[credit_guy]

I stand by what I said. Yes, beta-emitters are most hazardous when they are inside your body, if they are together and stay there for a long time. The main examples are Strontium-90 and Caesium-137. The problem with them is that they bioaccumulate. Strontium accumulates in the bones (it is chemically similar to Calcium) and Caesium in the pancreas (it's not clear why. it is chemically similar to Potasium, but it's not obvious why it should accumulate in the pancreas).

Tritium is very different. It is chemically just Hydrogen, which is present everywhere in the body. It just can't bioaccumulate.

In any case, if you don't believe me, here's a statement from the FDA regarding the tritiated water released by Fukushima:

  Tritium presents an extremely low human and animal health risk if consumed and any health risk would be further minimized with the dilution effects of discharge into the ocean.

[1] https://www.fda.gov/news-events/public-health-focus/fda-resp...