Ionising radiation constitutes a form of energy that is emitted by atoms, travelling as either electromagnetic waves (gamma or x-ray) or as particles (alpha, beta, neutron, positron). It is the transfer of energy from place to another.
There are six main types of ionising radiation: alpha, beta, positron, neutron, gamma and x-ray. Alpha, beta and positron radiations are all charged particles, whereas neutrons are uncharged particles.
Gamma rays and x-rays are non-particulate (no mass) they are just pure energy or ‘quanta’.
Whether particulate or not particulate, ionising radiation by definition generates ‘ions’ charged particles as energy is transferred and atomic structure disrupted.
Atoms are made up of a nucleus containing protons (positively charged particles) and neutrons (neutrally charged particles). Electrons (negatively charged particles) surround the nucleus (like planets orbiting the sun). A stable atom has equal numbers of protons, electrons and neutrons.
The energy emitted from a source of ionising radiation can disrupt the stability of atoms in our cells creating ‘ions’ – charged particles. Charged particles are more chemically reactive in our cells, so ionising radiation can cause damage either directly or indirectly to our cell structures, importantly our DNA.
Sources of ionising radiation:
There are two categories of ionising radiation sources: natural radiation and artificial radiation. We are surrounded by natural sources of radiation. These natural sources can be divided into three groups:
- Cosmic Radiation – sources of radiation that come from the sun or outer space.
- Terrestrial Radiation – radiation sources in the soil, water and vegetation. The main isotope for terrestrial radiation is uranium.
- Internal Radiation – all food and drink contain trace quantities of natural radioactivity.
Approximately 84% of our annual average exposure to ionising radiation is from natural sources. The remaining 16% comes from artificial sources, predominately from medical exposures with all other artificial sources contributing less than 0.5% of the average annual exposure.
Artificial ionising radiation uses:
- Gamma rays can be used for sterilising medical equipment and killing cancer cells
- Alpha emitters can be used in smoke detectors
- Beta emitters can used as tracers
- X-rays – the most identifiable use of x-rays, being diagnostic imaging, assessment of bones / teeth. Other uses include: cargo / luggage scanning; detecting cancer; inspection in industrial structures; security checking; inspection of historical artefacts and many more.
Effects of ionising radiation
An important risk to consider is ‘exposure’ to ionising radiation, which can have harmful biological effects. The nature and severity of the biological effects of ionising radiation, and how long it takes for them to appear, depends on the type of radiation; the amount of radiation absorbed; the rate at which it was received, and the organ or tissue affected.
For low levels of exposure, the biological effects are so small they can be undetectable. The body is able to repair damage from radiation, chemicals and some other hazardous materials. Living cells exposed to radiation could:
- repair themselves leaving no damage
- die and be replaced
- incorrectly repair themselves, resulting in a change or mutation
Exposure to high radiation doses can lead to a range of physiological affects, including skin burns, damage to the gastro-intestinal, cardiovascular, or nervous systems, and in cases of exceedingly high exposure it can be fatal.
The biggest health concern of the general public, when considering radiation exposure, is cancer. Epidemiological studies provide the primary data on the carcinogenic effects of radiation and evidence suggests ionising radiation is generally a weak universal carcinogen. The amount of ionising radiation most people are exposed to every day is minimal, resulting in a low risk of cancer development due to this exposure.
Regulations
The use of ionising radiation is regulated by the HSE via the Ionising Radiations Regulations 2017 (IRR17). Employers, using ionising radiation, are legally required to comply with these regulations in order to protect both their employees and the general public.
There are two legal appointments Employers using ionising radiation must make:
- a Radiation Protection Adviser – SGA can act in this capacity for you. See our Radiation Protection Advice page for further details.
- A Radiation Protection Supervisor – an internal appointment, and sufficient RPS’s must be appointed in order to provide continuity of cover. An RPS must have appropriate and adequate initial and ongoing training. See our Training page for further details.
