A quarter of North Korean defectors from regions near the northeastern Punggye-ri nuclear test site have shown chromosome mutations possibly attributable to exposure to radioactivity, data showed Monday. Radioactive exposure tests conducted in 2024 by the Korea Institute of Radiological & Medical Sciences (KIRAMS) on 35 North Korean defectors from eight regions near the Punggye-ri nuclear test site found that 12 of them, or 34 percent, showed chromosome mutations possibly linked to radiation exposure, according to the unification ministry. The regions include Kilju, Kimchaek and Paekam. Since 2006, the North has conducted all of its six nuclear tests at the Punggye-ri nuclear test site, located in Kilju County. In similar tests conducted last year, 15 of 59 defectors tested showed possible chromosome mutations, bringing the total number of North Korean defectors with such findings to 44 out of 174 individuals tested between 2023-25, or 25 percent. The tests measure levels of chromosome aberration in individuals to assess their accumulated radiation exposure, with the minimum detectable r