The cause of trace detection of radioactive iodine-131 in Europe has been identified as ‘most probably’ a release from a Hungarian factory making medical isotopes.
Authorities in that country today informed the International Atomic Energy Agency (IAEA) of their theory that the release may have begun at a facility run by Institute of Isotopes Ltd (Izotop) on 8 September and continued until yesterday.
Iodine-131 is one isotope that could be released by a nuclear reactor accident, such as occurred at Fukushima Daiichi earlier this year, but in that circumstance it would be accompanied by other isotopes such as caesium-137. No such fission products were detected in Europe, giving authorities full confidence to declare the iodine they detected could not have been from either Fukushima or any new nuclear accident.
The amounts of iodine-131 involved were tiny, but the substance decays quickly and therefore it is highly unusual for it to be detected in the environment by radiation monitoring networks. It is used to diagnose and treat cancers and disorders of the thyroid gland. All types of iodine are naturally transported by the human body to the gland, where large concentrations of iodine-131 are capable of delivering radiotherapy doses directly to tissues.
The IAEA said there were no concerns for public health: “If any member of the public were to breathe iodine for a whole year at the levels measured in European countries, then they would receive a dose in the range of 0.01 microsieverts for the year. To put this into perspective, the average annual background is 2400 microsieverts per year.”
The Izotop facility is near to the Budapest Research Reactor. As well as iodine-131 it supplies radioisotopes for pharmaceutical, scientific and industrial use including yttrium-90, technetium-99m, iodine-125, samarium-153, holmium-166 and lutetium-177.