Fukushima and Health

Updated December 21, 2015

The health impacts of the Fukushima accident will be assessed for the next several decades. Reports from several international agencies presenting findings are becoming available. The availability of further monitoring data and more detailed information about implementation of protective measures will allow for more refined assessments in the future.

The CNSC closely monitors reports and information published by credible organizations, reviewing new information as it becomes available. This knowledge is integrated into the CNSC's regulatory framework, when warranted.

Comparison of recent UNSCEAR and WHO Reports

The overall findings of the 2013 United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) Report are in good agreement with the two reports published by the World Health Organization (WHO, 2012; 2013). All reports conclude the predicted health risks as a result of the Fukushima nuclear accident remain low and no observable increases in cancer risks above baseline rates are anticipated for members of the public in Japan and elsewhere.  Likewise, no discernible increases in cancer or other diseases are expected among the majority of workers; however, the most exposed workers will continue to receive regular health checks.

The 2013 UNSCEAR Report used more comprehensive data than were available for the two WHO reports discussed below. It was therefore possible to make more realistic assumptions in parts of the assessment. For example, the UNSCEAR report contained more information regarding: the evacuated areas, patterns of movement of the evacuees, wind patterns, details on the implementation of protective measures and additional monitoring data for internal and external exposures. Furthermore, since doses were assessed for a longer time period (March 11, 2011 to October 31 2013), UNSCEAR was able to make projections regarding health risks over the first 10 years after the accident as well as up to the age of 80 years. In comparison, the WHO (2012) was unable to estimate doses beyond the first year as the report was based on relevant information collected up to mid-September 2011 and would have resulted in a great degree of uncertainty without more information.

The differences in follow-up time resulted in the WHO Health Risk Assessment including 23,172 workers during the first 12 months (compared to 24,832 workers during the first 20 months as reported by UNSCEAR), 12 of which were identified to have absorbed doses to the thyroid of 2 to 12 Gy (compared to 13 individuals as reported by UNSCEAR).

Additional analysis performed by UNSCEAR, but not considered by WHO, was an exposure assessment of selected plant and animal species (i.e,  non-human biota) in the environment. Exposures of both marine and terrestrial non-human biota following the accident were, in general, too low for acute effects to be observed; though there may have been exceptions because of local variability.

Detailed summaries of the findings of the UNSCEAR and WHO reports follow below.

UNSCEAR 2013 Report

Scientific Annex A: Levels and effects of radiation exposure due to the nuclear accident after the 2011 Great East-Japan Earthquake and Tsunami

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) conducted an assessment of the levels and effects of radiation exposure due to the Fukushima Daiichi nuclear power plant accident of March 2011. As a follow-up of the interim findings presented on May 23, 2012 at its annual meeting, UNSCEAR published today the full report titled "Levels and effects of radiation exposure due to the nuclear accident after the 2011 great east-Japan earthquake and tsunami".

The findings are based on estimates of the exposure of various population groups - including children - as well as scientific knowledge of health impacts following radiation exposure.

UNSCEAR's chairman Carl-Magnus Larsson said based on the findings: "UNSCEAR does not expect significant changes in future cancer statistics that could be attributed to radiation exposure from the accident".

UNSCEAR 2013 Report

Highlights of the Report

  • no discernible changes in future cancer rates and hereditary diseases are expected due to exposure to radiation resulting from the Fukushima accident
  • no increase in the rates of birth defects are expected as a result of the accident
  • there is a theoretical possibility of an increased risk of thyroid cancer among the group of children most exposed to radiation, but the situation will be followed closely and further assessed in the future
  • dose assessments to the workers are broadly consistent with reported doses, but uncertainties remain for exposures during the early phase of the accident
  • no discernible increase in cancer or other diseases is expected among workers; however, the most exposed workers will continue to receive regular health checks
  • radiation effects on terrestrial and marine ecosystems appear not to be permanent

WHO Health Risk Assessment

As lead health agency within the United Nations, the World Health Organization (WHO) is responsible for the international public health response in emergencies. As part of this responsibility, the WHO published a Health risk assessment (February 28, 2013) for members of the public and emergency workers after the Fukushima Daiichi nuclear accident.

This report, written by independent international experts in radiation risk modeling, epidemiology, dosimetry, radiation effects and public health, provides an assessment of the potential health impacts related to the releases of radiation after the nuclear accident.

