Tritium: Its relevance, sources and impacts on non-human biota

Controlled Release of Radioactive Water from the Fukushima Daiichi Nuclear Power Plant: Should We Be Concerned?

“…Although it is a β-emitter, the relative biological effectiveness (RBE) of 3 H in tissues is contested. Laboratory studies have shown that 3 H could be as potent as high-energy γ or X-ray radiation for the induction of chromosomal damage in fish. 8 A precautionary approach has been recommended while dealing with internal emitters, given that ionizing radiation could induce many other novel effects that have thus far not been considered in risk assessments.…”

“…It is known that 3 H (half-life of 12.6 years) in its inorganic form (i.e., HTO) quickly integrates into biological systems and can consequently associate with organic molecules [as organically bound-tritium (OBT)]. , The environmental persistence of OBT, including in sediments and soils, raises concerns about its potential transfer to the water cycle and its biomagnification through the food web . For example, in the Severn Estuary (U.K.), it has been suggested that bioaccumulation of anthropogenic OBT by benthic organisms and demersal fish largely occurs via a pathway of conversion of dissolved OBT into particulate OBT (through bacterial uptake and physicochemical processes) and subsequent transfer up the food web by sediment-dwelling microbes and meiofauna .…”

“…Moreover, the pattern of distribution of OBT among different tissues in organisms depends on not only the chemical or biochemical characteristics of each tritiated compound but also the metabolic activities of different tissues. , Data on HTO and OBT distribution, behavior, and potential effects are available for only a few taxonomic groups and are heavily biased toward laboratory species (Figure ). This contributes to considerable uncertainty in environmental risk assessments (ERA) for the radionuclide …”

“…Compared with human health, dose estimation for natural biota, which exhibit different geometric shapes and sizes, is challenging and not well-defined. , The external dose estimation based on energy levels of different qualities of radiation cannot be considered realistic and safe for either non-human biota or humans exposed through different routes (e.g., inhalation, food, water, and skin). In this context, chronic exposure to HTO can induce DNA damage at different life stages of marine species .…”

“…This contributes to considerable uncertainty in environmental risk assessments (ERA) for the radionuclide. 3 ■ RADIATION DOSE ESTIMATIONS AND EFFECTS…”