I don't fully understand the comment - but I think it's my lack of knowledge here. If I stand next to a sign made with a small amount of tritium I get a small dose of radiation. If I live near a river or ocean that has 0.76 PBq dumped into it, isn't that high concentration going to be a lot worse for me even if I drive past every exit sign in Tokyo? What if I end up growing a Tritium vegetable garden?