Natural levels of polonium-210 in urine

Abstract

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were extracted from studies reported in the literature; additional measurements were contributions of previously unpublished data by authors of more recent papers.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 and 11 mBq d in urine samples, respectively. While the overall range was from 0.3-111 mBq d, almost 90% of the measurements were less than 30 mBq d, 95% were less than 45 mBq d, and 99% less than 70 mBq d. Separate analysis of data for smokers and non-smokers suggested a modest increase in smokers of up to 5 mBq d. 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, China and Italy were notable exceptions, with greater than 20% of values above this level.

Collateral contamination concomitant to the polonium-210 poisoning of Mr Alexander Litvinenko

“…Based on an early and rapid review of natural background levels of 210 Po in urine, a value of 30 mBq d -1 was chosen as an excretion rate above which intake was unlikely to be wholly attributable to natural dietary sources. The extensive analysis by Hodgson (2017) showed that while there was a very large range in individual values of from 0.3 to 170 mBq d -1 , more than 90% of the measurements were less than 30 mBq d -1 , supporting the early judgment. Separate analyses of data for individual countries showed that 95% or more of results were below 30 mBq d -1 in most cases, including the UK, but that China and Italy were notable exceptions for which more than 20% of values were above this level.…”

“…Separate analysis of data for smokers and non-smokers suggested a modest increase in smokers of up to around 5 mBq d -1 . Reflecting the importance of dietary differences such as seafood consumption, a marked difference between countries was observed in the range of results (Hodgson 2017). 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.…”

“…Almost 550 measurements were extracted from studies reported in the literature (Black 1956, Globel et al 1966, DeBoeck et al 1971, Bale et al 1975, Okabayashi et al 1975, Juan and Balleos 1976, Holtzman et al 1976, Spencer et al 1977, Clemente et al 1979, Helmkamp et al 1979, Okabayashi et al 1982, Irlweck 1983, Mancini et al 1984, Azeredo & Lipsztein 1991, Hunt and Allington 1993, Santos et al 1994, Santos et al 1995, Naumann et al 1998, Santos et al 2000, Thomas et al 2001, Schafer and Seitz 2005, Hunt and Rumney 2007, Manickam et al 2010. The additional measurements were contributions of previously unpublished data, acknowledged by Hodgson (2017). The analysis of the measurements gave mean and median values of 14 mBq d -1 and 9 mBq d -1 , respectively.…”

“…It is a naturally-occurring radionuclide, present in our diets, body tissues and excreta as a member of the uranium-238 decay chain. Dietary intake varies substantially so that urinary excretion is also variable (Hodgson 2017). Interpretation of urine measurements to assess the probability of contamination from artificial sources must therefore take account of natural levels and their variability.…”

“…A detailed analysis of available data on natural concentrations of 210 Po in urine (Hodgson 2017) is referred to here in the interpretation of measurements on urine samples taken in the UK during the months following Mr. Litvinenko's death. Use is also made of the data provided by FMBA.…”