Biological Half-Life and Oxidative Stress Effects in Mice with Low-Level, Oral Exposure to Tritium

Abstract

Tritium ((3)H) may enter the environment from human activities, particularly at production, processing, or waste storage sites such as the Department of Energy's Savannah River Site, a former nuclear production facility in South Carolina. Understanding the dynamics and potential adverse effects of tritium in exposed organisms is critical to evaluating risks of tritium releases at such sites. Previous studies estimated the biological half-life of tritium in mice to be approximately 1.13 d; however, these laboratory studies were not conducted under environmentally realistic conditions. In this study, designed to be more representative of environmental exposure, mice were allowed to drink water containing tritium (activity about 300 Bq/ml) for a period of 2 wk. The induction of oxidative stress from tritium exposure was evaluated by comparing the activities of antioxidant enzymes (catalase, glutathione peroxidase, and superoxide dismutase) in exposed and control mice. From this experiment, the biological half-life of tritium was determined to be 2.26 +/- 0.04 d, almost double previous estimates. While positive controls (x-ray irradiated mice) showed responses in antioxidant enzyme activity, there was no indication of oxidative stress induction in mice exposed to tritium at this concentration.

Rodents as receptor species at a tritium disposal site

“…Previous studies have found that tritium causes harmful effects in rodents at concentrations several orders of magnitude higher than those found at the tritium disposal site (Brooks et al, 1976;Carsten and Commerford, 1976;Gao et al, 2002;Yamamoto et al, 1995). In addition, results from a laboratory study where exposure concentrations were comparable to those of mice inhabiting the tritium disposal site indicated that the tritium burdens of mice at the disposal site are insufficient to induce oxidative stress (Kelsey-Wall et al, 2005). As an isotope of hydrogen, the metabolic pathways for tritiated water in organisms are the same as those for water.…”

“…Because tritium does not bioconcentrate, and because tritium has a relatively short biological half-life (Kelsey-Wall et al, 2005), there should be a relationship between whole body tritium concentrations of exposed mice and the amount of tritium applied to their environment. With an increased availability due to irrigation with tritiated water, whole body tritium concentration of exposed mice should rise.…”

Tritiated Water Induces Toxicity in Human Umbilical Vein Vascular Endothelial Cells via IL8

“…10 However, consensus on the RBE of tritium has not yet been reached. [15][16][17][18] The UK Advisory Group on Ionizing Radiation released a report suggesting that given the large number of radiobiology studies that focus on tritium, its RBE should be classified as a minimum of 2 and that 3 should be considered for safety. 19 Although the biological effects of high doses of tritium have been defined and genetic and specific tumor effects have been identified in animal models after long-term exposure, epidemiological investigations into the health risks associated with exposure to tritium are not yet publicly available.…”

“… 10 However, consensus on the RBE of tritium has not yet been reached. 15 - 18 The UK Advisory Group on Ionizing Radiation released a report suggesting that given the large number of radiobiology studies that focus on tritium, its RBE should be classified as a minimum of 2 and that 3 should be considered for safety. 19 …”

Radiation Effects of Normal B-Lymphoblastoid Cells after Exposing Them to Low-Dose-Rate Irradiation from Tritium β-rays

“…Kulkarni et al found that mitochondrial mutant cells with mutations occurring at different mitochondrial DNA (mtDNA) sites exhibited distinct radio sensitivities to X-ray irradiation, which was related to diverse DNA damage responses triggered in the mitochondrial mutant cells [ 20 ]. Currently, many studies focus on nuclear DNA damage caused by tritium exposure [ 21 , 22 , 23 ], but the impact of mitochondrial function regulation on the biological effects of tritium radiation has not been reported.…”