Iodine-131, a radionuclide of anthropogenic origin, has recently been detected in tiny amounts in the ground-level atmosphere in Europe.
The radioactive anomaly 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. But the origin remains unknown.
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. However, officials were not able to determine the exact origin of the radioactive anomaly that spread across Euope in January 2017.
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, 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.
The highest concentrations were measured in Poland, but even there they were very far away from the concentrations, which could have any effect on human health. But still, they should be published.
In France, particulate 131I reached 0.31 µBq/m3 and thus the total (gaseous + particulate fractions) can be estimated at about 1.5 µBq/m3. In Norway, where the anomaly was first detected between January 9 and 16, the particulate 131I reached 0.5 µBq/m3 so a total (gaseous + particulate fractions) of about 2.5 µBq/m3. Here the results for Finland.
These radioactive anomalies have been shared between members of an informal European network called Ring of Five gathering organizations involved in the radiological surveillance of the atmosphere.