RESUMO
To determine the levels of aflatoxin M1 [AFM1] in produced cheeses by different plants in province of Tehran. Cross-sectional study. Eighty cheese samples. Chromatography was used for determining the presence of AFM1. one- way analysis of variance and Tukey test. AFM1 was found in 83.8% out of 80 cheese samples. The range of contamination levels varied among different months. AFM1 in June, September, December, and March ranged from 197 to 1423, 177 to 1274, 179 to 1506 and 219 to 2918 ng/kg, respectively. however, the mean values were 549.7, 503.9, 602.1 and 749.6 ng/ kg, respectively. Moreover, the highest mean concentration of aflatoxin M1 [AFM1] was registered in samples March [2918 ng/kg]. The lowest mean concentration of aflatoxin M1 was registred in samples of September [177 ng/ kg ]. Statistical evaluation showed that there were no significant differences [P>0.05] among the mean concentration of AFM1 in cheese samples of June, September, December and March. However, mean concentrations of AFM1 in cheese samples of spring and summer was significantly lower than autumn and winter [P=0.004]. It can be concluded that the high occurrence of AFM1 in cheese is probably due to the presence of aflatoxin in the feed. This condition should be considered as a probable hazard for human health