Aflatoxin M1 contamination in raw bulk milk and the presence of aflatoxin B1 in corn supplied to dairy cattle in Japan.

Aflatoxin M1 (AFM1) is a hydroxylated metabolite of aflatoxin B1 (AFB1), which has been found in the milk of dairy cattle fed AFB1-contaminated feeds. Since AFM1 has been evaluated as a possible human carcinogen, the cancer risk arising from AFM1 contamination in milk is a serious problem in food safety. To evaluate the risk of AFM1 contamination in milk, it is necessary to analyze the risk factors of AFB1 contamination in corn provided for concentrated feed in Japan. The AFM1 level in domestic raw bulk milk was measured at three sampling times, January, February and June in 2004. The AFB1 contamination in corn supplied to cows was determined at the same time as the sampling of raw milk. The AFM1 contamination levels in milk in January, February and June 2004 were 0.011, 0.007 and 0.005 ng/g, respectively. The AFB1 contamination level in the corn of the concentrated feed was higher from October of 2003 to February of 2004 than from April to June in 2004. This study provides evidence that AFM1 contamination level in milk is parallel to that of AFB1 in corn of concentrated feed, so monitoring of the AFB1 level in corn is important to prevent the risk of AFM1 contamination in milk in Japan.