Report
Working Group on Risk Management of Low-dose Radiation
Exposure

December 22, 2011
Office of the Deputy Chief Cabinet Secretary
General Table of Contents
1. Report Overview
2. Attachment 1
3. Attachment 2
4. Working Group on Risk Management of Low-dose Radiation Exposurematerials used in presentations by experts at each meeting＊temporary translation

ReportWorking Group on Risk Management of Low-dose Radiation
Exposure

December 22, 2011
Contents
1. Purport of the holding of the working group1.1. Purport of meetings
1.2. Fundamental issues
1.3. Progress in investigation
2. Scientific findings and international consensus
2.1. Health effects as understood using current scientific methods
2.2. Conceptualizing health risks from radiation
2.3. ICRP “reference levels”
2.4 Application of radiation protection
3. Assessment of the current situation in Fukushima / direction of future handling3.1. Assessment of the current situation in Fukushima
3.2. Direction toward protection from radiation (with priority on steps for protection ofchildren)
4. Conclusions
References
Reference (1) – Members of the Working Group on Risk Management of Low-dose Radiation
Exposure
Reference (2) – Background of deliberations by the Working Group on Risk Management of
Low-dose Radiation Exposure
Reference (3) – Handling to date by the government with respect to low-dose exposures11. Purport of the holding of the working group
Residents who evacuated from the area due to effects of the Tokyo Electric Power Co.
(TEPCO)’s Fukushima Daiichi nuclear power plant accident have conflicting desires of wanting
to return to their homes and not wanting to return to areas that could cause ill health effects fromradiation.

Those who were not evacuated also feel uneasy about health and other effects fromradioactive substances.

Given this situation, our working group held discussions with a focus

on effects of low-dose radiation exposure, in particular regarding risks associated with annual
exposure dose of 20 millisieverts (mSv), the current level in Japan for issuance of evacuation
orders, and about specific matters requiring special consideration such as the handling ofchildren and pregnant women.

We took particular note in our discussions of both domestic andinternational scientific findings related to low-dose radiation exposure, including results
obtained to date from epidemiological research on the A-bomb survivors of Hiroshima andNagasaki and the residents living around the site of the Chernobyl nuclear accident, among
others.

Moreover, the group engaged in debate regarding the proper way in which such risk

should be communicated to the public.
A wide disparity of opinion exists among even experts in the field of low-dose radiation
effects.

With the objective of gaining understanding of the Japanese people regarding thisworking group’s decision-making process, we decided to publicize the proceedings of ourmeetings, which were marked by discussions based on the participation of leading experts fromboth Japan and abroad with wide-ranging, even contradictory, views and opinions.
1.1. Purport of meetings
Carrying out of more appropriate risk management in the future regarding low-dose radiation
exposure is necessary as a measure to counter the radioactive substances emitted due to
TEPCO’s Fukushima Daiichi nuclear power plant accident.

Toward that end, full reference

must be made to the latest scientific findings submitted by international and other relatedorganizations and assessment of countermeasures made to the present.

Moreover, the issues

facing the accident survivors at the scene must be identified and handled appropriately.

Fromthis perspective and based on the request of Goshi Hosono, Minister for the Restoration fromand Prevention of Nuclear Accident of Japan, this working group relating to risk management of
low-dose radiation exposure was established, after which it committed to deliberations, under
the Radiation Contamination Countermeasure Advisory Council, as a venue for the scrutiny ofscientific findings and assessments from both inside and outside Japan, identification andselection of issues facing the regions affected by the accident, and review of the future direction
to take for handling of the situation.

21.2. Fundamental issues‘Cold shutdown’ and other targets have been achieved with regard to the Fukushima Daiichi
nuclear plant, representing completion of ‘Step 2’ of the decommissioning process.

Theinterest of the Japanese people, in particular those from Fukushima prefecture, is now shifting to
the question of when residents will be able to return to their homes.

However, the evacuees

and those still residing in Fukushima prefecture feel uncertain about the assessments made of
the risk from low-dose radiation exposure for individuals, in particular risks to the health ofchildren and pregnant women.

Moreover, fundamental concerns remain in terms of daily life,

including the question of whether local communities can continue to exist even if residents areable to return home.

Development of appropriate risk communication for such residents is thefundamental prerequisite for efforts aimed at recovery and reconstruction of Fukushima.

Amidsuch circumstances, this working group was entrusted with development of scientific views andopinions regarding the following three items.
1) First, the proper way to consider health effects from low-dose radiation exposure of 20
mSv annually, the current level used for issuance of evacuation orders:
The national government judged whether to issue evacuation orders on the basis of thisannual dose of 20 mSv as one of its determination references.

How exactly this standardof 20 mSv should be assessed from the perspective of health effects is a major issue forconsideration.
2) Second, communication of views and opinions regarding the nature of considerationnecessary for children and pregnant women, who are considered to be highly sensitive toradiation’s effects, to serve as source material for the government’s various management
efforts to respond to the situation:
Even as the emergency situation following the accident has abated somewhat, residents
face low-dose radiation exposure for the foreseeable future and perhaps over the long term.
Amid such circumstances, expression of views and opinions related to the handling ofchildren and pregnant women in particular is necessary, including identification of needed
measures that perhaps differ from those used in the emergency phase of the accident.
3) Third, since the start of the Fukushima nuclear accident, severe criticism of thegovernment’s disaster risk communication efforts:
In the future, when the evacuees return to their homes, views and opinions will need tobe conveyed regarding appropriate distribution of information on radioactive substancesand radiation doses in relation to health risks from low-dose radiation exposure.
Furthermore, the assessments made by the working group are based on scientific perspectives
at the present time and organized to include limitations of science in the current age, asking the3question regarding what of relevant opinions are scientifically consistent and also what of therelevant issues have not been based on science.
1.3. Process in investigation
The working group has made available to the public the inner workings of its discussions anddeliberations with the aim of gaining the understanding of the Japanese people regarding how
the aforementioned three points were determined, including the decision-making process itself.
The group also has posted live and prerecorded broadcasts of its proceedings online on theinternet.
The working group was able to garner the participation of overseas experts as well as various
leading specialists from Japan.

We determined to carry out debate based on the participationof experts able to recommend methodologies and approaches that perhaps differ from thegovernment’s efforts.

All working group meetings benefited from the participation of

government officials who engaged in active debate, including Minister Hosono.
2. Scientific findings and international consensus
Scientific findings regarding radiation’s health effects, in particular health effects fromlow-dose radiation exposure, are the result of humanity’s historical experience.

Directly

showing concrete association between radiation exposure dose and effects on human healthusing animal experiments, in vitro experiments, or gene studies is a challenging task.

However,such research can be utilized to complement scientific findings from studies in the past ofradiation’s effects on human health and mechanisms behind the cause of such effects.
Such scientific findings represent the foundation underlying our consideration of radiation
effects from the recent Fukushima Daiichi nuclear accident and countermeasures developed todeal with its aftermath.

Disparate findings involving radiation’s effects have been reported,and clear understanding of international consensus regarding these scientific issues is thus
necessary.

The international consensus should conform to reports put out by such internationalorganizations as the United Nations Scientific Committee on the Effects of Atomic Radiation(hereinafter referred to as “UNSCEAR,” an organization that reports its scientific findings to theUnited Nations), the World Health Organization (WHO), the International Atomic Energy
Agency (IAEA), and other such bodies.
Studies on human health effects from the atomic bombings of Hiroshima and Nagasaki serveas the foundation for worldwide epidemiological research into radiation for both their scope andprecision in this particular research field, with UNSCEAR also consistently publishing related
reports.

The Chernobyl nuclear accident serves as an example of many individuals sufferinginternal exposure.

When also taking into consideration low-dose exposures, at least 5.0
4

million residents of the areas surrounding Chernobyl, including children, were exposed.
Results of studies related to the Chernobyl accident have been reported in detail by suchinternational organizations as UNSCEAR, WHO, and IAEA.
2.1. Health effects as understood using current scientific methods(1) Risks from low-dose1 radiation
1. Current scientific findings related to health effects from low-dose radiation exposure arebased mainly on detailed data obtained over more than a half-century from the survivors of
the atomic bombings of Hiroshima and Nagasaki.

These data enjoy great credibility

internationally and serve as the foundation for UNSCEAR reports.
A) Reports from epidemiological studies of A-bomb survivors from Hiroshima andNagasaki have shown a dose-dependent increase in cancer risk starting at dose levels
slightly more than 100 mSv [1].
B) Risk of cancer development from radiation at levels of 100 mSv or lower is consideredso slight according to international consensus that risk is concealed by carcinogenic
effects from other causes.

