radiation

1. Ionizing Radiation
and Health

2. Learning outcomes
After lecture you should know:
Physical bases of ionizing radiation
Measurement units for activity and exposure doses
Environmental and medical sources of ionizing radiation
Acute and chronic health effects of ionizing radiation to
human body
Principles of protection from ionizing radiation

3. Radiation is energy carried by waves or a stream of particles
Electromagnetic radiation
(photons)
Heat waves
Radiowaves
Infrared light
Visible light
Ultraviolet light
X rays
Gamma rays
Radiation emitted by radioactive
materials
Alpha particles
Beta particles
Protons
Neutrons

4. Ionizing radiation is radiation with enough energy so
that during an interaction with an atom, it can remove
tightly bound electrons from the orbit of an atom,
causing the atom to become charged or ionized

5. Alpha particles
Alpha decay: a nucleus ejects
an alpha particle which is
identical to an ionized helium
nucleus

6. Beta particles
Beta minus decay happens
when a neutron within an
atom's nucleus transforms into
a proton and an electron and
an antineutrino are ejected out
of the nucleus of an atom. For
a beta plus decay a proton
transforms to a neutron and a
positron (similar to an electron
but with a positive charge) and
a neutrino are ejected out of
the nucleus

7. Neutrons
The neutron is an indirectly
ionizing particle. It is
indirectly ionizing because
it does not carry an
electrical charge.n

8. X rays and gamma waves
Longer wave length, lower frequency waves (heat and radio) have less
energy than shorter wave length, higher frequency waves (X and
gamma rays)

9. Isotopes
Atoms with the same number
of protons and different
number of neutrons are
called ISOTOPES. An isotope
may be defined as one or two
or more forms of the same
element having the same
atomic number (Z), differing
mass numbers (A), and the
same chemical properties

10. Activity
The activity of a radioisotope is simply a measure of how many atoms
undergo radioactive decay per a unit of time.
The SI unit for measuring the rate of nuclear transformations is the
becquerel (Bq). The becquerel is defined as 1 radioactive disintegration
per second.
The old unit for this is the curie (Ci), in honour of Pierre and Marie
Curie who discovered radium and polonium. The curie is based on the
activity of 1 gram of radium-226, i.e. 3.7 x 1010 radioactive
disintegrations per second.

11. Why is ionizing radiation dangerous?
When atoms in living cells become ionized one of three things usually
happen – the cell dies, the cell repairs itself, or the cell mutates
incorrectly and can become cancerous. Not all cells are affected by
ionizing radiation in the same way. The cells that reproduce the most
and are the least specialized are the most likely to be affected by
ionizing radiation, for example those in a forming fetus

12. Health effects of Ionizing radiation
• Acute health effects:
• Acute radiation syndrome (ARS) or radiation poisoning
• Acute radiation burns (cutaneous radiation syndrome)
• Chronic health effects:
• Chronic radiation syndrome (CRS)
• Cancer

13. Non-stochastic effects: effects that can be related directly to
the radiation dose received
Stochastic effects: effects that occurs on a random basis
independent of the size of dose.

14. Ionizing radiation and Health
Ionizing radiation can produce tissue damage directly by striking a vital
molecule, such as DNA, or indirectly by striking a water molecule and
producing highly reactive free radicals that chemically attack vital molecules.
The effects of radiation can kill cells, make them unable to reproduce, or
cause nonlethal mutations, producing cancer cells or birth defects in
offspring. The radiosensitivity of normal tissues or cancer cells increases with
their rate of cell division and decreases with their rate of cell specialization.
Highly radiosensitive cells include lymphocytes, bone marrow hematopoietic
cells, germ cells, and intestinal epithelial cells. Radiosensitive cancers include
leukemias and lymphomas, seminoma, dysgerminoma, granulosa cell
carcinoma, adenocarcinoma of the gastric epithelium, and squamous cell
carcinoma of skin, mouth, nose and throat, cervix, and bladder.

15. Harmful effects of radiation include serious disturbances of bone
marrow and other blood-forming organs, burns, and sterility. There
may be permanent damage to genes, which results in genetic
mutations. The mutations can be transmitted to future generations.
Radiation also may produce harmful effects on the embryo or fetus,
bringing about fetal death or malformations. Long-term studies of
groups of persons exposed to radiation have shown that radiation acts
as a carcinogen; that is, it can produce cancer, especially leukemia. It
also may predispose persons to the development of cataracts.

