Radiation Q&A

Radiation

Q&A
放射線 Q&A

Issued by Nagasaki University

Issued by Nagasaki University

Five years have now passed since the Great East Japan Earthquake
and the Fukushima Daiichi Nuclear Power Station accident ofMarch 11th, 2011. I would like to extend my deepest sympathy andsolidarity to the victims of the earthquake disaster, and to those
who were forced to seek shelter elsewhere after the accident. Thisbooklet contains an English translation of the questions that readers
found particularly interesting from a Q&A series on Radiation andRadioactive Materials, published in the local Fukushima newspaper
Fukushima Minpo from December of 2011 to October of 2013. The
aim of presenting this information is to enrich the readers’
understanding of the various issues related to radiation.

Noboru Takamura
Professor
Nagasaki University

Radiation

Q&A
放射線 Q&A

Issued by Nagasaki University

CONTENTS
Preface

If a pregnant woman receives an X-ray, will the fetus be safe?  36

What is the difference between radioactive material andradiation? 

6

What is the half-life of radioactive materials? 

8What types of radiation exist in nature? 

10What is the difference between an atomic bomb and a nuclear
power plant incident? 

12In terms of radiation exposure, what is the difference between
adults and children? 
14

Radiation Exposure and The Thyroid GlandBy what mechanisms does the thyroid gland absorb radioactive
iodine? 
40
What about screenings of children’s thyroid glands? 

42

Some children were found with cysts on their thyroids. Whatshould we make of this? 

44Should I be worried about a small nodule on my child’s thyroid
gland? 46

What is a whole body counter? 

16What is the effect of radioactive iodine? What is thyroid cancer? 48

18

What is the effect of radiation on future babies? 20

Why did thyroid cancer appear in victims several years after
the Chernobyl accident? 

50

What is meant by the baseline of 1 mSv? 

22

Why are radiation levels at monitoring posts and forindividuals different? 

52

What is the difference between “man-made” radiation effects
and “natural” radiation effects on health? 24

Does drinking water contain radiocesium? 

26

What is radioactive strontium? 28

Can children play outside? 

30

Does the length of time one is exposed to radiation cause
damage to one’s genetic material? 

32

What impact will radiation exposure have on children who
have yet to be born? 34Is radiocesium the only radioactive element detected by wholebody counters (WBCs)? 
54
What is the effect of low-dose exposure to radiation throughCT scans? 

56

What are the health effects of radiation on the human body? 

58

Are the effects of radiation exposure on a fetus bymother’s exposure? 60

Can exposure to radiation cause nosebleeds? 62How different are exposure levels in Chernobyl compared to
Fukushima? 

About Fukushima
Health Management Survey

64

Were there acute radiation exposure symptoms in Chernobyl?  66
68

Why are basic health screenings of prefecture residents
required? 

70How was the testing of radiation levels performed in Nagasaki
and Hiroshima? 
96What have been the genetic effects of exposure following theChernobyl accident? 

72

How is the increased risk for cancer from radiation exposure
measured? 98

Does the thyroid gland have weak resistance to radiation? 74

What types of thyroid cancer are there, and what are theircharacteristics? Postscript 

100

76

Noboru Takamura’s brief personal history 

101

What was the incidence rate of thyroid cancer in Chernobyl? 
Were there increases in non-thyroidal cancers around
Chernobyl? 

94

Food Safety and Radiation
I’m worried that the milk my children receive in their school
lunches contains radiation. 

80

Why was radiation detected in wild animals? 82

Are there any health effects related to eating wildmushrooms? 

84

Can radiocesium enter well water? 86What is the level of concentration of radioactive strontium andplutonium in tap water? 88What about tests of strontium and plutonium in food? 90

illustrator: Akiko Suzuki

Radiation

What is the difference between
radioactive material and radiation?

Q

Terms like “radioactive material,” “radioactivity,” and“radiation” are being used almost daily in newspaper
articles. Although we have a rough understanding of what theymean, please explain what their main properties are.

A

Materials or substances that emit radiation, such asradioactive iodine and radioactive cesium, are known asradioactive materials.
Radioactivity refers to the energy in radioactive materials thatemits radiation. Radioactivity is measured in becquerels (Bq).
Reference values for radioactivity in food are measured inbecquerels/kilogram (Bq/kg), denoting the amount of radioactivity
contained in 1 kg of food.
The radiation emitted by radioactive materials may include small
particles, such as alpha rays or beta rays, as well as rays featuring
waveforms, such as gamma rays and X-rays. The effect of thisradiation on the human body is measured in Sv.
1 millisievert (mSv) and 1 microsievert (μSv) correspond to one
thousandth and one millionth of a sievert (Sv), respectively.
Whether you are dealing with man-made radioactive materials or
those that exist naturally in the world, the type of radiation emitted
in both cases is the same. Just because the radioactive materials

6

Q& A

A material or substance that emits radiation is a radioactive
material, and radioactivity refers to the strength of radiation.

that were scattered by the nuclear power plant disaster were manmade, it does not mean that the type of radiation generated was
different in any way.
On the other hand, we know that the power of permeation varies
depending on the type of radiation. For example, although you canstop alpha rays (be shielded from them) using a sheet of paper, thisis not the case with beta rays. Beta rays can be stopped with a thinsheet of aluminum. The radiologists and other doctors who carryout X-ray examinations in hospitals wear aprons containing lead,in order to shield themselves from X-rays and minimize their
exposure to radiation.

7

Radiation

What is the half-life of radioactive
materials?

Q

When talking about radiation, we often hear the term
“half-life.” Does this term describe how certain
radioactive materials end up in a particular condition? Also,
please explain why radioactive materials emit radiation in thefirst place.

A

Just as the word itself suggests, this term denotes theamount of time required for radioactive materials, such asradioactive iodine and radioactive cesium, to be reduced by half ofwhat they were originally.
Radioactive materials have unstable structures. However, theygo through a process of seeking stability, and it is this process thatcauses the emission of radiation. For example, iodine-131, one typeof radioactive iodine, emits beta ray and gamma ray radiation, but
it ultimately transforms itself into a chemical element called xenon.
Even in gas form, xenon does not emit radiation. Iodine-131, with ahalf-life of approximately eight days, emits radiation, and after
approximately eight days, half of it turns into xenon. In otherwords, the half-life refers to the amount of time that radioactive
materials emit radiation before becoming a stable substance. This
is what is known as the “physical half-life.” Now that a year has
passed since the nuclear accident, so there is no danger of detecting

8

Q& A

The term “half-life” refers to the amount of time required
for radioactive materials to change and be reduced by half.

radioactive iodine within the prefecture.
On the other hand, we are currently faced with problems related
to radioactive cesium, which has a half-life of approximately two
years for cesium-134 and 30 years for cesium-137. However, thisdoes not mean that, if radioactive cesium gets inside the body, it
would take 30 years for its quantity to be reduced by half. In thiscase, it would take around two months for infants, and about threemonths for adults, for the amount of cesium in the body to be cut
down by half. This is because the human body is constantly
regenerating itself, and when this happens the cesium is expelledfrom the body. This is what is known as a “biological half-life.” Itis always important to make a distinction between a substance’s
physical half-life and its biological half-life.

γ-ray
β-ray
Xenon

9

Radiation

What types of radiation exist in nature?

Q

Apart from the radioactive materials scattered byincidents such as the Fukushima Daiichi nuclear power
plant accident, we have heard that radiation also exists in thenatural world. Please explain, what types of radioactive materials
are there, and what sort of radiation doses do they emit?

A

During a typical person’s lifetime on the surface of the
Earth, he or she is exposed to approximately 0.3 mSv of
external radiation per year. This radiation comes down from space(known as “space radiation”).
In addition, the ground around the world contains a fixed amountof radioactive materials, which are completely unrelated to nuclear
power plant accidents. People have always been, and will always
be, exposed to the external radiation emitted by these materials.
Similarly, wherever you go, the water and food that you eat every
day contain minuscule amounts of radioactive materials; therefore,
with some foods, people also end up being exposed to internalradiation. For example, greenish yellow vegetables and bananas,
potatoes, and other foods contain large amounts of potassium, andthat potassium contains the radioactive material potassium-40,
albeit in extremely small quantities.
In Japan, the amount of radiation that people are exposed to in

10

Q& A

Around the world, there is a fixed amount of radiation on
the ground, and some areas are even exposed to as muchas 10 mSv per year.

nature (natural radiation) is approximately 2.5 mSv per year,
whereas the world average is approximately 3.0 mSv.
We also k now that there are places in the world withenvironments showing comparatively higher radiation doses. For
example, the region along the Kerala coast, in Southern India, issaid to be subject to a relatively high dose of radiation due to theeffect of the naturally radioactive materials that get washed up on
the shore from the sea.
In that area, people are exposed to over 10 mSv per year. Simply
put, if you were to live along the Kerala coast for 10 years, you
would be exposed to 100 mSv. However, research carried out in theregion has shown that the percentage of leukemia and cancer
sufferers among thein habit ants is nodifferent than thosefound in other regionsof India.

11

Radiation

What is the difference between an atomic
bomb and a nuclear power plant
incident?

Q

Many victims suffered as a result of the atomic bombs
dropped on Hiroshima and Nagasaki. During the more
recent Tepco Fukushima Daiichi nuclear power plant accident,
large amounts of radioactive materials were released. Ourconcern is whether the damaging effects of this incident could
be the same as those of the atomic bombs. What is thedifference between an atomic bomb and a nuclear power plant
accident?

