The Japanese government
has made its first admission that
a worker at the Fukushima nuclear plant developed cancer as a following decontamination work after the 2011 disaster.
The man worked at the damaged plant for over a year, during which he was exposed to 19.8 millisieverts of radiation, four times the Japanese exposure limit. He is suffering from leukemia.
The former Fukushima manager Masao Yoshida also contracted cancer of the oesophagus after the disaster and died in 2013—but the owner and operator of the nuclear plant, Tepco, refused to accept responsibility, insisting that the cancer developed too quickly.
Three other Fukushima workers have also contracted cancer but have yet to have their cases assessed.
The Fukushima nuclear disaster followed the tsunami of 11 March 2011. Three out of four reactors on the site melted down, clouds of deadly radiation were released following a hydrogen explosion, and the nuclear fuel appears to have melted through the steel reactor vessels and sunk into, or through, the concrete foundations.
But that single 'official' cancer case is just the beginning. Hundreds more cancers have been and will be contracted in the local population.
A 30-fold excess of thyroid cancer has been detected among over 400,000 young people below the age of 18 from the Fukushima area.
According to the scientists, "The highest incidence rate ratio, using a latency period of 4 years, was observed in the central middle district of the prefecture compared with the Japanese annual incidence".
In a first screening for thyroid cancer among 298,577 young people four years after the disaster, thyroid cancer occurred 50 times more among those in the most heavily irradiated areas, than in the general population, at a rate of 605 per million examinees.
In a second screening round of 106,068 young people conducted in April 2014 in less irradiated parts of the prefecture, the cancer was 12 times more common than for the main population.
Thyroid cancer is commonly developed as a result of acute exposure to radioactive iodine 131, a product of nuclear fission. Because iodine concentrates in the thyroid gland, thyroid damage including cancer is a characteristic marker of exposure to nuclear fallout.
Exposure to iodine-131 presents a high risk in the immediate aftermath of a nuclear accident owing to its short half life of eight days, making it intensely radioactive. It is estimated to have made up about 9.1% of the radioactive material released at Fukushima.
The paper's authors note that the incidence of thyroid cancer is high by comparison with the Chernobyl nuclear disaster in 1986 at the same time following exposure—and warn that many more cases are likely to emerge:
"In conclusion among those ages 18 years and younger in 2011 in Fukushima Prefecture, approximately 30-fold excesses in external comparisons and variability in internal comparisons on thyroid cancer detection were observed in Fukushima Prefecture within as few as four years after the Fukushima power plant accident. The result was unlikely to be fully explained by the screening effect.
‘‘In Chernobyl, excesses of thyroid cancer became more remarkable four or five years after the accident in Belarus and Ukraine, so the observed excess alerts us to prepare for more potential cases within a few years’’.
Vol. 48, No. 29, Jan 24 - 30, 2016