Japan Institute for National Fundamentals

Speaking out

【#360(Special)】Breaking the “1 Millisievert” Curse

Keiichi Nakagawa / 2016.02.26 (Fri)

February 25, 2016

     During a speech on February 7 in Matsumoto, Nagano Prefecture, Minister of the Environment Tamayo Marukawa, referring to the decontamination targets following the accident at TEPCO’s Fukushima Daiichi nuclear reactor, said, “The Minister of the Environment at the time of the accident, without any scientific proof whatsoever, said suddenly that the radiation levels would be reduced to 1 millisievert.” On the night of February 12, though, Environment Minister Marukawa, speaking at a hastily-assembled press conference, retracted this statement, and issued a “heartfelt apology” to the victims of the nuclear disaster.
     It would seem that there are very few people in Japan—and Environment Minister Marukawa is not one of them—who have a correct understanding of the phrase, “1 millisievert or less per year.” The average citizen, based no doubt on the International Commission on Radiation Protection’s (ICRP) view that unnecessary exposure to radiation should be as minimal as possible, thinks that the radiation dose limit under normal circumstances is 1 millisievert annually. A recommendation to this effect is also incorporated into Japanese law. However, the annual dose of 1 millisievert indicates radiation from sources such as nuclear reactors, and is in addition to exposure to naturally-occurring radiation and radiation used for medical treatment.

The maximum permissible radiation dosage for Japanese people is 7 millisieverts
     Poor in resources such as uranium ore, the naturally-occurring radiation in Japan is 2.1 millisieverts per year, which is lower than the worldwide average. In radioactive resource-rich Finland, though, the yearly radiation exposure is 8 millisieverts, and in Sweden it is 7 millisieverts. There is, of course, no data indicating that the rate of cancer is high in Northern Europe.
     Furthermore, Japan is number one in the world in radiation exposure for medical treatment, at 3.9 millisieverts annually. This elevated level of medical treatment radiation exposure in Japan is due to the fact that Japanese people can undergo medical testing cheaply, whenever and wherever they choose. In actuality, Japan is far and away the world leader when it comes to the number of medical exams, with each Japanese person receiving medical attention three times more frequently than people in the United States. Our universal-coverage national health insurance system, which is the envy of the world, is what increases our exposure to medical radiation.
     Our exposure to radiation from natural sources is 2.1 millisieverts, and our exposure to medical treatment radiation is 3.9 millisieverts. This means that we in Japan are exposed to radiation on the order of around 6 millisieverts every year. Because the phrase “1 millisievert or less per year” does not include exposure to naturally-occurring radiation or to radiation used for medical treatment, each person in Japan, speaking in terms of average exposure, is permitted up to 7 millisieverts, or 6 millisieverts for natural and medical radiation plus 1 millisievert for radiation from nuclear reactors. An additional 1 millisievert of radiation exposure does not have any particular significance. If we become too obsessive over 1 millisievert, then we will end up producing droves of evacuees, such as we are witnessing with the situation in Fukushima today.

Evacuations increase the number of cancer patients
     The additional radiation exposure for evacuees has been, at the most, around 3 millisieverts—not enough to cause an increase in cancer. (Second-hand smoke and a vegetable-poor diet are equivalent to radiation exposure on the order of 100 millisieverts.) However, an evacuation that has stretched out to five years worsens lifestyle habits, such that diabetes, depression, and other ailments are on the rise. Diabetes increases carcinogenesis by as much as 20%, meaning that the ironic result of evacuating in order to avoid being stricken with cancer has been an increase in cancer occurrence. The most pressing task now is to break free from the “1 millisievert” curse.

Keiichi Nakagawa, Associate Professor, Tokyo University Hospital Department of Radiology