Tritium (3H) the radioactive isotope of hydrogen is a beta emitter with a half-life of 12.312 (25) years. It can integrate organics molecules of living organisms by following the water cycle and form the organically bound tritium fraction (OBT). In 2017, the IRSN published a report on the update of knowledge on tritium in the environment, taking up some of the questions that have been waiting to be answered since the publication of the Livre Blanc du Tritium by ASN in 2010. Among these, those concerning the behavior, fate and speciation of this radionuclide in the environment are still relevant. The existence of two forms of OBT is commonly accepted: a non-exchangeable fraction (NE-OBT) and an exchangeable fraction (E-OBT) with the near environment. However, there is no consensus on their definition, therefore several one can be found in the literature.