PHYSICAL HAZARD III:
RADIATION AND HEAT
Occupational Health EOH 3202
Dr Emilia Zainal Abidin
Environmental & Occupational Health
Faculty of Medicine and Health Sciences
University Putra of Malaysia
ERRATUM – AEROSOLS OF CHEMICAL
HAZARD ORIGIN
 FUMES

Solid aerosols generated by the condensation of vapors or gases from
combustion or other high temperature processes

Usually very small and spherical

Sources: Welding, foundry and smelting operations, hot cutting or
burning operations
 MISTS

Liquid aerosols generated by condensation from a gaseous state or by
the breaking up of a bulk liquid into a dispersed state

Droplet size related to energy input as in dusts and fibers

Examples: Metal working fluid from lathe, paint spray, liquid mixing
operations
OBJECTIVES OF LECTURE
Understand the sectors and occupations
associated with radiation use
Understand the fundamental points related to types
of radiation
Explain the effects of radiation on the cells and
other related health effects
Describe the control and management steps in
occupational setting
TYPE OF SECTORS ASSOCIATED WITH
RADIATION USE
 Science
 carbon dating to determine age
 instruments to measure density
 power satellites
 Medicine
 x-rays and nuclear medicine
 diagnose and treat illness
 Industry
 smoke detectors
 kill bacteria and preserve food
SOURCES OF OCCUPATIONAL
EXPOSURE TO RADIATION
HISTORY OF NUCLEAR TESTING ON
SOLDIERS
 Nuclear testing was carried out on Christmas Island in the
South Pacific
 Soldiers were deliberately exposed to radiation from
nuclear bomb testing at Christmas island and a few
other islands
 Countries wanted to study how the bombs would affect
bodies and minds of soldiers
 Test carried out not only by the British
government, but France and US
ENVIRONMENTAL SOURCES OF
RADIATION
 Radiation is part of nature
 All living creatures, from the beginning of time, have been, and are still being,
exposed to radiation
 Sources of radiation can be divided into two categories:
 Natural Background Radiation – terrestrial, cosmic, internal, radon
 Man-Made Radiation
 Lantern mantles, Medical diagnosis, Building materials, Nuclear power
plant, Coal power plants, Tobacco, Phosphate fertilizers
 Student activity: Guess which sources contribute the most to manmade radiation exposure
ANNUAL AVERAGE DOSE (MILI ROENTGEN
EQUIVALENT DOSE)
MAN-MADE SOURCE
Reference: Science, Society, and America's Nuclear Waste
70
60
50
40
30
25
0.2
0.15
Coal Plant
Medical
0
0.4
Lantern Mantles
4
Nuclear Plant
7
Phosphate Fertilizer
10
Building Material
20
Smoking (perWeek)
mR\EM/yearr
60
DEFINITION AND TYPES OF RADIATION
Radioactive atoms are unstable and to become stable,
release energy
 Radiation - release of particles or electromagnetic waves as
the radioactive atom decays
Ionizing and non-ionizing radiation
 Ionizing are radiation that can cause the atom that it hits to
become ion or charged (Alpha, beta, gamma, neutron, X-ray,
UV)
 Non-ionizing radiation travelling in waves (light, heat and radio
waves) carrying enough energy to excite atoms, but not
sufficient to cause ion formation
ELECTROMAGNETIC SPECTRUM
WAVELENGTH RANGE
IONIZING RADIATION - THREE MAIN
TYPES OF RADIATION
Three main types of radiation are alpha, beta, and gamma. Alpha and beta
are particles emitted from an atom. Gamma radiation is short-wavelength
electromagnetic waves (photons) emitted from atoms.
ALPHA RADIATION
 A heavy atom with positive charge – nucleus ejects 2 protons and
2 neutrons
 Release by elements such as uranium and thorium, polonium
 Able to penetrate skin surface and can be stopped by a piece of
paper
 If it is taken by the body through inhalation, food or drinks, body
tissues will be directly exposed
 Example of ingestion of Po-210 - Alexander Litvinenko a former officer
of the KGB, who fled from court prosecution in Russia and received
political asylum in the United Kingdom
 2006, he was ill with diarrhoea and vomiting after having tea at a hotel
 He was poisoned, Po-210 was sprayed in his teapot/teacup
BETA RADIATION
Consist of electrons or negative charge – produced
when neutron transformed to a proton
 Penetrating power is higher than alpha and smaller than
alpha
 Able to penetrate water as deep as 1-2 cm
 Can be stopped by a piece of aluminium of a few mm
thick
One of exposure source – tritium in nuclear
explosion test dropping
GAMMA RADIATION AND X-RAY
 Gamma is an electromagnetic radiation
No mass or charge, very high energy levels
Produced when nuclei are achieving more stable low energy state
Often emitted after alpha or beta emission
Has a very high penetrating power
Release by radioactive elements such as Co-60 which was used in
cancer treatment
 Can penetrate body and biological tissue but is completely absorbed
by a 1 m thick concrete





