THE EFFECTS OF RADIOACTIVITY
ON THE BODY
4.1

Design: ASN and IRSN Communications Departments - October 2021
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THE EFFECTS OF RADIOACTIVITY
ON THE BODY

BIOLOGICALEFFECTSOF RADIATION
Radiation damages the DNA of our cells.
Fortunately, cells have effective repair
mechanisms. Nevertheless, damage canremain and cause all sorts of malfunctions,
including cancer.

IRRADIATEDCELL
Exposure to radiation can damage DNA:• directly: an alpha or beta particle breaks the DNA molecule;• indirectly: X-rays or gamma rays cause chemical reactions
that lead to DNA damage.

DAMAGED CELLS HAVE
3 MODES OF BEHAVIOUR

THE CELL MUTATES
Very rarely, cells may bepoorly repaired or the selfdestruct order may be
prevented.
The cell will then multiply
abnormally and, over time,
become a tumour orcancer.

THE CELL REPAIRS ITSELF
Our immune and enzyme
systems are powerful repair
mechanisms. Depending on theextent of the damage, repairs
can be carried out in a matterof minutes or several days.
Cells can be poorly repaired
if the repair mechanisms are
weak or overloaded.
A high dose of radiation
received all at once is therefore
much riskier than if it is spreadout over time, giving the repair
mechanisms time to playtheir part.

THE CELL DESTROYS ITSELF
Cells have a natural self-destruction
mechanism that they activate when
they are damaged or too old.
In the event of extensive irradiation,a large number of cells can beeliminated. In the event of a very
high dose, this can lead to organ
dysfunction, serious illness oreven death.

SINGLEOR DOUBLE DAMAGE?
Every day, every cell in our body undergoes multiple attacks thatbreak the DNA.

Cells repair single-strand breaks
quite easily.

Radiation can breaka single strand of
the DNA chain or bothstrands in the sameplace.

Double-strand breaks are moredifficult to repair. Compared withnaturally occurring lesions, radiation
significantly increases the numberof double-strand breaks.

4.2

Design: ASN and IRSN Communications Departments - October 2021
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THE EFFECTS OF RADIOACTIVITY
ON THE BODY

IRRADIATION

OR CONTAMINATION?
A human being can be irradiated or contaminatedby a radioactive source.
The person is irradiated if they are externally exposed
to radiation from the source.
They are contaminated if radioactive particles aredeposited on them or are ingested or inhaled.

IRRADIATION
Irradiation occurs when the radioactive
source is located outside the body andthe radiation passes through the bodyor part of it. Irradiation diminishes with
distance from the source.
The person does not carry any
radioactivity with them after being
irradiated, but suffers any effects
produced by the radiation.

RADIATIONPENETRATION
Alpha radiation
does notpenetrate deeper than the firstcells of the upper layer ofthe skin.
is moreBeta radiation
penetrating and can reach theinner layers and cause burns.
penetrate
Gamma rays
beyond the layers of the skin,inside the body.

CONTAMINATIONEXTERNAL
When radioactive particles are deposited on theskin or clothing without penetrating the body,this is known as external contamination.
This can be eliminated by the person undressing
and washing.

INTERNAL
Internal contamination occurs when radioactive
elements enter the body through inhalation,
ingestion or injury by contaminated objects.
The body does not permanently fix mostradioactive particles. Depending on their nature,
the time they spend in the body varies.
Just because a person has been contaminatedinternally or irradiated does not mean that theypose a risk to those close to them.

INTERNAL CONTAMINATION
Depending on their chemical
nature, radioactive elements bindto different organs.

4.3

Design: ASN and IRSN Communications Departments - October 2021
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LOW

DEBATE

DOSES

mSv

Design: ASN and IRSN Communications Departments - October 2021
Graphic design and production: www.kazoar.fr - Pictograms: Freepik, Kazoar
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4.4

mSv

9

mSv

12

mSv

20

mSv

30

mSv

mSv

100

Some studies show that the risk diminishes
rapidly or is even eliminated below 100 mSv.

Other studies conclude that the risk diminishes
progressively and remains as long as the dose is
not zero. These studies form the basis ofregulations.

We do not yet know what the nature of the risk
is below 100 mSv. Epidemiological andexperimental studies are being carried out on
the subject.

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THE EFFECTS OF RADIOACTIVITY
ON THE BODY

DANGERTHRESHOLDSRadioactivity can be dangerous, but it all
depends on the dose received. In somecases, it is even used to treat illnesses.

SYSTEMATIC
EFFECTSRANDOM
EFFECTS

Following intense irradiation,
cells can be destroyed in large
numbers. Tissues or organs aredamaged.
Irradiation can damage DNA and may or may notcause subsequent effects. Radiation can increase
the likelihood of cancer and, at high doses, can have
immediate effects such as nausea.

These effects can be felt
immediately or after a few
days, and are certain to affectanyone exposed. Their severity
increases as the absorbed dose
increases.
After a certain time, consequences may appear, andonly for certain people: a few years for leukaemia andthyroid cancer in children, 20 to 40 years for othercancers.

Since cancers can have a variety of causes, sometimes
associated with one another, it is very difficult toattribute a cancer to irradiation with any certainty.

mSv
= 1Sv

1000

400

mSv

500

mSv

mSv

6

Sv

Sv

5

10
Sv

THE EFFECTS OF RADIOACTIVITY
ON THE BODY

ARE WEALL EQUALIN THE FACE OF
RADIOACTIVITY?
We are not all equal when it comes to radioactivity,
yet we are regularly exposed to it, particularly in the
medical sector. Differences in our genes, age or sex
explain these variations. In certain circumstances,such as pregnancy, special precautions may need
to be taken.

