RADIATION HAZARDS AND PROTECTION IS DESCRIBED IN DETAIL IN THIS PPT. CONTENT TAKEN FROM MULTIPLE BOOKS AND JOURNALS.

1. RADIATION HAZARDS AND
PROTECTION
MR. ROHIT BANSAL
ASSISTANT PROFESSOR (RADIO-
PHYSICS)
MAMC,AGROHA

3. RADIATION
Radiation is a form of energy which can travel
from one medium to another medium.

4. TYPE OF RADIATION
There are two type of Radiation
 Ionizing Radiation
 Non-Ionizing Radiation

5. Ionizing Radiation
 Ionizing radiation is radiation with sufficient
energy that produces ions in the matter at the
molecular level upon the interaction. If the
interacting matter is a human body, it can result
in significant damage including damage to DNA
and denaturation of proteins.
 Ionizing Radiation have harmful effect on human
body.
 Example: Alpha particles, Beta particles, Gamma
rays, X-rays.

6. Non-Ionizing Radiation
 Non-ionizing radiation is the term given to
radiation that has insufficient energy to cause
ionization. Humans and other organisms can
see some types of non-ionizing radiation,
such as visible light and infrared light.
 Non-Ionizing Radiation didn’t have harmful
effect of Radiation on human body.
 Examples: Ultraviolet radiation, Visible light,
Infrared, Microwave, Radio waves.

7. Source of Radiation
There are two main source of Radiation
 Natural Radiation
 Artificial Radiation

8. Natural Source
 The natural radiation sources includes
(i) Cosmic rays
(ii)Terrestrial (Primordial) radionuclides
(iii) Internal Radioisotopes
About 82% of the above exposure arise from
naturally occurring sources.

9. Cosmic Rays
Cosmic rays are extraterrestrial radiation that strikes
the earth’s atmosphere, that includes primary and
secondary. Primary cosmic rays, in which protons
accounts for 80%. The primary cosmic rays collide with
atmosphere, producing showers of secondary particles
(electrons, muons) and electromagnetic radiations. The
average per capita equivalent dose is 270 μSv per year,
which makes 8% of the natural background. Cosmic
exposures increase with altitudes.
A part of secondary cosmic ray particles collide with
stable atmospheric nuclei and produces cosmogenic
radionuclides.

10. Terrestrial Radionuclides
 Terrestrial radionuclides that have been present on earth since its formation
are called primordial radionuclides. Their physical half lives are comparable to
the age of the earth (4.5 billion yeras). Their decay products are the major
contributors of terrestrial radiations. They mainly contribute in the form of
external exposure, inhalation, and ingestion.
 External exposure: K-40, U-238, and Th-232 are mainly responsible for
external exposure and they account an equivalent dose of 280 μSv per year.
 Inhalation: Rn-222 (U-238) is a noble gas, decays to polonium-218 by alpha
emission with half life of 3.8 days. Its decay products are the most significant
source of inhalation exposure. It is deposited in the tracheobronchial region
of the lung. Radon inhalation accounts an equivalent dose of 2 mSv/year to
the bronchial epithelium.
 Ingestion: Ingestion of food and water is the second largest source of natural
background in which K-40 is the most significant. It is a naturally occurring
isotope of potassium having higher concentration at the skeletal muscle. It
accounts an average equivalent dose rate of 400 μSv/year.

11. Internal Radioisotopes
 Internal radionuclides includes K-40 and C-14,
which are present the in the human body.The
main contributor is K-40,which emits β and γ
rays and decays with a half life of 1.3 × 109
years.

13. Artificial Radiation
The artificial sources of radiation includes medical exposure,
radioactive fallout, nuclear power and occupational exposure.
Medical Exposure: The majority of the exposure is from
medical X-rays (Fluoroscopy & Computed tomography) which
contribute to 58% of the artificial radiation exposure. Next
contributor is the nuclear medicine which is 21%. It accounts
for about 69% of artificial radiation.
Consumer Products: It accounts to 16% of the artificial
radiation exposure. Substances in consumer products such as
tobacco, the domestic water supply, building materials, and to
a lesser extent, smoke detectors, televisions, and computer
screens, account for the above exposures.

