Aflatoxin M1 Contamination of Milk Samples in Virginia During 1981 to 1987

Aflatoxin B₁ (AFB₁ ), when fed to dairy cattle, has been shown to yield the milkborne metabolite aflatoxin M₁ (AFM₁)(Figure 1). AFM₁ carry over into milk via the secretory route is low (2% ± 1% of AFB₁ introduced), but has been shown to be increased by treatment with polyhalogenated biphenyls (Heeschen and Bluethgen, 1989). Higher levels of AFB₁ grain contamination in feed thus yields higher levels of AFM₁ in the milk produced (Zimmerli and Blaser, 1979). AFM₁ has been shown to be both toxic and carcinogenic (Hsieh et al., 1986). Even though AFM₁ is less toxic when compared to its unoxidized precursor, AFB₁, the risks that are posed to humans through the consumption of dairy products warrant concern. The toxicity and related carcinogenicity of AFM₁ has prompted the testing of milk and associated products for the its presence and is addressed via the U.S. FDA (Federal Regulation) action level of 0.5 ppb AFM₁. Methods for quantifying aflatoxin include, thin-layer chromatography (TLC), high pressure liquid chromatography (HPLC), and monoclonal antibody technology. The current Association of Official Analytical Chemists methods for analysis utilizes HPLC to quantify aflatoxins (Williams, 1984).