There have been many reports over the years about radioactive material leaking into the Columbia River, it all just gets white washed but all it takes is one isotope that is super lethal to get into your body and it is game over.
Cesium-137, Strontium-90 and Iodine-131 are the ones to watch out for, if you see reports listing those isotopes then you know you want to stay far away.

I have always found it astounding to me that people who would be outraged if you dropped a big shit in the middle of their living room rug and then told them not to worry because someone would come along eventually with an idea of how to clean that up, these same people have no problem putting toxic nuclear waste in a metal drum for someone else to clean up later.