In this blog post, we will examine the long-term effects of the Fukushima nuclear accident and explore the scientific verification and ongoing monitoring necessary to accurately understand radiation risks, as well as the roles of the government and citizens.
When the International Olympic Committee selected Tokyo as the host city for the Summer Olympics, there were concerns about whether it was appropriate to hold a large-scale international event while the cleanup from the Fukushima nuclear accident was still ongoing. The Tokyo Olympics were eventually held after being postponed once due to the COVID-19 pandemic. Seeing a world-class event take place and daily life continue in a city hundreds of kilometers away from the accident site might make it feel as though the nuclear accident is already a thing of the past. However, the state of recovery in the accident-affected area and its radiation safety cannot be judged solely by whether international events are held there or by the city’s vibrancy. Conversely, it is also unreasonable to consider all cities equally dangerous simply because they are located in the same country as the accident site. What is important is to consistently monitor actual contamination levels and management conditions, even as memories of the accident fade. The Fukushima nuclear accident remains an issue that the international community must continue to monitor with interest over the long term, even as time passes.
In March 2011, a nuclear accident occurred in Fukushima, Japan, that shocked the world. A massive earthquake off the coast of northeastern Japan and the subsequent tsunami caused the Fukushima Daiichi Nuclear Power Plant to lose its power supply and cooling functions; damage to the reactor cores in several units led to the release of radioactive materials into the environment. Those who remembered the Chernobyl nuclear accident worried that large-scale radioactive contamination and long-term health effects might be repeated. Although the Japanese government stated its commitment to resolving the accident and managing radioactive materials, such promises alone were insufficient to alleviate public anxiety. To assess the safety of a nuclear accident, it is necessary to examine not only explanations emphasizing technical capabilities but also actual release levels, radiation exposure doses to residents, environmental measurement results, and management outcomes. The extent to which Japan has mitigated the accident’s impact and how it will manage the remaining risks are issues that must be determined through ongoing verification.
First, let’s examine why a nuclear power plant accident requires long-term attention and management. To understand this, one might compare a nuclear explosion to a nuclear power plant accident, but it is not appropriate to measure the risks of these two events simply by their size or by a multiplier. A nuclear explosion releases enormous energy in an instant, causing damage through shock waves, thermal radiation, initial radiation, and radioactive fallout. Nuclear power plant accidents, even if they do not involve a nuclear explosion of the same type as a nuclear weapon, are serious because the loss of cooling capacity and fuel damage can lead to the release of radioactive materials into the environment. Although radiation dose rates may decrease significantly after a nuclear explosion as short-lived radionuclides decay rapidly, long-lived radionuclides remain; therefore, it cannot be said that the danger ceases after the initial phase. Various radioactive nuclides are produced inside the reactor even during normal operation, and the impact following an accident depends on which substances were released and in what quantities. For example, iodine-131 has a half-life of about 8 days, while cesium-137 has a half-life of about 30 years. For substances with short half-lives, initial response measures are particularly critical, while those with long half-lives may require long-term management in the soil and living environment. Although it is true that some uranium isotopes have very long half-lives, the duration of radiation exposure to residents or environmental contamination following the Fukushima accident should not be explained solely by the half-life of uranium. The amount of radioactive material decreases according to the decay characteristics of each radionuclide, and decontamination, shielding, and the recovery and isolation of contamination sources all contribute to reducing human exposure. However, since decontamination does not eliminate radioactivity itself, recovered waste must also be managed safely. Furthermore, while a nuclear power plant may contain far more nuclear fuel than a nuclear weapon, the total mass of the fuel does not directly correspond to the amount of radioactive material released into the environment. This is because the composition of the fuel, operational history, nature of the accident, containment capabilities, and actual release rates all vary. Therefore, rather than making generalizations—such as claiming that the release from a nuclear power plant accident is always hundreds of times greater than that from a nuclear bomb—it is necessary to examine the specific radionuclides actually released and the exposure pathways in detail. Explanation of Radioactive Fallout by the U.S. Environmental Protection Agency
In accidents requiring long-term management such as this, the government’s response and methods of communicating information are critically important. In Japan, tasting events and promotional activities involving celebrities were held to alleviate concerns about agricultural and marine products from Fukushima and to support the region’s recovery. However, simply showing someone eating these products is not enough to prove their safety. Safety must be demonstrated through inspections by production area and product type, measurements of radioactive material concentrations, distribution management, and exposure assessments based on consumption. Meanwhile, claims that directly link an individual’s illness to the consumption of a specific food—such as the story of a news anchor who was diagnosed with acute lymphocytic leukemia a few weeks after eating agricultural products from Fukushima—must also be handled with caution. One cannot conclude that a particular action caused an illness based solely on the chronological sequence in which the illness was discovered after that action. Similarly, claims that most celebrities who promoted Fukushima have contracted serious illnesses are difficult to accept as fact without verifiable investigations and medical evidence. Just as government publicity should not substitute for thorough verification, individual cases that stoke anxiety cannot replace scientific validation. What is needed is not a declaration of safety or rumors of danger, but data that anyone can verify and a responsible explanation of that data.