VARYING LEVELS OF SENSITIVITY
Our genes are different and our bodies
react differently to the aggressions ofradiation. It is estimated that 5 to 15%of the population is radiosensitive,
i.e. more vulnerable to radiation. This is
an important factor when it comes toundergoing radiotherapy for cancer,
for example.
ASN, which is responsible for monitoring
personal radiation protection, is keeping
a close eye on developments in this area.

PREGNANT WOMEN
Pregnant women may be exposed to radiation for avariety of reasons: occupational for workers, medical in
the case of imaging examinations (particularly scans).
Precautions must therefore be taken to protect both themother and the unborn child.
In the case of cancer, doctors and families are faced witha dilemma, as radiotherapy treatments can pose a risk to
the unborn child.

From 0 to 2 months

The development of the embryo is such that radiation
has an "all or nothing" effect: the embryo may or may
not survive, but there is no risk of malformation.

During the foetal period (from 2 to 9 months)

The risk of malformation or physical or mental disability
may materialize depending on the dose received.
Weeks post-conception

SEX AND AGE

39
Reduced risk

28
500 mmThe bodies of men, women, children and the elderly
react differently to ionising radiation.

Foetaldevelopment24

20
230 mmDevelopment of thecentral nervous
systemNo proveneffects

16

Risk of reduced intelligencequotient (IQ)

12

Area ofuncertainty
as to effects

High probabilityof profoundintellectual
disability

830 mm
Organogenesis

Pre-implantation
stage

Risks of malformationand intellectual disability(according to the ICRP 84).

Risk of malformations

No proveneffects

4
2
1
0

IF A MANIS CONTAMINATED,
he eliminates a radioactive substance more
slowly than a woman or a child.

No excess risk of malformation observed

0100
Usual range ofradiodiagnostics

200

500

1000

Dose to the foetus (mGy)Radiotherapists use this chart to decide, with families,
what choices to make when a pregnant woman has toundergo radiotherapy.

Cell renewal is very uneven, depending on theage of the individual and the tissues
concerned: it is particularly rapid in the foetus
and in children, but slower in adults and evenslower in the elderly. This means that amutation caused by irradiation will multiply
more rapidly in younger people.
In addition, certain organs are particularly
active in children, such as the thyroid, which
supplies growth hormones.

THE ORGANS
Some organs are much more sensitive than others(gonads, liver, thyroid, etc.).

4.5

Design: ASN and IRSN Communications Departments - October 2021
Graphic design and production: www.kazoar.fr - Pictograms: Freepik, Kazoar - Illustration: R. Grimaldi/IRSN - Photos: JackF/Adobe Stock, Sergejs Rahunoks/Adobe Stock
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THE EFFECTS OF RADIOACTIVITY
ON THE BODY

WHAT DOSESDOWORKERS
RECEIVE?

The doses received by workers in civil and militaryactivities and those exposed to natural radioactivity
are monitored and reported to IRSN, which establishes
an annual report. ASN controls the radiation protectionof workers.

NUMBER OF WORKERSMONITORED
395,040 workers underwent dosimetric monitoring in 2019, comparedwith 278,150 in 2006. 58% work in the medical field.
To this figure must be added more than 25,000 workers exposed tonatural radioactivity, mainly flight crews exposed to cosmic radiation.

Breakdown of workers monitored by field of activity in 201958%
MEDICAL

4%
INDUSTRY

3%
RESEARCH

22%
NUCLEAR

4%
UNDETERMINED

6%
NATURAL
RADIOACTIVITY(including aircraft)

MEASURING
EXTERNAL IRRADIATIONIn all circumstances, the person wears a passive dosimeter for individual referencemonitoring and, in work areas where the risk is greater, an operational dosimeter that can beread immediately, which indicates the dose received in real time and can trigger an alarm if
a predefined threshold is exceeded.

AVERAGE INDIVIDUAL DOSE BY AREA OF ACTIVITY IN 2019 (mSv)
There are major disparities between the different areas of activity. Flight crews have thehighest average individual doses, followed by workers in the non-nuclear and nuclear
industries. 76% of monitored workers received no dose. Few workers receive more than
20 mSv: 9 in 2014, 5 in 2019.

RESEARCH

0.27

MEDICAL

0.30

INDUSTRY

0.98

OTHER

1.04

NUCLEAR

1.46

AVIATION

2.18

MEASURINGINTERNAL CONTAMINATION
For workers likely to absorb radioactive substances (through inhalation, ingestion, skinpenetration or even injury), monitoring is based on anthroporadiometric examinations(in vivo measurements) and radiotoxicological analyses of urine or faeces (in vitro
measurements).

ROUTINE MONITORING
The main purpose of routine monitoring is to check that workers are not contaminatedunder normal working conditions.
In 2019, out of almost 230,000 examinations, 0.5% revealed contamination.

SPECIAL MONITORING
Routine monitoring is supplemented by special monitoring when a particular event
involving a suspicion of contamination is suspected or detected.
In 2019, out of approximately 10,000 examinations, 15% revealed contamination.

CALCULATETHE DOSE RECEIVED
Calculate the dose received
during a flight by scanning thefollowing QR Code or visiting
http://www.sievert-system.org/

FIND OUT MOREABOUT WORKER
EXPOSURE
Find out more about worker exposure
to ionising radiation in France (2019)at http://www.irsn.fr/travailleurs-2019

4.6

Design: ASN and IRSN Communications Departments - October 2021
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3%
OTHER