A

The effects of radiation from an atomic bomb are primarily
caused by external exposure. An atomic bomb emits large
amounts of radiation all at once through nuclear fission. In
Hiroshima and Nagasaki, this caused many victims to be subject tohigh doses of external exposure, causing them to suffer acuteradiation effects, and developing leukemia or solid tumors a few
years to a few decades later.
On the other hand, the Chernobyl nuclear power plant accident
released a large amount of radioactive materials, particularly
radioactive iodine, which caused inhabitants of the vicinity to be
exposed to internal radiation. Radioactive iodine is particularly
prone to accumulation in the thyroid gland, so this caused anincrease in thyroid cancer a few years later, particularly in children

12

Q& A

The difference between the release of an atomic bomb anda nuclear power plant accident lies in the types of diseases
that result from exposure to these materials. This difference
stems from whether people were subject to external orinternal exposure.
who had consumed contaminated milk and other foods.
To date, apart from leukemia and thyroid cancer, there have been
no confirmed increases in cases of solid tumors in the Chernobyl
area. Although it is still necessary to continue doing research into
this, the difference between Hiroshima, Nagasaki, and Chernobyl,in terms of the types of diseases with increased cases, lies inwhether the exposure to radiation was external or internal.
The problem posed to the local inhabitants by both theradioactive iodine and radioactive cesium released by the accident
at Fukushima Daiichi Nuclear Power Plant is the risk of internalradiation exposure. Because of this, and based on lessons learned
from the Chernobyl nuclear power plant disaster, Japan set
provisional reference values for radioactive iodine and radioactive
cesium immediately after the accident took place. Any food orwater that exceeded thosereference values was
subject to shipping andconsumption restrictions,
thereby minimizing theinternal radiation exposure
caused by the consumptionof contaminated food.

13

Radiation

In terms of radiation exposure,what is the difference between
adults and children?

Q

We have heard that the effect of radiation exposure ismuch greater in children than in adults. What are theactual differences found in exposure of adults and children?
Please provide concrete symptoms from past cases.

A

Due to the accident at the Chernobyl Nuclear Power Plant,
large amounts of radioactive materials, particularly
radioactive iodine were released, causing the inhabitants of thevicinity to be exposed to internal radiation, thereby instigating an
increase in thyroid cancers a few years later. We know that manyof the cases of thyroid cancer found in Chernobyl appeared inpeople who had been children at the time of the accident.
In general, we know that the effects of radiation are moremarked in actively proliferating cells, tissues, and organisms. This
is what is known as “sensitivity to radiation.”
Bone marrow is a tissue located on the back of the body that
goes through a constant process of cell division to produce blood
cells, such as red blood cells and white blood cells. In Hiroshima
and Nagasaki, the bone marrows of the atomic bomb victims were
subject to high doses of external exposure, causing an increase incases of leukemia, a cancer of the blood.
Based on this, we can say that bone marrow is an internal organ

14

Q& A

Children are highly sensitive to radiation. It is necessary toprovide standards and minimize risk.

with a high sensitivity to radiation. However, with the dose ratios
currently found in the air of residential areas in the prefecture, it isunlikely that any risk of internal radiation exposure exists there,
even in children. On the other hand, many cases of thyroid cancer
were found among people who were children at the time of theChernobyl disaster. One of the reasons for this is that, compared toadults, children are much more sensitive to radiation.
Immediately after the nuclear power plant accident in March
2011, provisional reference values were set in the prefecture forradioactive iodine and radioactive cesium. Any food or water thatexceeded those reference
values was subject toshipping and consumption
restrictions. Based on theexperience of Chernobyl,
this was implemented as a
key measure to minimize
children’s internal exposure
to radiation, since they areparticularly sensitive to it.

15Radiation

What is a whole body counter?

Q

The prefecture has been measuring levels of internalradiation exposure by using whole body counters.
However, many municipalities have also introduced them on
their own, in order to take measurements of their inhabitants.
How do they differ from dosimeters? Please provide an
explanation about this measuring device.

A

Pocket dosimeters and integrated dosimeter badges canmeasure doses of external exposure, but not internal
exposure. One method for assessing doses of internal radiation
exposure is using a whole body counter.
The whole body counter takes advantage of the fact different
types of radioactive materials have different radiation wavelengths.
The device measures the concentration of radioactive materials
inside the body, and uses those figures as a basis for measuring thedoses of internal exposure.
When radioactive cesium gets inside the body, it emits beta rays
and gamma rays. The gamma rays then permeate the body, and atthat point the device measures the amount that is emitted outside
the body. Based on these figures, the counter measures theconcentration of radioactive cesium inside the body to calculate thedoses of internal exposure.

16

Q& A

A whole body counter measures the concentration ofsubstances inside the body, and then uses those values as
the basis for calculating the total amount of radiation present.

Since the accident of March 2011, whole body counters havebeen introduced within the prefecture, and measurements havebeen taken regularly since then. However, if we look at the values
measured to date, the concentrations of radioactive cesium insidepeople’s bodies has been relatively low, so the actual doses ofinternal exposure within the body cannot be considered to beharmful to people’s health. Immediately after the accident,
provisional reference values were set in order to place restrictions
on the consumption of contaminated foods; it is believed that thismeasure is the reason for the decrease in the levels of internalradiation exposure.
Similar to other medical devices and dosimeters, whole bodycounters can present slight differences in accuracy, depending on
the type of device used, causing a potential scattering of results.
This effect is currently considered to bea problem; however, this dispersion of
results is only observed when measuring
radioactive materials with extremely low
concentrations of radiation. This meansthat there is no chance that doses strong
enough to have detrimental healtheffects could remain undetected.

17Radiation

What is the effect of radioactive iodine?

Q

We have heard that after the Chernobyl accident, there
was an increase in cases of thyroid cancer among the
inhabitants in the vicinity of the power plant. Even with the
Tepco Fukushima Daiichi accident, it looks like there was ascattering of radioactive iodine, which is known to cause
thyroid cancer. Are people safe?

A

After the Chernobyl accident, large amounts of radioactive
materials were spread over a wide area. We know that the
scattered radioactive materials were primarily radioactive iodine
and radioactive cesium. Between the two, radioactive iodine is themost likely to accumulate in the thyroid gland after entering thebody. This is because the thyroid is an internal organ that secretes
hormones, and these hormones are composed of iodine.
With the Chernobyl accident, the radiation (beta rays and gammarays) that emanated from the radioactive iodine penetrated people’s
thyroid glands, causing them to become exposed. It is believed that
this internal exposure caused the increase in thyroid cancer among
the inhabitants living in the vicinity of the Chernobyl plant.
After the accident in Chernobyl, no consumption or distribution
restrictions were put in place with regard to food and drinks (milkin particular) that had been contaminated with radioactive iodine.

18

Q& A

Restrictions were placed on the consumption of food anddrink, so an increase in cases of thyroid cancer is unlikely.

We now know that the inhabitants of the area who consumed large
amounts of these contaminated items suffered from internal
exposure to radiation.
After the accident at Fukushima Daiichi Nuclear Power Plant
caused by the Great East Japan Earthquake in March 2011, Japanset provisional reference values for radioactive iodine andradioactive cesium. Any food or water that exceeded those reference
values was subject to shipping and consumption restrictions.
Based on the experience of Chernobyl, this measure was
implemented in order to minimize, as much as possible, anyinternal radiation exposure caused by the consumption ofcontaminated foods. Because of this, unlike the incident at
Chernobyl, an increase in cases of thyroid cancer within theprefecture is thought to be unlikely.

19

Radiation

What is the effect of radiation on future
babies?

Q

Because we live in a prefecture with ambient radiation
doses that are higher than normal, we are extremely
concerned as to whether it would be safe to become pregnant
and give birth to babies just like before. Would future children
be affected by radiation? Also, what about the case of women
who are already pregnant?

A

In the case of the victims of the Hiroshima and Nagasaki
atomic bombs, there were reports of an increase in cases of
microcephaly in the babies of women who were exposed to highdoses of radiation in the early stages of their pregnancies. However,this condition only actually manifested itself in embryos that were
exposed to extremely high doses of over 200 mGy*. This is acompletely different scenario from the one currently experienced
by the prefecture.
The International Commission on Radiation Protection (ICRP),
an international organization that sets international guidelines onradiation, has issued the following recommendation: “Embryos
exposed to doses of less than 100 mGy must not be considered as areason for having a termination.”
This advice was decided based on research carried out on theatomic bomb victims of Hiroshima and Nagasaki. This means that

20

Q& A

At the current doses, there is no need for concern. There
have been no reports of any possible hereditary effects.

there is no need to worry aboutbabies who have been exposedt o l e s s t h a n 10 0 m G y ofradiation. From the time of thenuclear power accident to thepresent day, it is unlikely that ababy of a preg nant woman
living in the prefecture could
have been exposed to more than
100 mGy of radiation.
In addition, people may have concerns about the hereditaryeffects on children who will be born in the future. However, evenconsidering the hereditary effects on the atomic bomb victims of
Hiroshima and Nagasaki (research carried out on the second
generation), there have been no reports of an increase in cases ofcancer, leukemia, or other similar diseases. The current radiation
doses observed in the prefecture are much lower, hence people
should feel at ease about becoming pregnant and giving birth.
* mGy (Milligray)
An absorbed dose of radiation. For the radiation emitted by radioactive iodine
and radioactive cesium (beta rays and gamma rays), 1 mGy is equal to 1 mSv.

21

Radiation

What is meant by the baseline of 1 mSv?

Q

According to the health screening survey of prefecture
residents conducted in late February 2012, 58% ofresidents were exposed to an amount of radiation estimated tobe less than 1 mSv per year. What is meant by 1 mSv, which isoften cited as a baseline, and what are the health implications
for this level?

A

The International Commission on Radiological Protection(ICRP) suggests the public’s maximum allowable amount ofyearly exposure to radiation to be under 1 mSv.
Following radiation accidents of this nature, the ICR P
recommends constraining, to the greatest extent possible, radiation
exposure to the low end of a yearly range, between 20 and 100
mSv. After the accident site returns to normal, that thresholdshould be gradually lowered to between 1 and 20 mSv.
The ICRP recommendation, and others like it, is based on thecalculation that exposure to more than 100 mSv per year would pose
an increased health risk in the form of cancer and other issues; theyencourage the avoidance of radiation exposure under normal
circumstances to be as little as possible, and under 100 mSv in theevent of a radiation accident. These figures are based on the idea of
curbing radiation exposure to the most rational extent possible within

22

Q& A

If one gene in a cell is damaged, it can be repaired in ashort time, and there is no residual effect.

the given circumstances. As for 1 mSv, what does it mean, exactly?
As is often discussed, when a human cell is exposed to 1 mSv ofradiation, one gene in the cellular material is damaged. However,that damage doses not have an immediate effect on health. Humancells have the inborn ability to repair damaged genetic material.
When a gene is damaged by 1 mSv, it repairs itself in a shorttime. This process of damage and repair occurs normally when weare exposed to UV rays and other sources ; the process is believed
to occur several tens of thousands of times a day in a given cell.

