Natural levels of polonium-210 in urine

This paper presents a review and analysis of available data on background levels of polonium-210 in urine. It was established that 819 measurements could be considered to correspond to natural background levels, excluding a large number of values identified by the original investigators as potentially due to an artificial source or due to recognised enhancement of dietary intake. Almost 550 measurements were extracted from studies reported in the literature; additional measurements were contributions of previously unpublished data by authors of more recent papers. The majority of the measurements (462) were single samples from individuals but 357 values were repeat measurements provided by 81 subjects and for these the mean value for each subject was used. The final dataset consisted of measurements from 543 individuals. Analysis of the measurements confirmed the data was log normally distributed with mean and median values of 15.5 mBq d^-1 and 11 mBq d^-1 in urine samples, respectively. While the overall range was from 0.3-111 mBq d^-1, almost 90% of the measurements were less than 30 mBq d^-1, 95% were less than 45 mBq d^-1, and 99% less than 70 mBq d^-1. Separate analysis of data for smokers and non-smokers suggested a modest increase in smokers of up to 5 mBq d^-1. Perhaps reflecting the importance of dietary differences such as seafood consumption, a marked difference between countries was observed in the range of results. While for most countries, 95% or more of results were below 30 mBq d^-1, China and Italy were notable exceptions, with greater than 20% of values above this level.