The 2011 Great East Japan Earthquake and subsequent tsunami caused the accident at the Fukushima Daiichi Nuclear Power Plant (FDNPP), releasing radioactive material into the environment. Public concern persists regarding the long-term safety of the country. Over a decade later, the focus has shifted from emergency response to comprehensive, long-term environmental recovery and monitoring. This assessment details the current state of ambient radiation, the safety of the food supply, and the ongoing management of the FDNPP site. The data indicates that, for the vast majority of Japan, radiation levels are currently comparable to normal global background levels, but intensive monitoring efforts continue.
Current Status of Environmental Radiation Monitoring
Japan maintains an extensive, transparent monitoring network to track external radiation levels across the country, managed by government agencies and local prefectures. This network utilizes thousands of monitoring posts that continuously measure air dose rates. The difference between the designated exclusion zones near the FDNPP and the rest of Japan remains the primary distinction in radiation levels.
Outside of the difficult-to-return zones in Fukushima Prefecture, ambient radiation levels have decreased dramatically due to natural decay and widespread decontamination efforts. For instance, the air dose rate in Fukushima City, outside the restricted area, has fallen from 1.91 microsieverts per hour (µSv/h) immediately after the accident to approximately 0.11 µSv/h in recent years. This current level is now comparable to those found in major metropolitan areas around the world.
In populated areas near the former restricted zones, mean annual dose rates in 2022 were estimated to be comparable to the natural background radiation variations found across Japan, which averages about 2 millisieverts per year (mSv/y). Air radiation levels in the Aizu region of Fukushima have returned to pre-accident levels. The government continues to conduct detailed surveys of soil and air, ensuring that the environmental recovery remains on track.
Safety of Food and Water Sources
Internal radiation exposure risk through food and water consumption is managed by a rigorous, multi-layered testing system across Japan. The testing protocols are applied to a wide variety of domestic products, including agricultural crops, livestock, and marine products. Japan’s regulatory limit for radioactive cesium in general foodstuffs is set at 100 Becquerels per kilogram (Bq/kg).
This national standard is significantly stricter than the international guideline of 1,000 Bq/kg for radiocesium set by the Codex Alimentarius Commission. The Japanese limit is calculated to ensure that an individual’s additional annual radiation dose from food consumption does not exceed 1 mSv, a globally recognized standard for public protection. Testing results are regularly published, and compliance rates are high, with non-compliance cases rarely detected in recent years.
For drinking water, the standard limit for radioactive cesium is even lower, set at 10 Bq/kg. Since mid-2011, monitoring inspections have consistently shown that radioactive cesium levels exceeding this strict management value have not been detected in tap water sources or purified water. This comprehensive testing provides a safety margin for consumers, particularly for seafood and products from the Fukushima region.
Comparing Radiation Levels to Global Norms
To understand the current state of radiation in Japan, it is helpful to place the measurements within the context of global background radiation. Radiation dose is measured in millisieverts (mSv), which quantifies the health risk posed by exposure. Natural background radiation originates from cosmic rays, geological sources, and radionuclides in food and air.
The global average annual dose from natural background radiation is approximately 2.4 mSv. In Japan, the average annual dose from natural sources is slightly lower, estimated to be around 2.1 to 2.2 mSv. The measured radiation levels in major Japanese cities are consistent with this natural range, meaning that the additional exposure from the FDNPP accident is negligible in most areas.
Variations in natural background radiation are common worldwide, often depending on local geology and altitude. Some regions globally, such as parts of China, India, and Iran, naturally experience annual background doses that are seven to thirty times higher than the Japanese average due to high concentrations of natural radioactive materials in the soil. The current radiation environment in populated areas of Japan, outside of the restricted zones, is low-risk relative to these common global and natural variations.
The Ongoing Decommissioning and Management of Contaminated Water
The Fukushima Daiichi Nuclear Power Plant site itself remains the focus of decommissioning efforts and the source of ongoing environmental management. The accumulated volume of water used to cool the melted reactor fuel and water that has mixed with groundwater presents a challenge. This water is contained and treated using the Advanced Liquid Processing System (ALPS).
The ALPS technology effectively removes most radionuclides, including Cesium-137 and Strontium-90, down to levels that meet international regulatory standards. However, the system cannot remove tritium, a naturally occurring radionuclide that is challenging to separate from water. The treated water is stored in tanks and then further diluted with seawater before a planned, controlled release into the ocean.
The plan for the treated water discharge is subject to continuous, multi-year oversight by the International Atomic Energy Agency (IAEA). The IAEA’s comprehensive review concluded that Japan’s approach is consistent with international safety standards, determining that the controlled release would have a negligible radiological impact on people and the environment. The decommissioning process is a decades-long effort, and the management of the treated water is a controlled part of this long-term plan.