Cytogenetic damage analysis in mice chronically exposed to low-dose internal tritium beta-particle radiation.

Sandrine Roch-Lefèvre,Nick Priest,Amélie Fréneau,Matthew Flegal,Cécile Martin-Bodiot,Mohamed Benadjaoud,Melinda Blimkie,Eric Grégoire,Laurence Roy,Laura Bannister,Dmitry Klokov,Heather Wyatt,Jean-René Jourdain,Joan-Francesc Barquinero

doi:10.18632/oncotarget.25282

Abstract

The aim of this study was to carry out a comprehensive examination of potential genotoxic effects of low doses of tritium delivered chronically to mice and to compare these effects to the ones resulting from equivalent doses of gamma-irradiation. Mice were chronically exposed for one or eight months to either tritiated water (HTO) or organically bound tritium (OBT) in drinking water at concentrations of 10 kBq/L, 1 MBq/L or 20 MBq/L. Dose rates of internal β-particle resulting from such tritium treatments were calculated and matching external gamma-exposures were carried out. We measured cytogenetic damage in bone marrow and in peripheral blood lymphocytes (PBLs) and the cumulative tritium doses (0.009 – 181 mGy) were used to evaluate the dose-response of OBT in PBLs, as well as its relative biological effectiveness (RBE). Neither tritium, nor gamma exposures produced genotoxic effects in bone marrow. However, significant increases in chromosome damage rates in PBLs were found as a result of chronic OBT exposures at 1 and 20 M Bq/L, but not at 10 kBq/L. When compared to an external acute gamma-exposure ex vivo, the RBE of OBT for chromosome aberrations induction was evaluated to be significantly higher than 1 at cumulative tritium doses below 10 mGy. Although found non-existent at 10 kBq/L (the WHO limit), the genotoxic potential of low doses of tritium (>10 kBq/L), mainly OBT, may be higher than currently assumed.

Highlights

Tritium (3H), a radioactive isotope of hydrogen, is a byproduct of the nuclear industry released into the environment and it represents a significant public concern for potential health effects [1,2,3]
One-month treatment of mice with 10 kBq/L, 1 or 20 MBq/L of tritium in the drinking water as tritiated water (HTO) or organically bound tritium (OBT) did not lead to statistically significant changes in the frequencies of polychromatic erythrocytes containing micronuclei (mn-polychromatic erythrocytes (PCE))
Similar to the 1-month exposure, 8-month γ-irradiation did not produce higher rates of bone marrow mn-PCE. This data suggests that chronic exposure of mice to low doses of internal β-irradiation from HTO or OBT in drinking water at concentrations of 10 kBq/L, 1 or 20 MBq/L, as well as to external γ-irradiation at dose rates of 1.44 and 31 μGy/h, does not affect the level of cytogenetic damage in bone marrow cells

Summary

Introduction

Tritium (3H), a radioactive isotope of hydrogen, is a byproduct of the nuclear industry released into the environment and it represents a significant public concern for potential health effects [1,2,3] These concerns have been on a rise lately due to the expected growth of nuclear power production world-wide, the development of nuclear fusion technology, and the continuing uncertainties related to potential health effects of tritium [3, 4]. The current guidelines in situations of prolonged radiation exposure of the public are based on the approach proposed by the ICRP [13]. According to the ICRP, in existing exposure situations, it is prudent to restrict the prolonged component of the individual dose to 0.1 mSv from 1 year’s consumption of drinking-water [14]. There are remarkable differences in the drinking water tritium standards between countries (e.g. 100 Bq/L in most of countries of the European Union, 7,000 Bq/L in Canada, 7,700 Bq/L in Russia, 30,000 Bq/L in Finland and more than 76,000 Bq/l in Australia) [15]

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