Dr. Tsubokura's Radiation Lecture Vol.50

Author: Masaharu Tsubokura

Editors: Akihiko Ozaki M.D., Yuki Senoo

99. The calculated level of radiation exposure is overestimated

Various international organizations have published reports regarding the levels of radiation exposure and the radiation-induced health effects caused by the Fukushima Daiichi nuclear accident.

The report published by the United Nations in 2013 assessed the levels of radiation exposure more accurately than the report by the World Health Organization, taking various kinds of data into account. However, the United Nations’ calculation results still overestimated potential radiation exposure when considering what was actually observed in Fukushima Prefecture.

In particular, the estimates of internal radiation exposure by the United Nations were a few times higher than the actual levels of thyroidal radiation exposure in March 2011. Furthermore, it was also reported that the level of internal exposure measured by whole-body counters was much lower than the estimated value reported by the United Nations.

The report by the United Nations concluded that the radiation contamination caused by the Fukushima Daiichi nuclear accident is unlikely to cause “radiation-induced cancer” or “potential inherited health effects for descendants.” Their report further emphasized that adverse health effects of radiation exposure on fetuses are not expected, even if the radiation exposure occurred during pregnancy.

100. The impact of radiation on health is determined by the extent of exposure

We have introduced various information regarding radiation. In this article, we would like to come back to the principle of the health effects of radiation exposure—that is, that health effects of radiation exposure are not determined by the fact that one has been exposed to radiation, but the total dose of radiation exposure.

Radiation exists in our surrounding environment; all of us have been exposed to radiation from the universe or from radioactive substances in soil, air, and food. Due to the Fukushima Daiichi nuclear accident, the level of radiation exposure has increased to some extent due to radioactive substances scattered from the power plant. However, our body cannot differentiate between natural and artificial radiation. Therefore, the problem is that the amount of radiation increased due to the nuclear disaster.

Several investigations have been conducted for over 5 years to find this out. The levels of external radiation are different in each country and region. However, it was revealed that the radiation exposure increase due to the nuclear accident was, fortunately, within this range of regional differences in radiation levels.

At last, this series has finally reached its hundredth entry! I would like to express my gratitude to many people who have been supporting me.

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The Japanese version of the manuscript was originally published in Fukushima Minyu, a local newspaper in Fukushima prefecture, Japan, on November 27th and December 4th 2016 was reproduced for MRIC Global under the author's permission.