Oh! I had completely forgotten about coal. You're right. :) Granite kitchen countertops and clay cat litter are also common household sources of radiation. With, as you say, "unspecified concentrations of tritium" then reasonable layman calculations of risk are difficult. I've seen online social media claims that people have already stopped fishing in the area because of their uncertainty. And it definitely doesn't help that the sudden temperature change due to plant shutdown resulted in local fish kill, unrelated to any radiation concerns.