--- title: A Radioactive Cloud from Russia Swept Across Europe description: A radioactive cloud of Ruthenium 106 swept over most of Europe. Officials don't know why, but say it was harmless. canonical: https://time.com/5019323/radioactive-cloud-europe/ author: Jamie Ducharme article:opinion: false article:content_tier: free article:published_time: 2017-11-10T20:04:36.000Z article:modified_time: 2026-02-23T18:12:11.148Z article:section: Science og:title: A Radioactive Cloud Swept Europe — and No One Knows Why og:description: But officials say it was harmless og:url: https://time.com/5019323/radioactive-cloud-europe/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltde093bcdab65f2d0/6988d9b9bc6cfc69913e2a3c/time-logo.jpg?branch=production og:image:width: 1200 og:image:height: 675 og:image:alt: TIME og:type: article twitter:card: summary_large_image twitter:title: A Radioactive Cloud Swept Europe — and No One Knows Why twitter:description: But officials say it was harmless twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltde093bcdab65f2d0/6988d9b9bc6cfc69913e2a3c/time-logo.jpg?branch=production --- # A Radioactive Cloud from Russia Swept Over Europe — and No One Knows Why  by [Jamie Ducharme](https://time.com/author/jamie-ducharme/)  ## Jamie Ducharme Ducharme is a contributor to TIME. Nov 10, 2017 8:04 PM UTC  by [Jamie Ducharme](https://time.com/author/jamie-ducharme/)  ## Jamie Ducharme Ducharme is a contributor to TIME. Nov 10, 2017 8:04 PM UTC A mysterious radioactive cloud that swept through much of Europe this fall has officials baffled. The cloud was harmless and has dissipated, [France’s Institute for Radiological Protection and Nuclear Safety wrote in a statement Thursday](http://www.irsn.fr/EN/newsroom/News/Pages/20171109%5FDetection-of-Ruthenium-106-in-France-and-in-Europe-Results-of-IRSN-investigations.aspx), but between Sept. 27 and Oct. 13, the radioactive nuclide Ruthenium 106 was detected in “the majority of European countries.” Experts aren’t totally sure where the substance came from, though testing suggests it was first released during the last week of September in Russia or Kazakhstan, likely somewhere between Russia’s Volga River and Ural Mountains. “Russian authorities have said they are not aware of an accident on their territory,” IRSN Director Jean-Marc Peres [told Reuters](http://www.reuters.com/article/us-russia-nuclearpower-accident/french-institute-suspects-nuclear-accident-in-russia-or-kazakhstan-in-september-idUSKBN1D92LJ). Based on atmospheric tests, the report says, it’s unlikely that the cloud was the result of a nuclear reactor accident. Instead, it likely stemmed from a nuclear fuel treatment or nuclear medicine treatment center. Ruthenium 106 is produced when atoms divide in a nuclear reactor. It’s sometimes used in cancer treatment, specifically for melanoma of the eye, though it can be dangerous at high levels. The cloud drifting over Europe, however, never reached a concerning concentration, according to the IRSN report. “The concentration levels of Ruthenium 106 in the air that have been recorded in Europe and especially in France are of no consequence for human health and for the environment,” it says. ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/5019323/radioactive-cloud-europe/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/5019323/radioactive-cloud-europe/"},"headline":"A Radioactive Cloud from Russia Swept Over Europe — and No One Knows Why","datePublished":"2017-11-10T20:04:36.000Z","dateModified":"2026-02-23T18:12:11.148Z","description":"The radioactive nuclide Ruthenium 106 is believed to have originated in Russia or Kazakhstan","url":"https://time.com/5019323/radioactive-cloud-europe/","keywords":["europe","France","Nuclear","onetime","Science"],"thumbnailUrl":"","author":[{"@type":"Person","name":"Jamie Ducharme","jobTitle":"Ducharme is a contributor to TIME.","url":"https://time.com/author/jamie-ducharme/"}],"articleSection":"Science","image":[],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/science/","name":"Science"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/europe/","name":"europe"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/5019323/radioactive-cloud-europe/","name":"A Radioactive Cloud from Russia Swept Over Europe — and No One Knows Why"}}]}] ```