The fumonisins are mycotoxins produced mainly by Fusarium verticillioides and F. proliferatum in maize, the predominant cereal staple for subsistence farming communities in southern Africa. In order to assess exposure to these mycotoxins in the Bizana (now known as Mbizana) and Centane magisterial areas of the former Transkei region of the Eastern Cape Province of South Africa, the actual maize consumption by different age groups in these communities was measured. In the groups 1–9 years (n = 215) and 10–17 (n = 240) years, mean consumption (±standard error) was 246 ± 10.8 and 368 ± 10.3 g per person day⁻¹, respectively, with no significant difference (p > 0.05) between the magisterial areas. For adults (18–65 years) mean maize consumption in Bizana (n = 229) and Centane (n = 178) were significantly different (p < 0.05) at 379 ± 10.5 and 456 ± 11.9 g per person day⁻¹, respectively. An exposure assessment was performed by combining the maize consumption distribution with previously determined levels of total fumonisin (fumonisins B₁ and B₂ combined) contamination in home-grown maize in these two areas. Assuming an individual adult body weight of 60 kg, fumonisin exposure in Bizana, an area of relatively low oesophageal cancer incidence, was 3.43 ± 0.15 µg kg⁻¹ body weight day⁻¹, which was significantly lower (p < 0.05) than that in Centane (8.67 ± 0.18 µg kg⁻¹ body weight day⁻¹), an area of high oesophageal cancer incidence. Mean fumonisin exposures in all age groups in both Bizana and Centane were above the provisional maximum tolerable daily intake (PMTDI) of 2 µg kg⁻¹ body weight day⁻¹ set by the Joint FAO/WHO Expert Committee on Food Additives.

The investigation of adverse health effects associated with fungal mycotoxins requires the measurement of human exposure. Most frequently, this exposure is estimated from contamination levels of raw foodstuffs, which are the primary source of toxin exposure, and data on food consumption patterns. However, variations in food preparation methods, food intake, contamination level, intestinal absorption, toxin distribution and excretion lead to individual variations in toxin exposure that are more readily measured with a biomarker. Fumonisin biomarkers have been sought in the measurement of levels of the toxin in physiological samples such as serum, urine, faeces, hair and nails. However, due to the low bioavailability of fumonisin, these samples pose a variety of analytical challenges and also still require validation as biomarkers. The most widely researched fumonisin biomarkers have been those related to the disruption of de novo sphingolipid biosynthesis, namely elevated levels of the sphingoid base, sphinganine, or of its ratio with sphingosine. Elevation of these parameters in humans would potentially provide a biomarker of biochemical effect. A number of investigations into the possible elevation of sphinganine (or its ratio with sphingosine) in human blood and urine have generally failed to correlate with estimates of fumonisin exposure. The sphingoid bases occur naturally in human blood and urine such that their levels have normal ranges, which can be influenced by dietary factors other than fumonisin ingestion. The lower exposures from human diets, as compared with doses in experimental animals, have made detection of changes in these sphingoid biomarkers problematic.

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. Cancer Epidemiol Biomarkers Prev; 20(3); 483–9. ©2011 AACR.