The bioaccessibility of essential and potentially toxic trace elements in tropical soils from Mukono District, Uganda

It has been postulated that endomyocardial fibrosis (EMF), a common cardiac disease in certain tropical communities including parts of Uganda, may be related to the presence of elevated levels of dietary Ce, and deficient lev els of dietary Mg. In Uganda, significant variation in dietary exposure to both elements is likely due to variations in local soil geochemistry and di etary habits, including geophagia (the deliberate consumption of soil). Thi s paper reports the concentration and bioaccessibility (determined from a p hysiologically based extraction test-PBET) of Ce and other essential (Mg an d Fe) and trace elements in soils from the Mukono district of Uganda. Trace element concentrations varied markedly between soil samples (ground soils) and soils eaten deliberately, such as termite nest soils and traditional h erbal-soil remedies. The highest bioaccessibility values were reported for the chelate-rich, intestinal phase of the PBET. Median percentage bioaccess ibility values for Ce (1-15%), Mg (7-33%), Fe (0.1-2.9%) and other trace el ements varied considerably, but were generally higher in geophagic (herbal- soil remedies and termite nest soils) than common (ground) soil samples. On ly in the case of Fe does the ingestion of soil account for a major proport ion of recommended daily intake (RDI). The revised estimates of Ce and Mg d ietary intake (based on bioaccessibility data rather than an assumption of 100% bioavailability) significantly reduced the importance of geophagia rel ative to exposure through the ingestion of food and water.