The level of ²¹⁰Pb extraction efficiency in Polish herbal teas and the possible effective dose to consumers

The article presents the results of a study on the level of ²¹⁰Pb efficiency extraction in Polish herbal teas as a possible additional source of this radioactive isotope in the human diet. The twelve most popular herbal teas available in Poland and their infusions in filtered and tap water were analyzed as well as ²¹⁰Pb activity concentrations and effective doses (radiation) were calculated. The highest activity concentration of ²¹⁰Pb in dried plants was determined in cistus - 35.5 Bq kg^-1dry wt, while the lowest was in milk thistle - 3.25 Bq kg^-1dry wt what gives respectively for cistus 46.1 ± 0.7 and 6.50 ± 0.29 mBq for milk thistle per one tea bag. The extraction efficiencies in the filtered water oscillated from 5.1 ± 0.5 for milk thistle to 27.3 ± 0.8% for cistus, while for the tap water they ranged from 7.3 ± 0.6% for lime to 33.3 ± 2.2% for white mulberry. Based on the study, it was found that the analyzed herbal tea consumption would give a small portion of the annual effective dose of ²¹⁰Pb received in Poland - the annual effective radiation dose of ²¹⁰Pb taken with herbal tea infusions (one glass daily) was calculated from 0.08 ± 0.01 to 3.17 ± 0.08 µSv.