Fri, May 31, 2013 -
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.
VIENNA, 31 May 2013
(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 at
Fukushima-Daiichi).
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 development."
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.
For information only
- not an official document
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.
No radiation-related
deaths or acute effects have been observed
among nearly 25,000 workers (including TEPCO
employees and contractors) involved at the
accident site.
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
individual level.
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
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.
He added that the report
was a valuable resource, as it is the first
document that presents a comprehensive overview
of the effect of radiation on children in
totality.
Watch the webcast of
the press briefing on 31 May at 13.30 pm
at http://www.unis.unvienna.org/unis/en/webcast.html
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.