Iodine-131 Over Europe: Probably Medical

In early January, slightly elevated levels of iodine-131 were observed over northern and western Europe. The levels were measured during a temperature inversion, along with elevated levels of naturally occurring radioisotopes.

This, along with the deployment of an American WC-135 aircraft to the Mildenhall Royal Air Force Base in the UK, has led to speculation that the Russians have carried out a nuclear test. This is highly unlikely for several reasons.