 X ray are similar to gamma but less energy
 Generated by cosmic origin or machine
 Used for medical purposes
NON-DESTRUCTIVE TESTING FOR
INDUSTRY USE – GAMMA AND X-RAY
Industrial radiography is the use of ionizing
radiation to view objects in a way that cannot be
seen otherwise
Industrial radiography has grown out of
engineering, and is a major element of nondestructive testing
It is a method of inspecting materials for hidden
flaws by using the ability of short x-ray and gamma
ray to penetrate various materials
RADIATION EMISSION MEASUREMENT
 Radiation emission rate
 Emission rate=radioactive decay or λ
 Is the time required for one half of the atoms of a radioisotope to
decay spontaneously
 This concept is used in Curies (Ci) and Roentgens (R) standards
e.g. iodine-132 2.4 hour, Carbon-14 5700 y
 Unit radiation measurement for tissues
 RAD – radiation absorbed dose – amount of energy released in
tissue from radioactive source
 LET – linear energy transfer – rate of energy lost per unit of
distance upon exposure to radiation
 Alpha radiation – high LET – penetration is short distance and
energy lost quickly
 REM – Roentgen Equivalent Dose – takes into account RAD and
LET
RADIATION EFFECTS ON BIOLOGICAL
TISSUES
Radiation can cause




