The International Atomic Energy Agency (IAEA) [28] and the World Health Organization [29] indicate that radiation exposure can result in both short-term and long-term effects in every body organ. In the Fukushima accident, public concern focused on both acute radiation sickness and increased long-term cancer risk [30].

Three months after the Fukushima accident, 20 teams were dispatched to Fukushima to screen for human radiation exposure. More than 5,000 people were screened by the staff of Hirosaki University (Fig. 24.4), and the results showed no acute radiation injuries [31]. The six deaths associated with the operation of the NPP were not attributable to exposure to ionizing radiation [ 11] . However, biological responses after exposure to radiation are time-dependent (Fig. 24.5), and the lack of symptoms appearing in the short term does not indicate freedom from long-term adverse effects due to radiation exposure. In the case of the Chernobyl accident, although no cases of cancer were confirmed to be due to the radiation exposure, some studies suggest that the risk of thyroid cancer for children living in nearby

areas could have been increased by a factor of 2 to 5 per 1 Gy of thyroid dose [30]. The Japanese government invited children exposed to the radio­active releases at different districts to be evaluated for thyroid disorders. As at December 31, 2011, 14,442 children had undergone screening, and no cases of fluid-filled cysts larger than 20 mm in diameter were found. Between January and March 2012, 27,467 more children were screened for thyroid. Furthermore, starting in April 2014, a follow-up thyroid screening will be performed on 360,000 potentially affected children once every two years until age 20 and every five years above the age of 20 [11]. No information is currently available concerning the progress of the studies planned for pregnant women and evacuees.