16. Ionizing radiation units
The roentgen (R) is a unit of exposure dose applicable only to x-rays and
gamma rays. It is the amount of radiation that produces 2.58 × 10−4 coulomb
of positive and negative ions passing through 1 kilogram of dry air.
The rad is a unit of absorbed dose equal to 100 ergs of energy absorbed per
1 g of absorbing material; the absorbed dose depends both on the type of
radiation and on the material in which it is absorbed.
The rem is a unit of absorbed dose equivalent that produces the same
biologic effect as 1 rad of high-energy x-rays. For beta and gamma radiation,
1 rem is approximately equal to 1 rad; for alpha radiation, 1 rad is
approximately 20 rem.

17. Only the amount of energy of any type of ionizing radiation that
imparted to (or absorbed by) the human body can cause harm to
health.
To look at biological effects, we must know (estimate) how much
energy is deposited per unit mass of the part (or whole) of our body
with which the radiation is interacting.

18. Radiation units
(From Bushong,
2001 )

19. The international (SI) unit of measure for
absorbed dose
The gray (Gy), which is defined as 1 joule of energy deposited in 1
kilogram of mass. The old unit of measure for this is the rad, which
stands for "radiation absorbed dose." - 1 Gy = 100 rad.

20. Equivalent dose
The biological effect depends not only on the amount of the absorbed
dose but also on the intensity of ionisation in living cells caused by
different type of radiations.
Neutron, proton and alpha radiation can cause 5-20 times more harm
then the same amount of the absorbed dose of beta or gamma
radiation.
The unit of equivalent dose is the sievert (Sv). The old unit of measure
is the rem. - 1 Sv = 100 rem.

21. Coefficients of relative biological effectiveness
- RBE
Gamma and X rays 1
Beta particles 1
Alpha particles 10
Neutrons 5-20
Protons 10

22. Sources of Radiation Exposure
Radiation is permanently present throughout the environment, in the
air, water, food, soil and in all living organisms.
Large proportion of the average annual radiation dose received by
people results from natural environmental sources.
Each member of the world population is exposed, on average, to 2.4
mSv/yr of ionizing radiation from natural sources.
In some areas (in different countries of the world) the natural radiation
dose may be 5 to 10-times higher to large number of people.

23. Where does radiation exposure come from?

24. Effects of radiation dose to the entire body
• 0 – 5 rem received in a short period or over a long period is safe—we
don’t expect observable health effects.
• 5 - 10 rem received in a short period or over a long period is safe—we
don’t expect observable health effects. At this level, an effect is either
nonexistent or too small to observe.
• 10 - 50 rem received in a short period or over a long period—we
don’t expect observable health effects although above 10 rem your
chances of getting cancer are slightly increased. We may also see
short-term blood cell decreases for doses of about 50 rem received in
a matter of minutes.

25. Effects of radiation dose to the entire body
• 50 - 100 rem received in a short period will likely cause some observable
health effects and received over a long period will increase your chances of
getting cancer. Above 50 rem we may see some changes in blood cells, but
the blood system quickly recovers.
• 100 - 200 rem received in a short period will cause nausea and fatigue. 100
- 200 rem received over a long period will increase your chances of getting
cancer.
• 200 - 300 rem received in a short period will cause nausea and vomiting
within 24-48 hours. Medical attention should be sought.
• 300 - 500 rem received in a short period will cause nausea, vomiting, and
diarrhea within hours. Loss of hair and appetite occurs within a week.
Medical attention must be sought for survival; half of the people exposed
to radiation at this level will die if they receive no medical attention.

26. Effects of radiation dose to a smaller area of
the body
• 40 rem or more locally to the eyes can cause cataracts.
• 100 rem - 500 rem or more can cause hair loss for a section of the
body that has hair.
• 200 rem or more locally to the skin can cause skin reddening (similar
to a sunburn).
• 1,000 rem or more can cause a breakdown of the intestinal lining,
leading to internal bleeding, which can lead to illness and death when
the dose is to the abdomen.
• >1,500 rem or more locally to the skin can cause skin reddening and
blistering.

27. We are radioactive
0.012% of our body’s potassium is
radioactive
We expose ourselves to 40 mrem each
year due to the decay of naturally
occurring radioactive isotopes in our
bodies
We are exposed to 5 mrem of radiation
each time we fly roundtrip
If you eat a banana a day for a year you are
exposing yourself to about 3.6 mrem
Smoking a half a pack of cigarettes per day
adds 500 mrem/day

28. Radon
Inert radioactive gas.
Escapes easily from rocks
and soils into the air and
tends to concentrate in
enclosed spaces.
Soil gas infiltration is
recognized as the most
important source of
residential radon.

