Urinary biomarker-based seasonal mycotoxin exposure assessment in rural resident populations of North-central Nigeria

The concentrations of mycotoxins and their metabolites in adult first morning void urine (n = 286) from agricultural populations in two north-central Nigerian states (Nasarawa and Niger) across harvest and storage seasons were assessed using LC-MS/MS. In total, 97 % of the urine contained at least one mycotoxin; with 10 distinct mycotoxins quantified. Ochratoxin A (OTA) was the most frequently occurring (86 %), while aflatoxin M1 (AFM1) and fumonisin B1 (FB1) were quantified in 40 % and 71 % of the urine, at median concentrations of 0.2 and 11 µg/g creatinine, respectively. Other detected mycotoxins/metabolites were dihydrocitrinone (60 %), zearalenone (ZEN) (58 %), citrinin (37 %), nivalenol (14 %), deoxynivalenol (5 %), α-zearalenol (3 %) and β-zearalenol (1.4 %). Median urinary AFM1, citrinins, OTA and ZEN levels were significantly higher (p < 0.05) in Nasarawa than in Niger. Urine from Nasarawa and at the harvest season contained more diverse mycotoxin classes than urine from Niger and at the storage season, respectively. Only three mycotoxin classes (aflatoxins, citrinins and fumonisins) showed significant seasonal variations, with higher urinary levels during harvest than at storage in Nasarawa. In Niger state, citrinins were mostly higher in urine during storage compared to harvest season, whereas urinary FB1 was higher at harvest compared to storage. Margin of exposure calculations indicated a risk of chronic exposure to aflatoxin B1 (AFB1) (detected as AFM1 in urine) and OTA in both states and across seasons, while the estimated average probable daily intake values for CIT, FB1 and ZEN exceeded the EFSA established reference values in both states and across seasons. The results clearly demonstrate chronic exposure to (carcinogenic) mycotoxins and call for intensive efforts towards design and implementation of feasible mitigation actions to reduce mycotoxin exposures and prevent potential health risks in the long-term in the affected region.