At such low levels, clear increased risk of cancer

development from radiation is difficult to prove.

Scientific methods other thanepidemiological studies also are being utilized to elucidate cancer risk, but at present,such methods have not yielded unequivocal risk information for humans.
2. On the other hand, an extended duration is sometimes required before cancer develops afterradiation exposure.

With low-dose exposure to 100 mSv or less, cancer risk might

become apparent only with an even longer passage of time in the case of persistent
exposure.

In any case, wide-ranging preventative countermeasures are necessary,

including exhaustive efforts to decontaminate affected areas.
(2) Health effects from long-term radiation exposure
The 100 mSv figure under 1. of (1) above involves assessment in the case of short-term
radiation exposure.

For a cumulative dose of 100 mSv from continuous exposure over thelong term in a low-dose environment, health effects are assumed to be less severe than thosefrom short-term, or instantaneous, exposure (known as the ‘dose rate effect’).

Thisphenomenon has been verified scientifically in animal experiments.
A) In epidemiological studies of residents of the state of Kerala in India, a region with someof the highest levels of background radiation in the world, no increase in cancer risk was
observed even for cohorts with cumulative doses exceeding 500 mSv [2].

On the other

hand, however, in epidemiological studies of Techya River watershed residents, who were5

exposed to radiation through a series of radiation disasters at nuclear weapons facilities inthe southern Ural mountains of the former Soviet Union, risk increases have been reported
for a cumulative dose range of around 500 mSv [3].

Dose estimation and confounding

factors should be further analyzed in these reports, but in either studies no increase incancer risk was observed for dose levels of around 100 mSv.
B) Health effects from exposure to radioactive substances emitted into the environment due
to the Fukushima Daiichi nuclear accident represent a situation of long-term low-dose
exposure, with cancer risk thought to be lower than that in instantaneous exposure, even in
the case of identical doses.
(3) Differences between external and internal radiation exposures
1. One argument holds that internal radiation exposure has greater effects on human healththan does external exposure.

However, in the case of radioactive substances present

either externally or internally, the resulting radioactivity damages DNA, and thatcompromised DNA might, during the process of DNA repair, cause mutations that can inturn lead to cancer development.

For that reason, if equivalent doses2 affecting organs

are the same in external and internal radiation exposures, the risk is considered to beequivalent [4].
A) Among types of radiation, gamma rays are the most penetrating, which means thatabsorption of energy from such rays is not limited to the sites at which thesubstances emitting the radiation are deposited and piled up.
B) Issues that have been investigated in detail by international organizations regarding
when radioactive substances are inhaled or taken in through the diet include to whatorgans the substances concentrate, how much radiation dose each organ absorbs, andradiosensitivity of each of the organs, which is one of the factors involved in cancer
development.

According to such investigations, model calculations3 can be madedepending on differences in length of time in the body and organ to which theradiation concentrates for each of many hundreds of radioactive nuclides andisotopes, as well as depending on size and other characteristics of the absorbed
radioactive particles.

For example, if 1 becquerel of radioactive substance isinhaled or ingested orally these models can be used to calculate what organs havereceived approximately what exposure (equivalent dose and effective dose expressedin siebert,4 effective dose being arrived at by addition of risks of all organs).
Therefore, even with different nuclides, effects on human health are considered to beequivalent as long as radiation doses measured in units of sievert are the same after
differences in the radiation quality and organ radiosensitivity are taken into account.
6C) In clinical and epidemiological research, excess relative risk5 of thyroid cancer insubjects exposed in childhood has been shown to be nearly equivalent between
external and internal exposures [5].
D) Among the nuclides released in the Fukushima nuclear accident, plutonium, whichemits mainly alpha waves, and strontium, which gives off mostly beta waves, havelarge effective doses per unit amount of radioactivity (1 becquerel) in the case ofinternal exposure.6 Nevertheless, compared with cesium, the quantity of theseradioactive particles emitted into the environment was extremely small in the case of
Fukushima,7 with amounts taken up internally into the body also considered limited.
For that reason, exposure doses from these compounds are estimated to be smaller
than the radioactive cesium doses.
E) In the Chernobyl accident, the cause of increased thyroid cancer among children isconsidered to be selective internal exposure of the thyroid that was due toconsumption of milk contaminated by radioactive iodine during a period of up to
several months after the disaster.
F) Average exposure doses for residents living around the Chernobyl nuclear accidentsite were assessed in a 2008 UNSCEAR report to have been 33 mSv for 116,000
evacuees, more than 50 mSv for 270,000 residents of areas with the highest
contamination levels, and 10-20 mSv for 5.0 million residents of areas with low
contamination levels.

Observing such residents of these surrounding areas, there

are some physicians and other healthcare workers who have pointed out increases invarious other types of disease.

However, the consensus understanding among suchinternational organizations as UNSCEAR, WHO and the IAEA is that no increases
in leukemia or other illnesses have been scientifically confirmed among the general
population including children.
2. One report indicated increased bladder cancer incidence from internal exposure to lowlevels of radioactive cesium among residents of the Ukraine [6].8 However, the analyticalmethodology has been questioned and its findings are in contradiction to otherepidemiological study results.

For example, no findings of increased bladder cancer

incidence were obtained from epidemiological studies conducted continuously starting in
the 1960s of the Sami people of Scandinavia, who were exposed to high levels ofradiation internally through the consumption of reindeer meat contaminated byradioactive cesium emitted into the environment from atmospheric nuclear testing and theChernobyl nuclear accident [7].

Based also on results from other international

epidemiological studies, causal association between internal exposure of low levels of7radioactive cesium and bladder cancer has not been confirmed.
(4) Effects on fetuses and infants/children
Generally speaking, relative risk of cancer development tends to be higher with younger age
at exposure.

Among those in childhood/puberty, cancer risk from high-dose radiation exposureis greater than the risk among adults. In low-dose exposures, however, such disparity in cancer
risk profiles due to age-group differences is unclear.

On the other hand, research into in-utero

survivors of the atomic bombings has suggested that risk of developing cancer in adulthoodamong those exposed in utero is equivalent to, or perhaps slightly lower than, the risk of those
exposed in early childhood [8].
Moreover, at present no genetic effects from radiation have been detected in several tens of
thousands of offspring of the A-bomb survivors, based on long-term follow-up studies [9, 10].
In cancer radiotherapy, depending on the site of the cancer, testicular and ovarian organs are
exposed to higher radiation doses than those experienced by the A-bomb survivors, and yet no
genetic effects have been observed in large-scale epidemiological studies of the children of suchpatients (the parents) [11].
A) Studies following the Chernobyl nuclear accident showed that risk of thyroid cancer
development was lower in those exposed in utero than among those exposed inchildhood.
B) Compared with the thyroid exposure from the Chernobyl accident, thyroid exposure forchildren from the recent Fukushima Daiichi nuclear accident is thought to be limited,with exposure doses small and cancer risk extremely low.

According to results fromnumerous tests on childhood thyroid exposure, environmental radiation contaminationlevels, food contamination levels, and so on, it appears highly unlikely that large
amounts of radioactive iodine were ingested due to the environmental effects from the
Fukushima nuclear disaster, in stark contrast with the Chernobyl accident.
(5) Biological defense mechanisms
1. When radiation damages DNA, mutations arise, added to which are multi-stagetransmutations, together forming one of the mechanisms behind malignant transformationof normal cells.

On the other hand, biological organisms are equipped with biologicaldefense capabilities9 that form a protective system by which the process of carcinogenesis
is suppressed.
2. Even low-dose radiation exposure is known to damage DNA, leading to abnormalities in
the repair process, characterizing another mechanism behind cancer’s development.
However, also noted is that for low doses, the extent of DNA damage is limited, making it
8

apparent that both the repair-process accuracy and biological defense are functioning
sufficiently, with no increase in cancer risk resulting from such doses [12].
2.2. Conceptualizing health risks from radiation(1) Definition of risk
Radiation risk is a yardstick used to indicate the potential for manifestation of harm.

Risk isnot the antonym of “safety” nor does it mean simply “danger.”(2) Concept of models assuming linear increase in risk without threshold values
The concept that risk increases in linear fashion with radiation dose,10 even in cases of
low-dose exposure, is employed in the areas of radiation protection and management.
A) This does not mean, however, that the concept is accepted as scientifically proven fact,
but that it is employed as a determination to compensate for scientific uncertainty
standing firmly on the side of public health safety.
B) The idea of risk increasing in linear fashion with dose is merely a means with which tolimit exposure to radiation.

