Radiation

Radiation is energy that is transmitted in the form of waves or particles. Scientists divide radiation into two broad categories –ionising radiation, and non-ionising radiation. 

Ionising radiation is a proven hazard because it has enough energy to break apart molecules such as DNA which may, in time, lead to cancer. Non-ionising radiation does not have enough energy to cause such damage. 

We encounter ionising radiation constantly.  It occurs naturally in rocks and soil, in the food and water we eat and drink, and bombards the earth’s atmosphere from outer space.  It is produced artificially, and widely used in medicine, industry and research.  It is used in X-rays, in radiotherapy to treat cancers, in smoke detectors, and in many industrial processes.  The production of electricity from nuclear power generates ionising radiation as a by-product.

Non-ionising radiation is generated by everyday energy sources, including light, heat, TV and radio signals, mobile phone signals, microwaves, and electro-magnetic fields associated with power lines.  The Department of the Environment, Climate and Communications are currently responsible for the health effects of non-ionising radiation including electromagnetic fields. 

Ionising radiation has been with us since the birth of the universe.  Even if we could avoid artificially created radiation, we would still be exposed continuously to natural sources of ionising radiation.  Because it is present in the soil, we consume it in our food and water.  One type of natural radionuclide is radon gas that rises up from the ground  and we inhale it from the air when we breathe. We cannot avoid exposure to ionising radiation – but we can minimise our exposure to excessive dose from it. 

Ionising radiation transfers some of its energy to the atoms and molecules of the body, liberating electrons and so breaking molecular bonds. The effects of ionising radiation on the human body depend on the quantities of ionising radiation received. 

High doses  destroy human cells at a faster rate than they can be replaced by natural regeneration in the body. This is called necrosis and can cause radiation sickness leading to serious illness and death, but it can also be applied to small volumes in the body to kill diseased cells such as cancers. Radiation sickness has been observed in workers exposed by accident to industrial sources, and people who spent time close to the site of nuclear accidents, such as the fire-fighters in the Chernobyl accident - Low doses above background levels increase the risk of cancer. The chemical changes caused by ionisation damage tissues, which do not always repair themselves properly. In time, poorly repaired tissue may become cancerous. For most people, estimating increased risk of cancer from radioactivity is difficult to distinguish from other sources of risk such as chemical pollution. 

Where people are known to have been exposed to greater levels of radioactivity, their history of exposure may be used to estimate the increased risk cancer decades later. This has been applied to accident survivors, historic nuclear workers, and people exposed to elevated levels of radon either in their workplaces or homes.