Environmental radioactivity refers to radioactive materials that are produced from nature as well as from man-made sources. It is monitored automatically by national environmental radioactivity monitoring stations, which control and manage disasters related to nuclear and radiation exposure and prepare responsive measures. The Korea Institute of Nuclear Safety monitors environmental ra- dioactivity across the nation at all times and conducts radioactivity research on the living environment. There are 15 regional radioac- tivity monitoring stations and 128 central radioactivity monitoring stations that periodically measure particles, radioactive fallout, and beta and gamma nuclides from precipitation. Data is collected in real time to observe changes in radiation levels, and provided to the public through the “Integrated Environmental Radiation Monitor- ing Network (iernet.kins.re.kr).”