150702_International discussion on the effect of radiation exposure due to a nuclear accident

Japan Health Physics Society

Overview of the WHO reports
on dose estimation and health risk
assessment from the nuclear accident
after the 2011 Great East Japan
Earthquake and Tsunami

Makoto Akashi, MD, PhD
National Institute of Radiological Sciences (NIRS)
Chiba, Japan

World Health Organization
 Function: acts as the UN directing

and coordinating authority on
international health work Objective: "the attainment by all

peoples of the highest possible levelof health" Definition: "HEALTH is a state ofCOMPLETE physical, mental andsocial well-being and not merely theABSENCE of disease or infirmity"(Constitution, 1948)
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Health risk assessment
Purpose To fulfil WHO's role and responsibilities

under the Joint Radiation Emergency
Management Plan
 To give an indication of the radiation-

related health implications of the accident
 To Support the identification of needs andpriorities for public health action
 To provide information to policy makers

and health professionals, as well asinternational organizations
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Dose estimation & health risk assessment

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Dose estimation
HazardIdentification

Dose-response
Relationship
Risk
Characterization

Exposure
Assessment

4Dose estimation

This report was primarilyintended for use by theWHO Health Risk
Assessment Group to inform
an initial assessment ofhealth risks incurred as aconsequence of the FDNPS
accident5WHO and UN Reports
onradiation exposure from accident

2011

2012

2013

2014
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Preliminary dose estimation
 Radiation doses to the public for

the first year following the accident Doses characteristic of the average

doses, assessed for different age
groups in locations around the world Excludes– Doses within 20 km of the NPP– Doses to workers– Health risks and public healthactions
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Dose estimation
 Giving the limited information

available to the panel during thetime frame of its work, theassessment contains a number ofassumptions
 In particular, some assumptions

regarding the implementation ofprotective measures are conservative Some possible dose overestimation

may have occurred
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Assumptions (1) All people in Fukushima prefecture consumed only foodproduced in Fukushima prefecture (possible doseoverestimation)
 Losses due to radioactive decay between the point of food‘marketing’ and the time of consumption not included,
neither are losses due to food preparation and losses duringcooking
Food sourcing and normal food distribution practices likely tohave been significantly altered by the impact of the tsunami,
the earthquake, and public protection measures
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Assumptions (2) Movement of people– < 20 km radius: not considered (people evacuated)– 20-30 km: not specific considerations for sheltering– "Deliberate evacuation zone": the assessment assumed
relocation at 4 months
 Stable iodine: it was assumed that KI tablets were nottaken in Japan nor elsewhere Food and water restrictions: the assessment does not

explicitly model the effect of the imposition of food andwater restrictions, it is implicit since the assessment isbased on monitoring results reported by the GoJ
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Dosimetric endpoints

 Effective doses and equivalent doses to the thyroidfor the first year after the accident in:– 1 year old infants, 10 year old children and adults– Exposure through drinking tap water used in the preparation of
infant formula was considered for 6 month old infants– Foetus and breast-fed infants not separately calculated but
considered in the text

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Data for estimates of doses from external andinhalation exposure for non-evacuated areas
WHO• Measured ground deposition
data from Japan Government• bulk deposition velocity

UNSCEAR• 1 km Population density grid• 2 km MEXT deposition grid• 5 km WMO ATDM grid12

Geographical coverageGroup 1 :Two locations within
Fukushima prefecture (NamieTown, Iitate Village)

Group 2:Katsurao Village, Minami
Soma City, Naraha Town,Kawauchi Village, Date City,
Fukushima City, Nihonmatsu City,
Kawamata Town, Hirono Town,
Koriyama City, Tamura City,
Soma City

Group 3:The rest of Fukushima
prefecture (less affected) and otherprefectures in Japan

Group 4:Countries neighbouring
Japan and other regions of theworld

13Comparison of WHO and UNSCEAR assessment- Members of the public Location

WHO assessment

UNSCEAR assessment

First year

First year

EFFECTIVE DOSE TO ADULTS (mSv)
Evacuated Areas
Namie Town
Naraha Town
Iitate Village
Katsurao Village
Minamisoma City
Non-evacuated areas
Iwaki City
Rest of Fukushima Prefecture
Neighbouring prefectures