1 mSv radiation
Cell

23

Radiation

What is the difference between“man-made” radiation effects and“natural” radiation effects on health?

Q

I heard that there are two kinds of radiation. One is“man-made” radiation, such as that released during theaccident at Fukushima Daiichi Nuclear Power Plant, andanother is “natural” radiation. What is the difference between
the two, and what are their respective effects on the body?

A

Q& A

Both have the same effects on the body. What matters is
one’s amount of radiation exposure.

to radioactive cesium from foodstuffs. This value is similarly
computed based on what amount of radioactive cesium would havewhat impact on the body, and the maximum allowable threshold isderived. Specifically, the radioactive material found in eachfoodstuff is assessed, with a baseline of internal radiation exposure
to within 1 mSv a year.

There are two kinds of radioactive materials : those thatexist naturally, like potassium-40 and carbon-14, and manmade materials not found in nature, like iodine-131, cesium-137,
and cesium-134.
Radioactive material emits a range of small particle rays, likealpha, beta, gamma rays (with a wave formation), and X-rays. In
both man-made and natural radiation, the alpha, beta, gamma, andother rays emitted are the same. When a radioactive accident
occurs, the radioactive material that is dispersed is man-made, but
it does not exhibit any special properties.
Therefore, when considering the effects of radiation on thehuman body, the key is the amount of exposure. Incidentally, theterm “sieverts,” a measure of radiation quantity, specificallydescribes the extent of impact on the human body by radiation.
In Japan, the government has taken measures to implement
baseline values used to minimize the internal exposure in the body

24

25

Radiation

Does drinking water contain radiocesium?

Q

Since the accident at Fukushima Daiichi Nuclear Power
Plant, I’ve been worried about my everyday drinking
water. I am particularly concerned because radioactive cesium
has a long half-life. A year after the accident, does the wateraround us still contain cesium?

A

Like radioactive iodine, radioactive cesium was released
into the environment during the radiation accident.
However, while iodi ne was detected i n plu mbi ng water
immediately after the accident, radioactive cesium has been
scarcely detected thus far. This is because cesium is strongly
affected by filtration.
Standard waterworks in Japan filter stored water using a range ofmeans. The water is sterilized and then used as potable drinking
water. The majority of cesium is removed through this filtration
process, so it is seldom detected in plumbing water.
With wells, if a lid is kept on, radioactive cesium cannot enter,so it will not penetrate the water in the well. Some people worried
that radioactive cesium on the surface of the earth would seep into
the ground and thus into well water, but it is understood that
cesium adheres to the surface of the ground and does not sinkfurther. Therefore, it does not penetrate deeper into the earth, and

26

Q& A

Virtually no cesium has been detected in filtered water.

will seldom reach well water.
The prefecture has published the results of radiation density
measurements of wells and underground water reser voirs
throughout the prefecture on its official web site. As of this writing,no radioactive cesium has been detected in wells or undergroundreservoirs. You can check the status of well water in your region on
the web site.

27

Radiation

What is radioactive strontium?

Q

The level of radioactive cesium present in foodstuffs isused as a measure of their safety. I heard that, after theaccident at Fukushima Daiichi Nuclear Power Plant, there wasradioactive strontium among the radioactive material released.
What is strontium? Is it alright that there is no baseline levelset for it?

A

Unlike radioactive iodine and radioactive cesium, which
release gamma and beta rays, radioactive strontium only
releases beta rays, so it cannot be easily measured.
Strontium resembles calcium, and, as previously mentioned, it isprone to collecting in bone matter. For this reason, radioactive
strontium is used as a palliative aid for cancer patients sufferingfrom pain associated with multiple bone metastasis.
In September 2011, the Ministry of Education, Culture, Sports,
Science and Technology published the results of its measurementsof radioactive strontium in the environment. These found that thedensity of radioactive strontium found in the ground was,compared to radioactive cesium, 1/100th – a very low amount.
That data was then used to compute the future 50 year
accumulation of active strontium, and the amount was 0.12 mSv at
the highest. In other words, even in regions exposed to maximal

28

Q& A

When strontium enters the body, it collects in bone matter.
Its concentration in the environment is exceedingly low.

amounts of strontium, a 50 year accumulation would still yield anextremely low total of combined external and internal strontium
exposure.
For this reason, proper measures against radioactive cesium
should also function to cover radioactive strontium. By taking
measures such as paying attention to food safety data and avoiding
the long-term intake of foods with higher than average levels of
cesium, radioactive strontium exposure can be sufficiently curbed
as well.

tium
Stron trates
nconcee bone
in th

29

Radiation

Can children play outside?

Q

When spring comes and the weather warms, children
want to play outside. However, out of concern for
airborne radioactive material, I am keeping them indoors.
Since the accident at Fukushima Daiichi Nuclear Power Plant, I
have yet to let them outside. I am worried about the effects on
their health.

A

Levels of airborne radiation detected in the prefecture arebased on radiation released by radioactive cesium that has
now adhered to the ground, buildings, trees, and so on. Measuring
the actual radiation levels found in the air yields no amount, so it ishighly unlikely that allowing children to play outside during school
activities and the like will cause them to absorb radiation. Eventime spent outside for several hours produces extremely limited
levels of external radiation exposure.
For instance, the prefectural web site reported in April 2012 anairborne radiation reading of 0.78 μSv an hour in Fukushima City.
Daily outdoor activities of three hours, continued for one month,would yield a total 70 μSv of exposure – in other words, no morethan 0.07 mSv.
Even if one falls and sustains injury while exercising outdoors,radioactive material will not immediately enter the body through

30

Q& A

Appropriate exercise is extremely important. Wounds
should be thoroughly rinsed.

the wound. Simply rinse the wound thoroughly with water. Thereis a chance of radioactive material adhering to the hands, feet, andhair after playing outside, but this can be alleviated by thoroughly
washing and rinsing in the tub or shower.
Appropriate exercise is extremely important for children. A body
weakened by lack of exercise will impede a child’s growth anddevelopment, and the stress of being unable to play willaccumulate. While it is perfectly natural to worry about radiation
exposure, over-worrying can have the opposite effect of hinderingchildren’s wellbeing. It is important to allow your children to lead abalanced lifestyle.

31

Radiation

Does the length of time one is exposed
to radiation cause damage to one’s
genetic material?

Q

There are two kinds of radiation exposure: acuteradiation exposure, sustained all at once, and chronic
radiation exposure, which is sustained over time, such as thatsustained by residents of the prefectures affected by the Tepco
Fukushima Daiichi accident. What are the respective differencesof these, in terms of their impact on the human body?

A

Is the effect on the human body different in acute andchronic exposure, if the quantity of radiation exposure is thesame? Living on Earth, we are exposed to an average of 2.4 mSv
annually. This comes from radiation descending from outer spaceand from radioactive material in the ground, among other sources.
At the same time, there are some regions of the world exposed tohigher levels of radiation. One area of India, for instance, issubjected to higher levels of radiation that rise up from the seafloor.
A test was once conducted on those radiation levels by having
residents of Kerala, the region in question, wear badge-shaped
testers for accumulated radiation. The result showed these people
to be exposed to an average of 7 mSv per year. Those with thehighest intake had 14 mSv per year. In simple terms, 7 mSv per
year equates to over 100 mSv over a 15 year span. However, studies
thus far have found no abnormal incidence of cancer or proof of

32

Q& A

In acute exposure, cells are improperly repaired. Withchronic exposure, the body’s natural repair functions
prevent this.

shortened life span in the Kerala region. This fact suggests that the
impact of acute versus chronic radiation exposure differs.
When large quantities of radiation are absorbed through acuteexposure, damaged genetic material improperly repairs itself andmutates. However, it is believed that genetic material damaged byincremental exposure to radiation does not similarly mutate, as the
body is constantly in a process of ongoing repair and repairs cells
as they are damaged.

33

Radiation

What impact will radiation exposure haveon children who have yet to be born?

Q

I am worried about the effects of radiation exposure fromthe accident at Fukushima Daiichi Nuclear Power Plant
on children who have yet to be born. Will they be born with
illnesses? Were victims of Hiroshima and Nagasaki alright?

A

The children born to victims of Hiroshima and Nagasaki
were referred to as “second-generation” victims. The
question of whether radiation exposure can have a secondary effecton the next generation has been a major concern in regions
throughout the world, and long-term surveys have been conducted.
These surveys have not found any significant increase in cancers,or other ailments, in the children of radiation victims. Twenty-fiveyears after the events of Chernobyl, where victims were exposed tointernal radiation in the wake of a nuclear power plant accident, no
health issues have been found in the children born after those events.
Tests in animals have also found that, when bone marrow orinternal organ cells like the thyroid gland are exposed to radiation,no effects are passed on to the next generation. By contrast, if spermor oocytes are exposed to extremely high levels of radiation, theeffects are passed on, with effects such as chromosomal disorders.
There are currently several reasons postulated for why secondary
health effects have not been demonstrated. One reason is because,

34

Q& A

There is no radiation effect in “second-generation” victims.
The effects of radiation exposure do not pass on to later
generations.

unlike animal experiment, humans give birth very few times overthe course of their lives, so sperm or eggs from potentially
irradiated cells seldom go from fertilization to childbirth.
In addition, both internal and external radiation exposure levelsin the prefecture are much lower than those sustained in Hiroshima,
Nagasaki, and Chernobyl, so it is unlikely that there will be any
effects on the next generation.

35

Radiation

If a pregnant woman receives an X-ray,will the fetus be safe?

Q

I was experiencing nausea and loss of appetite, so I had
an X-ray at the hospital. I was found to be pregnant. At
the time of the X-ray, I was three months pregnant, and I
absorbed radiation from the test without realizing. Will myfetus be alright?

