1. 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

2. 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

3. 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

4. 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

5. Sources of occupational exposure to radiation

6. 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

7. 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 man- made radiation exposure

8. Annual Average Dose (mili roentgen equivalent dose) man-made source

9. 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
In general- radiation is release of energy from an atom
Non-ionizing radiation – the energy released in waves (light, heat and radio waves) strikes an atom, but leaves it the way it is without changes

10. Electromagnetic spectrum wavelength range

11. 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.

12. 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 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

13. 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

14. 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

15. 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 non- destructive 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

16. 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 hour, Carbon 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

17. 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)

18. The time scales for the short and long term effects of radiation are symbolized in the figure
OH radical attacks DNA-molecule.
ENZYMATIC REPAIR
Energy loss causes ionization and break-up of simple body molecules
Resulting biological damage depends on the kind of alteration and can cause cancer or long-term genetic alterations

19. Types of injuries 2 types of effects
Somatic effects --- injury to individual
Genetic effects changes passed on the future generations
Degree of injury depends on
Total dose
The rate of which the dose is received
The kind of radiation
Body part receiving it

20. -   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

21. 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 – 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

22. Relative sensitivity of body tissue to radiation
High sensitivity
Esophagus
Thyroid
Liver
Pancreas
Lung
Breast
Ovaries
Colon
Low sensitivity
Bone marrow
Spleen
Moderate sensitivity
Kidney
Brain
bone
Lymphatic tissue

23. 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)

24. 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

25. 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

26. If we know the dose rate - Max. acceptable exposure could be calculated
Instance exposure rate = 2.5 mR/h  40 hrs mR
But if you want to achieve 100 mR, with exposure rate = 25 mR/h, = 4 hrs of exposure only mR
This is important so that job schedule can be divided and no worker exceed the limit

27. 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
0.059
Thulium –170
0.027
0.007
0.002
0.0004

28. 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

29. 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

30. 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

31. Non-ionising radiation

32. Health effects of nir

33. 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

34. Sources of Infra-red light
Can be divided into
Near IR nm nm
Far IR nm - 1mm
Everything emits IR
Sun
Furnaces
IR lamps
Hot glass

35. Control of UV and IR UV is fairly easily controlled using Shields
Enclosures
Clothing
Goggles
Protective creams
Main possible controls include for IR
Shielding

36. Thank you for your attention
Suggested reading
Monitoring programs – personal, area and environmental monitoring for radiation