210Ро in black and green teas

Abstract

The 210Ро content in various grades of tea sold in St. Petersburg shops was determined, and the effective annual dose of internal irradiation from 210Ро at daily tea drinking was estimated. As shown by α-ray spectrometry, the activity concentration of 210Ро in tea leaves varies from 1.1 to 25 Bq kg–1. The 210Po content in black teas is, on the average, 1.7 times higher than in green teas. This difference is accounted for by specific features of processes for the production of black and green teas. From 1.5 to 56% of 210Ро passes into aqueous extracts. Despite higher polonium content in black teas, the amount of 210Po extracted from green teas is, on the average, 6.3 times higher than that extracted from black teas. This effect may be associated with the formation of water-soluble organic polonium compounds on the surface of tea leaves in the course of tea processing. The effective annual dose of internal irradiation from polonium at daily use of 10 g of dry tea is estimated at 0.8–9.5 μSv year–1 depending on the tea grade, or 0.5–5.8% of the average annual dose of irradiation of the Russian Federation population from the sum of the nuclides (210Pb, 210Po, 228Rа, 226Rа, etc., except 40K) getting into a human body with food and water.