Mysterious Radiation Cloud Over Europe Isn't "Harmless" at Source

An airborne plume of radioactive ruthenium 106 from a nuclear accident was detected "in the atmosphere of the majority of European countries," from late September through mid-October, according to France's Radioprotection and Nuclear Safety Institute (IRSN) — but the source is still unknown. As of November 10, 2017, the manmade element has been identified in at least 28 countries.  Read more.