In other words, the concept is meaningful whencomparisons are made between such different risks as those from estimated radiation
exposure and other health risks from, for example, measures used to protect a populationfrom radiation.
C) In accordance with this concept, however, application of the low-dose exposure risk fromradiation of 100 mSv or much less to a population (collective) dose for a large number ofpeople (unit: person-sievert) to predict number of deaths would lead to inordinately large
uncertainty and render the information unsuitable.

The ICRP has pointed out the sameproblem involving use of this concept [13].
(3) Understanding risk levels
1. Japan’s national government and TEPCO together share responsibility for the Fukushima
Daiichi nuclear accident, and therefore both parties must reflect deeply on theirinvolvement in causing societal uncertainty and anxiety due to low-dose radiation
exposure.
2. Simple comparisons between risks from radiation exposure due to such accidents as therecent one and risks from other factors such as medical exposure of patients that isoftentimes voluntary are not necessarily appropriate.

Comparisons with other factors,

however, can effectively assist in the understanding of risk levels.
A) According to mortality data from 2009, about 30% of Japanese people die fromcancers.

If a dose rate reduction effectiveness factor (DDREF) of 2 is applied to9the results of studies of the A-bomb survivors in Hiroshima and Nagasaki, estimatesshow a lifetime increase of about 0.5% in cancer risk mortality over the long term
for exposures of 100 mSv.

In contrast, however, disparity of at least 10% exists

among prefectures in Japan with respect to cancer mortality rates.
B) In order to understand the radiation health risk, it might be compared with risks
associated with other cancer causing factors.

For example, smoking is considered

to be equivalent to risk from between 1,000 and 2,000 mSv of radiation exposure,obesity11 between 200 and 500 mSv, and a lack of vegetables in the diet12 andpassive smoking13 [14] between 100 and 200 mSv.
C) From the perspective of radiation dose, a single CT scan, for example, leads toexposure of several mSv of radiation.

For a seriously ill patient to undergo

multiple CT scans during hospitalization is not at all rare.
D) Moreover, one round-trip air flight between Tokyo and New York exposes passengers
to roughly 0.2 mSv of radiation, due to increased cosmic rays from flying at highaltitudes.
E) The worldwide average for exposures due to natural sources of radiation is considered
to be 2.4 mSv annually, compared with the Japanese annual average of about 1.5
mSv.14

The worldwide average for radon exposure15 is 1.2 mSv annually,

according to an UNSCEAR report, with the range estimated to be vary between 0.2
and 10 mSv annually, depending on geographic location.

Japan’s figure for radon,by comparison, is 0.59 mSv annually.
F) Chloroform, a representative trihalomethane compound considered to havecarcinogenic effects, is commonly found in drinking water.

Even in cases ofcontinuous consumption of two liters of tap water on average per day, however,cancer risk is less than 0.01%, a level considered not high enough to warrant
concern.

Cancer risk from radiation of 100 mSv (for example, about a 0.5%

increase in lifetime probability of dying from cancer in the case of exposure overthe long term to 100 mSv) is greater than this risk from chloroform intake.
3. Based on the situation presented in the above 2., from the radio-protection perspective,
the concept of cancer risk increasing in linear fashion with radiation exposure is
extremely important, even in cases of low-dose exposure to 100 mSv or less.

When risk

is compared in accordance with this principle, health risks16 based on an assumed annual
dose of 20 mSv are considered to be lower than risks from other carcinogenic factors(such as smoking, obesity, diet lacking in vegetable intake, and so on), and roughly
comparable with risks associated with radiation protection measures (such as stress from10

evacuation, lack of exercise due to avoidance of outdoor activity, and other such factors).
2.3. ICRP “reference levels”
1. The International Commission on Radiological Protection (hereinafter referred to as the“ICRP”)17 classifies radiation exposure situations into three different types: “emergency,”“existing,” and “planned.”

As targets for the designing and carrying out of measures forprotection from radiation during the emergency exposure and the existing exposure
situations, the ICRP has recommended a radiation dose range (band) for each of thesituations, establishing “reference levels” within these ranges appropriate for the particularsituation and recommending application of such values for ensuring the safety of residents
in affected areas [13, 15, 16].
A) These reference levels take into account economic and societal factors and serve as targets
for the formulation of measures based on the principle of “optimization,”18 whereby
exposure levels are reduced to levels as low as reasonably achievable.
B) The reference levels are used for the carrying out of protective measures preferentially for
those thought to have been exposed to radiation exceeding those levels over a fixed
period of time, with the aim of achieving exposures lower than the reference values.
The levels also serve as indices for assessment regarding whether or not the protective
measures in place have been effective.
This does not mean, however, that exposure doses for all residents must immediately
fall below these reference levels; rather, the reference values are to be used as the basis
for devising measures aimed at the decrease of exposures below those values andreduction of radiation doses progressively over time.
C) The reference levels do not represent “limits” for radiation exposure.

Neither should

they be interpreted as indicating a boundary between “safe” and “dangerous.”
2. Respective reference levels for each situation are as indicated below:A) The reference level for emergency situations19 is selected from within the range of anannual 20 to 100 mSv.
B) The reference level for existing exposure20 situations is selected from within the range ofan annual 1 to 20 mSv for the general public.
C) As indices for efforts to gradually improve the situation in existing exposure, interim
reference levels can be established, with efforts made toward improvement based on along-term annual target of 1 mSv.
D) For planned exposure situations, establishment of “dose constraints,”21 rather than use ofreference levels, within the range of an annual 1 mSv or less, is recommended,11depending on the situation regarding the exposure status of the general public.
2.4. Application of radiation protection(1) Management based on the principle of optimization
When government policy for radiation protection with respect to low-dose exposure is
implemented, efforts must be undertaken to reduce radiation exposure to levels as low asreasonably achievable on the basis of scientific fact.
A) Various radiation-protection measures can be considered, depending on the sources ofradiation and pathways of exposure in question. Specifically, such measures include
decontamination limits on entrance into the areas with high levels of radiation, andcontrols on intake of food and drink suspected of having high levels of radiation
contamination, among others.
B) When such radiation-protection measures to be used are selected, both the benefits
associated with decreased radiation doses (in terms of health and psychological security,etc.) and the deleterious effects associated with avoidance of radiation (in terms of
economic harm caused by evacuation and relocation, destruction of community,
disadvantage from lost work, and mental and psychological effects from changes tolifestyle, etc.) should be taken into consideration, consistent with ICRP’s philosophy.
C) When carrying out government radiation-protection policy, special attention should be
paid to children and pregnant women.
D) Radiation-protection measures with respect to decontamination, health management, andfood safety are considered most effective when devised to indicate in intelligible terms
effectiveness of the measures and to notify the public of the target ranges, timeframe of
implementation of the measures, and targeted values.
(2) Managing the situations following Chernobyl
With respect to the response to the post-Chernobyl accident situation, some were of theopinion that the former Soviet Union’s government measures for relocation of individuals from
affected areas, among others, were worthy of emulation.

Other opinions from suchinternational organizations as the IAEA, however, have deemed the measures employed at thattime as excessive.
A) In terms of the response in the aftermath of the Chernobyl accident, if local radiationlevels in such countries as the Ukraine were found to exceed 5 mSv annually starting
around five years after the accident, in the 1990s, government measures were
implemented to relocate to other regions those residents living continuously incontaminated areas, with those efforts continuing today.
12B) Nevertheless, some residents continue to live even now in such areas, with it difficult to
say that the measures have been either consistent or exhaustive.

Moreover, the levels

for relocation of residents in the event of a new accident are now set at higher doses than
this annual figure of 5 mSv.22
C) The response in the aftermath of the Chernobyl nuclear accident included provisional dose
limits for the one year immediately after the accident set at an annual 100 mSv, withthose limits reduced progressively over time, and the level of an annual 5 mSv adopted
starting in the fifth year and thereafter following the accident.
D) On the other hand, within one month following the Fukushima Daiichi nuclear accident,
evacuation (exclusion) zones were established, based on a level of an annual 20 mSv ofradiation exposure.

