I was reading about radiation poisoning on wikipedia when I got to the section on its history. I am interested in knowing when people either put forward the theoretical idea of radiation poisoning, or when its effects were observed and they put two and two together.

The wikipedia section is lacking here--it goes from "A guy got radiation burns but didn't realize what they were" to "People got sick from radiation products in the thirties, but they didn't die, and it's not clear if they understood that it was the radiation doing it" to "Hiroshima/Nagasaki happened".

So, when did scientists/doctors become aware that radiation could cause illness and death? How did that idea develop?