Abstract: In order to detect aflatoxin M1 (AFM1) pollution in milk from a certain city in south China and quantify the health risk of AFM1 via dietary intake of milk for residents in the city, 379 fresh milk samples from different cow breeds (A, B, C, D and E) were collected during December 2015 to May 2016. AFM1 concentration in milk samples was determined by high performance liquid chromatography and a nonparametric probabilistic evaluation model was fitted to evaluate the health risk associated with dietary intake (exposure) of AFM1 using the @Risk software package by Monte Carlo simulation. The results showed that 75 of these 379 samples (19.79%) were found positive for AFM1 with mean and maximum concentration of 0.19 and 0.62 μg/kg, respectively. The mean concentrations of AFM1 in different milk sources were in the following descending order: D (0.22 μg/kg) > A (0.21 μg/kg) > C (0.20 μg/kg) > E (0.18 μg/kg) > B (0.13 μg/kg). The AFM1 concentration values for all investigated samples were fitted with the Pareto, Expon and Laplace distribution models, and the goodness of fit of the developed equations were checked by five statistical methods of Akaike’s Information Criterion (AIC), Bayesian Information Criterion (BIC), Chi-Squared test, Anderson-Darling test and Kolmogorov-Smirnov test. The results indicated that the AFM1 pollution in all milk samples conformed to the Pareto distribution with Risk Pareto (2.661 5, 0.029), (3.765 2, 0.029), (3.370 8, 0.029), (2.854 6, 0.029) and (2.423 5, 0.029) for A, B, C, D and E, respectively. After 10 000 iterations, the average daily exposure to AFM1 from the milk sources A, B, C, D and E were determined respectively as 0.000 23, 0.000 20, 0.000 21, 0.000 22 and 0.000 25 μg/(kg·d) by means of Monte Carlo simulation and the Bootstrap method according to the distribution characteristics of AFM1 pollution and the exposure assessment parameters, and the daily exposure to AFM1 from these milk sources at the 99th percentile were 0.000 82, 0.000 49, 0.000 57, 0.000 73, 0.000 97 μg/(kg·d), respectively. The carcinogenic and non-carcinogenic risk associated with dietary exposure to AFM1 through the consumption of milk for different populations was characterized by using the dietary exposure evaluation model based on combined margin of exposure (MOE) and hazard index (HI) values, respectively. It turned out that MOE values for all populations were significantly higher than 100 and that the HI values were higher than 1 at a tolerable daily intake (TDI) of 0.005 μg/(kg·d) suggesting that although the results of carcinogenic and non-carcinogenic risk evaluation were significantly different for different populations, the health risk associated with dietary intake of AFM1 from milk was very low. In conclusion, this study may provide useful information and guidance for milk quality and safety regulation and systematic risk assessment in the future.

Key words: aflatoxin M1, milk, health risk assessment, probabilistic evaluation model