Medical scans, air travel and nuclear industries
What is ionising radiation?
Ionising radiation is a type of radiation called ‘high energy’. The high energy that ionising radiation has means it can affect our cells, including mutating DNA which can lead to cancer. This is different to non-ionising radiation, which has less energy.
There are different types of ionising radiation, including gamma rays and x-rays.
It’s important to remember that we are exposed to radiation from natural sources every day. Radon gas from the earth’s crust contributes the largest amount of natural radiation to most people living in the UK. Cosmic rays from the sun, stars and outer space, natural radiation from the food we eat, the water we drink and the ground we walk on, also contribute to our natural exposure every day. Watch our video to find out more.
To help avoid the potential health effects of ionising radiation, any man-made exposures are tightly regulated.
Can X-rays and medical imaging increase the risk of cancer?
Medical x-rays and other types of imaging are very important to help diagnose different illnesses, including cancer. Some types of imaging, including X-rays and CT scans (Computed Tomography) use ionising radiation. The health risks from the radiation the imaging equipment uses are generally very low, and usually outweighed by the benefits of getting the right diagnosis and appropriate treatment. Nevertheless, there is evidence that exposure to diagnostic x-rays slightly increases the risk of getting diagnosed with cancer many years or decades later. About 6 in 1,000 cancers in the UK are caused by diagnostic radiation.
The dose received from medical imaging is usually less than what we'd be exposed to naturally over a few days or years (depending on the type of imaging technique used and the part of the body being scanned). Although medical x-rays add some extra radiation on top of natural radiation exposure, they also bring great benefits to patients. But unnecessary x-rays or medical scans should be avoided.
Common types of medical x-rays
There are different types of medical imaging tests using x-rays that you may come across:
- Radiography to look at broken bones or your teeth and chest
- Mammography to screen for breast cancers
- Computed tomography (CT) to detect different diseases, including some cancers
- Fluoroscopy, such as barium x-rays, to look at your digestive system
How much radiation does an x-ray give out?
These tests all involve different amounts of radiation. The level of risk from the radiation you receive will depend on:
- The type of scan you have – for example a chest x-ray poses a lower risk than a CT scan of the chest
- The area of the body – for example dental x-rays pose a lower risk than chest x-rays
- Age – young patients are at more risk. Unborn babies are also at higher risk so you should tell your doctor if you’re pregnant
- Gender – women have a slightly higher lifetime risk of developing radiation-induced cancers than men
In the UK, the Public Health England monitors the amount of radiation we receive from x-rays and makes sure they are as safe as possible. You can find out more about radiation from medical x-rays on the Public Health England website.
Are there ways to limit radiation if I need an x-ray?
When possible, your doctors will recommend other types of imaging that don’t use radiation, for example using ultrasound or magnetic resonance imaging (MRI scan). But in some cases an x-ray is the best way to do the job.
If you are concerned about having a large number of x-rays, you should talk to your doctor about it. You should also tell your doctor of previous x-rays you may have had. They may be useful for diagnosing, managing or treating your current condition. And they may mean that you do not need to have more x-ray tests.
What are the risks of commercially available body scans?
Some commercial companies offer ‘full body’ CT and PET (positron emission tomography) scans to the public. These are available to people who are willing to pay privately, even if the scans aren’t recommended by their doctor and aren’t medically necessary. These scans have risks, and when they are not needed or done on people with no medical symptoms, they are likely to do more harm than good.
A ‘full body’ PET CT scan (in which a PET and a CT scan are done at the same time) uses more than 1000 times the amount of radiation of a single chest x-ray. This may be necessary for people with a genuine medical need. But for healthy people without symptoms, the risks generally outweigh the benefits. And while scans are helpful for finding out what is causing a symptom, in people with no symptoms these scans can flag up harmless abnormalities, or conditions which would never have caused any problems. So they may lead to unnecessary tests and treatment.
Can air travel increase the risk of cancer?
Travelling by plane is a safe way to travel and is unlikely to affect your risk of cancer.
Does air travel expose people to radiation?
The Earth receives a lot of ‘cosmic radiation’ from space, but our atmosphere shields us from most of this. The atmosphere thins the higher you get, so someone flying in a plane would receive more cosmic radiation than someone on the ground.
A passenger would get a very small extra amount of radiation, but the low level of radiation that they would experience is very unlikely to seriously affect their cancer risk, even if they were a frequent flyer.
Do airport body scanners use radiation?
Body scanners are used in many airports across the UK and abroad. There are two types of scanner in the UK. One type uses millimetre radio waves that can “see” through clothing. The other type uses a very low dose of ionising radiation. Neither type has been shown to pose a risk to people’s health.
The first type of scanner uses radio waves, which are a form of non-ionising radiation that does not cause health effects at the low doses given off by airport scanners. Read more about non-ionising radiation, such as that used in mobile phones, wifi and power lines here.
The second type uses ionising radiation, which in high doses can be harmful. But the levels used in airport scanners are about 100,000 times lower than what an average UK person would naturally be exposed to each year. This dose is so low that it makes no noticeable difference to a person’s risk of cancer.
Can living near a nuclear power plant increase the risk of cancer?
So far, the evidence shows that it is unlikely that people who live near nuclear power plants are at a higher risk of cancer.
What does the evidence say?
Most of the evidence to date comes from small studies looking at childhood cancers, particularly childhood leukaemia. Larger studies on this topic are difficult to do, as there aren’t that many children living near nuclear power plants who develop leukaemia or other cancers.
Recently, a group of researchers combined the evidence from several small European studies, showing that overall there is no increased risk for those aged under 15 years living within 25km of a nuclear power plant.
But for children under 5 who live closer (within 5km) to a nuclear power plant the evidence is more mixed. Some studies found a small but increased risk of leukaemia, while others did not. This may have to do with different study designs, differences between the countries in which the studies were done, or other factors that could influence the risk of leukaemia (such as infections).
Based on the evidence available at the moment, the government’s Committee on Medical Aspects of Radiation in the Environment (COMARE) has concluded that “there is no evidence to support the view that there is an increased risk of childhood leukaemia and other cancers in the vicinity of nuclear power plants in Great Britain”.
Nuclear disasters and cancer
Nuclear disasters are events that may expose populations to higher levels of ionising radiation. Examples include the nuclear power plant accidents in Chernobyl and Fukushima, as well as the nuclear bombings of Hiroshima and Nagasaki.
Studies of survivors of these events have found that the risk of developing thyroid cancer is higher in these populations, particularly in those who were aged less than 18 at the time of the disasters. But because cancers usually take a number of years to develop after radiation exposure, it’s difficult to say with certainty which cancers were caused by the extra radiation. And there is also evidence that – at least in the case of Fukushima – increased screening efforts can lead to the detection of more thyroid cancers, including cancers that weren’t caused by radiation and that would never have caused harm in someone's lifetime – this is called overdiagnosis.
There is no evidence that the risk of other cancer types rises considerably by exposure to ionising radiation from nuclear accidents in people in the general population – mostly because the doses received are too low to have major effects. But there is some evidence from Chernobyl that clean-up workers, who were exposed to very high levels of radiation, have a higher risk of some types of cancer, particularly leukaemia. For survivors of the nuclear bombings, risk of some types of cancer is also increased.
Studies looking at the long-term effects of nuclear disasters, particularly the Fukushima Daiichi Nuclear Power Plant accident in 2011, are still ongoing.