The handling of evacuation with regard to the Fukushima Daiichi

accident is clearly stricter at present than the response following the Chernobyl accident,
based on the concept of reference levels used to reduce exposures progressively overtime.
(3) Residents’ participation and communication of risk
1. While the Fukushima nuclear power plant has achieved ‘cold-shutdown’ status, the firstpriority in securing the safety and security of residents in a situation in which theenvironment is already contaminated is the restoration of lost confidence between theresidents and the government and other officials involved and the rebuilding of a
relationship of trust.
2. The fact that expert opinions varied with regard to safety and the danger and health effects
from radiation when expressed by the mass media and others led to feelings of uncertainty
and unease on the part of the local area residents and thereby invited chaos.

Withreflection on this situation, factors now considered to be of crucial importance are review ofthe scientific findings obtained to date and provision of such information to local residents
in a format that ensures ready understanding of risk assessment consistent with the ongoingsituation in Fukushima.

Based on these efforts, it is necessary to ensure that residents areable to handle such situations on their own if necessary, based on accurate understanding ofradiation and radioactivity.
3. It is crucially important to explain to the public whether the numerical values used in thearea of risk communication indicate scientifically verified health effects or are targets set bygovernment policy for radiation protection (values involving ICRP reference levels) in orderto obtain their understanding and avoid causing chaos.
4. Based on the experience of the Chernobyl nuclear accident, active participation by area
residents amid existing radiation exposure toward long-term solutions to the situation are13

indispensable.
In contrast to the emergency response that governments must immediately adopt in casesof emergency exposure situations, an existing exposure situation requires consideration of
the varied and numerous values and beliefs held by citizens, whose participation isabsolutely critical.
5. To convey scientific facts of such a situation to citizens in as intelligible manner as possible,
administrative personnel/bureaucrats such as government officials as well as experts fromvarious fields, including the social sciences and psychology, must communicate
information about risk founded on the development of a relationship of trust withresidents/citizens.
A) Through communication with residents and with cooperation from government andexperts, all involved can understand the risks and thereby devise appropriate measuresfor dealing with the situation.
B) In particular, the roles of experts such as local medical and local school officials whoshare the specific values of the residents and can explain the situation’s health risks areof utmost importance.
C) A most important role of the government in such a scenario is the provision of
intelligible information about efforts at monitoring radiation levels and accurate
information about the risks involved.
3. Assessment of the current situation in Fukushima / direction of future management
To this point in time in Fukushima, the government has employed levels that call for
evacuation at an annual exposure level of 20 mSv, but actual exposure doses on average havebeen assessed far below that level.
Even in zones in which doses are no more than 20 mSv, the government must make efforts to
reduce exposure as a matter of policy.

The top priority for such policy is protection fromradiation for children, who are highly sensitive to radiation’s effects, and in particular infants,
whose parents are greatly concerned about radiation’s health effects, making it necessary to
carry out deliberate protective measures.

3.1. Assessment of the current situation in Fukushima(1) Fukushima’s current situation
1. The accident at the Fukushima Daiichi nuclear power plant was categorized as a level ‘7’
according to the International Nuclear and Radiological Event Scale (INES), a nuclear
accident the equivalent of which had never before been experienced in Japan, with the14

government adopting a myriad of protective measures since the time of the accident.

The

Chernobyl accident also measured a 7 on the same scale, but the Fukushima accident bycomparison resulted in only around one-seventh the amount of Chernobyl’s radioactivity
released into the environment, indicating that the two accidents can be considered vastlydifferent, even from the perspective of health effects on local residents.
2. When devising its protective measures for the evacuation zones, the government adopted,
from the standpoint of ensuring safety, the most conservative level of 20 mSv annually
among the reference levels suggested by the ICRP for evacuation in emergency exposure
situations (20-100 mSv on an annual basis).

However, precisely because the government

adopted this model with its priority on safety when assessing radiation exposure doseamong humans, the actual doses for the one-year period since the accident to which mostresidents were exposed are expected to be significantly lower than this 20 mSv level.
A) In more detail, with respect to external exposure, the results from measurements using
personal dosimeter devices for 36,478 children and pregnant women in the city ofFukushima indicated that about 80% of this population had been exposed to additionaldoses of up to 0.1 mSv over the one-month period of September 2011, according to
information released by the Fukushima City Disaster Countermeasure Headquarters
on November 1, 2011.

On the other hand, the air dose rate23 in the city of Fukushima

was measured at 0.92 microsieverts per hour, and estimates of doses with the method24
used for establishment of the evacuation zones based on these values led to estimatesof an annual dose of around 4.8 mSv and a monthly dose of about 0.4 mSv.

A simplecomparison of the two results thus indicates that the actual exposure doses measured
with dosimeters in Fukushima were about one-quarter of the estimated values.
B) Moreover, measurements with personal dosimeters by the Ministry of Education,
Culture, Sports, Science and Technology (MEXT) that took place of educational staff
members as representatives of the children in their charge resulted in observed
measurement values of 0.8 times25 on average the estimated exposure doses resulting
from multiplication of each of air dose rates both inside and outside buildings bylength of time spent in each of the respective locations (source: Outline of “Results ofmonitoring using simplified integrating dosimeter (4),” June 23, 2011, Ministry of
Education, Culture, Sports, Science and Technology).
C) For the 1,589 residents (except for radiation workers) in the regions (Kawamata-machi[Yamakiya district], Namie-machi, Iitate-mura) targeted in the priority review
conducted by the Fukushima prefectural government’s “Prefectural resident healthmanagement survey,” estimates of cumulative exposure doses over the four months
after the accident were made based on actual activity records of that period.
15

Among

that total, 998 (62.8%) were thought to be exposed to less than 1 mSv, 1,547 (97.4%)
to less than 5 mSv, and 1,585 (99.7%) to less than 10 mSv, with the remaining fourindividuals exposed to levels exceeding 10 mSv, and one person exposed to 14.5 mSv,
the largest dose of all.
D) As for internal exposure, measurements of 6,608 individuals using whole body counters
carried out by the Fukushima prefectural government yielded the following figures:
Those exposed to committed effective doses26 of 1 mSv or less of cesium-134 or
cesium-137 comprised 99.7% of the total, and those exposed to greater than 1 mSv
totaled 0.3%, with the maximum dose measuring less than 3.5 mSv (as of the end of
October 2011), according to materials released by the Regional Medical Departmentof the Health and Welfare Office of the Fukushima prefectural government.

As

reference, the average annual amount of natural radiation taken in by the Japanesethrough intake of foodstuffs is considered to be roughly 0.41 mSv.
E) Regarding exposure associated with food intake, which is considered likely to comprisethe major source of internal exposure in the future, the Pharmaceutical Affairs andFood Sanitation Council estimated actual doses using measurement data of radioactive
concentrations in food and drink products collected by the Ministry of Health, Labourand Welfare.

The Council’s assessment was that such exposure only amounted to

low levels (about 0.1 mSv annually as a median value; as an assumption made on theside of safety, even foodstuffs in the 90th percentile27 of radiation concentration would
yield internal exposure of only 0.244 mSv annually even with continuous intake overthat period28), according to material No. 4 of the Food Sanitation Subcommittee of thePharmaceutical Affairs and Food Sanitation Council, dated October 31, 2011. Theseestimates, while not limited to the residents of Fukushima prefecture, are valuable forsuch assessments, given that generally speaking the residents consume foodstuffs
produced in various locales.
F) Internal exposure associated with inhalation of deposited radioactive materials
re-suspended in the air has been assessed at the relatively small amount of only several
percent of the total of both internal and external exposures (1.9%, according to thereport “Assessment of internal exposure associated with use of school playgrounds,”
Material No. 3-1, 31st Nuclear Energy Safety Council, Ministry of Education, Culture,
Sports, Science and Technology, May 12, 2011).
3. Assessment methodologies of radiation exposure doses at the time of formulation of
relevant regulations made to date placed priority on safety in emergency situations.

Inthe future, it will be necessary to deliberate on methodologies that are more precise from16

the perspective of dose-assessment experts through careful examination of disparities
between the radiation doses assessed with the current assessment methodologies andindividual dose assessments based on estimates from activities carried out by individuals
and the air dose rates of the locations at which those activities took place or actual
measured exposure doses.
(2) Risk avoidance for residents of the Fukushima Daiichi nuclear power plant accident
Japan’s national government has set its evacuation standard at the level of 20 mSv annually,
adopting the strictest value from the perspective of safety from among the reference levels forradiation exposure in emergency exposure situations.

