Occupational Health EOH 3202Dr Emilia Zainal Abidin

Environmental & Occupational Health

Faculty of Medicine and Health Sciences

University Putra of Malaysia

PHYSICAL HAZARD III: RADIATION AND HEAT

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 LECTUREUnderstand the sectors and occupations

associated with radiation useUnderstand the fundamental points related to types

of radiationExplain the effects of radiation on the cells and

other related health effectsDescribe the control and management steps in

occupational setting

TYPE OF SECTORS ASSOCIATED WITH RADIATION USEScience

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 man-made radiation exposure

ANNUAL AVERAGE DOSE (MILI ROENTGEN EQUIVALENT DOSE)

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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 decaysIonizing 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 RADIATIONConsist 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

thickOne 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-RAYIndustrial 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

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 TISSUESRadiation 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

Energy loss causes ionization and break-up of simple body molecules

OH radical attacks DNA-molecule.

Resulting biological damage depends on the kind of alteration andcan cause cancer or long-term genetic alterations

ENZYMATIC REPAIR

TYPES OF INJURIES 2 types of effectsI. Somatic effects --- injury to individualII. Genetic effects ----- changes passed on the future

generations Degree of injury depends onI. Total dose II. The rate of which the dose is receivedIII. The kind of radiationIV. 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 daysDiarrhoea, loss of hair, sore throat, inability for blood to clot, heamorrhaging, bone

marrow damage

Delayed effectsLeukemia, cataracts, cancer, life span decreased

Other effectsReproductive effects – sterility, miscarriages, still births, early infant deaths

RELATIVE SENSITIVITY OF BODY TISSUE TO RADIATIONHigh sensitivity

Thyroid Lung Breast Colon Bone marrow

Moderate sensitivity Brain

Lymphatic tissue Esophagus Liver Pancreas Ovaries

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)  TIMEII) DISTANCEIII) 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 - Max. acceptable exposure could be calculated

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

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

DISTANCE - emitter and radiation levels at various distances from

the source

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 materialii)    container - heavy walls and coveriii)   thick high density concrete walliv) 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 sunMercury discharge lamps -low pressure lamps

produce mainly UV C and high pressure lamps produce emissions in UV B and UV C

Some fluorescent tubesElectric arc welding

SOURCES OF INFRA-RED LIGHT

Can be divided intoNear IR 700nm - 1400nmFar IR 1400nm - 1mm

Everything emits IRSunFurnacesIR lampsHot 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 ATTENTIONSuggested reading Monitoring programs – personal, area and

environmental monitoring for radiation