Jayde Lovell, scientist and host of SciQ told IBTimes UK that the most likely explanation was simply Europe's abundance of nuclear reactors - the ones that make electricity - although trace radiation is not usually detectable.
The WC-135C Constant Phoenix, better known to its operators as the "sniffer" or "weather bird", was reportedly deployed in response to higher than normal levels of radioactive iodine-131 in the air across much of Europe in mid-January. They are saying that Russian nuclear testing on Arctic are the main reason this cloud appeared.
Norway was the first to measure the radioactivity, but France was the first to inform the public about it.
Iodine-131 - which causes mutation and death in cells it penetrates - was detected in Norway, Finland, Poland, Czech Republic, Germany, France and Spain.
Iodine-131 has a half-life of just eight days, so any detection is proof of a sudden and recent release of the radioactive chemical.
The Russian Army traditionally conducts low-yield nuclear tests in the Arctic.
GETTYThere has been a spike in Iodine-131
"It would be incredibly abnormal to be able to detect iodine 131 in these amounts from a Russian nuclear test", she explained. It is used for a number of things, including in treatment for thyroid cancer.
It was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, as well as the Chernobyl disaster in 1986 and Fukushima nuclear crisis in 2011.
Iodine-131 is a manmade radioactive material. It constantly changes the direction of the cloud, and that prevents the scientists from finding the source of the radiation.
According to the NPRA a facility in Eastern Europe is a potential source of the isotope.
"Due to rapidly changing winds, it is not possible to track exactly where it came from".
The Aviationist reports that an American "nuclear sniffer" aircraft, WC-135 has been deployed to the United Kingdom - but it's not known if it's linked to the iodine particles.
Nintendo Switch Bundle Packs Are Here Now For Pre-order
In the case of a lost, stolen, or defunct system, only Nintendo itself could restore purchases to an affected user. It's almost two weeks until the official release of the Nintendo Switch, Nintendo's latest console.