Fukushima Health Reports

Updated March 28, 2013

The health impacts of the Fukushima accident will be assessed for the next several decades. Reports from several international agencies presenting preliminary findings are now 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 published by expert organizations. Its specialists review new information as it becomes available. This knowledge is integrated into the CNSC’s regulatory framework, when warranted.

UNSCEAR

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) is conducting an assessment of the levels and effects of radiation exposure due to the Fukushima Daiichi nuclear power plant accident of March 2011.

To do this they have drawn expertise from various fields, including biology, radiation biology, environmental toxicology, terrestrial and aquatic ecology, environmental chemistry, atmospheric dispersion modelling, radioecology, health physics, and medical radiology. These experts are estimating doses and assessing potential health consequences for both the public and workers.

Wolfgang Weiss, Chair of the UN Scientific Committee on the Effects of Atomic Radiation.
Courtesy: IAEA/Dean Calma

On May 23, 2012, UNSCEAR’s interim findings were presented as part of its annual meeting, stating a good understanding of the nature and composition of the releases to the atmosphere from the four damaged Fukushima reactors. “There is very detailed information so as to assess the public doses but it will be more challenging to validate the workers’ exposure,” said Wolfgang Weiss, Chair of UNSCEAR.

The full report is expected to be finalized by the end of 2013.

Highlights of Interim Findings

• To date, emergency workers exposed to radiation have not shown any visible health effects as a result of their exposures.
• Seven workers have died since the accident, but none of the deaths were linked to radiation.
• Although several workers were exposed to high levels of contamination on their skin, no clinically observable effects have been reported.
• The health of over 1,000 children who lived nearest to the site of the accident and for whom precise measurements are available will be monitored closely by UNSCEAR.
• The UNSCEAR assessment is being undertaken by over 70 international scientists from over 25 countries and will be presented towards the end of 2013.

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.

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.

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.

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.