Individual fumonisin exposure and sphingoid base levels in rural populations consuming maize in South Africa

Low and high oesophageal cancer incidence areas of the former Transkei region of South Africa have been associated with corresponding low and high levels of fumonisin contaminated home-grown maize. This is the first study in South Africa assessing fumonisin B (FB) mycotoxin exposure by quantifying individual maize consumption with weighed food records and FB levels from maize in each participant's household and concurrently evaluating sphinganine (Sa), sphingosine (So) and Sa/So ratios in plasma and urine of these participants as possible biomarkers of FB exposure. The high consumption of maize in Bizana (n=36) and Centane (n=30) of 0.41+/-0.21 and 0.39+/-0.19 kg/day, respectively, confirms the reliance on maize as the dietary staple. Mean total FB (FB(1)+FB(2)+FB(3)) levels in home-grown maize were 0.495+0.880 and 0.665+0.660 mg/kg in Bizana and Centane, respectively. Mean fumonisin exposure based on individual consumption was 3.9+/-7.3 and 4.1+/-7.6 microg/kg body weight/day, respectively, for Bizana and Centane. The mean combined sphinganine/sphingosine ratios in Bizana and Centane were similar and ranged from 0.10-0.55 in plasma (n=41) and urine (n=62). There was no association between sphingoid base levels and/or Sa/So ratios in the plasma and urine and individual fumonisin exposure, negating the sphingoid bases as potential biomarkers of fumonisin exposure in humans.