Environmental radiation Environmental radiation

Environmental radiation

Environmental radiation

Fukushima nuclear power plant accident

Fukushima nuclear power plant accident

The Fukushima Dai-ichi nuclear power plant located on the east coast of Japan was severely damaged on 11 March 2011, and radioactive substances were released for several days into the sea and the area surrounding the plant. The damage was caused by a magnitude 9 earthquake and the resulting tsunami. The earthquake and tsunami killed 15,000 people and injured 6,000.

The released quantities of radioactive iodine (I-131) and cesium (Cs-137) have been estimated to be 10 per cent of the releases of the Chernobyl nuclear power plant accident. The immediate and late effects of the accident affect all of Japan.

Approximately 170,000 persons were evacuated from the areas surrounding the plant. Thanks to the protective measures, radiation doses remained small. Radiation doses received by people have been determined based on their location of residence and data on their whereabouts at the time of the accident. The evacuees received a radiation dose of 1–10 millisieverts; the dose is double for a 1-year-old child. In other areas of Japan, the radiation exposure of the population was lower.


Direct harmful effects of radiation have not been detected

The health effects of the Fukushima nuclear power plant accident on a population of 2 million people are monitored and examined in the Fukushima Health Management Survey project. The radiation dose received by the people has been estimated and their physical, psychological and psychosocial condition is followed in this longitudinal study by interviews and medical examinations.

None of the employees of the nuclear power station or members of the public got radiation sickness or received local radiation injuries requiring treatment. Deaths are associated with evacuation and other health effects than those caused by radiation. Due to a political decision, employees who get cancer will receive compensation, even if the cancer is not caused by radiation. Working in the power plant for more than a year after the accident is sufficient grounds for compensation.

Workers participating in the aftermath of the accident are monitored with thorough and regular health check-ups. According to estimates by WHO, UNSCEAR and IAEA experts, the radiation exposure resulting from the accident will not materially increase the occurrence of cancer in members of the public. Changes in people’s lives due to the accident have been observed to cause psychosocial effects and mood problems and increase the risk factors of many diseases.

Children and the youth are being followed up with detailed studies Thyroid screening of children was started soon after the accident both in the area of increased radiation and in reference areas. Moreover, the health of women who were pregnant or had small children at the time of the accident is being monitored. Doses affecting the thyroid gland have been small, and the increase in thyroid cancers has not been undeniably proven.

The indirect effects not associated with the radiation exposure are significant

Tens of thousands of pregnant women and young mothers participated in a follow-up study in 2011 and 2012. The numbers of stillbirths, miscarriages or developmental disorders were not found to differ from corresponding groups in other areas. Breastfeeding decreased somewhat due to fears of radioactivity in breast milk. The number of pregnancies decreased in the beginning, but returned to normal in 2013. For a while, the number of abortions was higher than in the rest of Japan.

The worrying observations after the earthquake and tsunami suggest an increase in risk factors of lifestyle diseases. In 2014, the suicide rate in the area was higher than in previous years or in other areas in Japan.

Compared to the rest of the population, the nuclear power station workers experienced more psychological problems. The problems were largely due to loss of their homes and the discrimination they experienced.

Several follow-up projects are underway that will bring new and more comprehensive information on the health effects of the accident, especially on the psychological and psychosocial effects. After the accident, research projects on the socioeconomical and psychosocial causes and effects of radiation-related incidents were also launched in other countries.

Handling of radioactive waste

As a result of the Fukushima nuclear power plant accident and the following clean-up operations, large amounts of radioactive waste have developed outside of the Fukushima nuclear power plant  and in the area surrounding the plant. Outside of the power plant, low-level radioactive waste has developed as a result of the extensive clean-up operations related to cleaning the areas classified as contaminated.

Millions of cubic metres of water that has undergone a cleaning process and has been used to cool down the damaged reactors is stored in tanks in the area of the Fukushima nuclear power plant. For the most part, radioactive substances have been cleaned off the waste water; however, tritium in the water presents a problem as it cannot be chemically separated from the water.

In 2020, IAEA evaluated the possible plans of Japanese authorities related to the processing of this waste water and discovered that it is possible to release the water into the sea in a controlled manner.

​​​​Radioactive substances originating from the Fukushima accident were observed in Finland

The Finnish Radiation and Nuclear Safety Authority STUK monitors the levels of radioactive substances in the outdoor air and the deposition at eight localities in Finland. Radioactive substances released into the atmosphere during the Fukushima nuclear power plant accident travelled to Finland through the air, causing a temporary rise in activity concentrations. Observations were made at all eight localities mainly during March and April 2011. The concentrations of radioactive substances originating from the Fukushima accident were very low in Finland and at no point were on a level that would be harmful to health.

During the monitoring of radioactive substances in the outdoor air, a rise in cesium-137 concentration could be detected after the Fukushima nuclear power plant accident. However, the activity concentration of cesium-137 returned to the normal level by May 2011. In addition to cesium-137, other artificial radioactive substances, such as iodine-131 and cesium-134, could also be detected.

More information about monitoring the levels of radioactive substances outdoors and location-specific measurement results can be found on the Radioactivity in outdoor air page.

Radioactive substances originating from the Fukushima nuclear power plant accident could also be detected in the deposition samples. In addition to cesium-137, small amounts of iodine-131 and cesium-134 were detected in the collected samples.

More information about deposition monitoring can be found on the Radioactivity of the deposition page.
More information about the radioactive substances originating from the Fukushima nuclear power plant accident detected in Finland can be found in the report Surveillance of Environmental Radiation in Finland: Annual Report 2011 (Julkari.fi).