Contamination of Cow Milk by Heavy Metals in Serbia

Background: Dairy cows are exposed to numerous environmental hazards, such as heavy metals. Milk and dairy products could be harmful to humans when maximum tolerable amounts of heavy metals are exceeded. Analysis of heavy metals in milk is important because milk is a source of essential nutrients and is an indicator of environmental contamination. Some heavy metals are essential to maintain proper metabolic activity in living organisms, but at exceeded levels they could be toxic to living organisms. The main objective of the present study was to determine the residue levels of ten heavy metals (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in cow milk in Serbia. Materials, Methods & Results: The experiment was conducted at three farms at Vojvodina district, Serbia. Cows from all three farms were on pasture during spring and summer time. Randomly 50 cows from each farm were taken for this experiment. The cows have similar body condition score they were in their third or fourth lactation and gave approximately the same amount of milk in the previous lactation. Total 150 milk samples were collected from cows during the morning milking, in the period between April to May in 2016. All 150 milk samples were transported to laboratory as soon as possible and analyzed for the heavy metals. Heavy metals were analyzed by Inductance coupled plasma - optical emission spectrometry. Data are presented as mean values +/- sd. Statistical analysis was done by one way repeated measures analysis of variance (ANOVA). The level of significance was set at P LT 0.05. The highest average concentration in cow milk was determined for Iron (283.9 mg/kg), then for Zinc (60.21 mg/kg) and Copper (4.404 mg/kg), while the lowest concentration was for Cobalt and Lead (less than 0.005 mg/kg). Discussion: Bioaccumulation is one of the biggest problems with heavy metals. Heavy metals residues in milk can be very dangerous for the calves and humans as well. The existence of trace elements and heavy metals