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Background: ELISA is a widely used method for aflatoxin M 1 (AFM 1 ) quantification in dairy products. This study was conducted to compare ELISA kits from different manufacturers for AFM 1 quantification in milk. Methods: High sensitivity ELISA kits (for up to 250 ng AFM 1 /L), including AgraQuant (Romer Labs), Bioshield M1ES (Prognosis Biotech), Helica 96 (Helica Biosystems), Veratox (Neogen, Inc.), and the medium sensitivity kit Immunolab AM1E01 (Immunolab GmbH; for 10-1000 ng AFM 1 /L) were tested against a certified reference AFM 1 whole milk having 44 ng AFM 1 /L and its 10-fold dilution, and a 50 ng AFM 1 /L standard. In another experiment, Prognosis Bioshield M1UF (70-1000 ng AFM 1 /L), Romer's AgraquantPlus (10-2000 ng AFM 1 /L), and Immunulab's AM1E01 kits were compared to test a 500 ng AFM 1 /L solution. Results: In both of the experiments, the quantification of the tested AFM 1 levels did not differ ( P ≥ 0.310) between the kits from various manufacturers. In the case of 4.4 ng AFM 1 /L, recovery of the toxin was close to the assigned value under the kit by Neogen, Inc. In case the of 44 ng level, better recoveries were seen under the kits by Immunolab and Prognosis Biotech. In both the cases, low relative standard deviation (RSD) values were obtained only for the kit by Prognosis Biotech. In the case of the 50 and 500 ng AFM 1 /L solutions, the kits by Prognosis Biotech and Romer Labs provided recoveries close to the assigned values as well as low RSD. Conclusions: These data indicate that all the studied ELISA kit brands had comparable efficacy for AFM 1 quantification. Recovery of the toxin and RSD may, however, differ between kits from various manufacturers.

A longitudinal one-year study was conducted to determine aflatoxin M₁ levels in different types of milk marketed in Pakistan. Processed and raw liquid milk from 21 sources, two milk powder and six tea whitener brands were sampled on monthly basis from Islamabad. The aflatoxin M₁ levels in liquid milk were lower ( p < 0.05) in summer (April to July) compared with the levels in winter (January, November and December). The mean aflatoxin M₁ levels were 254.9, 939.5, and 1535.0 ng/L in UHT, pasteurized, and raw milk, respectively (differing at p < 0.001). The mean toxin level in powdered milk after reconstitution was 522.1 ng/L. Overall, 12.9, 41.0, 91.9 and 50.0% of the UHT, pasteurized, raw and powdered milk samples, respectively, exceeded the Codex maximum tolerable limit of 500 ng of aflatoxin M₁/L. It was estimated that consumers of raw and processed milk were exposed to 11.9 and 4.5 ng aflatoxin M₁, respectively, per kg of body weight daily. The study indicates potential aflatoxin M₁ exposure risks for the consumers of raw milk in the country. The levels of the toxin though comparatively lower in milk powder, requires attention as this type of milk is consumed by infants.