Estimated average effective doses to adults, 10-year-old children and 1-year-old infants over the first year after the nuclear power plant (NPP) accident in Japan (2011) in the most contaminated Fukushima prefecture were, respectively, 1.0-4.3, 1.2-5.9 and 2.0-7.5 mSv. Worldwide annual exposures to natural radiation sources are generally expected to be in the range of 1-10 mSv, with 2.4 mSv being the estimate of the central value. Some national averages exceed 10 mSv. In the USA the average exposure to natural radiation is around 3.10, in Japan - 1.5 mSv/year; medical exposures add approximately the same value (in the USA more than in Japan). In Europe, average annual doses from the natural background exposure are above 5 mSv in several countries. Additional doses to the residents of the most contaminated Fukushima prefecture have thus remained during the first year after the accident within the limits of the natural radiation background, being far below the limits for professional exposures. For comparison, a single computed tomographic (CT) examination produces a dose within the range 2-20 mSv, while doses from interventional diagnostic procedures usually range from 5 to 70 mSv. Health risks including perinatal mortality have never been proven for the doses discussed above; an overview is in.
According to the concept discussed previously, with the dose rates tending to the background level, radiation-related risks would tend to zero, and can even fall below zero in some dose range in accordance with hormesis. Although not all animal experiments supported the hormesis concept, current experimental evidence in favor of hormesis is considerable.[9-12] This means that a part of experimental data is at variance with epidemiological studies, including those cited in. However, epidemiological studies of low-dose radiation effects may be prone to biases,[14-16] for example, dose-dependent selection or self-selection, higher participation rates of cases (e.g. cancer patients) compared to controls etc. The better recollection by cases of the facts related to radiation exposure (recall bias) may be conductive to the overestimation of doses in the cases. The selection and self-selection bias is a potentially serious problem of the epidemiological research. It is known e.g. from studies on the low frequency magnetic fields, where, similarly to low-dose low-rate ionizing radiation, there is some epidemiological association with cancer but neither supporting laboratory evidence nor biophysical plausibility.[18-20] In populations exposed to ionizing radiation, the self-selection bias must be stronger than for magnetic fields because carcinogenicity of the former is generally known. People knowing their higher doses would probably come to medical institutions more frequently being given averagely more attention.
It is not surprising that cataclysms with evacuation of people, associated with stress, temporary derangements of perinatal care services, of diets, etc., are accompanied by an increase in the perinatal mortality. Another factor potentially contributing to some reported dose-effect relationships might be an ideological bias and conflicts of interest aimed at the strangulation of nuclear energy, which agrees with the interests of fossil fuel producers. Nuclear power has returned to the agenda because of the concerns over increasing global energy demand and climate changes. NPP emit virtually no greenhouse gases in comparison to fossil fuels. The global development of nuclear energy must be managed by a powerful international executive based in the most developed parts of the world. It would prevent from spreading of nuclear technologies to unstable regions, where conflicts and terrorism are not excluded. It would also permit construction of NPP in optimally suitable places, disregarding national borders, considering socio-political, geological and other preconditions, quality of working by local workers, etc. In this way, nuclear accidents like in Japan (2011), caused by the formidable earthquake and tsunami, or in Chernobyl (1986), favored by disregard for written instructions, would be prevented. Moods and motivations of workers and engineers may be of importance, possibly related to the observation of their human rights. Note that Chernobyl accident coincided with destabilization of the Soviet society.
In conclusion, the study does not prove any dose-effect relationships but creates an exaggerated impression about the consequences of the Fukushima accident. According to the judgment by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), no discernible increased incidence of radiation-related health effects is expected among exposed members of the public or their descendants after the above-named accident. Certainly, radiation exposure of the developing embryo or fetus can cause damage. In addition to the induction of congenital malformations, the central nervous system is particularly affected, which can enhance the prenatal mortality. Mainly on the basis of animal studies and some observations following high-dose exposures of pregnant women, the UNSCEAR considered that there is a threshold for these effects at about 100 mGy i.e. much higher than the doses discussed above. Dose-response relationships at low radiation doses can be further clarified in large-scale animal experiments involving different mammal species, comparable doses and dose rates, reliably shielded from biases and conflicts of interest.
Sergei V. Jargin
Peoples' Friendship University of Russia
Clementovski per 6–82,
115184 Moscow, Russia
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