Environmental impact of the Fukushima accident: Radiological situation in Japan

Deposition of caesium-137 in Japan following the Fukushima reactor accident Source: UNSCEAR 2013 Report, Volume I, ANNEX A, Figure B-VIII / reproduced by permission of UNSCEAR

The reactor accident in Fukushima in 2011 resulted in the release of radioactive material (radionuclides) into the atmosphere. The radioactive fallout was dispersed locally, regionally and globally over land and sea by the weather (wind and precipitation).

After the accident in Fukushima, areas to the north-west of the reactor plant received high levels of contamination, particularly in the prefecture of Fukushima. Outside of Japan, the level of contamination with radioactive material from the Fukushima reactors was low.

Relevant radionuclides

Radionuclides of the elements iodine, tellurium (which decays into radioactive iodine) and caesium were particularly relevant in terms of the radioactive contamination of the environment, as well as that of humans.

• Half-lives of up to eight days mean that radioactive iodine released in a reactor accident disappears from the environment after about three months. This was also the case in Fukushima.
• Contamination with radioactive caesium, with a half-life of up to around 30 years, remains in the environment for a long time. It is principally responsible for the increased radiation levels still present in the area around Fukushima.

Contamination of foodstuffs and water in Japan

Foodstuffs were contaminated by radioactive material that was deposited on the leaves or directly on agricultural produce such as fruit and vegetables, or that was absorbed via the roots of fruit and vegetable crops.

As a result of the Fukushima accident, not only was radioactive material released into the atmosphere, but it also entered the water – primarily the water that was fed into the reactors for emergency cooling, but also the groundwater penetrating into the reactor. Large quantities of contaminated water were pumped out of the reactor, cleaned of radioactivity by filtering and stored in numerous tanks on the reactor site.

Information on the radiation exposure of the Japanese population can be found in the article "Health consequences of the accident of Fukushima".

Travel to Japan

Lantern in a park in Japan (Tokyo)

As a result of the Fukushima accident, people on trips to the affected areas are exposed to increased levels of radiation. Unlike the local population, however, tourists are only exposed to the radiation for a short time. Accordingly, the potential additional radiation dose from a typical visit remains well below one millisievert.

For comparison, the average radiation dose received by people in Germany due to natural radiation (from the ground, for example) is about 2–3 millisieverts per year.

Example: visiting the city of Fukushima as a tourist

The city of Fukushima is outside of the exclusion zone and has an average dose rate of approximately 0.1 to 0.5 microsieverts per hour (for comparison, the average dose rate in Germany is about 0.1 microsieverts per hour). A one-week visit to the city of Fukushima would result in an additional radiation dose of up to about 0.1 millisieverts, which remains within the range of variation for annual natural radiation exposure in Germany.

Exclusion zone around the Fukushima power plant

Given the high ambient dose, people are only permitted to enter the exclusion zone around the Fukushima power plant with special authorisation, in protective clothing and with a dosimeter.

Situation outside of Japan

Air dust collector at the BfS monitoring station Schauinsland

Outside of Japan, worldwide measurements following the accident showed that contamination with radioactive substances from the Fukushima reactors was low, partly because 80% of the radioactive material was distributed into the atmosphere in the direction of the Pacific Ocean. This material was primarily dispersed in the northern hemisphere, where it became diluted.

Minimal quantities of the material could be detected by trace measurements, such as those taken in Germany by the BfS on the Schauinsland mountain near Freiburg. In the period from mid-March to mid-May 2011, extremely low concentrations of iodine-131 and caesium-134/137 could be detected in the air in Germany.

Japanese imports

Imported goods from Japan undergo spot radiation checks by the customs authorities, especially in the case of goods arriving by container ship. The Japanese limits applicable to the import of food and feed from Japan into the European Union (EU) until 02.08.2023 were replaced by EU limits on 03.08.2023. In Germany, the customs authorities monitor the legal import of Japanese foodstuffs.

Increased contamination of shipping units following the accident in Fukushima was very rare. The authorities also inspected ships and aircraft.

For a shipping unit, the surface contamination was not allowed to exceed four Becquerels per square centimetre. If this limit was exceeded, the freight had to be decontaminated. If that was not possible, the goods were returned to sender.

Data basis

The information presented here on radiological data, measures and planning in Japan is based on information from Japanese government authorities, Fukushima Prefecture authorities, TEPCO, measurements by private individuals (safecast.org), scientific publications and BfS's own estimates and expert assessments.