No “observable” increases in cancer rates are anticipated for the general population as a result of the Fukushima Daiichi nuclear accident in Japan, according to a new report from the World Health Organization. However, the two-year study has found that the risk of developing certain cancers has marginally increased for some residents of Fukushima prefecture.

‘Health Risk Assessment from the nuclear accident after the 2011 Great East Japan Earthquake and Tsunami based on preliminary dose estimation,’ released 28 February, said that the lifetime risk for some cancers may be "somewhat elevated" above baseline rates in certain age and sex groups that were in the two areas of Japan most affected.

In terms of specific cancers and for residents of Namie Town and Iitate Village (which received preliminary estimated radiation effective doses of 12 to 25 mSv during the first year), the estimated increased risks over what would normally be expected are:

  • all solid cancers – around 4% in females exposed as infants;
  • breast cancer – around 6% in females exposed as infants;
  • leukaemia – around 7% in males exposed as infants;
  • thyroid cancer – up to 70% in females exposed as infants

The report noted that: "Due to the low baseline rates of thyroid cancer, even a large relative increase represents a small absolute increase in risks." For example, the baseline lifetime risk of thyroid cancer for females is just 0.75% and the additional lifetime risk estimated in this assessment for a female infant exposed in the most affected location is less than 0.50%.

It said that the radiation doses from the damaged nuclear power plant are not expected to cause an increase in the incidence of miscarriages, stillbirths and other physical and mental conditions that can affect babies born after the accident.

It also found that around one-third of emergency workers involved in the Fukushima Daiichi accident would have an increased cancer risk. The remaining two-thirds or workers were estimated to have risks in line with the general population.

The 200-page report is the first analysis of the global health effects due to radiation exposure after the Fukushima accident.