At establishment of the current

evacuation zones, doses were estimated on the high side for safety’s sake, without any factoring
in of natural decay of radioactivity or other such factors, one of the reasons why it is now
possible to assess actual average annual exposure doses as far less than this limit of 20 mSv.
Orders to evacuate as a measure for handling the emergency exposure situation wereaccompanied by significant burden on the daily lives of residents.

In a situation of existing

exposure, however, a more varied complement of measures than used in the case of emergency
exposure must be considered, while taking into account the burden placed on the region and its
residents.

Moreover, measures must be adopted based on the idea of approaching a lifestyle

close to that lived prior to the accident, based on the devising of comprehensive measures aimed
at reduction of risk, such as decontamination centered on daily life environment and securing offood safety.
3.2. Direction toward protection from radiation (with priority on steps for protection ofchildren)(1) Efforts including decontamination aimed at reduction of exposure doses
Radiation protection levels adopted by Japan at the current time are set at an annual exposureof 20 mSv.

In the future, however, it will be necessary to further reduce exposure doses asmuch as possible.
A) When carried out, this process must be adopted in step-by-step fashion, with progressive
improvement taking place starting in those regions assumed to have high exposure forresidents.

Steps aiming at a long-term target of 1 mSv per year (the ICRP estimates aperiod of several decades) should be devised from the perspective of aiming at complete
recovery.
B) At the same time, to effectively utilize resources invested when carrying out such steps
related to decontamination of areas of daily life and to health management, and so on,
appropriate and reasonable prioritization of efforts and clarification of intermediate17reference exposure levels are measures considered to be effective.
For example, the government’s policy regarding its announced measures for decontamination
aims at a situation in which additional radiation doses29 on an annualized basis for the generalpublic are reduced around 50% by the end of August 2013, compared with the figures at the endof August 2011, including physical decay of radioactive substances, setting the long-term target
for additional exposure doses at a level of no more than 1 mSv per year.

For residents in areas

estimated to have exposure levels at 20 mSv per year, this policy would mean reduction inradiation exposure to an annual 10 mSv in two-year period, which could be considered anintermediate reference level.

Moreover, even after such targets are attained, it would benecessary to continue making stepwise progress in decontamination efforts, leading to possible
targets of the further halving of exposure doses, for example (at that point, 5 mSv per year forareas with annual exposure to residents of 10 mSv).
(2) Carefully thought out steps with priority on children
When implementing steps to reduce radiation exposure, it is necessary to carry out carefully
thought out protective measures with priority placed on children, who are considered highly
sensitive to effects from radiation, and infants, whose parents naturally have great concerns
about radiation’s effects.
A) First, importance should be placed on the understanding of assumed radiation doses, withstudies conducted on the pathway by which major exposures are taking place, including
both internal and external exposures.

Moreover, accurate investigation and grasping ofactual radiation exposure levels is also necessary.
B) External radiation, which is thought to be the major exposure pathway for the present, isthe result of radiation emitted from radioactive substances in soil and other sources,
making decontamination a high priority for the environments in which children arepresent and active.
The national government has determined guidelines, for example, regarding measuresrelated to decontamination and so on, aiming at realization of about 60% reduction in
additional annual radiation dose levels for children, including physical decay ofradioactive substances, by the end of August 2013, compared with the levels at the endof August 2011, through priority decontamination of the environments in which children
are present and active.

It is recommended that the same policy regarding exhaustiveand comprehensive decontamination of activity zones for children, such as pathways
used for travel to and from schools and as well as public parks where children play,among other areas, is also adopted in evacuation zones following the lifting of the18

evacuation orders.
C) Outside the evacuation zones, the government has provided economic support fordecontamination of soils for schools measured to have air dose rates of more than 1
microsievert per hour in schoolyards and kindergarten grounds.

As a result, the air

dose rates in nearly all such schoolyards and kindergarten grounds now fall below thatlevel of 1 microsievert per hour.
In the future, when evacuation orders are lifted, protective measures aiming at
exposure doses for the evacuation zones that are equivalent to those used for schools
outside the evacuation zones must be adopted.

Specifically, prior to the reopening ofschools in the evacuation zones with air dose rates in schoolyards and kindergarten
grounds and so on of more than 1 microsievert per hour, exhaustive decontamination
efforts including of the surrounding areas must be undertaken with an eye to reducing
levels beneath that cutoff.
In addition, comprehensive decontamination of areas in which children are present
and active, such as pathways for travel to and from school and public parks, and so on,
not only the schools themselves, should be undertaken, aiming at additional annual
exposure doses of less than 1 mSv over the long term for the areas in which children arepresent and active.
Also necessary is work aimed at reduction of external exposure from extracurricularschool activities by carrying them out in areas with relatively low dose levels, as well as
efforts to maintain the physical and mental health of children.
D) Appropriate management is also required for prevention and reduction of internal
exposure.

Toward this end, the setting of appropriate and reasonable standards

regarding radiation concentration in foodstuffs and strict observance of such standards
are considered crucial, through efforts to measure radioactive concentration in foodstuffs,
for example, that are suited with the local conditions and needs in the region concerned.
Upon implementation, introduction of radiation contamination testing of school lunches
should be seriously considered, from the perspective of employing stricter measures withrespect to children.

Moreover, to assess internal exposure from food intake, continuous

screening for internal exposure should also be considered.
E) When radiation doses are measured in individual children, some with high measurement
values are bound to appear.

For such children, a kind, attentive, and compassionate

response on an individual basis is called for by physicians, radiation technicians, publichealth nurses, radiation experts, and school staff and educators, among other related
personnel.

Such efforts should be designed to identify the source of the high radiationlevels, provide assistance in terms of lifestyle issues when required, and offer
19

psychological support, as a complement to further decontamination efforts adopted in the
problem areas in question.
(3) Risk communication from the viewpoint of residents intimately tied to the region
When conducting countermeasures to reduce radiation doses, risk communication based on
scientifically identified facts, and that from the viewpoints of the residents of the affected areas
are essential.

Such a task is one of the keys for restoration of confidence in government.

A) Local government officials engaged in active risk communication with residents in theaffected regions have pointed out that continuous activities aiming at improvement of theenvironment conducted by the residents themselves, such as decontamination work, arethe best risk communication methods, as they lead to elimination of anxiety andrestoration of vitality in daily lives.

Expansion of such active participatory citizen

efforts to endeavors besides decontamination work is an important subject forinvestigation.
B) Moreover, it is important for the government to provide the means whereby individuals
can obtain information on their own, thereby enabling them to understand and assess
their own particular circumstances, as well as to foster the environment in which
continuous voluntary efforts are possible toward recovery and restoration.
C) Not only understanding of the emotional state of residents by government officials andexperts but also direct communication between the government, experts and such
residents can lead to all parties working together on measures to reduce radiation
exposure from the same viewpoint based on mutual understanding.
(4) Health countermeasures to reduce cancer risk
At present, Fukushima prefecture residents and evacuees face anxiety about radiation’s healthrisks, in addition to numerous psychological and social burdens because of limits on lifestyleassociated with measures used for radiation protection.
That such continued protective measures have led to increased psychological and mental
burdens for such residents is another issue requiring consideration.

However, the handling ofradiation’s health effects represents an opportunity to make more progress than ever before withrespect to cancer-prevention measures.

Enhanced efforts at reduction of cancer risk, the issueof utmost concern for residents, by improving lifestyle habits, such as smoking, diet andexercise, other than radiation, and achievement of early cancer detection through improvementof the cancer screening participation rate, which is currently low, are essential.
national government should be actively involved in the support of such efforts.

20

Finally, the4. Conclusions
1. In the TEPCO Fukushima Daiichi nuclear accident, Step 2 of the decommissioning process
has concluded with attainment of ‘cold shutdown’ of the power plant itself, among otheractions.

However, due to radioactive substances emitted from the plant until this point in

time, residents now face the issue of low-dose radiation exposure over the long term.
The simple return of residents to the areas previously categorized as evacuation zones
would not indicate resolution of the problems inherent in the situation.

The national

government and TEPCO share responsibility for the Fukushima Daiichi accident, and bothmust therefore engage in the earnest handling of societal fear and anxiety spawned by theconsequent low-dose radiation exposure.

Until those affected by the disaster can return totheir homes and rebuild their communities of natural beauty and human warmth, thenational government must expend considerable energy. To achieve this goal, national,
prefectural, city/town/village governments and area residents need to cooperatively engage
in persistent efforts over the long term.

