Four defectors from the area near North Korea's nuclear testing site showed symptoms that could be attributed to radiation exposure, but scientists said they could not conclude that the health problems had been caused by a nuclear test, the South Korean government said today.
The four arrived in South Korea from Kilju, a county in northeastern North Korea that includes Punggye-ri, where the North has conducted all six of its nuclear tests in tunnels dug deep beneath the mountains. South Korea began conducting medical exams of defectors from that region in October, a month after the North conducted its biggest test explosion yet.
The size of that detonation on 3 September, which the North claimed was produced by a hydrogen bomb, raised fears of a possible escape of radioactive material into the environment.
Those fears were compounded by a series of small earthquakes reported from Kilju in recent weeks that have been attributed to underground cave-ins caused by the powerful test. Commercial satellite images have also found evidence of landslides near the test site, increasing fears of a further release of radioactive fallout if the North were to conduct another nuclear test there.
Unconfirmed news reports claimed that some residents in Kilju had fallen sick from radiation exposure. Earlier this month, an official newspaper in a Chinese province adjoining North Korea offered its readers tips on how to protect themselves from nuclear fallout.
Such fears prompted the South Korean government to commission the medical exams of North Korean defectors from Kilju, to see if they showed signs of exposure.
Researchers said the results, released on Wednesday, could not produce any definitive findings because of a lack of data.
According to the study, there were 114 North Koreans from Kilju living in South Korea who have defected since the North's first nuclear test in 2006.
However, all of them arrived in the South before the North's most recent nuclear tests, including the September blast. This prevented researchers from studying the effects of the large nuclear test.
Moreover, only 30 defectors volunteered for the government-funded checkups, which were not mandatory.
In their report today, the researchers said they could not find any statistically meaningful amount of radioactive substance inside the bodies of the 30 defectors they examined. But they did find alterations in the chromosomes of four defectors.
They said these could have been caused by exposure to radiation, though they also cautioned that such abnormalities could also have other causes, like heavy smoking or exposure to pesticides or medical radiation. They said they did not have enough medical data from the defectors' lives in North Korea to produce any conclusive findings.
The unification ministry, a South Korean government agency in charge of North Korean affairs, said today it would try to run tests on more defectors and offer medical help if any were determined to suffer from radiation exposure.