitoring programme for the copper mining industry. The programme should be based on established standards such as the European Standardisation Committee (CEN) standard (BS EN 689:2018), or the South African Mining Industry Code of Practice as the socio-economic conditions of miners are similar in Zambia and South Africa.