A

Q& A

There are no risks of damage from X-ray photography. Put
your mind at ease and enjoy a stress-free childbirth.

stress-free childbirth.
Note that if you are pregnant or may be pregnant, care must also
be paid to any medicines administered, not just to screenings using
radiation. When undergoing an examination, convey your concerns
to the doctor or nurse and discuss whether or not you should
undergo a particular screening or treatment.

The International Commission on Radiological Protection(ICRP) advises that radiation under 100 mGy (equivalent to
100 mSv) should not be taken as grounds for abortion.
Children born to mothers who sustained radiation in Hiroshima
and Nagasaki – in other words, those fetally exposed to extremely
high levels – manifested illnesses like microcephaly. However,microcephaly and other illnesses have not been observed in cases
under 100 mSv. The ICRP’s recommendation is based on this data.
This applies both to radiation exposure from an accident and thatsustained during regular health screenings.
In X-ray photography of the stomach, the actual amount ofradiation the child is exposed to is 200 μSv – in other words, about
0.2 mSv. This amount is far below 1 mSv.
At the very least, you have absolutely no need to worry about the
impact of the screening on your child. By contrast, the stress you
feel can have an impact on your child, so we advise relaxing for a

36

37

Radiation Exposure
and The Thyroid GlandRadiation

Q&A

Radiation

By what mechanisms does the thyroid
gland absorb radioactive iodine?

Q

I was told that radioactive iodine released during the
Tepco Fukushima Daiichi accident is absorbed by the
thyroid gland. In what way is it absorbed? Also, why are
Japanese people are more likely to absorb it?

A

Iodine forms part of the hormones secreted by the thyroid
gland. For this reason, iodine entering the body tends toaccumulate in that region.
Iodine is particularly found in marine products and seaweed.
The Japanese diet includes considerable daily amounts of seaweed
and kelp. Even those people who do not eat much raw kelp are
exposed, however, by other foods, such as soup stock made fromkelp. In this way, Japanese people consume, if not just adequate
amounts, then somewhat excessive amounts, of iodine.
Looked at globally, there are few regions that “overconsume”
iodine in this way. By contrast, there are many parts of the world
where an under-intake of iodine is found. In particular, landlocked
countries do not have sufficient iodine in the diet, and this isreferred to as iodine deficiency. In such regions, enlarged thyroid
glands and decreased thyroid function are seen. In recent years,
measures such as the addition of iodine to table salt have been
employed in order to remedy these issues.

40

Q& A

Japanese people are more likely to absorb radioactive
iodine than other people are because of an accumulation
due to hormone synthesis. The Japanese diet includes
many seaweeds, and often involves overintake of iodine.

Immediately following the March 2011 Fukushima Daiichi
Nuclear Power Plant accident, large quantities of iodine werereleased into the environment. Like ordinary iodine, radioactive
iodine tends to accumulate in the thyroid gland when it enters the
body and is one cause of internal radiation exposure. For thisreason, a provision threshold was set after the accident (now thebaseline level) calling for a decrease over-consumption of foods
contaminated with radioactive iodine and the attendant reductionof internal radiation exposure to the thyroid gland.

41

Radiation

What about screenings of children’s
thyroid glands?

Q

Following the accident at Fukushima Daiichi Nuclear
Power Plant, health screenings for prefecture residents
were being issued, with thyroid screenings for children among
them. When the thyroid is checked, what is checked, and inwhat way?

A

There are several ways of screening the thyroid gland. The
thyroid gland is an organ on the surface of the body, so if it
is enlarged, it can be checked directly by touching the neck.
In addition, the thyroid gland secretes hormones, so thehormones released, as well as those released by the pituitary gland(an organ in the cerebrum which releases thyroid-stimulating
hormones), which regulates the thyroid hormone secretions, can bemeasured to assess the condition of the gland.
For instance, in conditions like Grave’s disease, where thethyroid is aggravated, thyroid hormone production increases, while
thyroid-stimulating hormones decrease. By contrast, when thyroid
function decreases, thyroid hormones, in turn, decrease, andthyroid-stimulating hormones increase. Antibodies for theserespective conditions can be measured to make a determination onpresent thyroid function.
The ultrasonic screenings being used in the first round of

42

Q& A

The thyroid gland is felt directly and hormone levels aremeasured. Ultrasonic waves are used for more detailed
analysis.

screenings for prefectural residents are extremely effective.
Ultrasonic screenings allow not only for the assessment of the
shape, but also the size and, occasionally, the quantity of blood in
the thyroid to be observed in detail. In recent years, the quality ofultrasonic machinery has increased markedly, including its image
resolution capabilities, allowing for the depiction of detailed
structures in ways that were not previously possible.
In this way, there is a range of thyroid screenings that arevariously used or combined, depending on the ailment or condition.

43

Radiation

Some children were found with cysts on
their thyroids. What should we makeof this?

Q

Following the accident at Fukushima Daiichi Nuclear
accident and the prefectural health screenings of residents’
thyroids, some children with lumps or cysts in the thyroid have
not required further examinations. Is this really alright?

A

The majority of children who received ultrasonic screenings
and had lumps of 5 mm in diameter or lower, or cysts of 20
mm in diameter or lower, and were given an “A2” designation,
indicating that they had thyroid cysts.
In cysts of the thyroid, a cystic (fluid-containing) pouch develops
in the thyroid gland. This is sometimes present at birth andsometimes appears over the course of growth and then disappears.
Thyroid gland cysts are found in many people, including children,
during ultrasonic screenings.
In particular, today’s ultrasonic imaging technology has greater
fidelity, so extremely small cysts not previously visible can now befound, with many children having cysts.
Cysts containing no solid parts can be treated as benign, andthey seldom require fur ther treatment. Cysts with a hardcomponent are occasionally malignant, so those treated not as
cysts, but as nodules (lumps), and those with a diameter exceeding
5.1 mm require a designation of “B,” indicating the need for a

44

Q& A

Many people develop cysts on their thyroid; this is not
unusual. Cysts of under 20 mm in diameter do not require
further examination.

secondary screening. For this reason, children receiving an “A2”designation do not require further examination.
Until now, there have been no large-scale thyroid screenings ofchildren in Japan surveying the occurrence of various symptoms.
Ultrasonic screenings of children in Nagasaki and other regions
beyond the Fukushima Prefecture are now being carried out, withplans to compare that data against information obtained in the
Fukushima Prefecture.

Adam's apple

Thyroid

Trachea45

Radiation

Should I be worried about a small
nodule on my child’s thyroid gland?

Q

The hea lth scre en i ngs that the prefe c t ure andFukushima Medical University have launched use
ultrasonic technology to check children’s thyroid glands. I often
hear of cases where small nodules are detected, but it seems
people are told that these lumps have no effect on their health.
Is this really true?

A

Among those children who received ultrasonic thyroid
gland screenings as part of the prefectural health screenings
were some found to have with nodules under 5mm in diameter or
cysts under 20mm in diameter. These were given a class “A2”designation. The majority of A2 designations are for thyroid cysts(fluid-containing pouches). In some cases, a child is born with athyroid cyst, while in others they develop as part of the natural
growth process and then disappear. Thyroid nodules (lumps) andcysts are not unusual even in children, and most are benign.
For this reason, as with those designated “A1” for no nodules orcysts, there is no need for a secondary blood or urine sample. For
those cases where a cyst with a solid part is found, or for a node
exceeding 5.1 mm in diameter, a “B” designation is given,indicating the need for secondary screening.
Thyroid cancer develops comparatively very slowly, and is it

46

Q& A

This is not unusual, and in most cases the nodules are benign.
In some cases, these nodules go away as the child grows.

known for seldom reaching complications leading to death. Afterone year and three months since the accident at Fukushima Daiichi
Nuclear Power Plant, there is no estimated further impact fromradiation exposure. Going forward, the long-term observation ofsymptoms is now crucial.
Currently, the prefecture is administering the first round of
ultrasonic screenings of the thyroid. Once that phase completes, asecond round is planned. Ongoing checks to ensure that the
nodules and cysts have not changed since the last screening must
be carried out.

47

Radiation

What is thyroid cancer?

Q

I am worried about the possibility of thyroid cancerfrom the radioactive iodine released in the accident at
Fukushima Daiichi Nuclear Power Plant. I understand thatmany cases of thyroid cancer appeared after the Chernobyl
nuclear accident. Just what sort of a sickness is thyroid cancer?

A

As the name suggests, thyroid cancer is a cancer of the
thyroid gland. It is classified into several types, depending
on its shape under a microscope. The most common, in over 80%
of cases, is a type called papillary cancer.
It is known that papillary thyroid cancer develops more slowly
than all other cancers of the organs, and it does not show specificsymptoms. For this reason, even if a thyroid cancer papule just a
few mm in diameter appears, many people lead their lives without
noticing.
A past survey by autopsy of the rate of thyroid cancer in the
population found thyroid cancer in about 10 to 20% of people postdeath, with some variation by country. In other words, thyroid
cancer is comparatively common and, moreover, many people lead
their entire lives without noticing it.
Screenings for thyroid cancer involve using ultrasonic scans andextracting the cells believed to be cancerous and observing them

48

Q& A

Thyroid cancer shows a high incidence of appearance anddevelops slowly. Many people live with thyroid cancer
without knowing it.

under the microscope. In cases where a diagnosis of thyroid cancer
is given and t reat ment is required, su rger y is generally
administered to remove the cancerous area. Because the thyroid
gland is an organ that releases growth hormone, removing the
majority of it causes this hormone to stop being released. In suchcases, patients take thyroid gland hormone medication and regulate
their hormone level concentrations to a regular amount.

I didn’tknow that !

49

Radiation

Why did thyroid cancer appear in victims
several years after the Chernobyl
accident?

Q

I heard that the radioactive iodine released in the accident
at Fukushima Daiichi Nuclear Power Plant has a shorthalf-life of just a few days. In spite of that, I understand thatthyroid cancer occurred in victims of the Chernobyl accident
some few years to dozen years after the fact. Why is that?