Produce free radicals
Break chemical bonds
Produce new chemical bonds and cross-linkage between
macromolecules
Damage molecules that regulate vital cell processes
 Direct action is based on direct interaction between radiation particles
and complex body cell molecules, (for example direct break-up of DNA
molecules)
 Indirect action depends heavily on the energy loss effects of radiation
in the body tissue and the subsequent chemistry
 Immediate effects (radiation sickness)
 Long term effects which may occur many years (cancer) or
several generations later (genetic effects)
THE TIME SCALES FOR THE SHORT AND LONG TERM
EFFECTS OF RADIATION ARE SYMBOLIZED IN THE FIGURE
OH radical attacks
DNA-molecule.
Energy loss causes
ionization and breakup of simple body
molecules
Resulting biological damage
depends on the kind of
alteration and
can cause cancer or long-term
genetic alterations
ENZYMATIC REPAIR
TYPES OF INJURIES
 2 types of effects
I.
Somatic effects --- injury to individual
II.
Genetic effects ----- changes passed on the future
generations
 Degree of injury depends on
I.
Total dose
II.
The rate of which the dose is received
III.
The kind of radiation
IV.
Body part receiving it
- if received slowly for ever a long period of time need to have larger dose to have the same degree
of injury compared to total received in short
period.
-
Some small doses -  effect if given once but if
continued long enough - shorten life span,
produce abnormalities
- ‘latent period’ - time between the exposure to the
first sign of radiation damage in term of genetic
effect - defective genetic material - birth defects
- The larger the dose – the shorter the latent period
RADIATION AND HEALTH
 Lethal dose levels
 300 RADs – half of people died within 60 days
 650 RADs – few hours to few days
 Symptoms of radiation sickness – 50-250 RADs
 Immediate
Nausea, vomiting
 2-14 days
Diarrhoea, loss of hair, sore throat, inability for blood to clot, heamorrhaging,
bone marrow damage
 Delayed effects
Leukemia, cataracts, cancer, life span decreased
 Other effects
Reproductive effects – sterility, miscarriages, still births, early infant
deaths
RELATIVE SENSITIVITY OF BODY TISSUE
TO RADIATION
High sensitivity
 Esophagus
 Thyroid
 Liver
 Lung
 Pancreas
 Breast
 Ovaries
 Colon
 Bone marrow
Moderate sensitivity
 Brain
 Lymphatic tissue
Low sensitivity
 Spleen
 Kidney
 bone
LAWS AND EXPOSURE LIMIT
 Atomic Energy Licensing Act 1984
 Establishes standards on liability for nuclear damage and matters connected to it
 It lays responsibility to the licensee to provide protection of health and safety of the
workers from ionizing radiation such as monitoring of exposure to ionizing radiation,
providing approved personnel monitoring devices and providing medical examination
to exposed workers
 In Radiation Protection (Basic Safety Standards) Regulations 1988 the standards for
annual dose limit for whole body and partial body exposure of a worker to ionizing
radiation are also stipulated.
 For example the annual dose limit for the whole body exposure of a worker is 50
millisieverts (mSv)
 Specific group of workers are prohibited to work in an area that expose them to
ionizing radiation including pregnant women, nursing mothers, and person under
sixteen years of age (Malaysia 1988)
CONTROL OF IONIZING RADIATION
 Radiological controls can be grouped into two
broad categories - engineered controls and
administrative controls
 The basic control method are associated with:
I) TIME
II) DISTANCE
III) SHIELDING
TIME
- The longer the exposure, high chance of radiation injury
- If reduce exposure time by half, the dose received also
reduce by half
Time
Dose
1 hr
100 millirems
2 hrs
200 mR
4 hrs
400 mR
8 hrs
800 mR
 If we know the dose rate exposure could be calculated
Max. acceptable
Instance exposure rate = 2.5 mR/h  40 hrs - 100
mR
But if you want to achieve 100 mR, with exposure
rate = 25 mR/h, = 4 hrs of exposure only - 100 mR
This is important so that job schedule can be
divided and no worker exceed the limit
DISTANCE -  emitter and radiation levels at various
distances from the source
Isotope
0.3 m
0.6 m
1.2 m
2.4 m
4.8 m
Cobalt – 60
14.5
3.6
0.9
0.23
0.145
Radium –
226
9.0
2.3
0.6
0.14
0.09
Cesium 137
4.2
1.1
0.26
0.07
0.042
Iridium –
192
5.9
1.5
0.4
0.09
0.059
Thulium
–170
0.027
0.007
0.002
0.0004
0.00027
SHIELDING
• Commonly used to protect against radiation and
radioactive sources
• Mass of protection high to low radiation exposure
• E.g: use water and graphite because ability to absorb
ionization
SHIELDING
- Shield - may be in forms of :i)
cladding on radioactive material
ii)
container - heavy walls and cover
iii) thick high density concrete wall
iv) deep layer of water for shielding
NON-IONIZING RADIATION
 NIRs usually interact with tissue through the generation of heat
 There are still much uncertainties about the severity of effects of
both acute and chronic exposure to various types of NIRs
 General biological effects
 Cause thermal motion of molecules in tissues and heat is
generated
 Temperature increases and cause burns, cataracts and birth
defects
 Alteration of normal metabolic functions
 DNA damage – chromosome breaks, increases in incidence of
skin cancer
NON-IONISING RADIATION
HEALTH EFFECTS OF NIR
SOURCES OF ULTRA VIOLET
Main source is the sun
Mercury discharge lamps -low pressure lamps
produce mainly UV C and high pressure lamps
produce emissions in UV B and UV C
Some fluorescent tubes
Electric arc welding
SOURCES OF INFRA-RED
LIGHT
 Can be divided into
Near IR
700nm - 1400nm
Far IR
1400nm - 1mm
 Everything emits IR
Sun
Furnaces
IR lamps
Hot glass
CONTROL OF UV AND IR
 UV is fairly easily controlled using
 Shields
 Enclosures
 Clothing
 Goggles
 Protective creams
 Main possible controls include for IR
 Shielding
 Goggles
 Clothing
THANK YOU FOR YOUR ATTENTION
Suggested reading
Monitoring programs – personal, area and
environmental monitoring for radiation