Fukushima and health

Scientific Annex B

UNSCEAR

This publication is an advance copy of scientific annex B of the Committee's report to the General Assembly, approved at the UNSCEAR 67th session (November 2–6, 2020).

Volume I – Report to the General Assembly – Scientific Annex A: Levels and effects of radiation exposure due to the nuclear accident after the 2011 great east-Japan earthquake and tsunami

UNSCEAR

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 to the interim findings presented at its annual meeting in May 2012, UNSCEAR published 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 were 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 that, based on the findings, UNSCEAR did not expect significant changes in future cancer statistics that could be attributed to radiation exposure from the accident.

Highlights

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

Health risk assessment from the nuclear accident after the 2011 Great East Japan earthquake and tsunami, based on a preliminary dose estimation

WHO

As the 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 in February 2013 for members of the public and emergency workers, further to the Fukushima Daiichi nuclear accident.

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

Highlights

Increased risk was reported as estimated relative increases above background rates.
For the general population:

• For those outside of the geographical areas most affected by radiation, and even in some locations within Fukushima prefecture, the predicted risks remained low and no observable increases in cancer risks above baseline rates were anticipated.
• Among residents of the most impacted areas of Fukushima prefecture, conservative dose estimates indicated potential increases in some cancers risks above baseline rates in certain age and sex groups, but were 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, lifetime risk 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 were anticipated.
• Approximately one-third of workers (~30%) received a total effective dose of approximately 30 mSv. The youngest workers were 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 were 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 was estimated, especially for young workers, although these values carry large uncertainties.

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

Preliminary dose estimation from the nuclear accident after the 2011 Great East Japan earthquake and tsunami

WHO

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

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

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 were estimated for the first year after the accident.

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

Higher levels of Fukushima cesium detected offshore

Woods Hole Oceanographic Institution

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.

Current cesium results

Center for Marine and Environmental Radioactivity

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.

Evaluation of radiation doses and associated risk from the Fukushima nuclear accident to marine biota and human consumers of seafood PNAS

A study published by Proceedings of the National Academy of Sciences of the United States of America (PNAS) examined the committed effective dose received by humans based on average annual consumption of Pacific bluefin tuna contaminated from the Fukushima-Daiichi accident. The study showed this dose was comparable to, or less than, the routine dose from naturally occurring radionuclides in many food items, medical treatment, air travel or other background sources.

To put this into perspective, the study indicated that the dose was only about 5% of the dose from eating one banana.