Identifying human health risks from precious metal mining in Sierra Leone

Water pollution results in more than two million human deaths every year, with a disproportionate amount of mortality occurring in developing countries. Tracing how and where water-borne pollutants enter the human body during everyday practices, and estimating the potential risks of these interactions, is critical to effective mitigation or adaptive practices to reduce health impacts. To understand these local processes, we worked with human communities along the Pampana River in Sierra Leone, Africa, from its headwaters at Lake Sonfon in the northeast-an area with both active and abandoned gold mining sites-to its confluence with the Jong River in the center of the country. We first measured the concentrations of heavy metals in fish that people eat and in riverbank soils where people congregate. We then estimated the risk people face, distinguishing carcinogenic risks from non-carcinogenic risks, as well as quantifying the risk to different age groups (i.e., adults vs children) at varying distances from the mining areas and operations, and in different seasons (wet vs dry season). We found dangerously high levels of heavy metals in fish and soil and conclude through life practice analysis that people living along the Pampana River face significantly elevated health risks in their everyday lives due to contamination from metals. The mean adult cancer risk was 1.01 x 10(-3), while the mean child cancer risk was 9.42 x 10(-3). Higher risks are associated with the wet season and living either downstream or closest to the mining operations and were particularly acute for children. Mining operations that directly impact riverine human settlements represent an area of concern for developing countries such as Sierra Leone.