Mercury in Sub-Saharan Africa: Developing an Exposure Assessment Framework for Ghana and Uganda

Abstract

Exposure to environmental toxins is a major contributing factor to the expected increase in chronic disease within developing countries in the next 20 years. Due to its ubiquitous distribution and persistent nature, mercury (Hg) is an example of a toxic substance that has garnered global concern because of its known detrimental effects on human and ecosystem health. Although fish consumption is the predominant source of Hg exposure to humans in developed nations, studies in developing countries have shown that high Hg concentrations in humans cannot be explained by fish consumption alone. The estimated daily intake (EDI) and the relative contribution of various sources of Hg to humans differ significantly between individuals, ethnic groups, and across continents. Health Canada is currently attempting to regulate the anthropogenic release and exposure dose of Hg to its citizens based on known EDIs, however the greatest sources of Hg exposure across sub-Saharan Africa (SSA) are still unknown, thus impeding the regulatory process. This thesis focuses on four major sources of Hg exposure in SSA: skin-lightening cosmetics, soil geophagy, small-scale gold mining, and fish consumption. An exposure assessment model has been developed to identify the sources of greatest concern for various age groups in Ghana and Uganda and is presented using published and unpublished data, as well as experimental Hg bioaccessibility data. The results indicate that occupational exposure and lifestyle choices (mining and use of skin-lightening cosmetics) have the greatest contribution to overall increases in Hg toxicity in adults. The health of infants, however, is most likely to be compromised before birth and in the first few days of life due to maternal consumption of fish with elevated Hg concentrations and the use of Hg-containing cosmetics. It is imperative that further research of these sources be carried out to prevent the possible long-term negative social and economic consequences of chronic illness in SSA.