Tritiated Water Exposure in Zebrafish (Danio rerio): Effects on the Early‐Life Stages

International audienceTritium, a radioactive isotope of hydrogen of natural and anthropogenic origin, is ubiquitously present in theenvironment. Effluents of nuclear centers of production are significant anthropogenic sources. With the upcoming project of thermonuclear fusion, tritium releases in the environment may increase. It is therefore important to characterize the ecologicalrisk linked to tritium. The effects of tritiated water (HTO) were therefore studied in zebrafish larvae exposed for 10 d todifferent dose rates, 1.1 × 102, 4.1 × 102, and 3.8 × 103 μGy/h for larvae corresponding, respectively, to a water contaminationof 104, 105, and 106 Bq/mL of HTO. Those dose rates were higher than 10 μGy/h, which is the threshold recommended tostart monitoring ecosystems where radiological contaminants are present. Mortality, embryo‐larval development, immune toxicity, genotoxicity, neurotoxicity, and alterations of tissues were investigated. The results showed that HTO exposure induced DNA damage and reactive oxygen species production and modulated the expression of genes involved in detoxificationprocesses. Moreover, modifications of the muscular tissues (degradation of myofibrils at 4 d post fertilization anddisorganization of mitochondria at later stages) were observed. The results differed with HTO dose rates and with developmentalstages. These results will drive future research for the development of new HTO‐sensitive biomarkers and willallow us to progress in the characterization of the modes of action of tritium in fish