Nuclear scientists are struggling to determine the source of small amounts of nuclear radiation that bloomed over Europe throughout January.France's IRSN institute, the public body for radiological and nuclear risks, announced in a statement on February 13 that Iodine-131, a radionuclide of human origin, was detected in trace amounts at ground-level atmosphere in continental Europe. First detected in the second week of January over northern Norway, Iodine-131 presence was then detected over Finland, Poland, Germany, Czech Republic, France, and Spain. However, the levels have since returned to normal and scientists have yet to determine the source of the radiation.Norway's Radiation protection Authority (NRPA), which first detected the Iodine-131 over its northern Russian border, told Motherboard over the phone today that the levels present essentially no risk to human health. "I can assure you that the levels are low," said a press a spokesperson.But with a half-life of just eight days, the detection of Iodine-131 is proof of a recent release, said IRSN in its statement to the media.Rumors are circulating, of course, that Russia has secretly tested a low-yield nuclear weapon in the Arctic, possibly in the Novaya Zemlya region—historically used for Russia's nuclear tests. Iodine-131, discovered by two University of California researchers in 1938, is a radioisotope synonymous with the atomic bomb tests carried out by the US and Russia throughout the 1950s, and has recently presented threats from leaking during the Chernobyl nuclear power plant disaster and the 2011 Fukushima nuclear accident.Read the rest of this article on MOTHERBOARD.