Continuous cooperation from experts andspecialists in the relevant fields also is a must.
2. The following views represent the results of debate to the present with respect to the threeissues that this working group has been charged to investigate:
1) According to scientific findings based on international consensus, increased risk ofcancer from low-dose radiation exposures at 100 mSv or less is so small as to beconcealed by carcinogenic effects from other factors, making verification of any clear
cancer risk from radiation exceedingly challenging.
Nevertheless, from the perspective of radiation protection, special measures should
be adopted to reduce risk from exposure by making determinations on the side ofsafety, based on the concept that risk increases in linear fashion with radiation dose,even in such cases of low-dose exposures of 100 mSv or less.
Health risks from annual radiation exposure of 20 mSv, the current level for
issuance of orders to evacuate an affected area, are quite small particularly whencompared against the risks from other carcinogenic factors.

From the perspective ofprotection from radiation, protective measures such as decontamination of mainly
areas of daily life and management of food safety should be continued, and throughsuch efforts, this level should be sufficient to allow avoidance of risk.

Furthermore,when carrying out such radiation protection measures, the issue of what measures toadopt should be deliberated upon from a policy perspective, based on comparison of
the risks associated with adoption of such measures (stress associated with evacuation,
cessation/insufficiency of exercise due to avoidance of outdoor activity, and so on).
21

With this in mind, the level of an annual dose of 20 mSv is believed to be an
appropriate starting point toward further reduction of dose exposures in the future.
At the time the current evacuation zones were established, radiation exposure dose
estimates were made on the side of safety, without any consideration paid to thenatural decay of radioactivity, or other factors, meaning that actual average exposure
doses are, thus, estimated to be far below the annual level of 20 mSv.
2) Cancer risk from low-dose radiation exposure of 100 mSv or less for children and fetus
is so small as to be concealed by carcinogenic effects from other factors, the same asin the case with adults, making verification of any clear increase in cancer risk
extremely challenging. On the other hand, however, in cases of high-dose exposure
exceeding 100 mSv, children through puberty are at higher cancer risk from radiation
than are adults.
With this in mind, even in low-dose exposures of no more than 100 mSv, adoptionof measures for radiation protection with a priority placed on children is appropriate,given the significant unease experienced by residents of the affected area.

However,

because children are thought to be highly sensitive to the effects of stress and so on
associated with attempts to avoid radiation exposure, deliberate measures for caring
children are considered to be of paramount importance.
3) Clear communication to people and affording a better understanding regarding whether
the values used with the aim of radiation protection are scientifically verified or are
the result of government policy is an important point.

Based on the Chernobyl

experience, having residents actively participate in both long-term and effective
radiation protection efforts is crucial.

For that reason, government and specialists

must take on risk communication from the viewpoint of residents that provides
intelligible and transparent information based on widely accepted scientific facts.
Based on the above opinions, our working group hereby offers the following five suggestions:
1. For decontamination efforts, an appropriate order of priority should be set inprogressive fashion, by establishing reference levels, for example, of an annual 10
mSv in the two-year period.

And after that goal is met, the exposure level would be

reduced to an annual 5 mSv as the next step.

Moreover, these reference levels must

be used as targets and as markers for attainment of such targets when carrying out
radiation protection measures, backed by clear and simple explanations about theconcepts, not as values for expression of radiation exposure “limits.”
22

Moreover, thenational government should take responsibility for decontamination efforts inpartnership with local cities, towns and villages, creating an effective andcomprehensive system for such efforts.
2. Priority should be placed on decontamination of environments in which children arepresent and active.

In the future, when decontamination is conducted for theevacuation zones, protective measures should be adopted that aim at achieving
radiation doses equivalent to those of schools outside the evacuation zones, with thepolicy for exhaustive decontamination of children’s activity zones, such as pathways
to and from schools and public parks, and the like, to be the same in these evacuation
zones after the lifting of evacuation orders.

More specifically, for schoolyards andkindergarten grounds and other such areas measured with air dose rates of 1
microsievert or more per hour, that figure must be reduced to less than 1 microsievert
before the schools in the evacuation zones are reopened.

Moreover, exhaustive

decontamination efforts for zones in which children are present and active, such as
pathways to and from schools and public parks, and so on, must be carried out withthe aim of long-term additional exposure of no more than 1 mSv on an annual basis.
3. Special consideration is necessary regarding foodstuffs provided to children, withestablishment and observance of appropriate and reasonable standards regarding
radiation concentration therein.

Along with health management and exposure dose

measurement for children, distribution of radiation detectors for measurement ofradiation in foods should be distributed quickly to affected areas to allow residents tounderstand their own radiation exposure situation, with the aim of attaining
transparency of such information and active citizen participation.

Exhaustive efforts

must be made to educate residents regarding methods for measurement of radiation
using such devices.
4. To achieve proper understanding of the situation and carry out countermeasures,
government officials and specialists with a wide range of expertise need to take part incontinuous conversation with residents at the level of the local community withrespect to health and other issues, starting first with effects from radiation exposure.
Also necessary is the training of experts intimately familiar with the region.
5. The age-adjusted mortality rates from cancer in Fukushima prefecture in 2005 per
100,000 population were 193.3 for men and 95.1 for women, ranking that prefecture
24th and 26th from the highest, respectively, with respect to cancer mortality among all
prefectures in Japan.30,31

After the report was released, the Fukushima prefectural

government announced its aim to reduce age-adjusted cancer deaths (among thoseunder the age of 75 years)32 by 20% over the following ten-year period, in accordance
23

with the Cancer Prevention Promotion Plan that the prefectural government
formulated in March 2008.33

It is now imperative for this prefecture’s government

to establish new targets upon verification of the status of progress in its efforts
regarding the current plan, with the aim of making Fukushima Japan’s lowest
prefecture in terms of mortality from cancer in about 20 years for example, while forthe present putting into practice the various measures for steady attainment of theoriginal target of 20% reduction.

Toward that end, reduction of other carcinogenic

risks is called for through improvement of lifestyle and other habits such as smoking,diet and exercise, and so on, along with packaging of such improvements in agovernment policy that includes increasing the numbers of people electing to undergo
health examinations.

In this way, Fukushima should strive to become in the future a

region heralded throughout the world for its cancer-prevention measures, paving theway toward realization of its residents’ wishes in the future.

24

Footnotes
1. There is no clear definition of ‘low-dose exposure’ based on international consensus, but mostrecent information refers to a level of 200 mSv or less.
2. Level of biological effects differs depending on type of radiation.
the same energy, the extent of biological effects can vary.

Even in cases of exposure to

Equivalent dose is defined as dosesthat cause roughly equivalent biological effects and is derived by multiplication of absorbed
dose (absorbed energy per unit mass) by “radiation weighting factor,” which reflects differencesin extent of biological effects from different types of radiation.

Equivalent dose is a measureused for purposes of radiation protection, with sievert (Sv) the unit of measurement.
3. When stipulating radiation sensitivity, this method is based on average values for gender and age.
For that reason, actual risk values may include such fluctuations as children’s higher sensitivity
to radiation.
4. Addition of “tissue weighted factor,” which reflects extent of risk of cancer in organs and tissues,
to the equivalent dose results in whole organ dose information, with sievert (Sv) the unit ofmeasurement.
5. For certain health effects, “relative risk” is used to express how many times greater the risks arefor an exposed group compared with a control group. Relative risk of 1 means that radiation
exposure has not affected risk in that particular instance.

Excess relative risk is the result when

1 is subtracted from the relative risk for the risk factor targeted for study (in this case, radiation
exposure).
6. For example, according to ICRP Pub. 71, these doses in an infant at three months of age forstrontium-90 would be 2.3 x 10-4 mSv per 1 becquerel; for cesium-134: 2.6 x 10-5 mSv per 1
becquerel; and for cesium-137: 2.1 x 10-5 mSv per 1 becquerel.
7. According to the Japanese government report titled “Report of Japanese Government to the
IAEA Ministerial Conference on Nuclear Safety - The Accident at TEPCO’s Fukushima Nuclear
Power Stations” (Nuclear Emergency Response Headquarters, June 2011), the (total) amounts ofradioactive emissions into the atmosphere were considered to be roughly the following:cesium-134 at a level of 1.8 x 1016 becquerel and cesium-137 at 1.5 x 1016 becquerel, withstrontium-90 at 1.4 x 1014 becquerel or roughly 1/100th the levels of cesium.