There was a time in the past when the depreciation of the yen reduced the cost of travel to Japan for South Korean tourists. At that time, interest in affordable travel opportunities grew, and discussions ensued regarding the recovery of tourism in various regions, including Fukushima. However, it cannot be definitively concluded that the weak yen was the result of the Japanese government intentionally lowering the exchange rate to attract back tourists lost due to the nuclear accident. Exchange rates are influenced by various factors, including monetary policy, interest rate differentials between countries, economic outlooks, and international capital flows. Since Japan’s large-scale monetary easing at the time was implemented with the goals of stabilizing prices and reviving the economy, it is unreasonable to attribute it solely to the purpose of attracting tourists. The fact that travel costs became cheaper is not a basis for judging radiation safety, and the observation that no apparent changes were noted after many people visited does not, in and of itself, prove safety. The decision to travel should be based not only on the exchange rate but also on entry restrictions in the destination, environmental monitoring results, and the specific accommodations and activities planned.
Concerns were raised that long-term health effects might not have been fully apparent during the first few years following the accident. The experience of an increase in thyroid cancer among those who were children and adolescents at the time of the Chernobyl accident demonstrates why an initial response and long-term follow-up studies are necessary. However, it is not valid to apply these historical examples directly to Fukushima and conclude that there will inevitably be a sharp increase in thyroid cancer or congenital abnormalities in the future. The two accidents differed in terms of the scale of radioactive material released, the level of radiation exposure among residents, and response measures such as food intake restrictions and evacuations. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) found that no health effects directly attributable to radiation exposure from the accident had been reported among Fukushima residents and concluded that, given the assessed exposure levels, any future increase in radiation-related diseases would likely be difficult to statistically identify with certainty. Furthermore, the committee found no reliable evidence supporting an increase in congenital abnormalities related to radiation exposure. It also assessed that the discovery of a large number of cancers during thyroid examinations was largely due to the fact that detailed ultrasound screenings detected lesions that would not have been found under normal circumstances. These results should not be interpreted as a declaration that there is absolutely no risk, but rather as a judgment based on currently available data. Therefore, rather than categorizing all of Fukushima and its surrounding areas as hazardous, it is reasonable to differentiate contamination levels and access restrictions by region and to continue necessary health surveys and environmental monitoring. The United Nations Scientific Committee on the Effects of Atomic Radiation’s Assessment of Fukushima
The characteristics of radioactive substances that travel through water and air are another reason why continued attention is necessary. Since substances released by the accident are affected by wind, precipitation, rivers, and ocean currents, contamination cannot be determined solely based on administrative boundaries or distance from the nuclear power plant. To use the example of radioactive substances exceeding standards being detected in mulberries from Aichi Prefecture—which is far from the plant—as evidence, one must first verify the actual place of production, the time of harvest, the nuclides and concentrations measured, and the standards in effect at the time. It is also necessary to distinguish whether the location where the food was sold or inspected is the same as where it was actually produced. While the fact that the details of a specific case have not been verified does not negate the need for wide-area monitoring, one cannot extrapolate from an uncertain case to conclude that food throughout Japan is dangerous. Similarly, the fact that radioactive substances move along ocean currents is distinct from the claim that the entire Pacific Ocean is contaminated to levels harmful to human health. To predict future dispersion, various factors—such as discharge volume, dilution, radioactive decay, and ocean circulation—must be considered together; health impacts should not be judged based solely on the extent of dispersion. The ongoing ocean discharge of water treated by the Advanced Liquid Processing System (ALPS) must also be examined separately from the uncontrolled releases that occurred at the time of the accident; however, the discharged water and surrounding waters must be continuously monitored and independently verified. Since these substances can travel across national borders, it is crucial not only for Japan but also for neighboring countries and international organizations to share data and participate in monitoring efforts. International Atomic Energy Agency (IAEA) Monitoring of ALPS-Treated Water Discharges
