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 < 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 in dairy products and milk has been recorded in various countries since it is considered as one of the most dangerous aspects of food contamination. The presence of heavy metals in cow's milk may be attributed to contamination due to exposure of lactating cow to environmental pollution or consumption of contaminated feeding stuffs and water. Heavy metals after intake in cow organism distributed to all organs and glands such as udder. By that, secretory udder tissue gets intoxicated with heavy metals and after that they can be found in milk. After analyses the results in this experiment the highest average concentration of Fe in cow milk it might be because cows were fed with hay from pasture rich in iron between April to May. Some researchers found the amounts of Cu in the milk of individual varied from 0.2 to 0.8 mg/kg. Contrary to this finding, in current study the average value of Cu in cow milk was 4.404 mg/kg. It is found that the highest concentration of Zn in cow milk is 10.75 mg/kg, lower compare to result in current study (60.21 mg/kg). Arsenic (As) concentration was 0.058 mg/kg, cadmium (Cd) was 0.01 mg/kg, cobalt (Co) was 0.002 mg/kg, chrome (Cr) was 0.018 mg/kg, manganese (Mn) was 0.493 mg/kg, nickel (Ni) was 0.119 mg/kg and lead (Pb) was 0.08 mg/kg what is just above recommended values by International Dairy Federation. The results showed that most of the milk samples from the different farm contained all the studied metals with concentration higher than those recommended by International Dairy Federation and Codex for cow milk.