~~Published on Feb 18, 2017
Iodine-131 (131I), a radionuclide of anthropogenic origin, has recently been detected in tiny amounts in the ground-level atmosphere in Europe. The preliminary report states it was first found during week 2 of January 2017 in northern Norway. Iodine-131 was also detected in Finland, Poland, Czech Republic, Germany, France and Spain, until the end of January.
Iodine-131 is a radionuclide with a short half-life (T1/2 = 8.04 day). The detection of this radionuclide is proof of a rather recent release.
Besides the iodine release, the origin of which is still unknown, the poor dispersion conditions due to the thermal stratification  of the atmosphere also affected the observed concentration levels, including those of naturally occurring radionuclides such as Lead-210 (210Pb) , or fine particles (PM2.5 and PM10) leading to pollution episodes, particularly in the Western part of Europe during week 4 of January.
It must be pointed out that only particulate iodine was reported. When detectable, gaseous iodine is usually dominant and can be estimated to be 3 to 5 times higher than the fraction of particulate iodine.