This article in Scientific American from 2014 is the most comprehensive discussion of tritium that I have read. As far as I can tell nothing has changed with tritium since then. It covers all the angles and does not try to force any one conclusion on the reader. A long read but well worth it.
“This new evaluation is likely to prove challenging, however, as tritium is difficult to get a grip on from both a radiological and human health perspective. On the one hand, there is evidence that the risk from tritium is negligible and current standards are more than precautionary. On the other, there is also some evidence that tritium could be more harmful than originally thought.
Or, as a health physicist who has studied tritium for years observes, in the 1970s, the EPA did not rely on any health studies in setting its original standards. Instead, the EPA back-calculated acceptable levels of tritium in water from the radiation exposure delivered by already extant radionuclides from nuclear weapons testing in surface waters. “It’s not a health-based standard, it’s based on what was easily achievable,” remarks David Kocher of the Oak Ridge Center for Risk Analysis, who has evaluated health risks from tritium and spent 30 years at Oak Ridge National Laboratory. “