Natural radioactivity estimation and heavy metals concentration in commercial tea brands - a baseline study on human health risk hazards due to tea consumption in Tamilnadu, India

In the current study, natural radioactivity and heavy metal concentration were analysed in the most commonly consumed 30 tea brands, available at Tamil Nadu, India. Heavy metal concentration in all the tested tea samples followed the order as Mn > Fe > Pb > Zn > Cu > Ni > Cr > Co > Cd. The concentration of heavy metals was comparatively higher in black tea when compared to that of green tea and indicates that the load of heavy metals gets reduced nearly 10 times after the process of brewing. With respect to radioactivity, the gross alpha activity in all the tea brands were below the detectable limits. The gross beta activity for the black tea ranged from 0.69-1.29 Bq/2 gm and for green tea, it was 0.54-0.86 Bq/2 gm. The gross beta activity was very low in the infused or brewed extracts, when compared to that of the raw tea. The study found the ratio of dissolution to be 4:1, where only 25% of radionuclides got transferred from 2 g of tea to the aqueous extract using 100 ml of boiling water with 5-where minute infusion time. The internal dose received by the people due to their regular tea drinking habits were however below the recommended limit of 0.3-0.8mSv/y for the beta emitters, as prescribed by WHO and below 1 mSv/y as set by ICRP. The quantity of heavy metals that one might uptake by consuming this beverage, was minimal and within the acceptable limits.