Plutonium-239

and plutonium-240 were considered to be 3.2 x 109 becquerel, or about 1/10,000,000th thelevels of cesium.
8. Pointed out in research about the Chernobyl nuclear accident by Dr. Fukushima, the director of
the Japan Bioassay Research Center
9. Such as anti-oxidation substances, repair of DNA damage, elimination of mutant cells,
elimination of cancer cells
10. Called the Linear Non-Threshold Model (LNT)
25

11. Risk for the group with BMI (index for measurement of obesity calculated on the basis of heightand body weight) of 30 or greater compared to the group with BMI of 23.0-24.9
12. Risk for the group consuming 110g per day (median value) compared with the group consuming
420g per day
13. Risk for the group of women whose husbands were non-smokers compared with the group of
women whose husbands were smokers
14. According to “Lifestyle environmental radiation” (1992), Nuclear Safety Research Association
15. Reference to radon typically refers to radon-222, which is generated at the time of decay ofradium-226, the daughter nuclide of uranium-238. This radon is a noble gas element with ahalf-life of 3.8 days, and it exists everywhere in our daily environment.

The world indoor

radon concentration average is 40 becquerel per cubic meter, and great variety is observed
among countries with regard to this average, from 10 becquerel per cubic meter to the Czech
Republic’s 140 becquerel, with northern Europe having generally high levels.

Japan’s

average is 21 becquerel per cubic meter, about half of the world average.
16. Assuming residents of areas considered to have an annual exposure of 20 mSv calculated on thebasis of the air dose rate as of August 2011 were to continuously reside in the locations for the
next ten years, the radiation exposure dose would be estimated at about 95 mSv over that period,
even without decontamination effects (trial calculation from materials of the Nuclear Emergency
Response Headquarters, dated August 26, 2011).

Actual exposure doses, however, are thought

to be below that value.
17. An international scientific organization that provides recommendations about arrangements forradiation protection for people and the environment from the perspective of experts andspecialists
18. Indicates the principle known as ‘As Low As Reasonably Achievable’ (ALARA)
19. A situation in which emergency actions are necessary to avoid or reduce undesirable effects
from such situations as a nuclear power accident or radiation emergency
20. When management decisions are required in a situation of existing exposure, including
long-term exposure in the recovery stage following a state of emergency
21. With respect to planned exposure situations, limits on individual exposure can be applied inplanned stages, with predictability of such doses to ensure without fail that the upper limits are
not exceeded, as differentiated from reference levels.
22. For example, based on the experience of the Chernobyl nuclear accident, new standards wereadopted in Russia as a long-term measure in 1996 that do not require relocation from theaffected area if the first-year exposure level is 50 mSv.
23. The average monthly value measured over a period of one month (September 2011) at a fixed
number of sites (25 sites) by the Ministry of Education, Culture, Science, Sports and Technology,
26

and other ministries, and the governments of Fukushima prefecture and Fukushima city
24. Estimated on the basis of duration of time spent outdoors per day (8 hours) and radiation
shielding effect (0.4) for duration spent indoors (16 hours) in a wooden shelter
25. Comparison between estimates of exposure doses derived from multiplication of the measured
air dose rate values in mainly school buildings and grounds of 55 schools and kindergartens inFukushima prefecture by the actual duration of time spent in said locations, and themeasurement results from personal dosimeters used during the period from June 6 to June 19
26. This is the effective dose of internal exposure after the intake of radioactive substances into thebody.

In the case of adults, the committed time is 50 years after intake, whereas in children it

is until the age of 70, with the committed effective dose considered to be equivalent to the doseof the year of intake.

For a definition of effective dose refer to footnote #5.

The conversion

factor for the standard person is calculated using anatomical models and computational
physiological models.
27. This refers to the value at the level of the 90th percent when radiation concentration data isorganized in the order of smallest value to highest
28. Estimate results using a method (deterministic dose estimate) for estimation of exposure doses
based on the assumption of continuous intake of an average Japanese dietary intake with acertain concentration of radioactive substances (representative values)
29. Radiation dose exposure from which has been subtracted natural radiation dose andtherapeutic/medical radiation dose

30. Demographic statistics from the Statistics and Information Department, Minister’s Secretariat,
Ministry of Health, Labour and Welfare.

The crude mortality rate (ordinary mortality rate

derived by dividing number of deaths by population) due to cancer as of 2010 is now 305.7

for men and women combined per 100,000 population.
31. The crude mortality rates by prefecture are affected by the age demographics in each of theprefectures.

For example, even if the mortality rates by age group are the same, the crude

mortality rates would be higher in prefectures with a higher number of aged people andlower in prefectures with a higher number of young people.

Therefore, age-adjusted

mortality rate (per 100,000 population) is the mortality rate adjusted for age demographics
in order to allow comparison of mortality situations among prefectures with different age
demographics.

Using this age-adjusted mortality rate makes possible more accuratecomparisons of mortality in groups with different age demographics.
32. The national government’s Cancer Prevention Promotion Basic Plan (June 2007) calls for a
reduction in age-adjusted mortality rate (for those under the age of 75) from cancer, because
these target values are considered appropriate as highly precise indices that eliminate aging
effects to the extent possible.
2733. In materials submitted by the members of the Ministry of Health, Labour and Welfare’s
Cancer Control Office (May 2007), precise calculations based on certain sets ofassumptions were carried out, establishing throughout Japan the goal of “20% reduction incancer mortality over the ten years starting in 2005 (under 75 years of age, age-adjusted).”The government announced as concrete means toward this goal (1) reduction of smoking
rates through anti-smoking efforts; (2) diffusion and precision management of healthexaminations with established effectiveness; and (3) similar levels of cancer treatment
available to all members of society, as the basis for the aforementioned rate of reduction inreflection of the contribution of each of these efforts.

Using such information as reference,

the national government formulated its Cancer Prevention Promotion Basic Plan, and thegovernment of Fukushima prefecture then established its own Cancer Prevention Promotion
Plan in line with the national government’s framework.

28

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30

Reference (1) – Members of the Working Group on Risk Management of Low-dose Radiation
Exposure-

ENDO, Keigo: President, Kyoto College of Medical Science; Vice Chairman, Japan
Radiological Society-

KAMIYA, Kenji: Vice President, Fukushima Medical University; Director, Hiroshima
University Research Institute for Radiation Biology and Medicine-

KONDO, Shunsuke: Chairman, Japan Atomic Energy Commission, Emeritus Professor, The
University of Tokyo-

MAEKAWA, Kazuhiko: (Co-chair of the working group), Emeritus Professor, The
University of Tokyo; Chairman, Radiation Emergency Medicine Network Meeting,National Institute of Radiological Sciences-

NAGATAKI, Shigenobu: (Co-chair of the working group) Emeritus Professor, Nagasaki
University; Former Director, Radiation Effects Research Foundation-

NIWA, Ohtsura: Emeritus Professor, Kyoto University-

SAKAI, Kazuo: Director, Research Center for Radiation Protection, National Institute ofRadiological Sciences; Visiting Professor, Department of Nuclear Engineering andManagement, The University of Tokyo Graduate School-

SASAKI, Yasuhito: Permanent Director, Japan Radioisotope Association; Former Director,
National Institute of Radiological Sciences-

TAKAHASHI, Tomoyuki: Member, Radioactive Substances Countermeasure Section
meeting, Food Sanitation Subcommittee, Pharmaceutical Affairs and Food Sanitation
Council; Associate Professor, Kyoto University(Names indicated in alphabetical order, with last names in capital letters appearing first)[Government agency participants]-

HOSONO, Goshi: Minister of the Environment, Minister for the Restoration from andPrevention of Nuclear Accident of Japan-

NAKATSUKA, Ikko: Senior Vice-Minister of the Cabinet Office-

SONODA, Yasuhiro: Parliamentary Secretary of the Cabinet Office-

TAKAYAMA, Satoshi: Parliamentary Secretary of the Environment

31

Reference (2) – Background of Deliberations by the Working Group on Risk Management of
Low-dose Radiation Exposure(1) 1st Working Group Meeting (November 9)Expert members – KODAMA, Kazunori: Chief Scientist, Radiation Effects Research
Foundation
SAKAI, Kazuo: Director, Research Center for Radiation Protection,
National Institute of Radiological Sciences
After explanations were provided regarding health effects from radiation, the meeting
engaged in deliberations on effects of low-dose radiation exposure over the long term,
differences in effects depending on radionuclide, biological defense capabilities, and othertopics.
(2) 2nd Working Group Meeting (November 15)
Expert members – SHIBATA, Yoshisada: Professor, Nagasaki University Graduate School of
Biomedical Sciences
KIMURA,

