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Physical hazard III: Radiation and Heat

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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

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