Seasonal study of aflatoxin M1 contamination in milk in five regions in Iran.

Between April 2003 and February 2004, 98 samples of raw milk were obtained from milk tanks in one dairy plant in each of five regions in Iran. These were chosen with mean distances apart of 400 km, whereby they have different ecologies (temperature, relative humidity, etc.) and different agricultural products were used for animal feeding. Samples (24-25 per season) were laboratory heat treated and were analyzed for aflatoxin M1 with a validated High Performance Liquid Chromatography (HPLC) system. The overall mean of all samples was 0.041-0.065 microg/L (95% confidence) and the adjusted mean based on statistical modification was 0.039 ppb: 61 samples had 0.000-0.050 microg/L, 29 samples were contaminated with 0.05-0.10 microg/L, and the remaining 8 samples had 0.1-0.39 microg/L. All of the samples were lower than Codex Alimentarius and FDA standards (0.5 microg/L). Levels of aflatoxin M1 were higher in winter and spring than in summer and autumn, but the differences were not statistically significant (P>0.07). However, the level of aflatoxin in milk from one region (Hamedan) was significantly lower (P<0.05) than in those of the other regions (Gorgan, Rasht, Shiraz, Tehran).