What is Radiation?
Radiation [or Electromagnetic Radiation (EMR), is energy in a wave form. It is described by its frequency (measured in hertz) and its wavelength (measured in metres). Sometimes it is referred to as Electromagnetic Energy (EME).
An Electromagnetic Field (EMF) is made up of an electric field and a magnetic field. Electrical fields occur whenever there is a voltage - the higher the voltage, the stronger the electric field. These are measured in volts per meter (V/m). Magnetic fields occur where there is a current - the greater the current, the stronger the magnetic field. A magnetic field only exists when the current is switched on. Magnetic fields are measured in units of gauss (G). Both the fields become weaker the further away from the source.
EMFs occur naturally and also come from sources created by human activity. Natural EMFs comes from sources such as the earth's own magnetic field, electrical storms, the sun and even the body's own essential electric activity. These natural EMFs are of a very low strength. Manufactured EMFs, which have higher frequencies, come from overhead power lines, electric wiring in buildings, radio towers, laser tools, and so on. It is these that are of more concern.
Radiation can potentially interfere with the body and cause harm. Frequency and wavelength are used to classify different types of radiation. The electromagnetic spectrum spans a wide range of frequencies and wavelengths, from extra-low frequency (for example from the electric power supply) to extremely high frequency (X-rays).
EMR can be either ionising or non-ionising:
Non-ionising Radiation
Non-ionising radiation is made up of low frequency, long wavelength and low energy electromagnetic waves. It includes ultraviolet light, visible light, infrared light, radiofrequency, very-low and extra-low frequency radiation. Manufactured sources include photocopiers; welding equipment; TV, radio and telecommunication transmission towers; mobile phones; microwaves; visual display units; power lines.
| Non-ionising Radiation Spectrum | ||||||
|---|---|---|---|---|---|---|
| Long waves/low frequency ---------> shorter waves/higher frequency | ||||||
| Extra Low(ELF) | Very Low(VLF) | Low | Radio Frequency | Infrared(IR) | Visible Light | Ultraviolet |
| TV & computer screen fields, electric power supply, communication services | TV & Radio transmissions, Microwave, mobile phones | Radar | Document copying, Electric welding, sunlight | |||
| Lasers | ||||||
There is a separate page on this website with more information on non-ionising radiation, including health effects and an Action Plan for OHS Reps.
Ionising Radiation
This radiation is high frequency and high-energy and can penetrate the body. It has enough energy to break up atoms and molecules as it passes through the body (ie, it can cause ionisation). This radiation includes cosmic rays, X-rays and gamma rays, as well as particles emitted from radioactive materials. Manufactured sources include industrial and medical radiography and testing equipment.
| Ionising Radiation | ||
|---|---|---|
| Very short wavelengths, very high frequency | ||
| Alpha & Beta Particles | X - Rays | Gamma Rays |
| Lasers (lower end), industrial and medical radiography and testing equipment | ||
There is a separate page on on this website with more information on ionising radiation, including health effects and an Action Plan for OHS Reps.
Measurement
With lower frequency, longer wavelength radiation, the dose is often measured in terms of the strength of the field (in Gauss or milliGauss). With higher frequency radiation, the dose is described in terms of energy absorbed by the body (in Sieverts).
This means that units of measurement vary with the different types of radiation, and that there is no single instrument that can measure the intensity of EMR right across the spectrum.
What are the health effects of exposure to Radiation?
The health effects of radiation vary with the type of radiation and the dose received. Higher frequencies can cause changes to the body's cells. As the frequency decreases, there are health effects related to the heating of body tissues - but there is growing evidence that there are negative health effects which are not related to heating.
Some health effects of radiation (particularly ionising radiation) are well known and researched. This is partly due to nuclear warfare and radiation accidents. The health effects of exposure to ionising radiation are serious, including cancer and death.