DETERMINATION OF HEAVY METALS IN IRANIAN AND IMPORTED BLACK TEA

Tea is the most popular beverage in the world and contains several essential nutrients, which are beneficial for human health. The contamination of tea leaves by heavy metals may pose a serious threat to human, because they are not biodegradable and remain in environment and pass to food chain. In this study, the concentration of heavy metals of Cd, Pb, Ni, and Al and macro-elements of Fe, Zn, Cu, and Mn were determined by atomic absorption spectrometry on 30 samples of black tea cultivated in Iran and compared with the results for 30 samples of imported black tea in 2006. The results of analysis showed that the mean level of Al was 699.2±172.7mg/kg for Iranian and 388.3±98.3mg/kg for imported black tea. However, the values for Cd, Pb, and Ni were non-detectable. The most abundant nutritive metal was manganese with 155.2-214.2mg/kg and 96.7-332.9mg/kg in Iranian and imported black tea, respectively. The average contents of detectable heavy metals were significantly (p<0.05) higher in Iranian black tea. According to the results of this study, it is justifiable to set maximum residue level for heavy metals in tea, such as Al which appears to be very high in concentration.