The occurrence of aflatoxin M1 (AFM1) in milk samples commercialized in the Metropolitan area of Monterrey (Mexico) was evaluated by employing the competitive enzyme linked immunosorbent assay (ELISA) technique. For this, 84‐fluid milk samples, with diverse origin (80% national production, 20% imported milk) and heat treatments (26% pasteurized and 74% Ultra High Temperature (UHT)‐treated) were collected in different sales points. In all the evaluated samples, the AFM1 was detected, with values oscillating from 0.1 to 1.27 μg/L. According to the Food and Drug Administration (FDA) and Mexican standards, concerning a maximum limit of 0.5 μg/L, 39% of the analyzed samples were out of the standard limit, with different results depending on the milk origin (46% and 18% for national and imported milks, respectively) and heat treatment applied (45% and 23% for UHT and pasteurized samples, respectively). Based on these results, it is necessary a higher effort to control AFM1 levels in milk consumed in Mexico. Practical applications The practical application of this document is to serve as a first approach to know the presence of aflatoxins in milk in northern Mexico, both in domestic and imported products, and under different heat treatments applied and from this, take different measures by authorities and producers with a view to reducing their presence in milk and other dairy products.

The occurrence of aflatoxin M1 (AFM1) in infant formulae commercialized in the metropolitan area of Monterrey (Nuevo León, Mexico) was determined by using immunoaffinity column clean-up followed by HPLC determination with fluorimetric detection. For this, 55 infant formula powders were classified in two groups, starter (49 samples) and follow-on (6 samples) formulae. Eleven of the evaluated samples (20%) presented values above the permissible limit set by the European Union for infant formulae (25 ng/L), ranging from 40 to 450 ng/L. The estimated daily intake (EDI) for AFM1 was determined employing the average body weight (bw) of the groups of age in the ranges of 0–6 and 6–12 months, and 1–2 years. The results evidenced high intake values, ranging from 1.56 to 14 ng/kg bw/day, depending on the group. Finally, with the EDI value, the carcinogenic risk index was determined, presenting a high risk for all the evaluated groups. Based on these results, it is a necessary extra effort by the regulatory agencies to reduce the AFM1 presence in infant formulae consumed in Mexico.