Finland’s Radiation and Nuclear Safety Authority (STUK) said it has found small amounts of radioactive isotopes of cobalt, ruthenium and caesium in air samples collected in Helsinki between 16 and 17 June. Radiation authorities in Sweden and Norway have reported similar findings.
Pia Vesterbacka, who heads environmental radiation surveillance at STUK, said there was no cause for alarm as the detected radioactive material was too minute to pose any risk.
"The amount of radioactive particles is very small and has no impact on the environment or human health," she explained.
Samples from Finland’s seven other radiation monitoring stations have yet to be analysed.
"Radiation from the Chernobyl disaster is still circulating. These readings are only slightly elevated in relation to the regular radioactive backdrop," Vesterbacka said, adding that STUK would naturally investigate the source of the radiation.
On Friday the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), tweeted it had detected higher-than-usual amounts of radiation between 22 and 23 June, posting a map indicating a potential source region including Denmark and Norway, southern Sweden, Finland, the Baltic countries and part of western Russia.
Vesterbacka did not want to speculate whether the radiation could have originated in Russia, saying STUK would calculate radiation spreads in cooperation with the Finnish Meteorological Institute (FMI).
"Investigations are still ongoing...at this point we would not want to come out and say the radiation originated in Russia," she said.
Vesterbacka underlined that the elevated levels do not indicate an explosion occurred, saying that an environmental leak would yield readings that were tens of times higher.
STUK is due to publish the results of its investigation next week.