Where you sit has no effect because the radiation is very hot stuff coming down from outer space.

On the other hand, the risk appears to be minimal. Estimates have been made of the increased cancer rates that would be expected amongst aircrews--but they don't show up.

So far every data point we have on the risks of low-level exposure says it's harmless or even beneficial. None of them are conclusive, though, as the numbers are small.

This is not to say that high level exposures are safe--there's no doubt of the risk there. The question is whether at low levels the result is to stimulate the body's defenses more than the risk that came with the radiation.