An expert committee sanctioned by the Fukushima Prefectural Government has approved the final draft of a midterm report stating that the proportion of child thyroid cancer cases being found in Fukushima Prefecture is many times higher than the national average.
At the same time, the committee says it is "difficult to imagine" that the higher incidence is due to radiation.
The committee, consisting of experts in fields including epidemiology and cancer, examined health survey data for Fukushima Prefecture children who were 18 or younger at the time of the Fukushima No. 1 Nuclear Power Plant disaster.
Committee Chairman Hokuto Hoshi said at a press conference that the higher rate of thyroid cancer was due to "simultaneously checking" many patients at once.
The final draft is based on an initial round of diagnoses given between October 2011 and the end of April last year. Around 300,000 of about 370,000 potential survey subjects were examined. Based on national statistics, the survey should have only found around two people who were under 18 at the time of the disaster with thyroid cancer, but instead 100 people with the cancer were found. Additionally, 15 suspected cases were found.
"We may be diagnosing many cases of cancer that would otherwise be diagnosed later in life or that are not life-threatening," part of the draft reads.
Among the reasons that the committee considers radiation exposure unlikely as a reason for the higher incidence of thyroid cancer are: the radiation exposure levels from the Fukushima disaster are low compared to those of the Chernobyl disaster, no thyroid cancer cases have been found in children who were 5 or younger at the time of the disaster, and no large differences in the rate of discovered cases were found by area within the prefecture.
Still, while the report calls the influence of radiation small, it says it cannot be ruled out, and it recommends that diagnoses continue. It also calls for the patients to be informed of the risk of causing them needless anxiety by diagnosing cancer cases that are not expected to worsen in the future.
In the second round of diagnoses that began from April 2014, as of the end of last year, 16 people who had not been diagnosed with thyroid cancer or suspected thyroid cancer in the first round had been newly diagnosed with it, and 35 people had been newly diagnosed with suspected cases of the cancer.
The midterm report will become official in March.