Prevalence of aflatoxin M1 in milk and its potential liver cancer risk in Taiwan.

Pasteurized milk may contain the liver carcinogen aflatoxin M1 (AFM1) if the cows that produce the milk ingest feed contaminated with aflatoxin B1. In this study, we collected 144 milk samples of three main brands in Taiwan twice a month over a 1-year period and purchased two samples each of eight domestic and imported brands of infant formula at two different times in 2005. Samples underwent solid-phase extraction, cleaning in immunoaffinity columns, and quantification by liquid chromatography-tandem mass spectrometry. We found autumn and winter levels of AFM1 to be higher than those in the spring and the summer. We also found higher concentrations of AFM1 in low-fat milk than in whole-fat milk. We were able to detect trace amounts of AFM1 (1.17 to 54.7 ng/liter) in all of our milk samples, but there was only one sample in which the level of AFM1 slightly exceeded the regulatory limit of the European Union (50 ng/liter). We were unable to detect AFM1 in any of the infant formulae. Using a World Health Organization method of evaluating risk of liver cancer, the group we found to be at greatest risk was 6- to 9-year-old girls (average, 12.2 additional cases per billion); the group with the lowest risk was men of 45 to 64 years of age (average, 3.45 additional cases per billion), the latter consuming less milk than all other groups. Consequently, the risk for liver cancer due to ingestion of milk contaminated with AFM1 was estimated to be low in Taiwan.