Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Biological Effects of Ionising Radiation
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Chemical composition :
Water
Proteins
Fatty Substances
Carbohydrates, including sugars
DNA and other nucleic acids
Others
70%
18%
5%
2%
1%
4%
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Deoxyribonucleic Acid -
Adenine
Guanine
Cytosine
Thymine
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Potential Chromosome Damage
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
In a biological system, ionisation of a
molecule can lead to Direct or Indirect
damage to the system.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Direct Damage
1 – cell may be undamaged
2 – cell may repair and work normally
3 – cell repaired but abnormal
4 – cell may die
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Indirect Damage
Ionising radiation causes cleavage of a covalent bond,
fragmenting the molecule, each fragment retaining one of
the paired electrons or by instigating chemical changes
which produce free radicals.
This damage to the system depends on the concentration of
free radicals and this in turn depends on the number of
ionisation events per unit mass.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Quantifying the damage:
Energy required to produce a single ionisation event is a few tens Ev
Ionising radiation generally has energy of keV or MeV.
Potential for a great many ionisation events.
The unit of Absorbed Dose (DT) is Gray.
1 Gray = Dissipation of 1 Joule/kg.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Equivalent Dose (HT ) and Radiation Weighting Factor (WR )
-particle
50 ionisations/nucleus
-particle
12,500 ionisations/nucleus
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Equivalent Dose (HT) and Radiation Weighting Factor (WR )
Equivalent Dose is a measure of the biological damage:
HT = WR DT
Unit is the Sievert (Sv)
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Each type of radiation has been given a
‘Radiation Weighting Factor’ (WR) :
Alpha Particles
20
Beta Particles
Photons
Neutrons
1
1
5 - 20
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Effective Dose (E) and Tissue Weighting Factor (WT )
Effective Dose for any particular organ is given by:
E = WT HT
And if more than one organ is involved:
E = T WT HT
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
We use ‘effective dose’ when there is a non-uniform irradiation
of the body.
Tissue or Organ
Gonads
Bone Marrow
Colon
Lung
Stomach
Bladder
Breast
Liver
Oesophagus
Thyroid
Skin
Bone surface
Remainder
WT
0.20
0.12
0.12
0.12
0.12
0.05
0.05
0.05
0.05
0.05
0.01
0.01
0.05
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
The Effects on Health
Deterministic and Stochastic Effects
Deterministic Effects
Radiation doses involved here are usually substantial and
delivered over a short space of time and there is a threshold dose
below which no clinical effect is observed. These type of effects
are called Deterministic.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Stochastic Effects
Since the probability for cancer at high doses increases with
increasing dose, this relationship is assumed to hold true with low
doses. This type of risk model is called stochastic.
Stochastic Effects - No lower dose limit
Probability of effect
2 prediction models
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Additive Model
A given dose produces a risk that is constant with time.
Multiplicative Model
A given dose produces a risk which is a constant multiple
of the pre-existing spontaneous risk of cancer.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Important Radiation Effects
• Molecular
• Subcellular
• Cellular
• Tissue, Organ
• Whole Animal
• Populations
Damage to enzymes, DNA etc. and
interference to biological pathways
Damage to cell membranes, nucleus,
chromosomes etc.
Inhibition of cell division, cell death,
transformation to a malignant state
Disruption to central nervous system, bone
marrow, intestinal tract. Induction of
cancer
Death; 'radiation lifeshortening‘
Changes in the genetic characteristics of
individual members
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Acute (short-term) vs chronic (long-term) effects
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Summary :
Deterministic Effects- The risk is more or less certain.
Stochastic Effects
- The risk is not certain - a ‘probability’ exists.
Additive model
- The risk is constant in time.
Multiplicative model - The risk is a constant multiple of the
spontaneous risk.