14. Radioactive Fallout: It arises from atmospheric testing of
nuclear weapons and consists of Carbon-14 (70%) and
other radionuclides including H-3, Mn-54, Cs-136, 137, Ba-
140, Ce-144, plutonium and trans-plutonium elements. It
contributes 2% of the manmade radiation exposures.
Nuclear Fuel Cycle: The contribution from nuclear power
production is very minimal, which is about 1% of artificial
radiation. . It involve all phases of fuel cycle; mining,
manufacturing, reactor operations, and waste disposal.
The most significant contributor is Carbon-14.
Occupational Exposure: The occupational exposures
associates with uranium mining, nuclear power
operations, medical diagnosis and therapy, aviation and
research, non uranium mining, and application of
phosphate fertilizers. It contributes about 2 % of the
artificial radiation exposure.

16. The term exposure (X) refers the radiation quantity
measured in terms of ionization in air, in a small volume
around a point. Exposure from an X-ray source obeys inverse
square law.The unit of exposure is roentgen (R).
The unit may also be defined in terms of SI unit as
1R = 2.58 × 10-4 C / kg of air
There are some difficulties in the unit of roentgen. It is not a
unit of dose, which is a measure of absorbed energy. It can be
used only up to a photon energy of 3 MeV. It is defined only
for x and gamma radiation in air.
Exposure (Roentgen)

17. The roentgen is independent of area, or
field size. When a large square (A) is
exposed to 1 R, each increment of the
square receives 1 R. If the square is
divided into multiple smaller squares (B),
each of these squares receives 1 R of
exposure.

18. Absorbed Dose—Rad/Gray The term absorbed dose
(D) refers the amount of energy absorbed per unit mass
of the substance. The unit of absorbed dose is rad (r),
which means radiation absorbed dose.
1 rad =100 ergs/gram
This unit is independent of type of radiation and the
medium.The SI unit of absorbed dose is Gray (Gy).
1Gy = 1 J / kg
The unit rad is related to gray as 1Gy = 100 rads, 1 rad =
1 cGy (centigray) .
Absorbed Dose—Rad/Gray

19. The biological effects of radiation depend not only on absorbed
dose (D) but also on the type of radiation. Hence, the ICRP report 26
(1977) introduced the dosimetric quantity Equivalent dose (HT). It is
the absorbed dose averaged over a tissue or organ and weighted for
the radiation quality that is of interest, and is given as
HT=D ×WR
Sievert (Rolf Sievert, Swedish Radiologist) is the SI unit of
equivalent dose and one Sievert (Sv) =1 Joule/kilogram. Also 1
Sv=100 Rem (Radiation equivalent men), where Rem is the special
unit of equivalent dose.
In practice, milli sievert (mSv) unit is used.
1 Sv = 1000 mSv
1 mSv = 100 mRem
Equivalent Dose

21. The whole body exposures are not uniform and dose
equivalents for various tissues may differ markedly. Hence,
the radiation induced effects vary with the sensitivity of the
organ. To account these non uniform irradiation and organ
sensitivity variation, the ICRP-26 introduced the term
effective dose (E), which describes the dose to the whole
body and is derived from equivalent dose. It is defined as
E =WT × HT
where WT is the weighting factor for the tissue T, HT is the
mean equivalent dose received by the tissue and E is the
summed organ or tissue doses as an overall whole body dose.
EFFECTIVE DOSE OR EFFECTIVE DOSE EQUIVALENT

23. The harmful effects of radiation in human body are
classified as
(i) Somatic effects and
(ii) Genetic effects.
The radiation effects, arises due to the damage
of the somatic cell are called somatic effects.
The magnitude of the somatic effects vary with
nature of exposure (whole body or partial
exposure). The hereditary effects are due to
damage to reproductive cells.

24. Somatic effects may appear immediately after exposure,
within a few hours to weeks or much later (after years -
decades). The early effects are due to an acute exposure
(large doses over a short period of time) and attributed to
depletion of cell population due to cell death. The amount of
radiation damage depends on the rate at which the radiation
is delivered. High dose delivered in a short time may result in
severe damages to tissues. The same dose delivered over
several months allows the repair mechanisms to function
fully.
Early Somatic Effects (Whole
Body Irradiation)

26. Partial body exposure to the above dose ranges produces only
local effects. A whole body exposure to a dose of 4 Gy can be
lethal. But exposure of a part of the body to the dose will not
be life threatening. However, it can produce certain serious
local effects. The seriousness of the local effects too depends
on the dose rate and the period of exposure etc. All the early
somatic effects do have a threshold dose, below which they do
not occur. Beyond the threshold dose, severity of the effect
increases with the dose.
Early Somatic Effects (Partial
Body Irradiation)

