The levels of radioactive substances detected throughout South Korea are decreasing.

The Korean Institute of Nuclear Safety on Friday said that it tested radiation levels in the air at 12 monitoring stations around the nation.

Radioactive iodine was found in eleven regions except Cheongju, but the radiation levels were significantly low, with the highest figure being 0.213 millibecquerels per cubic meter.

Radioactive cesium was found in just five regions including Seoul and Chuncheon, with the levels up to 0.0683 millibecquerels.

The institute said that overall radiation levels are very low, with little impact on humans. He added that radioactive substances in air are steadily decreasing.