This is the first analysis of the global health effects due to
exposure after the Fukushima accident done
with the aim to estimate its potential public health impact so that future
possible health needs can be anticipated.
This health risk assessment was conducted by independent international experts
who were selected by WHO for their expertise and experience in
radiation risk modelling,
epidemiology, dosimetry, radiation effects and public health.
What happened exactly on 11 March 2011 in Japan?
On 11 March 2011, a magnitude 9 earthquake and a series of large tsunami waves
hit the east coast of Japan, causing widespread damage to infrastructures. At
the Fukushima nuclear power plant, the power supply and the means to control and
cool the reactors, were knocked out. In the days that followed, three reactors
experienced meltdown, and a series of hydrogen gas explosions released
radionuclides into the environment. A 3-km evacuation zone was established and
then quickly increased to a 20-km evacuation zone. Other protective actions were
implemented to reduce doses in the longer term, including the relocation of
people in some areas. Stable iodine for
thyroid blocking was distributed but
it is thought that only a small number of people actually used it.
What are the potential consequences of a radioactive material release?
Adverse health effects of ionizing
radiation may result from two distinct
- cell killing, which may cause functional impairment of the exposed tissue
or organ, if a sufficient number of cells are affected;
- non-lethal changes in molecules of a single cell, most commonly in the DNA
molecule, which may result in an increased risk of disease long after exposure.
Evidence from historic events confirms that any major, uncontrolled release of
radiation should be cause for
immediate response and scientific assessment of potential health effects.
What were the exposure levels of the various populations and main associated risks identified?
Lifetime organ doses were estimated for the general population within
geographical locations ranging from the most affected areas of Fukushima
prefecture to the rest of the world. The lifetime risks were estimated for both
sexes and three different ages at exposure (1
year [infant], 10 years [child], and 20 years [adult]). Health risks for male
emergency workers were estimated for three different ages (20 years, 40 years,
and 60 years.
No acute effects of radiation
exposure such as
acute radiation syndrome or skin
injuries have been observed among the general population.
Apart for the workers who were carrying dosimeters, it is very difficult to
evaluate the amount of radiation that
people were exposed to. Estimates are
deliberately made to limit the possibility of underestimating eventual
health risks. In general, females show a greater increase in risk of
cancer compared to males, and
people exposed as infants show a greater increase in risk than people exposed as
children or adults.
- Among Fukushima Daiichi nuclear power plant emergency workers:
- The risk that they might develop
cancer or another solid cancer
is increased compared to the general population.
- Twelve of the emergency workers were
exposed to larger amounts of
radioactive iodine and
may develop non-cancer thyroid disorders.
- In the most affected area of Fukushima prefecture, the estimated
radiation doses for the first
year ranged from 12 to 25 mSv. In this situation, the largest estimated
lifetime risks increase over baseline cancer rates are:
- all solid cancers -
around 4% for females exposed as infants, 3% for males;
- breast cancer - around 6% for females exposed as infants;
- leukaemia - around 6% for females exposed as infants, 7% for
- thyroid cancer - around 70% for females exposed as infants,
around 60% for males.
These are exposure increases over the
baseline level which means, for instance, that if the expected risk of
cancer in females over their lifetime is
0.77%, and that the additional lifetime risk assessed for females
exposed as infants is 70%, that is
0.52%; then the total expected risk is 1.29%.
- Outside the geographical areas most affected by
radiation, even in locations within
Fukushima prefecture, the predicted risks remain low and no observable
increases in cancer above natural
variation in baseline rates are anticipated.
- Outside Japan this health risk assessment concludes that no
discernible increase in health risks from the Fukushima event is expected.
- The radiation doses in Fukushima prefecture were well below certain
radiation dose levels which, when exceeded, may produce a direct impact on
health, and therefore such effects are not expected to occur in the general
Health effects other than cancer may
include thyroid diseases (nodules,
dysfunction), visual impairment (lens opacities,
cataracts), acute skin reactions,
hematopoietic, gastrointestinal and neurovascular disturbances, depending on the
What are the uncertainties around these risk estimates and priorities set for the coming years?
The relationship between radiation
exposure and lifetime risk of
cancer is complex and varies
depending on several factors, mainly radiation dose, age at time of exposure,
sex and cancer site. These factors can influence the uncertainty in projecting
radiation risks, in particular when assessing risks at low doses.
These estimates provide valuable information for setting priorities in the
coming years for population health monitoring, as has already begun with the
Fukushima Health Management Survey.
Because scientific understanding of
radiation effects, particularly at low
doses, may increase in the future, it is possible that further investigation and
additional dose estimations may change our current understanding of the risks of
this radiation accident.
GreenFacts highlights of the WHO report: "Health risk assessment from the nuclear accident after the 2011 Great East Japan earthquake and tsunami, based on a preliminary dose estimation (2013)" http://www.who.int/ionizing_radiation/pub_meet/fukushima_risk_assessment_2013/en/