People may think that even if radioactive substances spread, they can avoid harm simply by avoiding agricultural and marine products from contaminated areas. However, in reality, food production origins and distribution channels are diverse, and radiation exposure does not occur solely through food consumption. People may be exposed to external radiation from radioactive substances remaining in the environment, or radioactive substances may enter the body through contaminated air, food, or water. This does not mean, however, that individuals must personally test all the food and water they encounter in their daily lives. Radioactive substances cannot be detected by sight, smell, or taste, and it is difficult to accurately analyze low levels of radioactivity in food and drinking water using only standard portable detectors. Therefore, the roles of public agencies and specialized testing institutions are crucial. To put citizens’ minds at ease, information must be disclosed in a way that allows them to understand not only the test results but also the items being tested, the frequency of testing, the measurement methods, the detection limits, and the measures taken when levels exceed standards. Demanding that the government verify safety is not an expression of vague anxiety but a legitimate request to access information about their living environment.
The concerns raised by residents regarding the safety of drinking water must be handled with particular care and responsibility. Claims that residents near Fukushima requested testing but were told by local authorities that no measurement data was available for the two years following the accident—and that it later emerged the water treatment plant had been shut down, forcing residents to continue drinking contaminated water—must be verified through the records of the relevant facilities and local governments. Without confirmation of the water treatment plant’s name, the reason for its closure, the test results for raw and treated water, and the actual concentration of the water supplied, it cannot be concluded that residents drank contaminated water for an extended period or that this caused health problems. A distinction must also be made between cases where radioactive substances are detected in contaminants or sludge separated during the water treatment process and cases where tap water supplied to households exceeds regulatory standards. In Japan, since the accident, authorities have compiled and disclosed the results of tests for radioactive substances in tap water, and have established monitoring methods and response policies for cases where levels exceed the standards. While the mere existence of such a system does not mean that the response at every site was sufficient, it is also inaccurate to generalize that there were no measurements or management measures in place at all. What is important is to answer residents’ questions with concrete data, and when data is unavailable or measurements are insufficient, to explain those gaps and conduct the necessary tests. Guidance on Testing Tap Water for Radioactive Substances from Japan’s Ministry of Health, Labor and Welfare
Although a long time has passed since the Fukushima nuclear accident, the cleanup and accountability for the accident do not end simply because time has elapsed. Since the Japanese government, relevant agencies, and international organizations are disclosing data on plant decommissioning and environmental monitoring, it is inaccurate to claim that they are providing no information at all regarding the progress of the accident. However, the fact that information is disclosed and the ability of citizens to fully understand and verify it are two separate issues. The Japanese government and the plant operator must continuously explain the difficulties of the decommissioning process, the management of radioactive waste, and the results and uncertainties of environmental measurements, and must fulfill their responsibility to help residents restore their daily lives and rebuild trust. The South Korean government must also cooperate with international monitoring and information sharing while implementing policies that prioritize the safety of South Korean citizens. Since an import ban is already in effect on all seafood from eight Japanese prefectures, including Fukushima, this ban must be enforced effectively, and other imported foods must be thoroughly verified through inspections and origin tracking. While some may call for a complete ban on all Japanese agricultural and fishery products, the decision to maintain or expand regulations must be based on actual contamination data, the reliability of the testing system, and risk assessments. Travelers should be provided not only with information on cost savings but also with clear details regarding access restrictions and safety information for their destination, and they should be helped to avoid relying on vague reassurances or exaggerated fears. Citizens, too, need to stay informed about radiation and radioactive materials and distinguish between unsubstantiated claims and verified facts. Remembering the Fukushima nuclear accident does not mean repeating prophecies of doom, but rather insisting on measurement, verification, information disclosure, and responsible management until the very end.