The model introduced in 1990 is the Multiplicative model.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
There are at least three ways to measure the effect
of radiation :
• Becquerels (Bq)
• Grays (Gy)
• Sieverts (Sv)
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Risk Factors: ICRP 1990
Fatal cancers - 4%/Sv - , X or  only
Non-fatal cancer - 1.2%/Sv
Genetic factors - 0.6%/Sv
Overall - 5.8%/Sv
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Estimated Years of Life Expectancy Lost
6.5
6
5
4
3
2.7
Industry Type Or Activity
Janice Brock
University RPO
day
cigarettes a
Smoking 20
20%
Overweight by
0.9
Quarrying
0.83
Mining and
0.15
0.76
Construction
0.12
Government
30 years
Radiation –
years
1 mSv/yr for 70
0
3.4 mSv/yr for
0.13
0.09
Manufacturing
1
Agriculture
2
Radiation -
Estimated Years Lost
7
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Risk in perspective – Scenarios with one in million chance of death:
• A 5 hour flight by jet aircraft
Cancer (Cosmic Rays)
• Living for 2 weeks in a granite building Cancer (radioactivity)
• Travelling 100 km by car
Road Accident
• Travelling 1,000 km by air
Accident
• Smoking 1 - 3 cigarettes
Cancer & Lung Disease
• Drinking a half bottle of wine
Liver & Other Disease
• Working as a Radiographer for 1 month Cancer (X-Rays)
• Working as a Radiologist for 2 weeks
Cancer (X-Rays)
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Conclusions Regarding Health Risk
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Radiation Contamination, Brazil 1987
•
•
•
•
•
Cesium Capsule Left Behind.
2 Years Later, Capsule Removed.
Localised burns and arm amputation.
Object Sold to Junk Yard Owner.
Workers opened lead casing, 2 died.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Radiation Contamination Continued :
•
•
•
•
•
•
Scraped dust from source.
Daughter ate, absorbing radioactive material.
Daughter applied “blue powder” to body.
Worker painted blue cross on his skin.
Junk yards wife noticed people becoming ill.
Scrap metal sold to another scrapyard.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Radiation Contamination Continued :
•
•
•
•
Scrap metal taken on bus to hospital.
Object placed in garden.
Physicist confirmed presence of radioactivity.
Wife died month later.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Other affected persons
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Resulting Legalities:
3 Charged with criminal negligence
Shows importance of record keeping
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Treatment
Whole Body v Partial Body Exposure
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Exposure Levels and Symptoms
0.05 - 0.2Sv
No symptoms
0.2 - 0.5Sv
No noticeable symptoms
0.5 - 1Sv
Mild radiation Sickness
1 - 2Sv
Light radiation poisoning, 10% Fatality after 30 days
2 - 3Sv
Moderate radiation poisoning, 35% fatality after 30 days
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Exposure Levels and Symptoms
3 - 4Sv
Severe radiation poisoning, 50% Fatality after 30 days
4 - 6Sv
Acute Radiation Poisoning, 60% Fatality after 30 days
6 - 10Sv
Acute radiation poisoning, Near 100% Fatality after 14
days
10 - 50Sv
Acute radiation poisoning, 100% Fatality after 7 days
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
The mouth of a man who has
suffered a 10 to 20 Gy dose 21
days after the exposure, note that
damage to normal skin, the lips
and the tongue can be seen.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
The Conqueror, 1956
Did John Wayne die of cancer caused
by a radioactive movie set?
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
The crater-scarred landscape of the Nevada Test Site.
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Summary:
Ionising radiation causes damage at the cellular level
Absorbed dose (D) gives a measure of the damage
Unit is the Gray
1 Gy = 1 J/Kg
Equivalent dose (H) accounts for different types of radiation
Equivalent dose = Absorbed Dose x Radiation Weighting
Factor
Unit is the Sievert
e.g. for beta 1 Sv = 1 Gy
Janice Brock
University RPO
Radiation Protection Service
University of Glasgow
Biological Effects of
Ionising Radiation
Summary Continued:
Effective dose (E) is used for single organ doses
Effective dose = Equivalent dose x Tissue Weighting
Factor
Unit is the Sievert (Sv)
Deterministic effects are known effects above a certain dose
Stochastic effects have a probability of occurrence
Janice Brock
University RPO