Biotoxins are an increasing problem in human foods. Climate change helps toxins to emerge in new (northern) regions while increasing their occurrence of events in already vulnerable regions. This is specifically true for mycotoxins and cyanotoxins, as their origin organisms benefit from a warmer climate, and they seem more and more present in areas where it was not the case, some decades ago. A major data gap still exists concerning the co-occurrence of these toxins and their combined toxicological effect on humans.

Therefore, our study evaluated the occurrence of a common mycotoxin (Aflatoxin-M1) and eight microcystins in milk. Initially, an analytical method was established to assess all toxins with one validated method. This method was used to analyze 113 milk samples collected from different Belgian areas. Additionally, the potential synergistic effects of the toxins on mitochondrial dysfunction in HepG2 cells were evaluated at sub-cytotoxic levels.

Both toxin groups were not detected in the milk samples. However, the inhibition of cell viability and a hyperpolarization in the mitochondrial membrane potential was observed during toxicological tests after the combined exposure of HepG2 cells to 100 ng mL^-1 AFM1 and 1000 ng mL^-1 MC-LR for 48h. Additionally, extracellular flux analysis revealed inhibitions of several key parameters of mitochondrial function.