A survey of seasonal variations of aflatoxin M1 in raw milk in Tangshan region of China during 2012-2014

Total 530 samples of raw milk were collected from the dairy farms in the Tangshan region of north China during four seasons each year from 2012 to 2014, and aflatoxin M1 (AFM1) contents were measured using HPLC-MS/MS. The results showed that AFM1 was detected in 280 samples (52.8%) at the range of 10-200 ng L−1, and the mean level of AFM1 was 73.0 ng L−1, which was below the China and US legal limit of 500 ng L−1. The incidences of AFM1 contamination were 27.5% in spring, 39.0% in summer, 71.7% in autumn and 78.9% in winter, respectively. It indicated that seasonal variations should be considered for the AFM1 control particularly during winter season. In comparison with the data from different years, the incidences of AFM1 contamination in raw milk samples were 87.8% with a range of 10.0-160 ng L−1 in 2012, 29.9% with 10.0-190.0 ng L−1 in 2013 and 36.7% with 12.0-111.0 ng L−1 in 2014. Hence, present study exhibits a significant decrease in the incidence of AFM1 contamination in Tangshan region after 2012.