Health Risk Assessment

Highlights

Increased risk is reported as estimated relative increases above background rates.

For the general population:

  • For the general population outside of the geographical areas most affected by radiation, and even in some locations within Fukushima prefecture, the predicted risks remain low and no observable increases in cancer risks above baseline rates are anticipated.
  • Among residents of the most impacted areas of Fukushima prefecture, conservative dose estimates indicate potential increases in some cancers risks above baseline rates in certain age and sex groups, but are likely to be below detectable levels. A slight increase in risk was found for all solid cancers, breast cancer, leukemia and thyroid cancer:
    • all solid cancer – around 4% in females exposed as infants;
    • breast cancer – around 6% in females exposed as infants;
    • leukemia – around 7% in males exposed as infants;
    • thyroid cancer – up to 70% in females exposed as infants.

It is important to note that large relative increases typically represent small absolute increases in risk. These percentages represent estimated relative increases over the baseline rates and are not estimated absolute risks for developing such cancers. For example, the baseline lifetime risk of thyroid cancer in females is 0.75%, and the estimated relative increase of 70% in females exposed as infants results in an additional lifetime risk of 0.50% (70% of 0.75% = 0.5%). Therefore, for this group of females, their lifetime risk has increased from 0.75% to a total of 1.25%.

For emergency workers (~23,000 workers):

  • Approximately two thirds of the workers (~66%) received low doses (below 5 mSv of effective dose) and no observable increases in cancer risks above baseline rates are anticipated.
  • Approximately one third of workers (~30%) received a total effective dose of approximately 30 mSv. The youngest workers are at a 20% increased relative risk of thyroid cancer above baseline rates.
  • Less than 1% of workers received a total effective dose of approximately 200 mSv. The youngest workers are at a 28% increased relative risk of leukemia and thyroid cancer above baseline rates.
  • A few workers (<0.01%) received a very high dose of iodine-131 to the thyroid (also represented as a total effective dose of 700 mSv). An increased relative risk of thyroid cancer above baseline rates is estimated, especially for young workers, although these values carry large uncertainties.

The authors of the report caution members of the public about the uncertainty related to their estimates and state that “dose estimates and assumptions used in this assessment were deliberately chosen to minimize the possibility of underestimating eventual health risks.” They also call for ongoing health and environmental monitoring, and warn against neglecting the psychosocial impact of the tsunami and nuclear accident on health and well-being of the population.

WHO Preliminary Estimate of Radiation Doses

As part of the overall health risk assessment being carried out by the World Health Organization (WHO) of the global impact of the accident at the Fukushima Daiichi nuclear power plant, the WHO published a Preliminary dose estimation (May 23, 2012) report.

This report, written by an international expert panel, gives preliminary estimates of public radiation exposure resulting from this accident. Doses are assessed for different age groups and locations. The Health risk assessment, published separately was discussed above.

Preliminary Dose Estimation

Highlights

The effective dose (unit of mSv) is a measure of dose designed to reflect the amount of damage caused by radiation exposure to the whole body. Doses have been estimated for the first year after the accident.

  • In the most affected areas of Fukushima prefecture the estimated effective doses are within 10−50 mSv.
  • In the rest of Fukushima prefecture, the estimated effective doses are within 1−10 mSv.
  • In prefectures neighbouring Fukushima, the estimated effective doses are within 0.1−1 mSv.
  • In all other Japanese prefectures, the estimated effective doses are within 0.1−1 mSv.
  • In the rest of the world, estimated effective doses are less than 0.01 mSv and are usually far below this level.

This dose assessment should be considered as preliminary. The availability of further monitoring data and more detailed information about implementation of protective measures will allow for more refined assessments in the future.

Ask an Expert: CNSC video series on Fukushima-related health questions

The CNSC has launched a video series to address some of the many questions asked by the public following the Fukushima accident. In these videos, CSNC staff experts answer common health-related questions in simple language:

  1. How are children protected after a nuclear accident? Aren't they more vulnerable?
  2. After a nuclear accident like Fukushima, why aren't all members of the public monitored continuously?
  3. Why do guidelines allow orange juice to contain more cesium-137 than bottled water?
  4. Do dried fruit contain more radioactivity than fresh fruit?
  5. Is it safe to eat rice, produce and fish imported from Japan?

