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Radiation safety watchdog hunts source of radioactive iodine tagged in air samples

The Finnish Radiation and Nuclear Safety Authority STUK has begun efforts to trace the origin of small quantities of radioactive iodine detected across the country. STUK said that within a one-week period, sensors picked up traces of I-131 in Rovaniemi, Helsinki and Loviisa, but the source of the radioactive substance is still unknown.

STUK -kyltti säteilyturvakeskuksen seinässä.
Image: Yle

The radiation and nuclear safety watchdog STUK has said that its monitoring stations have detected small quantities of radioactive iodine in the atmosphere in Finland. STUK said that in the quantities recorded, the substance would have no effect on human health, but noted that the readings were above normal levels.

The safety authority said that the origin of the radioactive iodine was not known and that the substance was detected in Rovaniemi, Helsinki, and Loviisa between October 19 and 25.

Officials in neighbouring Estonia also reported small amounts of radioactive iodine in air samples in the capital Tallinn and in Narva, near the Russian border in eastern Estonia. STUK and its corresponding organisation in neighbouring countries are investigating the source of the iodine.

"That we don’t know. Neither do we know if we will ever even find out," said STUK director Tarja K. Ikäheimonen.

Radioactive iodine is typically associated with nuclear energy, medical diagnostics and treatment and natural gas production. It was released following Russia's Chernobyl nuclear disaster in 1986 and accounted for a large degree of contamination hazard in the early weeks after Japan's earthquake-triggered Fukushima nuclear reactor meltdown in 2011.

Reactor leak in Norway not a likely source

At the beginning of last week a research nuclear reactor in Halden, southern Norway, experienced a small radioactive leak. STUK said that it is unlikely that the iodine detected in Finland and Estonia can be traced back to Norway. The organisation noted that during the period when samples were collected, air currents weren’t coming from the direction of Norway, but originated in the southeast.

"If there were a leak from some reactor, then we would see other radioactive substances apart from Iodine-131," Ikäheimonen added, referring to the substance by its scientific name.

However that was not the case. The STUK director pointed out that in previous instances when monitoring stations detected iodine, it had been traced to a leak from the pharmaceutical industry in Hungary.

Iodine-131 is often used to treat thyroid cancer and hyperthyroidism, a condition in which the body produces excessive amounts of thyroid hormone. I-131 is commonly administered in liquid or pill form and since the thyroid absorbs iodine, it is absorbed and concentrated in the gland. It destroys the thyroid tissue but does not affect any other body tissue.

STUK said it will intensify monitoring and draw additional samples for testing during the weekend. The constantly organisation nromally examines radioactivity in eight municipalities across the country.

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