A

One of the representative forms of radioactive iodine is
iodine-131. Iodine-131 has a comparatively short half-life ofeight days, but it releases radioactive beta and gamma rays duringthat time.
After the Chernobyl nuclear accident, children consumed food,in particular cow’s milk, contaminated with iodine-131 and otherradioactive iodine isotopes. This caused an excess intake ofradioactive iodine in the thyroid gland, with the radiation released
therefrom causing internal radiation exposure.
The half-life of radioactive iodine is, in fact, short, so it erodes
after a few months. However, genetic material is damaged by theradiation produced during that time. Most damaged material isrepaired by the body’s repair processes, but when large quantities
of genetic material are damaged by high radiation output at once, it
occasionally produces genetic material that is improperly repaired.
These mutations pose the risk of becoming cancer in later years, or

50

Q& A

Cells damaged from radiation are not able to repair
themselves properly, which leads to higher risks.

even dozens of years, after the fact.
This process is what caused radioactive iodine, with its shorthalf-life, to cause internal radiation in victims of the Chernobyl
accident and caused an increase in thyroid cancer. Based on this,following the March 2011 Fukushima Daiichi Nuclear Power Plant
accident, a provisional threshold was set immediately after theincident, intended to curb the excess consumption of foodstuffs
contaminated with, in particular, radioactive iodine and theattendant risk of internalradiation. Currently, an evenstricter threshold is in place.

51

Radiation

Why are radiation levels at monitoring
posts and for individuals different?

Q

If you simply add up the ambient radiation levels
measured at monitoring posts, they are much higher
than the measured individual radiation doses. Why do suchdifferences occur?

A

Many municipalities in the Fukushima Prefecture aremeasuring radiation levels based on personal dosimetersand publicizing those results.
For example, in Fukushima City, personal dosimeters were
distributed to all children junior high school age and younger for
three months, from November 2012 to January 2013, to measure
their personal radiation exposure. The results showed that most ofthese children had an exposure of 0.5 mSv or less for these threemonths. However, simply adding the ambient radiation levels
published for the city would yield a higher value.
The gamma rays, for example, that are emitted from radioactive
cesium are blocked by concrete and lead. Therefore, being indoors
considerably reduces radiation exposure. For instance, being insidea wooden home reduces exposure by about half, and being inside a
steel-frame house reduces exposure by about 90%, so exposure is
reduced by that much during the time the person is indoors.
Furthermore, while outdoors, it is not often the case that people

52

Q& A

Individual radiation doses vary by residence and behavior they also do not match ambient radiation levels.

remain in one place for a long time. So, the values measured atmonitoring posts do not necessarily match individuals’ exposure.
Currently, the Fukushima Prefecture and its municipalities are
publishing the results of measurements by personal dosimeters on
their web pages. We recommend that you combine personal
exposure measurements taken from your own dosimeter with datafrom monitoring posts to reference in your daily life in the future.

53

Radiation

Is radiocesium the only radioactive
element detected by whole-bodycounters (WBCs)?

Q

In Fukushima, internal exposure tests are being
conducted using whole-body counters (WBC). Are theradioactive substances detected with the WBCs restricted toradiocesium? Do they not detect other radioactive substances?

A

By detecting the gamma radiation that is emitted from theradioactive substances in your body, a WBC can evaluate
the quantity of radioactive material in your body and the internal
exposure it causes.
Currently, in the WBC studies conducted in Fukushima, thenaturally occurring radioactive material potassium-40 is detected,
as is the artificially produced radioactive cesium, which is aradioactive material produced by the nuclear accident.
The artificially produced radioactive material emitted during the
Tepco Fukushima Daiichi Nuclear Power Plant accident four years
ago was radioactive iodine, which has a half-life of eight days, andradioactive cesium, which has a relatively long half-life.
These emissions included approximately the same amount of
cesium-134 and cesium-137. Therefore, in the inspections
conducted in the early days following the accident, there weremany cases where equal amounts of cesium-134 and cesium-137
were detected. However, most people are currently not detecting

54

Q& A

WBC can always detect potassium, but cesium is detectedwith less frequency.

any cesium-134, which has a half-life of two years. Many people
are detecting only cesium-137.
As the frequency with which cesium-137 is detected is extremely
low, the internal exposure caused by it is far below 1 mSv. In
addition, the WBCs in Fukushima are not detecting any artificial
radioactive substances other than radioactive cesium.
On the other hand, potassium-40 accounts for about 0.01% of thepotassium that exists in the body. There are between 3,000 and 6,000
Bq in an adult’s body, so it would show up on anyone’s WBC scan.

Onlyradiocesium ?

55

Radiation

What is the effect of low-dose exposure
to radiation through CT scans?

Q

My child was complaining of headaches, so we went to
the hospital for a CT scan of his head. I am worried
about the scan’s effect on his health, considering the low dose ofradiation he already received following the Tepco Fukushima
Daiichi accident.

A

A CT scan uses X-rays to take cross-section images of the
body and can be used to visualize medical abnormalities
that cannot be seen in detail on normal X-rays. CT scans are usedwidely in the medical field. CT scans have proliferated more widelyin Japan than in any other country, with a rate of about 90 CT
scans per million people, which is overwhelmingly higher than CT
scan rates in the US or UK.
The amount of radiation delivered during a scan depends upon
the body part in question, but for a CT scan of the head, there is anaverage radiation exposure of 3 - 4 mSv, or 3,000 - 4,000 μSv.
Exposure to radiation through medical treatment is referred to as“medical exposure.” Research to date has not scientifically shown
any adverse health effects from one time exposure at these levels.
The International Commission on Radiological Protection(ICRP), which sets international radiological protection standards,
has said that ''it would not be appropriate to set upper limits for

56

Q& A

If you are concerned about the purpose or effects of CT
scans, consult your nurse or doctor.

radiation due to medical exposure.'' This is because the use ofradiation in medical treatment benefits the patient, and it isassumed that these benefits outweigh the disadvantages of any
medical exposure.
On the other hand, physicians who conduct radiologicaltreatments and tests must, of course, take into account whether thetest or treatment is truly beneficial for the person undergoing it. In
the future, when your child receives radiological treatment or
exams, you may want to
ask the doctor or nurse
the purpose, effect, andamount of exposure, if
you are concerned.

57

Radiation

What are the health effects of radiationon the human body?

Q

The health effects of radiation are divided into two
categories: “deterministic effects” and “stochastic
effects.” What are the characteristics of these effects?

A

Health effects from radiation exposure can present as either
deterministic effects or stochastic effects. Deterministic
effects are those that occur after you exceed a certain dosage ofradiation (called a “threshold”). Most acute symptoms are
deterministic effects. For example, men show a transient decreasein sperm count after exposure to more than 250 mSv at once, andthere is a reduction in bone marrow after exposure to more than
500 mSv. This is known to cause a reduction in blood cells, such as
white blood cells, red blood cells, and platelets. However, these
symptoms do not occur after exposure below these thresholds.
On the other hand, stochastic effects do not have a threshold, but
the probability of them occurring increases with greater exposure.
Stochastic effects include cancers and leukemia that are caused byradiation exposure. It is often said that, based on surveys of nuclear
bomb survivors, exposure to 200 mSv increases the likelihood ofdying from cancer by 1%. With exposures above that amount, thelikelihood of cancer increases along with the increased exposure.
On the other hand, with exposures of less than 100 mSv, the risk of

58

Q& A

The difference between a “deterministic” and “stochastic”
effect is the presence or absence of a threshold.

cancer is so low that no increase in its incidence has been proven.
In addition, stochastic effects on the genes of plants and insects
have been found, but there have not yet been any reports of genetic
effects of radiation exposure in humans.

Deterministic effects
Threshold

Radiation
doses

Radiation
doses

Stochastic effects

59

Radiation

Are the effects of radiation exposure
on a fetus by mother’s exposure?

Q

Are there any cases of increased illnesses among people
who survived nuclear explosions while exposed as
fetuses? I am concerned that there will be children born inFukushima with disabilities, due to the effects of the Tepco
Fukushima Daiichi accident.

A

Nuclear bomb survivors who were exposed while inside theuterus are referred to as “in-utero survivors.” Studies
following their exposure have confirmed that in-utero survivors
showed an increase in a disease called microcephaly. Children withmicrocephaly have a significantly smaller head circumference,compared to children of the same age, which causes delays inmental development and growth.
In surveys of in-utero survivors of the Hiroshima and Nagasaki
nuclear explosions, it was confirmed that fetuses exposed to over
300 mGy between 8 and 15 weeks of pregnancy, or between 500
and 700 mGy from the 16th week of pregnancy on (weeks 16-40)
showed severe mental retardation. Furthermore, in-utero exposure
to 1,000 mGy or more has been shown to result in a 3-4% increasein developmental disorders by age 18.
On the other hand, no increase in microcephaly has been shownin in-utero survivors whose exposure was below these levels. Based

60

Q& A

Birth defects can result after high-dose exposure from
nuclear explosions, but they are unlikely to occur due tothe Fukushima nuclear power plant accident.

on these facts, the International Commission on RadiologicalProtection (ICRP) has recommended that “in-utero exposure to lessthan 100 mGy should not be considered grounds for abortion.”
Between the Fukushima nuclear accident and now, there havenot been any fetuses that might have been exposed to over 100
mGy. For this reason, it isunlikely that there will be
an increase in microcephaly
in Fukushima, as there wasamong in-utero survivorsof the nuclear explosions of
the 1940s. You do not need
to worry about pregnancy
and giving birth.

61

Radiation

Can exposure to radiation cause
nosebleeds?

Q

I recently came across a comic that had a scene where
the main characters, all of whom had visited the Tepco
Fukushima Daiichi Nuclear Power Plant, experienced
unexplained nosebleeds. Could exposure to radiation in
Fukushima cause nosebleeds?