Relevant Third Party Research

Levels of radioactive cesium from the 2011 Fukushima Daiichi nuclear power plant accident detected off the U.S. west coast pose no health risks, according to experts at the Woods Hole Oceanographic Institution. The highest level reported to date (11 Bq/m3) is more than 500 times lower than U.S. government limits for drinking water. It is also well below limits of concern for direct exposure while swimming, boating, or any other recreational activity. This recent data was released by Our Radioactive Ocean, a citizen science sampling effort launched by Dr. Ken Buesseler in 2014 to monitor ocean waters for radionuclides from the Fukushima accident.

A recent study published by the National Academy of Sciences of the United States of America shows that the committed effective dose received by humans based on one year's average consumption of Pacific bluefin tuna contaminated from the Fukushima-Daiichi accident is comparable to, or less than, the dose we routinely receive from naturally occurring radionuclides in many food items, medical treatment, air travel or other background sources. To put this into perspective, the study indicates that the dose is only about five percent of the dose from eating one banana.

Selected Quotes from International Radiation Protection Specialists

Below are selected quotes from letters sent by international radiation protection specialists to Japan's Nuclear Disaster Expert Group. These letters collectively highlight that the potential effects of radiation exposure are minimal compared to the observable effects of stress and stigmatisation on Fukushima residents.

"In summary, the international experts have concluded that this catastrophic accident has providentially resulted in very small radiation doses in general and therefore in no discernible health effects."

Abel J. González
Academician at the Argentine Academies of Environmental Sciences and of the Sea
Vice-Chairman of the International Commission on Radiological Protection (ICRP)
Representative in the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)
Member of the Commission of Safety Standards of the International Atomic Energy Agency (IAEA)
Senior advisor to the Argentine Nuclear Regulatory Authority.

"All the scientific evidence suggests that no-one is likely to suffer damage from the radiation from Fukushima itself, but concern over what it might do could cause significant psychological problems. It is therefore important to understand that the risk to health from radiation from Fukushima is negligible, and that undue concern over any possible effects could be much worse than the radiation itself."

Geraldine Anne Thomas, BSc PhD
Professor of Molecular Pathology, Imperial College,
London Director of Chernobyl Tissue Bank

"Risks from radioactivity and ionizing radiation as a genotoxic agent have to be taken seriously and assessed with utmost care. Media and political actors often lack the necessary prudence and appropriate knowledge. This results in improper comparisons and the creation of fear from simplistic concepts like the LNT-hypothesis taken out of its radiation protection context."

Werner Burkart
Professor for Radiation Biology at the Faculty of Medicine of the Ludwig Maximilians University in Munich
Former Deputy Director General of the International Atomic Energy Agency (IAEA).

"Since 2011, I participated in two international projects focused on the assessment of health effects of the FDNPP accident organized by two respected bodies, the World Health Organization (WHO) and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Both of them came to similar conclusions that future radiation-induced health effects in the population of the Fukushima prefecture were unlikely."

Mikhail Balonov,
Professor Former Member of the International Commission of Radiological Protection (2001-2013)
Consultant to the World Health Organization and the United Nations Scientific Committee on the Effects of Atomic Radiation.

"Two major international reports (from WHO and UNSCEAR) assess the future health risks after the accident at Fukushima. Although these reports used somewhat different data and methods, they both come to similar conclusions: the health risks linked to radiation exposure due to the events at Fukushima Dai-ichi nuclear power plant will remain low (though probably not zero for some groups including young people living in areas near the plant)."

Hajo Zeeb,
Professor of Epidemiology,
Leibniz Institute for Prevention Research and Epidemiology, and University of Bremen, Germany.

"The health risks from radiation exposure have been studied for over 100 years and are quite well-known. Current independent estimates by the World Health Organization (WHO) and the United Nations Scientific Committee on Effects of Atomic Radiation (UNSCEAR) indicate that the risk of future cancer from the accident is very low although nobody can say a small risk does not exist."

Fred A. Mettler Jr. MD, MPH.
Professor Emeritus and Clinical Professor at the Department of Radiology at the University of New Mexico School of Medicine
U.S. Representative, United Nations Scientific Committee on the Effects of Atomic Radiation
Emeritus Commissioner, International Commission on Radiological Protection.