The 2nd round screening of thyroid cancer in childhood has revealed the 1st case recently. It will have been 4 years very soon since the accident. As the rapid increase in the number of the cases of the illness in Chernobyl was observed in 4 or 5 years after the accident, we should go on being careful about the incidence of the cases from now.
One reason why we could not be optimistic for the effect of the radiation in Fukushima is that the data published by the government doesn't totally reliable.
One example of question for the data is that of Sr, a radioactive substance highly carcinogenic to human. Both Sr and Cs have the similar characteristics as radioactive substances, so that they behave in the same way once released into the natural environment. Cs has been reported to be widely distributed in inverse proportion to the distance from Fukushima. On the other hand, Sr is reported to be quite low all around. The Cs/Sr ratio deposited in soil around Fukushima is about 1000 times of that around Chernobyl. Sr activity in soil is not disproportionate to the distance from the nuclear plant in Japan. These findings of Sr in the environment make us suspect the data is arbitrarily handled for some purpose. The government and the power company have their motivation to hide some important data which involves our health.
Of course, the thyroid cancer related with the nuclear power plant accident is believed to be caused by radioactive Iodide with relatively short life span. It may not be related with the other kinds of radioactive substances. However, we should claim the government to publish all the data as it is. Even though there is little evidence that cancer cases are increasing in number in Fukushima and the adjascent areas, we should keep eyes wide open to the follow up data for them.