I heard an expert talking about some of the differences today. It's not all the same. And length of exposure appears to be key. "Radiation" is a blanket. Xrays are Gamma? This stuff included all manner of toxic shit. One of them has plutonium, which apparently is much worse. Dunno, I was on my way to work and just got the gist before I had to go.
I'm not primarily focused on this "plume" and the US by the way, I'm thinking about Japan specifically and nuclear energy in general.