A

Exposure to an extremely high amount of radiation at once
can result in some symptoms, either immediately after
exposure or several days or weeks later. This is called “acuteradiation syndrome” and results from radiation exposure. On theother hand, cancer caused by radiation exposure does not occur
until several years or even decades later. These are referred to as“delayed effects” or “aftereffects.”
For example, exposure to more than 500 mGy of radiation at
once can result in damage to the bone marrow, which makes blood
cells, and reductions in the number of white blood cells, red blood
cells, and platelets, so victims are more susceptible to infections
and anemia and have blood-clotting problems. Exposure to morethan 1,000 mGy (1 Gy*) at once can cause systemic symptoms,
such as nausea and general malaise. These symptoms of acuteradiation sickness are called “deterministic effects” and appear
when exposure exceeds a certain level (threshold), but do not

62

Q& A

Nosebleeds are possible after exceeding a certain level ofradiation, but not possible in the case of Fukushima.

appear for quantities of radiation below that threshold.
Between the nuclear accident and now, there have not been any
cases of general Fukushima residents exposed to enough radiation
to result in acute radiation sickness. Nosebleeds are known to havea variety of causes, but it is notconceivable that nosebleeds inFukushima would be caused byradiation exposure.

* Gy (Gray)
An absorbed dose of radiation. For the radiation emitted by iodine-131 andcesium-137 (beta rays and gamma rays), 1 Gy is equal to 1 Sv.

63

Radiation

How different are exposure levels in
Chernobyl compared to Fukushima?

Q

I heard that about 1/6 th the amount of radioactive
material was emitted by the Tepco Fukushima Daiichi
accident, compared to that emitted by the Chernobyl nuclear
accident. About how much radiation were local residents
actually exposed to?

A

A basic survey of the health of Fukushima residents
estimated their external exposure to radiation based on aquestionnaire. More than 532,000 responses were received as ofMarch 31, 2015. The results estimated that there was an averageexternal exposure of about 0.8 mSv.
After the Chernobyl nuclear accident, Ukrainian evacuees had
an average exposure of 20 mSv, and Belorussian evacuees had an
average exposure of 30 mSv, so, in terms of external exposure,
Fukushima residents’ exposure was about 1/10th that of Chernobyl’s
area residents.
Internal exposure, and in particular thyroid exposure toradioactive iodine soon after the nuclear reaction, was found to be
between 200 and 500 mSv, and averaged about 300 mSv, among amajority of Ukrainian and Belorussian evacuees. On the other
hand, in a survey of the radiation exposure of 1,000 people in themunicipalities of Iwaki, Kawamata, and Iitate, the highest per-

64

Q& A

Local residents were exposed to less than 1/10th theexternal exposure of those exposed in Chernobyl, and they
have even less internal exposure to iodine.

person exposure was 43 mSv, and nearly 90% of the children tested
had exposure rates of less than 20 mSv. Therefore, the internal
exposure to radioactive iodine in Fukushima was far less than
1/10th of the exposure at Chernobyl.
The differences between the inter nal exposure rates in
Chernobyl and Fukushima were due to measures taken in
Fukushima to reduce internal exposure, such as establishingtemporary standards directly after the accident. We are currently
taking ongoing measures to ensure food safety.

less than
20 mSv

300 mSv

Chernobyl

Fukushima

65

Radiation

Were there acute radiation exposure
symptoms in Chernobyl?

Q

After the 1986 Chernobyl nuclear accident, did workers
who were involved in the emergency recovery work at thepower plant show symptoms of acute radiation syndrome or die?

A

Immediately after the Chernobyl nuclear accident, many
firefighters and military personnel went into the plant forrecovery work. Especially at the time of the accident, efforts toprotect workers from the high levels of radiation were insufficient,and many workers were exposed to extremely high levels ofradiation. As a result, 134 people developed acute radiation
syndrome, and 28 of them died within three weeks.
Comparisons of mortality and radiation exposure showed that, ofthe more than 90 people who were exposed to 4,000 mSv or less,only one died. By contrast, of the 22 people who were exposed to
between 4,000 and 6,000 mSv, seven died from severe infections
or skin and intestinal disorders. In addition, among the 21 people
exposed to 6,000 mSv or more, 20 died of similar conditions. As
these numbers demonstrate, mortality from acute radiation
exposure depends upon the amount of exposure.
On the other hand, there were no evacuees from the area aroundthe Chernobyl plant who showed symptoms of acute radiation
syndrome. This was due to the fact that external exposure among

66

Q& A

Many of the Chernobyl recovery workers showed
symptoms of acute radiation syndrome, but these were notseen in residents of the surrounding area.

evacuees in the region averaged 20 - 30 mSv, which was much lessthan the workers inside the power plant.
The general population in Chernobyl did not exhibit signs ofacute radiation syndrome. However, since they ate and drank
agricultural products, and especially dairy products with highconcentrations of radioactive iodine soon after the accident, there
were increased cases of pediatric thyroid cancer several years later,
due to internal exposure in the thyroid.

Numberof death

Chernobyl

mSv

67

Radiation

What was the incidence rate of thyroid
cancer in Chernobyl?

Q

I heard that there was an increase in children developing
thyroid cancer due to the effects of the 1986 Chernobyl
nuclear accident. Specifically what age children saw thisincreased rate of thyroid cancer?

A

The Cher nobyl nuclear accident caused radioactive
materials, especially radioactive iodine and radioactive
cesium, to be spread over large swaths of land in what is now
Belarus, Russia, and Ukraine.
At the time of the accident, no measures were taken to prevent
people from eating vegetables and drinking milk contaminatedwith radioactive iodine, so exposure spread among residents who
consumed them. It is believed that internal thyroid exposure amongevacuees averaged 200 - 300 mSv.
For five years, beginning in 1990, which was five years after theaccident, thyroid screenings were conducted for the approximately
120,000 children who were 10 and younger at the time of theaccident in the three countries surrounding Chernobyl. This wasdone with the participation of experts from Nagasaki andHiroshima Universities. The results showed an increase in theincidence rate of thyroid cancers among those who were three
years old or younger at the time of the accident. It was also shown

68

Q& A

Thyroid problems increased in incidence among children
ages three and younger at the time of the accident; there wasa proven causative relationship with their radiation exposure.

that the incidence of pediatric thyroid cancer was especially high in
the Gomel province of Belarus, which had the most serious
radioactive contamination from the accident.
In general, it is believed that, even among children, the incidenceof thyroid cancer increased with age. However, since thyroid cancer
in Chernobyl was found to be concentrated among the generationthat was three years old or younger at the time of the accident –those who were most sensitive to radiation, which was high in theGomel province, where contamination was most severe – it wasscientifically proven that there was a causal link between thepediatric thyroid cancers
seen in this region andradiation exposure fromthe accident.

69

Radiation

Were there increases in non-thyroidal
cancers around Chernobyl?

Q

It is known that the incidence of thyroid cancer amongresidents near Chernobyl increased due to the healtheffects of exposure to radiation caused by the nuclear power plant
accident. Were there increases in other types of cancer as well?

A

As a result of the Chernobyl nuclear plant accident, there
was a high incidence of thyroid cancer among residents inthe area, and, in particular, pediatric thyroid cancer. This is thought
to be because of inter nal exposure to radioactive iodine
immediately following the accident; the thyroid, which accumulates
iodine easily, was exposed to high levels of radioactivity.
In 2011, the United Nations Scientific Committee of the Effectsof Atomic Radiation (UNSCEAR), marking 25 years since theaccident, put together a report on the health effects of the incident.
It points out that “6,000 people, a substantial number, who werechildren at the time of the accident and drank unrestricted
quantities of contaminated milk developed thyroid cancer.”
On the other hand, the report clearly states, “There is no scientificevidence of health effects occurring due to exposure among thegeneral population other than thyroid cancer.” In other words, there
is no scientific evidence of an increase in cancers, other than thyroid
cancer, among the residents who lived near Chernobyl.

70

Q& A

There has been no scientifically proven link to heightenedlevels of cancer in the Chernobyl area, but ongoingassessments are necessary.

There is scientific evidence that the survivors of the nuclear
explosions in Hiroshima and Nagasaki had increased rates ofleukemia and various solid cancers. While exposure from theHiroshima and Nagasaki nuclear explosions was mostly external,
exposure at Chernobyl was mostly internal and due to radioactive
iodine. It is believed that these differences in type of exposure
resulted in different effects on cancer incidence. However, it willremain necessary to conduct ongoing evaluations of the healtheffects on residents in Chernobyl, especially for those who werechildren at the time of the accident.

71

Radiation

What have been the genetic effects of
exposure following the Chernobyl
accident?

Q

I heard that there were no genetic effects on the nuclear
explosion survivors in Hiroshima and Nagasaki. Were
there any genetic effects due to internal exposure after the
Chernobyl accident?

A

After Hiroshima and Nagasaki were hit by nuclear bombs,
there were no genetic effects found among the children ofsurvivors (the so-called “second generation survivors”). In addition,
there is ongoing research tracking the incidence of cancer death
rates among the children of survivors, as well as the incidence oflifestyle-related diseases. To date, there has been no evidence foundof increased rates of diseases among second generation survivors.
Similarly, there have been no genetic effects found in thechildren of survivors born after the Chernobyl accident. In
addition, there has been no scientific evidence found of genetic
effects on humans in studies performed on subjects other than the
nuclear bomb and Chernobyl survivors.
Even in animal experiments where the subjects' bone marrow,thyroids, and organ cells (somatic cells) were exposed to radiation,
the effects of radiation exposure were not passed on to the next
generation. On the other hand, it is known that, if sperm or egg
cells are exposed to high levels of radiation, some effects, such as

72

Q& A

There are no scientifically proven genetic effects of nuclear
accidents, so this is unlikely to occur in Fukushima.

chromosome disorders, can be passed on to the next generation.
There are a few possible reasons why genetic effects have notbeen seen after human exposure to radiation. Unlike most animals,
humans have an extremely low lifelong birth rate, so it is believedthat very few exposed sperm and egg cells fertilize and develop tobirth. Moreover, the exposure levels inFukushima were much lower than thoseat either Hiroshima and Nagasaki or
Chernobyl, so it is unlikely that there
will be any lingering genetic effects.

73Radiation

Does the thyroid gland have weakresistance to radiation?

Q

Since the Tepco Fukushima Daiichi Nuclear Power Plant
accident, there has been attention drawn to thyroid
issues. Is the thyroid gland “weak” against radiation?