28. A deterministic effect (non stochastic) is one “which increases
in severity with increasing absorbed dose in affected
individuals”. It results in cell killing due to degenerative
changes in the exposed tissues. It may appear at higher doses
(> 0.5 Gy) and soon after the dose is received. It have threshold
dose, below which the effect is not seen. All somatic effects
except cancer, as mentioned above are deterministic effects of
radiation. All these effects will definitely appear in the exposed
individual, if the radiation dose received is above the respective
threshold doses. Examples are skin erythema, epilation, organ
atrophy, fibrosis, cataract, blood changes, and reduction in
sperm count. The radiation dose required to produce such
effects are very large and are likely to occur only as the result of
radiation accidents and patients irradiated in radiotherapy
Deterministic Effect

30. A stochastic effect is one in which “the probability of
occurrence increases with increasing absorbed dose rather
than its severity”. It is very important at very low levels (< 0.5
Gy). Any dose, however small, is effective for a certain level of
risk for induction of stochastic effects. The risk increases as
the dose increases. It have no threshold dose and the chance
of occurrence increases with dose and independent of sex and
age. Stochastic effects are the principle health risk from low
level radiation, which is likely in diagnostic radiology and
Nuclear medicine. Radiation induced cancer and genetic
effects are examples for stochastic effects. Hence the risk of
stochastic effects cannot be completely avoided. However, it
can be minimized to an acceptable level.
Stochastic Effect

31. Ten day rule’ was postulated by ICRP for woman of
reproductive age. It states that “whenever possible, one
should confine the radiological examination of the lower
abdomen and pelvis to the 10 day interval following the onset
of menstruation.” The original proposal was for 14 days, but
this was reduced to 10 days to account for the variability of the
human menstrual cycle.
28 day rule: According to 28 days rule any radiological
examination, if so justified, can be carried throughout the
cycle until a period is missed. Thus, the focus is shifted to a
missed period and the possibility of pregnancy. If there is a
missed period, a female should be considered pregnant unless
proved otherwise
TEN DAY RULE

32. DISCOVERY OF X RAY
 Discovered in 1895 by German physicist named
Wilhelm Roentgen.
 While studying cathode rays (stream of electrons) in
a gas discharge tube.
 He observed that another type of radiation was
produced (presumably by the interaction of
electrons with the glass walls of the tube) that could
be detected outside the tube.
 This radiation could penetrate opaque substances,
produce fluorescence, blacken a photographic plate,
and ionize a gas.
 He named his discovery "x rays" because "x" stands
for an unknown.

33.  In 1895,Wilhelm Roentgen, a professor of physics in Bavaria, was
working on an experiment with cathode ray tubes to learn if
cathode rays could travel through a vacuum tube. He applied a
high voltage to the tube and noticed that the positive and
negative electrodes within the tube caused it to emit light.
 He then covered the tube with black paper to see if the light
would shine through, and a nearby screen treated with a chemical
called barium platinocyanide began to glow.
 He concluded that a type of radiation must be at work from inside
the tube. He soon learned that the rays had very short
wavelengths that enabled them to pass through human flesh and
leave a shadow of the underlying bones on the screen.
 He named this radiation X-ray, with X standing for unknown. He
created the very first X-ray by capturing the image of the bones of
his wife’s hand.When she looked at the image, his wife is said to
have cried, “I have seen my death!”
 For his discovery of radiation, Roentgen won the very first Nobel
Prize in physics in 1901. But he couldn’t have known that his
discovery would become one of the cornerstones of modern
medicine.

34. RADIATION PROTECTION
Radiation is a double edged weapon, analogous to fire,
which possess both benefits and hazards.
Radiation hazards were realized in the beginning of
20th century. The X-rays were used indiscriminately in
the early years and have caused visible damage to
several physicians and X-ray enthusiasts. Within 6
months of their use, several cases of erythema,
dermatitis and alopecia were reported among X-ray
operators and their patients. In 1902 the first X-ray
induced skin cancer was reported. In 1921 Ironside
Bruce, a pioneering radiologist in a London Hospital
died of cancer at the age of 38. Similarly several lives
were lost due to excessive X-ray exposures.

