Occurrence and Risk Assessment of Aflatoxin M1 in Fermented Dairy Products from the Croatian Market

Aflatoxin M1 (AFM1), a hydroxylated metabolite of aflatoxin B1, is a persistent food safety hazard in the dairy production chain. This study investigated AFM1 occurrence in fermented dairy products collected from the Croatian market in spring 2025 and assessed associated dietary exposure risks. A total of 81 samples were analyzed using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) following immunoaffinity column clean-up. AFM1 was detected in 48.1% of samples, with a mean concentration of 0.015 µg/kg. Products with thermophilic and probiotic bacterial cultures showed the lowest incidence rates, at 33.3% and 40.0%, respectively. Significantly higher AFM1 occurrence was found in Croatian samples than in imported ones (p < 0.05). Exposure assessment, based on estimated daily intake (EDI), hazard index (HI), and margin of exposure (MOE), identified toddlers and children as the most at-risk groups, with EDI ranging from 0.21 to 0.93 ng/kg bw/day, depending on AFM1 concentration. HI exceeded 1 even at mean AFM1 levels, while MOE fell below the safety threshold of 10,000 in worst-case scenarios, indicating potential health concerns. These findings underscore the need for continuous monitoring and targeted risk mitigation strategies for vulnerable populations, and support expanding regulatory limits to include processed dairy products.