Traces of radioactive iodine have been detected in five cities across the country following the nuclear crisis in the quake-stricken nuclear power plant in Japan, a state-run nuclear safety agency said Friday.
The Korea Institute of Nuclear Safety (KINS) said an analysis of air samples taken from 12 places across the nation on Thursday found minuscule traces of radioactive iodine-131 in Daegu, Busan, Cheongju, Gangneung and on Jeju Island.
Gangneung, 237 kilometers east of Seoul on the east coast, is the only city that continued to report iodine traces in the air after Seoul began releasing data on Tuesday.
The institute, however, said all readings in the five locations were far below the one millisievert (mSv) exposure level set by the government.
Iodine-131 is a by-product of fission reaction and poses health risks if large quantities accumulate in the thyroid gland. The material has an effective half-life of just 7.6 days and loses its radioactivity relatively quickly.
The institute added that the iodine came from the crippled Fukushima nuclear power station, which began to suffer explosions on March 12, a day after a devastating earthquake and subsequent tsunami rocked Japan.