35. In 1915, the British Roentgen Society made the first
radiation protection recommendations. To regulate
the safe use of radiation the “British X-ray and
Radium protection committee” was formed (1921). It
was made as an International Committee in 1928 and
later (1950) transformed as “International
Commission on Radiological Protection”(ICRP). The
ICRP is the first standard setting body formed, for
the purpose of radiological safety. The similar
organization at the USA is the National council on
radiation protection and measurements (NCRP),
which was formed in 1946. These bodies issue
periodical reports on radiation safety aspects of
various application of ionizing radiation

36. The Atomic Energy Regulatory Board (AERB) - An
Indian regulatory body that regulates and control the
radiation exposure. Formed on 15 November 1983,
under atomic Energy act 1962 and environmental
(protection) Act 1986.
The Mission of the AERB is to ensure the use of
ionising radiation and nuclear energy in India does
not cause undue risk to the health of people and the
environment. The constitution of AERB together with
the Atomic Energy (Radiation Protection) Rules,
2004, has mandated AERB to develop and issue
safety codes and standards and to develop safety
policies in radiation and industrial safety areas.

38. 1) JUSTIFICATION: No practice shall be adopted unless its
introduction produced a net positive benefit
2) 2) OPTIMIZATION OF EXPOSURES: All exposures shall be
kept As Low As Reasonably Achievable (ALARA),
economic & social factors being taken into account
3) 3) DOSE LIMITS: Dose to individuals shall not exceed
recommended limits (Applicable to occupationally
exposed personnel)
Exposure due to natural background radiation & medical
exposure excluded in arriving at the dose limits
Basic Principles of Radiation Protection

39. Basic Three Factors for Radiation
Protection (Working Personnel &
Public)
•Time
• Distance
• Shielding

46. ICRP EFFECTIVE RADIATION DOSE IN
ADULTS
ABDOMINAL REGION Procedure Approximate effective
radiation dose
Comparable to natural
background radiation
for:
ComputedTomography
(CT)–Abdomen and Pelvis
7.7 mSv 2.6 years
ComputedTomography
(CT)–Abdomen and Pelvis,
repeated with and without
contrast material
15.4 mSv 5.1 years
ComputedTomography
(CT)–Colonography
6 mSv 2 years
Intravenous Urography
(IVU)
3 mSv 1 year
Barium Enema (Lower GI X-
ray)
6 mSv 2 years
UpperGI Study with Barium 6 mSv 2 years

47. BONE Procedure Approximate effective
radiation dose
Comparable to natural
background radiation for:
Lumbar Spine 1.4 mSv 6 months
Extremity (hand, foot, etc.)
X-ray
Less than 0.001 mSv Less than 3 hours
CENTRAL NERVOUS
SYSTEM
Procedure Approximate effective
radiation dose
Comparable to natural
background radiation for:
ComputedTomography
(CT)–Brain
1.6 mSv 7 months
ComputedTomography
(CT)–Brain, repeated with
and without contrast
material
3.2 mSv 13 months
ComputedTomography
(CT)–Head and Neck
1.2 mSv 5 Months
ComputedTomography
(CT)–Spine
8.8 mSv 3 years

48. CHEST Procedure Approximate
effective radiation
dose
Comparable to
natural background
radiation for:
Computed
Tomography (CT)–
Chest
6.1 mSv 2 years
Computed
Tomography (CT)–
Lung Cancer
Screening
1.5 mSv 6 months
Chest X-ray 0.1 mSv 10 days
DENTAL Procedure Approximate
effective radiation
dose
Comparable to
natural background
radiation for:
Dental X-ray 0.005 mSv 1 day
Panoramic X-ray 0.025 mSv 3 days
Cone Beam CT 0.18 mSv 22 days

49. NUCLEAR MEDICINE Procedure Approximate effective
radiation dose
Comparable to natural
background radiation
for:
Positron Emission
Tomography–
ComputedTomography
(PET/CT)Whole body
protocol
22.7 mSv 3.3 years
WOMEN'S IMAGING Procedure Approximate effective
radiation dose
Comparable to natural
background radiation
for:
Bone Densitometry
(DEXA)
0.001 mSv 3 hours
Screening Digital
Mammography
0.21 mSv 26 days
Screening Digital
BreastTomosynthesis
(3D Mammogram)
0.27 mSv 33 days