A

It is known that, as a rule, the health effects of radiation
exposure are more likely to develop in structures or parts ofthe body engaged in active cell division. For example, the bonemarrow creates red and white blood cells and platelets, so it
engages in frequent cell division. For this reason, when the bonemarrow is exposed to high levels of radiation, there is an increased
risk of acute symptoms such as reduced blood cell count andleukemia, a disease of the bone marrow.
The thyroid gland is involved in the production of thyroid
hormone, so it does not engage in as active cell division as the bonemarrow. Nevertheless, the reason there was an increased incidenceof thyroid cancer among children after the Chernobyl nuclear
accident was because of the radioactive iodine released, whichaccumulated in their thyroid glands.
Thyroid hormones produced by the thyroid gland contain iodine,
which is found in ample quantities in seaweed and seafood.
Therefore, even under normal circumstances, iodine tends toaccumulate in the thyroid. The radioactive iodine released in

74

Q& A

Iodine tends to accumulate, so the Fukushima Prefecture
has set a provisional threshold on radiation exposure.

Chernobyl was collected, in terms of the food chain, in highconcentrations in dairy milk. When children drank this milk,radioactive iodine collected in their thyroid glands and exposed
them to high levels of internal radiation. It is believed that this is
the reason why the incidence of thyroid cancer was high five years
after the Chernobyl accident.
With the above in mind, the Fukushima Prefecture set a
provisional exposure threshold immediately after the accident andtook measures to curb internalr a d i a t io n e x p o s u r e f r o mradioactive iodine in residents’
thyroid glands.

75

Radiation

What types of thyroid cancer are there,
and what are their characteristics?

Q

Thyroid cancer was widespread after the Chernobyl
accident, so there were concerns of a similar problem
developing in the Fukushima Prefecture following the events of
the Tepco Fukushima Daiichi accident. What types of thyroid
cancer are there, and what are their characteristics?

Q& A

There are four types of thyroid cancer, all of which develop
quite slowly when compared to other cancers.

A past study by autopsy found that, while there is some variationby country, papillary cancer was present in 10-20% of all people
af ter death. I n other words, papillar y thy roid cancer iscomparatively common and, in most cases, people lead full lives
without noticing it.

A

Thyroid cancer is divided into four types, based on its
appearance under a microscope; these are papillary cancer,
follicular cancer, medullary cancer, and undifferentiated cancer.
Of these cancer types, nearly 80% of cases are papillary cancer.
As the Latin root suggests, under a microscope, the cells can beseen propagating in a papule (nipple) shape. It is most commonly
found among women in their 30s. Beyond feeling a lump on thethroat, there are no particularly defining symptoms, but phenomena
such as a hoarse voice, throat pain, and trouble swallowing canoccur. With advancements in ultrasonic testing, papillary cancer issometimes found during regular health screenings, before theperson even notices any symptoms.
Compared to all other types of cancer, including that of otherorgans, papillary thyroid cancer progresses slowly, so, in manycases, people live with extremely small papules a few mm in size
without realizing it or being affected by them.

76

77

Food Safety and Radiation

Radiation

Q&A

Radiation

I’m worried that the milk my children
receive in their school lunches contains
radiation.

Q

Since the Tepco Fukushima Daiichi accident, I’ve been
worried about my child’s school lunches, because of theradiation problem. I’m particularly worried about the milk.
Should I be concerned?

A

Following the March 2011 accident, levels of radioactive
iodine exceeding the provisional threshold were found in
fresh dairy milk. Today, it is known that radioactive iodine is prone
to concentrating in dairy milk, and that this led to widespread
thyroid cancers after the Chernobyl nuclear accident in 1986.
Following that incident, radioactive material released from thepower plant, in particular radioactive iodine, entered the watersupply and then the pastures on which cattle grazed, thereby
becoming concentrated in their milk. Children, in particular, went
on to consume this tainted milk. The radioactive iodine thenentered their bodies and accumulated in their thyroid glands,causing high levels of internal radiation exposure. It is believed that
this process contributed to the higher incidence of thyroid cancer inthe years thereafter. However, radioactive iodine has a short halflife; at present, it has not been detected in any fresh milk or otherfood products in the Fukushima region.
Radioactive cesium, on the other hand, is known to concentrate

80

Q& A

Regular tests are performed in Fukushima, and noradiation has been detected since January 2014.

in wild mushrooms and boar, but it does not concentrate in dairy
milk. Thus far, there have been no reports of dairy milk in the
Fukushima Prefecture with levels of radioactive cesium exceeding
the threshold. In addition, the prefecture periodically tests the entire
single serving of school lunches and reports the ongoing levels ofradioactive material detected. As of January 2014, 212 meals had
been tested, and no radioactive cesium was found in any sample.
School lunches are important, both for their contribution tochildren’s healthy growth and for giving children a proper
understanding of the role of foodin everyday life. There is no needfor concern at present. We suggest
continuing to monitor the resultsof survey data going forward.

81

Radiation

Why was radiation detected in wild
animals?

Q

I have heard that, since the Tepco Fukushima Daiichi
accident, radioactive material has been detected in themeat of wild animals, like boar. Although such levels are no longer
being detected in livestock, why do they persist in wild animals?

A

Tests by the prefecture have detected high levels ofradioactive cesium in wild animals, and in wild boars, inparticular.
Boars are omnivorous, and they are known to consume food likeacorns and worms directly from the ground, with the soil mixed in.
It is believed that radioactive cesium tends to concentrate in worms
relatively easily, and it is additionally believed that, because theboars eat soil from the surface of the ground, on which radioactive
cesium is adhered, they are more prone to having cesium collect intheir bodies.
There are currently inspection measures in place for livestock
products like dairy and meat sold on the market. Products withlevels of radioactive cesium that exceed the threshold are unlikely
to enter the consumer supply. However, radioactive cesium thatexceeds the threshold is being detected in not only wild boar, but inwild animals such as bear and pheasant, so the simple domesticationof these animals for home consumption should be avoided.

82

Q& A

Animals consume material from the ground, so radiation
accumulates in their meat. Avoid domesticating theseanimals for home consumption.

In recent years, most municipal governments have beenmeasuring radiation levels. If you are concerned about the meat of
the wild animals you have hunted, or of meat you have received
from a hunter, we suggest having it tested.
Even if you were to eat the meat of a wild animal with radioactive
cesium levels exceeding the threshold, the level of internal radiation
you would be exposed to would be limited. If you have since ceased
continuing to eat those products, the amount of internal radiation
you would be exposed to should be sufficiently curbed.

83

Radiation

Are there any health effects related toeating wild mushrooms?

Q

Radioactive cesium is frequently detected in wildmushrooms. Are there any negative health effects fromeating them just a few times? What about mushrooms sold on
the market?

A

It is known from the Chernobyl accident that radioactive
cesium is prone to collecting in mushrooms. Nagasaki
University installed a satellite office in Kawauchi in 2013 andcollected and dried mushrooms from the area, and then measured
the levels of radioactive material found in them.
The results indicated that nearly 90% of the 150 dried
mushrooms measured contained more than the 100 Bq/kg ofradioactive cesium stipulated as the threshold in the Food
Sanitation Act.
What inter nal radiation would one be exposed to fromconsuming mushrooms over this limit? As an example, eating 100
g of mushrooms containing 200 Bq/kg of radioactive cesium would
expose a person to 0.26 μSv of radiation. If one were to continue
eating these mushrooms every day for a year, the amount would be
100 μSv, or 0.1 mSv.
This may seem like a surprisingly small amount, but that is
because the current threshold is set very low, so as to ensure that

84

Q& A

There are minimal negative health effects that could occur
from eating wild mushrooms a few times, and there are noissues with mushrooms sold on the market.

annual exposure does not exceed 1 mSv. While levels of radioactive
cesium must continue to be monitored, if one were to eat
mushrooms a few times that exceeded the threshold, there would
be no impact on one’s health.
In addition, the majority of mushrooms on the market are
cultivated in greenhouses, undergo testing for radioactive content,
and are guaranteed to be below the threshold, so there is no threat
to one’s health from eating cultivated mushrooms.

85

Radiation

Can radiocesium enter well water?

Q

It has now been nearly four years since the Tepco
Fukushima Daiichi Nuclear Power Plant accident. I use
well water at home, so I am worried about radioactive cesium
entering the water over time. Should I be concerned?

A

The prefecture publicizes data on its web site on the amountof radioactive cesium detected in wells in each region. No
radioactive cesium has been detected in well water. This is largely
due to the fact that cesium is easily filtered.
After the nuclear reactor incident, radioactive cesium drifted
through the air and reached the ground. Today, the majority ofwells in the country are covered with lids, which block exposure,so the cesium cannot enter them. In addition, radioactive cesium
adheres to the ground, but does not absorb into the soil, so it will
seldom, if ever, penetrate deeper over time or into well water.
In 2013, Nagasaki University collected soil samples from sites
12-15 km away from the Chernobyl nuclear power plant andmeasured them for the presence of radioactive cesium. The levelsof radioactive cesium contained in the soil from 5-10 cm below theground were between 1/7 and 1/10 of the levels in the soil from 0-5
cm below the ground. In other words, even in Chernobyl, where
over a quarter of a century had elapsed since the incident occurred,

86

Q& A

Radiation does not penetrate deep into the ground, so
there are no concerns about its effect on well water, evenover time.

the majority of cesium has remained on the soil’s surface and not
penetrated further.
However, climatological conditions, such as heavy rains andlandslides, can cause radioactive cesium to shift, changing thelevels of concentration in the topsoil. Detailed monitoring and datacollection will be required going forward.

87

Radiation

What is the level of concentration ofradioactive strontium and plutonium
in tap water?

Q

I often hear that tests of tap water do not find any
radioactive cesium, but I’m worried about radioactive
strontium and plutonium. Can I continue drinking this water?

