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

Tritium (³H) is a radioactive isotope of hydrogen that is abundantly released from nuclear industries. It is extremely
mobile in the environment and in all biological systems, representing an increasing concern for the health of both
humans and non-human biota (NHB). The present review examines the sources and characteristics of tritium in the
environment, and evaluates available information pertaining to its biological effects at different levels of biological organisation
in NHB. Despite an increasing number of publications in the tritiumradiobiology field, there exists a significant
disparity between data available for the different taxonomic groups and species, and observations are heavily
biased towards marine bivalves, fish and mammals (rodents). Further limitations relate to the scarcity of information
in the field relative to the laboratory, and lack of studies that employ forms of tritiumother than tritiated water (HTO).
Within these constraints, different responses toHTOexposure, frommolecular to behavioural, have been reported during
early life stages, but the potential transgenerational effects are unclear. The application of rapidly developing
“omics” techniques could help to fill these knowledge gaps and further elucidate the relationships between molecular
and organismal level responses through the development of radiation specific adverse outcome pathways (AOPs). The
use of a greater diversity of keystone species and exposures to multiple stressors, elucidating other novel effects
(e.g., by-stander, germ-line, transgenerational and epigenetic effects) offers opportunities to improve environmental
risk assessments for the radionuclide. These could be combined with artificial intelligence (AI) including machine
learning (ML) and ecosystem-based approaches.