Shinzo:Director,

Fukushima

Office,International

Epidemiology Research Laboratory, Associate Professor, Radiation
Hygiene, Dokkyo Medical University
After explanations were provided regarding health effects from the Chernobyl nuclear
disaster, the meeting engaged in deliberations on the idea that no increases in cancers will beobserved, besides thyroid cancer, from radiation exposure among children (Professor Shibata),
and the basis for creation of the standard of 5 mSv per year by the Ukrainian government(Associate Professor Kimura), among other issues.
(3) 3rd Working Group Meeting (November 18)
Expert members – NIWA, Ohtsura: Emeritus Professor, Kyoto University
SHIMADA, Yoshiya: Group Leader, Experimental Radiobiology forChildren’s Health Research Group, Research Center for Radiation
Protection, National Institute of Radiological Sciences
After explanations were provided regarding risks to children and pregnant women fromlow-dose exposure, the meeting engaged in deliberations on other effects besides healtheffects such as severe psychological and societal effects, greater cancer risks from smoking
32and obesity than from radiation exposure at a level of 100 mSv, and necessity of explanationsof correct information with a scientific basis, and so on.
(4) 4th Working Group Meeting (November 25)
Expert members – KODAMA, Tatsuhiko: Professor, Research Center for Advanced Scienceand Technology, The University of Tokyo
KAI, Michiaki: Professor, Oita University of Nursing and Health Sciences
After explanations were provided regarding the thinking about risk management for
low-dose radiation exposures, the meeting engaged in deliberations on such issues as
behaviors and different effects of each kind of radionuclide in the human body, research into
possible health effects from the perspective of genomics, differences in effects from internal
exposure depending on radionuclide, and comparisons of risks between radiation and otherrisk factors, among other topics.
(5) 5th Working Group Meeting (November 28)
Expert members – CLEMENT, Christopher H.: Scientific Secretary, ICRPLOCHARD, Jacques: Member (Chair of Committee 4), ICRP Main
Commission
After explanations were provided regarding ideas from an international perspective related
to low-dose radiation exposure, the meeting engaged in deliberations on such issues as theprioritization of measures with regard to the government’s reference levels and ideas about
the relocation of residents in the Chernobyl situation.
(6) 6th Working Group Meeting (December 1)
Expert members – NAKAYACHI, Kazuya: Professor, Faculty of Psychology, Doshisha
University
KAMIYA, Kenji: Vice-president, Fukushima Medical University
After explanations were provided regarding the manner in which risk should becommunicated to the public, the meeting engaged in deliberations on such issues as methods
for quantitative risk understanding and elimination of related anxiety and stress, methods for
obtaining trust of the public, and activities related to risk communication employed in theaffected local areas, among other topics.

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(7) 7th Working Group Meeting (December 12)
Expert members – TANAKA, Shun-ichi: Contamination Advisor, Fukushima Prefecture;
Chairman, Research Organization for Information Science andTechnology
NISHIDA, Shoji: Mayor, Date City, Fukushima Prefecture
After explanations were provided regarding issues arising at the local level and the direction
necessary for future countermeasures with regard to the situation, the meeting engaged indeliberations on such issues as methods of conveying relevant information from thegovernment and experts, necessity of residents’ participation, and importance of measuringexposure doses and amount of radiation present in the immediate environment, among otherissues.
Following the above, a draft compilation was discussed.
(8) 8th Working Group Meeting (December 15)
The draft compilation was discussed.
*Each meeting’s expert members submitted CVs (summaries of publications), which will be
added in Attachment 1.
Messages from the following experts attending the working group meetings will be added in
Attachment 2.
-

BALONOV, Mikhail: Member, ICRP Main Commission
Consultant, World Health Organization (WHO)Consultant, United Nations Scientific Committee on the Effects ofAtomic Radiation (UNSCEAR)-

BURKART, Werner: Former Deputy Director General, IAEA-

CLARKE, Roger: Emeritus Member, ICRP Main Commission-

BOICE, John D. Jr.: Member, ICRP Main Commission
Professor, Medicine at Vanderbilt University School of Medicine
Scientific director, the International Epidemiology Institute-

IVANOV, Victor: Deputy Director, the Medical Radiological Research Center, Russian
Ministry of Health and Social Development
Chairman, Russian National Commission on Radiological Protection-

ZEEV, Hajo: Head, Department of Prevention and Evaluation at the Bremen Institute forPrevention Research and Social Medicine
34

Reference (3) – Handling to date by the government with respect to low-dose exposures(1) The fundamental process involves the government taking into consideration ICRP
recommendations and adopting measures for handling of the situation after obtaining
opinions based on expert viewpoints from such committees as the Nuclear Safety
Commission.
(2) As measures for handling of the emergency exposure situation, the government establishedinitial evacuation and refuge zones March 11-12, 2011, expanded the zones, and ultimately
established an evacuation zone covering an area with a radius of up to 20 km from thenuclear power plant.

On March 15, the government established an indoor-evacuation zone

covering a range of 20-30 km from the plant site.

In addition, in consultation of the ICRP

reference levels, the government adopted the strictest level of annual dose exposure of 20
mSv from within the emergency exposure levels from the perspective of safety, thenestablished its planned evacuation zones and issued its evacuation orders.

For locations

with a continued air dose rate estimated to exceed 20 mSv of cumulative dose over the
one-year period since the accident in some of the areas in which the spread of radiation
regionally did not warrant establishment of planned evacuation zones (with respect to“Planned Evacuation Zones” and “Emergency Evacuation Preparedness Zones,” by Atomic
Energy Safety Commission, April 10, 2011), the government created “Designated Locations
for Recommended Evacuation,” after consultation with the relevant local governments, andstarted its support for evacuation and initiated calls for precautions to take in daily life,
among other measures.

In such circumstances (“Handling for designated locations

estimated to have cumulative doses in the one-year period following the accident exceeding
20 mSv,” Nuclear Emergency Response Headquarters, June 16, 2011), the government
relied on conservative calculations, by considering annual exposure of 20 mSv to be theeffective dose rate for measurement values of air dose rate, with outdoor exposure of 8hours and indoor of 16 hours, a shielding coefficient of 0.4 for indoor exposure, and no
attenuation thereafter.
(3) For handling of the existing exposure situation, the government determined guidelines fordecontamination measures, making certain based on ICRP standards that annual additional
exposure was at or below 1 mSv as a long-term goal, and by the end of August 2013, thatabout a 50% reduction, including physical decay of radioactive substances, could beachieved compared with the annual additional exposure for the public at large as of the endof August 2011 (“Regarding basic ideas related to radiation protection toward future liftingof evacuation, restoration,” Atomic Energy Safety Commission decision, July 19, 2011;“Basic ideas toward decontamination promotion” and “Basic policy for decontamination in35

emergencies,” Nuclear Emergency Response Headquarters, August 26, 2011; “Basic policy
for special measures related to dealing with environmental contamination caused byradioactive substances emitted due to the nuclear power accident accompanying the Great
East Japan Earthquake of March 11, 2011,” by Cabinet decision, November 11, 2011).
(4) With special consideration paid to children and pregnant women, the government iscurrently carrying out a program of lending dosimeters to individuals and conducting
ultrasonic thyroid screening (alongside Fukushima prefecture’s efforts).

Even with regard

to decontamination and other measures, the government has made the determination to
reduce annual additional radiation dose by roughly 60%, including physical decay ofradioactive substances, by the end of August 2013 compared with the levels measured at theend of August 2011, through the process of decontamination of environments in whichchildren are present and active in priority fashion.

In addition, the government determined

its own policy of measures related to decontamination, and so on (“Basic ideas toward
decontamination promotion” and “Basic policy for decontamination in emergencies,”
Nuclear Emergency Response Headquarters, August 26, 2011; “Basic policy for special
measures related to dealing with environmental contamination caused by radioactive
substances emitted due to the nuclear power accident accompanying the Great East Japan
Earthquake of March 11, 2011,” by Cabinet decision, November 11, 2011).
(5) The government also is engaged in distribution of information to the public and residents,
such as by the monitoring of environmental radiation (emergency monitoring conducted by
the Ministry of Education, Culture, Sports, Science and Technology, among others),
measurement of food products for radiation contamination levels (screening by local andregional governments), and establishment of consultation services regarding concerns about
radiation (Health Consultation Hotline by the Ministry of Education, Culture, Sports,
Science and Technology, among others), to list some of the efforts.

36