The use of atoxigenic Aspergillus species to reduce aflatoxins in maize, based on competitive exclusion of toxigenic fungi, is a promising bio-control strategy. However, no research has been executed on the secondary metabolic repertoire of these so-called atoxigenic Aspergillus species and potential favourable production of fumonisins by Fusarium species. Furthermore, the direct comparison of mycotoxins treated with bio-control and non-treated maize has never been performed. Therefore, through a case-control study in 10 Tanzanian villages, the risk in humans will be assessed through multi-mycotoxin biomarker analysis in urine and plasma.