A

Compared to radioactive cesium, which releases gamma andbeta rays, radioactive strontium and plutonium release beta
and alpha rays, respectively. For this reason, they are comparatively
harder to detect than radioactive cesium.
In 2013, water samples were collected from 20 tap water source
sites, two water supplies, and seven underground water supplies
across 29 regions in the Fukushima Prefecture, and the water wastested for radioactive strontium and plutonium.
The results found 26 sites with radioactive strontium-90, but thehighest concentration in water sources was 0.0028 Bq/L, and allsites posted numbers within the allowable thresholds in place frombefore the March 2011 accident. In addition, the amount of
plutonium in all samples was below the detectable limit.
If, for instance, a toddler consumed 1 L of water withstrontium-90 at the highest concentration found in the samples, andcontinued doing so daily for a year, the level of internal radiation
exposure would be no more than 0.075 μSv.
Excess consumption of and exposure to radioactive strontium

88

Q& A

No plutonium has been detected in the Fukushima area,and strontium is within safe levels.

and plutonium can lead to internal radiation exposure, but theabove test demonstrates that, like foodstuffs, water contains
acceptable levels of radioactive cesium, strontium, and plutonium
and is safe to drink. If adequate measures against radioactive
cesium are taken, their effects would apply to radioactive strontium
and plutonium as well.

89

Radiation

What about tests of strontium andplutonium in food?

Q

Levels of radioactive cesium in food from inspections
conducted by the Fukushima Prefecture are listed in thenewspaper. However, there is no data listed on radioactive
strontium and plutonium. Are these compounds being tested for?

A

Q& A

Twelve sites nationwide were measured for food safety in2013, and the government has ensured the safety of all
food on the market.

can lead to internal radiation exposure, but the above tests indicatethat foodstuffs on the market contain safe levels of radioactive
cesium, strontium, and plutonium. If adequate measures against
radioactive cesium are taken, their effects also apply to radioactive
strontium and plutonium.

While radioactive cesium releases gamma and beta rays,
radioactive strontium and plutonium release beta and alpharays alone, respectively, so they are more difficult to detect thancesium.
In 2013, the Ministry of Health, Labor and Welfare measured thelevels of radioactive strontium and plutonium in foodstuffs anddrinking water sold in 12 regions across the country, including theHamadori, Nakadori, and Aizu regions in the Fukushima Prefecture.
The results found radioactive strontium in seven out of 20 samples,but they were at levels that predated the March 2011 accident, andplutonium was below the detectable threshold in all samples.
In addition, in tests measuring the exact types of meals
consumed by people and using real food products, the level ofradioactive strontium was within the allowable threshold frombefore the accident, and plutonium was below the detectable
threshold in all samples.
The excess consumption of radioactive strontium and plutonium

90

91About Fukushima
Health Management Survey

Radiation

Q&A

Radiation

Why are basic health screenings ofprefecture residents required?

Q

The health screenings of prefecture residents following
the Tepco Fukushima Daiichi accident involve questions
about personal habits four months after the accident. I don’t
remember my actions in detail, so I’m concerned. What arethese questions for?

A

Part of the health screening includes a basic survey. This
component surveys the activities of each resident in theprefecture in the four months after the March 11, 2011 accident.
The objective is to estimate the levels of external radiation
exposure over that four month span.
External radiation levels vary based on the air dose rate at eachlocation, and the degree of shielding of the radiation. Measuring
the degree of external exposure of an individual, therefore, requires
knowing where that person was and for how long he or she wasindoors and outdoors.
So far, 27% of residents have responded. An analysis of their
responses, excluding those directly involved as nuclear workers,
found that external radiation exposure was under 1 mSv for 62% ofresidents and under 2 mSv for 94% residents. Further, 99.8% ofresidents had radiation exposure under 5 mSv.
If you undergo a computerized tomography (CT) scan at a

94

Q& A

Those sections of the screening test are used toestimate levels of external radiation exposure.
Simplified questionnaires are being distributed to
non-respondents.

hospital, you will sustain between 5 and 10 mSv of externalradiation. Compared to this, the levels of external radiation
sustained by prefectural residents are limited, so one could say that
potential risks from that exposure are unlikely.
Currently, in order to improve the response rate on these basic
surveys, the prefecture is distributing a questionnaire with simple
questions on it to residents who have yet to respond. We suggest
taking this opportunity to look over the simplified version andsubmit your response.

Simpleedition95

Radiation

How was the testing of radiation levels
performed in Nagasaki and Hiroshima?

Q

I heard that the Fukushima Prefecture is undertaking
basic health screenings to determine residents’ levels of
external radiation. How did Nagasaki and Hiroshima measure
for radiation after the detonation of the atom bombs?

Q& A

Radiation levels were measured based on proximity toground zero and the person’s location.

Taking these figures and comparing them against symptoms
seen in victims allowed for establishing causal relationships andconducting long-term health screenings of radiation exposure.

A

The basic sur vey, as par t of the prefect ural healthscreenings, measures the level of external radiation in thefour months after the accident based on questionnaire responses.
Based on an analysis of the current responses from about 450,000
people, the average level of external radiation is 0.8 mSv, with
99.8% of residents under 6 mSv.
By contrast, atomic bomb victims were exposed not only to
gamma rays, but also to neutron radiation. In that case, the major
factor in their radiation exposure came from the instant of the
explosion. Estimating the amount of survivors’ exposure required
determining in detail what distance victims were from ground zeroand where they were at that time (outdoors, indoors).
This data allowed scientists to estimate the degree of radiation
exposure by person and by organ of the body. Those estimatesfound that, in Nagasaki, those outside near ground zero andexposed to gamma rays sustained 320,000 mSv ; those 1 km away
sustained 860 mSv; and those 2 km away sustained 140 mSv.

96

97

Radiation

How is the increased risk for cancerfrom radiation exposure measured?

Q

I heard that, if one is exposed to above a certain level ofradiation, the risk of cancer increases. How is theincreased risk actually measured scientifically?

A

98

100 mSv translates to an increased risk of 0.5%. Causal
relationships are demonstrated through group surveys.

axis) and the amount of radiation exposure, age at the time of
exposure, et cetera (what would correspond to the X axis), one caninvestigate whether there was a causal relationship between the twogroups of factors. For example, after the Chernobyl accident,
children between the ages of 0 and 5 at that time, who have greater
sensitivity to radiation exposure, showed a greater incidence of
thyroid cancer; the relationship of the two was therefore
scientifically demonstrated.

Cancer incidence

You have likely heard the statement that exposure to one
instance of 100 mSv increases the risk of death from cancer
by 0.5%.
Currently, 30% of Japanese people die of malignant growths
from cancer and other diseases. For a sample size of 1,000 Japanesepeople, this would mean that 300 die. If, for example, 1,000 ofthese people were exposed to a one time level of 100 mSv, the total
would increase to 305 people dying from cancer. This corresponds
to the 0.5% described above.
Unfortunately, with current science, it remains impossible topinpoint which of those five people out of the 305 sustained cancer
because of radiation exposure. Determining whether the increased
ca ncer r isk was cau sed by r a d iat ion exposu re requ i res
demonstrating the causal relationship between radiation exposureand cancer through group surveys. This, in turn, requires methodsof demonstrably proving that relationship.
Specifically, by accurately assessing the relationship of, as on agraph, the incidence of cancer (what would correspond to the Y

Q& A

Exposure dose
Age at exposure99

Since the Great East Japan Earthquake and the Fukushima Daiichi
nuclear power plant accident of March 11th, 2011, I have been
acting as a Fukushima Radiation Health Risk Management
Advisor, delivering lectures to the inhabitants of Fukushima
Prefecture on the topic of radiation and health. Following a requestthat I received to publish a series of Q&A articles on radiation andhealth from the local Fukushima newspaper Fukushima Minpo, I
found as many as 150 articles published from December of 2011 to
October of 2013.
This new booklet contains a selection of the published Q&A
articles after translating the content into English and making slightrevisions for clarity. I hope that this booklet will help people
understand the gravity of the current situation in Fukushima, thus
facilitating the development of a system that would allow people
around the world to provide much needed support for the
restoration of Fukushima.
To conclude, I would like to thank those who provided us with
their help and support in the publication of this booklet, including
the Ministry of the Environment, the Nuclear Safety Research
Association, and those who kindly assisted in the serialization of
the Q&A articles on Fukushima Minpo and the development of thisbooklet. I would also like to extend my gratitude to the staff fromthe Department of Global Health, Medicine and Welfare at theAtomic Bomb Disease Institute of Nagasaki University for theirincredible support.
March 2016

Noboru Takamura
Professor
Nagasaki University

100

Noboru Takamura, M.D., Ph.D.
Date of Birth: July 11, 1968

Specialty: Radiation Health Sciences, Hygiene,
Molecular Epidemiology, Endocrinology, Internal
Medicine
Career:3/1993
5/1997-10/2001

9/1999-7/2000
11/2002-

03/2003-

04/2008-

01/2010-09/2010

Graduate at Nagasaki University School of
Medicine
Assistant Professor, Department of International
Health and Radiation Research, Atomic Bomb
Disease Institute, Nagasaki University School of
Medicine
Technical Officer, World Health Organization
Associate Professor, Department of Preventive
Medicine and Health Promotion, Nagasaki
University School of Medicine
Associate Professor, Department of Public Health,
Nagasaki University Graduate School of
Biomedical Sciences
Professor, Department of Radiation Epidemiology,
Atomic Bomb Disease Institute, Nagasaki
University
Technical Officer, World Health Organization

Society membership: The Japan Endocrine Society, The Japan Radiation
Research Society, Japanese Society of Hygiene
Honorary professorships : Honorary Professor, Gomel State Medical
University (Gomel, Belarus) and Honorary Doctor, Belarussian State
Medical University (Minsk, Belarus)
Social activities : Advisor on radiation health risk control of Fukushima
Prefecture101

Radiation Q&A
放射線 Q&A

Published March 11, 2016
▪Issued by
Nagasaki University▪Supported by
Ministry of the Environment▪Editing cooperation
The Fukushima Minpo Newspaper publishing Company
13-17, Ohtamachi, Fukushima City
Fukushima Prefecture, 960-8602, Japan
Tel : +81-(0)24-531-4182▪Printing and Bookbinding
Minpo Printing Corporation
Tel : +81-(0)24-594-2170