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.  

Yes, there is a scientific consensus that ionising radiation can trigger changes in human tissue that can, in some circumstances, mutate into cancer.  The risk rises in line with increased exposure to ionising radiation, in the same way that the risk of skin cancer grows with increased exposure to the sun’s rays. 

No. For a given amount of radiation, there is no difference between the harm caused by natural or artificial radiation.

Radon is the second biggest cause of lung cancer in Ireland and worldwide after tobacco smoking.  Radon is responsible for around 300 lung cancer cases in Ireland every year. 

Yes.  Like tobacco smoke, radon is classified as a Class A carcinogen.  The combination of tobacco and radon magnifies the risk of lung cancer. Smokers account for approximately nine out of ten radon-linked lung cancer cases in Ireland.  The radon risk to an active smoker is 25 times greater than to a lifelong non-smoker. 

X-rays are a vital tool in medicine, ensuring the precise diagnosis of certain illnesses.  The radiation dose from a simple X-ray is extremely small and therefore the risk is correspondingly small. 

During a chest X-ray, the radiation dose received is comparable to two days normal background radiation exposure.  Therefore, the risk is very small and can be justified on the basis that an illness may go undiagnosed without the X-ray and may have a higher risk. 

The radiation dose from a chest CT scan is roughly the equivalent of that received from 250 chest X-rays.  Although substantially higher than the dose from a simple X-ray, the dose from a CT scan is still within acceptable risk limits.  The procedure will only be carried out if your consultant judges that the benefits outweigh any risk. 

If the procedure is justified on medical grounds, the simple answer is no.  Pregnant women should be especially cautious, and should discuss the procedure in advance with a medical practitioner to ensure that any risk to the pregnancy is minimised. 

Radioactivity has been monitored in the Irish Sea since 1982.  The levels found would have no significant health effect on the public whether sailing, swimming, or diving in the Irish Sea.  On-going monitoring has shown that discharges of radioactivity have diminished over time.  

Yes.  The consumption of fish and shellfish is the main way the Irish public are exposed to radiation from Sellafield.  EPA constantly monitors radioactivity in seafood from the Irish Sea. For people who eat very large quantities of fish and shellfish, we have calculated the radiation doses and found that they represent less than one four thousandth of the total annual average dose received by someone living in Ireland.  

The earth is permanently exposed to a stream of atomic particles, which originate from the solar system and beyond.  Frequent flyers, particularly airline crew on long-haul routes, can receive radiation doses comparable with those who work directly with ionising radiation.  Air operators are legally obliged to evaluate the risk to air crew. For casual flyers, any health risk from air travel is likely to be low. 

Based on available dose assessments, it is generally safe to visit these countries.  In the area around Chernobyl itself, the more heavily contaminated areas have been sealed off to the public.  If you are in these countries for a prolonged stay it may be wise, as a precautionary measure, to avoid eating mushrooms, berries, fresh-water fish and game as these foodstuffs can concentrate radioactivity.