Fumonisin B1 as a urinary biomarker of exposure in a maize intervention study among South African subsistence farmers.

BACKGROUND The consumption of maize highly contaminated with carcinogenic fumonisins has been linked to high oesophageal cancer rates. The aim of this study was to validate a urinary fumonisin B1 (UFB1) biomarker as a measure of fumonisin exposure and to investigate the reduction in exposure following a simple and culturally acceptable intervention. METHODS At baseline home-grown maize, maize-based porridge, and first-void urine samples were collected from female participants (n=22), following their traditional food practices in Centane, South Africa. During intervention the participants were trained to recognize and remove visibly infected kernels, and to wash the remaining kernels. Participants consumed the porridge prepared from the sorted and washed maize on each day of the two-day intervention. Porridge, maize, and urine samples were collected for FB1 analyses. RESULTS The geometric mean (95% confidence interval) for FB1 exposure based on porridge (dry weight) consumption at baseline and following intervention was 4.84 (2.87-8.14) and 1.87 (1.40-2.51) μg FB1/kg body weight/day, respectively, (62% reduction, P<0.05). UFB1C, UFB1 normalized for creatinine, was reduced from 470 (295-750) at baseline to 279 (202-386) pg/mg creatinine following intervention (41% reduction, P=0.06). The UFB1C biomarker was positively correlated with FB1 intake at the individual level (r=0.4972, P<0.01). Urinary excretion of FB1 was estimated to be 0.075% (0.054%-0.104%) of the FB1 intake. CONCLUSION UFB1 reflects individual FB1 exposure and thus represents a valuable biomarker for future fumonisin risk assessment. IMPACT The simple intervention method, hand sorting and washing, could positively impact on food safety and health in communities exposed to fumonisins.