29. Exposure to Radon
Exposure to radon in the home and workplace is one of the
main risks of ionizing radiation causing tens of thousands of
deaths from lung cancer each year globally

30. Radiation
Protection

31. Penetrating capacity of different types of
radiation (Ignatavicius and Workman, 2002)

32. Penetrating capacity of different types of
radiation
Ionizing Radiation
Length of run in
air, m
The ionization
density (the
number of ions in
1 μl)
Alpha particles 0,01 6000
Beta particles 10 6
Gamma waves 600 0,1

33. ALARA Principle
“As Low As Reasonably Achievable” means making every
reasonable effort to maintain exposures to ionizing radiation as far
below the dose limits as practical, consistent with the purpose for
which the licensed activity is undertaken, taking into account the
state of technology, the economics of improvements in relation to
state of technology, the economics of improvements in relation to
benefits to the public health and safety, and other societal and
socioeconomic considerations, and in relation to utilization of
nuclear energy and licensed materials in the public interest.

34. Distance
Increasing distance from the radiation source reduces the dose
according to the inverse-square law for a point source. Distance
can sometimes be effectively increased by means as simple as
handling a source with forceps rather than fingers. This could
reduce erythema to the fingers, but the extra few centimeters
distance from the body will give little protection from acute
radiation syndrome

35. Time
The longer that humans are subjected to radiation the larger the
dose will be.
"Quickly putting or dumping wastes outside is not hazardous once
fallout is no longer being deposited. For example, assume the
shelter is in an area of heavy fallout and the dose rate outside is
400 roentgen (R) per hour enough to give a potentially fatal dose in
about an hour to a person exposed in the open. If a person needs
to be exposed for only 10 seconds to dump a bucket, in this 1/360
of an hour he will receive a dose of only about 1 R. Under war
conditions, an additional 1-R dose is of little concern.« (C Kearny)

36. Shielding
Low atomic number materials are recommended to shield beta particles
High atomic number materials are very effective in shielding photons
Shielding is of special importance when time and distance cannot be
completely utilized as safety factors. In such instances lead, which is an
extremely dense material, is used as a protective device. The walls of
diagnostic x-ray rooms are lined with lead, and lead containers are used
for radium, cobalt-60, and other radioactive materials used in
radiotherapy.
Monitoring devices such as the film badge, thermoluminescent
dosimeter, or pocket monitor are worn by persons working near sources
of radiation.

37. Reduction of incorporation into the human
body
Where radioactive contamination is present, a gas mask, dust
mask, or good hygiene practices may offer protection, depending
on the nature of the contaminant. Potassium iodide (KI) tablets
can reduce the risk of cancer in some situations due to slower
uptake of ambient radioiodine. Although this doesn't protect any
organ other than the thyroid gland, their effectiveness is still highly
dependent on the time of ingestion which would protect the gland
for the duration of a twenty-four hour period. They do not prevent
acute radiation syndrome as they provide no shielding from other
environmental radionuclides.

38. Fractionation of dose
If an intentional dose is broken up into a number of smaller doses, with
time allowed for recovery between irradiations, the same total dose
causes less cell death. Even without interruptions, a reduction in dose
rate below 0.1 Gy/h also tends to reduce cell death. This technique is
routinely used in radiotherapy.
The human body contains many types of cells and a human can be
killed by the loss of a single type of cells in a vital organ. For many short
term radiation deaths (3 days to 30 days), the loss of two important
types of cells that are constantly being regenerated causes death. The
loss of cells forming blood cells (bone marrow) and the cells in the
digestive system (microvilli which form part of the wall of the
intestines) is fatal.

39. Reference
• Feynman, Richard; Robert Leighton; Matthew Sands (1963). The Feynman
Lectures on Physics, Vol.1. USA: Addison-Wesley. pp. 2–5.
• European Centre of Technological Safety. "Interaction of Radiation with
Matter" (PDF). Radiation Hazard. Retrieved 5 November 2012.
• Fundamental Quantities and Units for Ionizing Radiation (ICRU Report 85)".
Journal of the ICRU 11 (1). 20
• Prasad KN. Handbook of Radiobiology, 2 nd ed. New York : CRC Press, Inc.;
1995.
• Donnelly EH, Nemhauser JB, Smith JM; et al. (June 2010). "Acute radiation
syndrome: assessment and management". South. Med. J. 103 (6): 541–6.