The Radioactive Breath

One thing that has always seemed odd to me was the lack of any mention
of Godzilla's breathing fire. In the first film in particular when Godzilla
melts the high tension wires down, Raymond Burr says only something like:
"I can't believe whats just happend George" But he does not explain what
did happen. In fact no one talks about it through out the film or most of
the entire series.

I thought this was a dubbing error, but when I at last saw the original
Japanese version it didn't mention it either!

Is it just a given that dinosaurs had radioactive breath?