Investor Presentaiton
Doses to the public
The previous UNSCEAR report was based on data until October
2012, while the 2020 Report made use of new information from
measurements made on people and in the environment to make
more realistic and validated estimates of levels of exposure of
the public.
New data also enabled more realistic external exposure
models to be used, quantitative assessments to be made of
the uncertainties in the estimated levels of exposure and of the
ranges of exposure levels in the population groups considered.
An example of the results from the 2020 Report is shown in
figures 1 and 2. This shows estimates of the average effective
doses in the first year after the accident to infants in municipalities
that were not evacuated and average annual doses in 2021. For
perspective, the annual average dose in Japan from natural
radiation is 2.2 mSv. The updated, more realistic estimates of
doses to members of the public have generally either decreased
or are broadly comparable with the Committee's previous
estimates. The contribution of ingestion of food and water is
much less than previously estimated, and the contribution of
external exposure is larger.
For those who were evacuated, the estimated average effective
doses to infants in the first year for the different evacuation groups
ranged from about 0.2 mSv to about 8 mSv. The evacuation of
municipalities averted or significantly reduced the exposure of
the affected population. High doses did not occur because of
the evacuation (but also due to other non-human factors, mainly
the wind blowing towards the ocean during the first two days of
the accident).
Doses have reduced since the accident. In 2021, the estimated
average annual effective doses were less than 0.5 mSv in parts
of Fukushima Prefecture that were not evacuated and below
0.1 mSv elsewhere in Japan. In the evacuated communities
where evacuation orders have been lifted, estimated annual
average effective doses in 2021, taking account of remediation
work, were generally less than 1 mSv.
In addition to the average doses to defined groups of members
of the public, which were the focus of the Committee's previous
report, the Committee has also estimated the ranges of doses
to individuals in the population groups, taking account of
38°N
37°N
38°N
37°N
NIIGATA
GUNMA
SAITAMA
NIIGATA
GUNMA
SAITAMA
TOCHIGI
TOCHIGI
140°E
140°E
YAMAGATA
MIYAGI
141°E
O FDNPS
FUKUSHIMA
IBARAKI
Figure 1
YAMAGATA
MIYAGI
141°E
FDNPS
FUKUSHIMA
IBARAKI
Figure 2
Dose range (mSv)
>5 (max. 5.3)
2-5
1-2
0.5-1
0.2-0.5
0.1-0.2
<0.1
Areas not assessed
at municipality level
Areas assessed
separately
0 12.5 25
50 km
Dose range (mSv)
>5
2-5
1-2
0.5-1
0.2-0.5
0.1-0.2
<0.1
Areas not assessed
at municipality level
Areas assessed
separately
N
0 12.5 25
50 km
uncertainties and variabilities. Typically, nine out of ten people in
each population group were estimated to have received doses
in the range of three times lower than the average dose to three
times higher than the average.
The estimated municipality- and prefecture-average absorbed
doses to the thyroid for infants in the first year are in the range of
about 2 to 30 mGy for municipalities that were evacuated, about
1 to 20mGy for other municipalities in Fukushima Prefecture,
about 0.6 to 6 mGy in neighbouring prefectures, and about 0.09
to 0.7 mGy for prefectures in the rest of Japan.
Decontamination workView entire presentation