For information only - not an official document
31 May 2013
No Immediate Health Risks from Fukushima Nuclear Accident
Says UN Expert Science Panel ~ Long Term Monitoring Key
VIENNA, 31 May (UN Information Service) - "Radiation exposure
following the nuclear accident at Fukushima-Daiichi did not cause
any immediate health effects. It is unlikely to be able to
attribute any health effects in the future among the general public
and the vast majority of workers," concluded the 60 th session of
the Vienna-based United Nations Scientific Committee on the Effect
of Atomic Radiation (UNSCEAR).
The effects of radiation exposure on humans and the environment
following the accident at the Fukushima-Daiichi nuclear power plant
in March 2011 is one of the major issues being discussed at the
Committee's annual session which started on Monday, 27 May. The
second important issue is related to the short and long term effects
of exposure to radiation on children. This covers medical as well
as other kinds of exposure (not specifically related to the accident
The report that is finally adopted by the Committee will be
presented to the United Nations General Assembly when it meets later
this year, and the scientific data and evaluation underpinning
that report will be published separately.
1.Radiological impact of the Fukushima-Daiichi accident:
More than 80 leading international scientists have worked on
analysing the information available on the levels and effects of
exposure following the events of 11 March 2011 in Japan. Material
they prepared was scrutinized by the 27 countries on the Scientific
Committee at their annual session. When the Committee's report is
published, it will be the most comprehensive international
scientific analysis of the information available to date.
"The experience from the 1986 Chernobyl accident has shown us that
apart from any direct impact on physical health, the social and
societal effects, and their associated health consequences in the
affected population will need special attention in the coming
years," said Carl-Magnus Larsson, Chair, UNSCEAR. "Families are
suffering, and people have been uprooted and are concerned about
their livelihoods and futures, the health of their children…it is
these issues that will be the long-lasting fallout of the accident.
At the same time, it is important to maintain a long-term medical
follow-up for the exposed population, and in relation to certain
diseases to provide a clear picture of their health status
The draft report was deliberated at length by the Committee,
including more recent data received from Japan. Methodologies,
assessments and doses were scrutinized in detail, and the Committee
has made some recommendations that will be incorporated into the
draft, which is now in the process of being finalized for
presentation to the General Assembly. "The Report has the full
confidence of the Committee," said Larsson.
On the whole, the exposure of the Japanese population was low, or
very low, leading to correspondingly low risks of health effects
later in life. The actions taken to protect the public (evacuation
and sheltering) significantly reduced the radiation exposures that
would have otherwise been received, concluded the Committee "These
measures reduced the potential exposure by up to a factor of 10. If
that had not been the case, we might have seen the cancer rates
rising and other health problems emerging over the next several
decades," said Wolfgang Weiss, Chair, UNSCEAR report on radiological
Impact of the Fukushima-Daiichi accident.
The doses delivered for the two most significant radionuclides were
quite different: doses to the thyroid mainly from iodine-131 ranged
up to several tens of milligray and were received within a few weeks
after the accident; the whole-body (or effective) doses mainly from
caesium-134 and caesium-137 ranged up to ten or so millisieverts
(mSv) and will be received over the lifetime of those exposed. The
additional exposures received by most Japanese people in the first
year and subsequent years due to the radioactive releases from the
accident are less than the doses received from natural background
radiation (which is about 2.1 mSv per year). This is particularly
the case for Japanese people living away from Fukushima, where
annual doses of around 0.2 mSv from the accident are estimated,
arising primarily through ingestion of radionuclides in food.
Given the small number of highly exposed workers, it is unlikely
that excess cases of thyroid cancer due to radiation exposure would
be detectable. Special health examinations will be given to workers
with exposures above 100 mSv including annual monitoring of the
thyroid, stomach, large intestine and lung for cancer as a means to
monitor for potential late radiation-related health effects at the
The assessment also concluded that although the rate of exposures
may have exceeded the levels for the onset of effects on plants and
animals several times in the first few months following the
accident, any effects are expected to be transient in nature, given
their short duration. In general, the exposures on both marine and
terrestrial non-human biota were too low for observable acute
effects. Potential exceptions are water plants, especially located
in the area where radioactive water was discharged into the ocean.
"At this point, we can say that there is a potential risk to some
organisms in the areas of highest exposure, but it is difficult to
quantify it in detail with the available information," said Malcolm
Crick, Secretary, UNSCEAR (The UNSCEAR secretariat is administered
by the United Nations Environment Programme, UNEP). "The exposures
of organisms in the environment are unlikely to cause anything more
than transient harm to their populations," he added.
2. UNSCEAR Report on Effects of Radiation Exposure of Children
2. 子どもの放射線被曝影響に関するUNSCEAR 報告書
Because of anatomical and physiological differences, radiation
exposure has a different impact on children compared with adults.
The Committee had started a general review of these differences
before the Fukushima-Daiichi accident; its conclusions on this
subject are considered in this year's report to the General Assembly.
There are differences in the doses received by children and adults
from exposure to the same distribution of radioactive material in
the environment, for example, when there are elevated levels of
radionuclides on the ground. Children can also receive significantly
higher doses than adults in situations such as medical exposure if
the technical settings are not adapted appropriately.
If radionuclides are ingested or inhaled, the presence of
radionuclides in one organ can give higher radiation doses to others
because the organs of children are in closer proximity to one
another than those of adults. In addition, both the metabolism and
physiology depend on age, which also affects the concentrations of
radionuclides in different organs and thus the dose to those organs
for a given intake.
After radiation exposure, children are clearly more radiosensitive
for about 30 per cent of tumour types when compared with adults.
These types include leukaemia and thyroid, skin and brain cancer.
They have the same sensitivity as adults when it comes to 25 per
cent of tumour types such as kidney and bladder, and are less
sensitive than adults when it comes to 10 per cent of tumour types
including lung cancer.
For effects that are bound to occur after high doses, the Committee
concluded that as seen with carcinogenesis, there are some
instances in which childhood exposure poses more risk than adult
exposure (e.g. for effects in the brain, cataracts, and thyroid
nodules). There are other instances where the risk appears to be
about the same (e.g. neuroendocrine system and effects in the
kidneys) and there are a few instances where children's tissues are
more resistant (lung, immune system, marrow and ovaries).
"More research is needed to fully understand the risks and effects
following childhood exposure to radiation. This is necessary (and
possible) because there are many individuals who were exposed as
children (such as the survivors of the atomic bombings) who are
still alive. Their experiences must not be lost," said Fred Mettler,
Chair, UNSCEAR Report on Effects of Radiation Exposure on Children.
The mandate of the United Nations Scientific Committee on the
effects of Atomic Radiation (UNSCEAR), established in 1955, is to
undertake broad reviews of the sources of ionizing radiation and
the effects on human health and the environment. Its assessments
provide a scientific foundation for United Nations agencies and
governments to formulate standards and programmes for protection
against ionizing radiation.
UNSCEAR has conducted a scientific evaluation of the levels and
effects due to radiation exposure resulting from the Fukushima
accident. It does not deal with or assess nuclear safety or
emergency planning issues.