10-501-1010-50
1-10
1-10

5.0a
3.7a
8.0b
6.0b
5.7

1-10
1−10
0.1-102.2
1.0−4.3
0.2−1.4

ABSORBED DOSE TO THYROID OF 1-YEAR-OLD (mGy)
Evacuated Areas
Namie Town
Naraha Town
Iitate Village
Katsurao Village
Minamisoma CityIwaki City
Non-evacuated areas
Rest of Fukushima Prefecture
Neighbouring prefectures

100-200
10-10010-10010-10010-10010-100

81c
82c
56c
73
53c
52

10-100
1-10

33−52
3−15

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Health risk assessment

Independentexperts+Observers

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Risk assessment
Includes-General population in Fukushima Prefecture*
General population in the rest of Japan
General population around the world
FDNPS emergency workers**

Not includes- First responders (e.g. police, fire fighters, Japan selfdefence forces)

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Risk assessment*Definition of the general population in Fukushima
Prefecture̶̶̶

Geographic location
4 distinct geographic areas
Age group
1-year-old infant / 10-year-old children / 20-year-oldadults(Health risks from exposure in utero was considered
but not quantitatively)
Both sexes**Definition of the emergency workers̶ Male workers in age groups of 20-, 40- and 60year-old17

Risk assessment
Four distinct geographical areas wereidentified based on estimated doses Group 1: the two locations within Fukushima prefecturewith effective doses of 12– 25 mSv;
 Group 2: locations in Fukushima prefecture whereeffective doses are between 3 and 5 mSv;
 Group 3: the less-affected locations of Fukushima

prefecture and the rest of Japan, where effective dosevalues are around 1 mSv;
 Group 4 – the neighbouring countries and the rest of theworld, where effective doses are well below 1 mSv;
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Health endpoints considered Cancer risks were estimated by using

risk models for– all-solid cancers incidence– leukaemia incidence– thyroid cancer incidence– female breast cancer incidence Non-cancer risks were considered

but not modeled– thyroid nodules, thyroid dysfunction,
visual impairment, circulatory diseases,
reproductive dysfunctions, risk toembryo and fetus

19Cumulative cancer risk over
15 years after exposure

Thyroid cancer

LAR/LBR ~ 70%Psychological impact
 The psychological impact canoutweigh direct radiologicalconsequences (lesson from Chernobyl) Soon after the accident, WHOrecommended improving availability
and access to community mental
health services in the affected areas ofJapan This remains a challenge today, andmay require special considerations
22Conclusion (1)- Radiation doses from the damaged nuclear power
plants in Fukushima are not expected to cause anincrease in the incidence of miscarriages, stillbirths
and other physical and mental conditions that canaffect babies born after the accident- The report notes that the psychosocial impact may
have a consequence on health and well-being23Conclusion (2)- In terms of specific cancers, for people living in the mostcontaminated locations, the estimated increased risks overwhat 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 (thenormally expected risk of thyroid cancer in females overlifetime is 0.75% and the additional lifetime risk assessed forfemales exposed as infants in the most affected location is0.50%)
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Conclusion (3)- For people living in the second most contaminatedlocations of Fukushima Prefecture, the estimatedrisks are approximately one-half of those in thelocation with the highest doses.
- For 2/3 of the emergency workers (< 10 mSv), allcalculated risks were of similar magnitude as thenormal fluctuations in the baseline cancer risks25

Conclusion (4)- For 1/3 of the emergency workers (10 - 100 mSv), therelative increase over background for thyroid cancer isestimated to be up to 20% for the youngest workers- For less than 1% of the emergency workers ( > 100 mSv1),
the relative increase over background for leukaemia andthyroid cancer is as high as 28% in the youngest workers- For those few emergency workers who received very highdoses to the thyroid (> 100 mSv2), a notable risk of thyroid
cancer is estimated, especially for young workers
1external effective doses
2internal effective doses

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