Radiation, pollution and cancer risk
Can radiation and pollution increase cancer risk?
Outdoor air pollution and diesel exposure
Air pollution is linked to a slightly increased risk of cancer. Sources of air pollution range from those caused by human activity, such as vehicle fumes and smoke from burning fuels, to natural pollutants such as desert dust and radon gas.
In particular, a specific type of pollutant called particulate matter, which is in diesel and petrol exhaust fumes (and tobacco smoke), has been shown to increase the risk of cancer, especially lung cancer. Levels of particulate matter and other air pollutants are relatively low in most of the UK, though levels are higher in some cities, and they can vary according to factors such as traffic density and weather conditions.
However, it’s important to remember that smoking – including breathing second-hand smoke – increases your cancer risk much more than air pollution does. Not smoking, followed by maintaining a healthy weight through keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
The main sources of indoor air pollution are tobacco smoke and radon gas. Exposure to tobacco smoke in your home, including passive smoking through exposure to other people’s smoke, increases your risk of cancer.
Radon is a naturally occurring radioactive gas which is associated with a slightly increased risk of lung cancer. In areas where the gas occurs naturally in high concentrations (such as south-west England and parts of Wales), it can build up to high levels.
In the UK, if you live in an area with high levels of radon, guidance is available from UK Radon on how you can reduce the amount of radon exposure to a safe level. However, exposure to radon is associated with a very small amount of lung cancer cases – estimated at only 3% in the UK – in comparison with the number caused by smoking. Most of these are actually caused jointly by radon gas and smoking – smokers living in areas with high levels of radon gas are more than 20 times more likely to develop the disease. Not smoking, followed by maintaining a healthy weight through keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
Some types of radiation can cause us harm, including raising the risk of cancer, if we are exposed to too much of it. Ionising radiation has enough energy to damage DNA and increase the risk of cancer. Non-ionising radiation has lower energy and in most cases has not been found to increase the risk of cancer, unless exposed at much higher levels than experienced in daily life. However, some technologies are relatively new, or the ways in which they are used have changed, and in these cases there is not yet enough data for scientists to be certain about the level of cancer risk.
Radiation at the levels experienced by most people in most situations carries only a very small health risk, if any. Not smoking, followed by maintaining a healthy weight through keeping active and eating a healthy diet, are the most effective ways to reduce your cancer risk.
Ionising radiation: naturally occurring radiation
Naturally occurring radiation is ionising radiation given off by natural sources (see radon), but the vast majority of people are rarely exposed to amounts high enough to cause damage.
Our main exposure to ionising radiation is through diagnostic medical X-rays and other types of body imaging such as radiography. It is estimated that about six in 1,000 cancers are associated with diagnostic radiation but it’s important to remember that, while it’s worth avoiding unnecessary X-rays or scans, medical X-rays are generally used where they are the best solution and the need for the investigation outweighs the small potential risk. Where possible, doctors will recommend other types of imaging that don’t use radiation (such as ultrasound or an MRI scan). Talk to your doctor if you are concerned about having an X-ray, and tell them about any previous ones you may have had.
In the UK, Public Health England monitors the amount of radiation given off by X-rays to ensure they are as safe as possible.
Most airports now use body scanners as part of their security measures. These scanners use either radio waves or ionising radiation, but in both cases at such small doses that they do not raise your cancer risk.
Mobile phones are an example of where there is not yet enough data to draw strong scientific conclusions. Some smaller studies have found a possible link between use of mobile phones and cancer, but these studies were not considered of good enough quality to be certain of a true effect. The largest study carried out so far has found no link. However, mobile phones have only been in use in relatively recent years, so there has not yet been enough research into their long-term effects.
The radiofrequency electromagnetic radiation that mobile phones give off is very weak and cannot directly cause cancer. In 2012, an independent report concluded that there is no convincing evidence that health risks could be caused by exposure to radiofrequency fields, including those from mobile phones, mobile phone masts and base stations, at levels within international guidelines.
Studies in this field are continuing but, in the meantime, most governments recommend avoiding heavy mobile phone use by, for example, using a hands-free set and keeping calls short. And as there has not been enough research into the effects of mobile phone use on children’s health, it is advised that children under the age of 16 should only use mobile phones for essential calls.
The type of radiation given off by power lines is low-frequency electromagnetic radiation, which does not have sufficient energy to damage cells and thereby cause cancer. However, some studies have suggested a link between exposure to magnetic fields and a small increase in the risk of childhood leukaemia. The evidence for this is limited but a risk cannot be ruled out. No link has been found with health risks in adults.
Computer screens and monitors do emit electromagnetic radiation, but only at low levels that are considerably below the safe levels laid down by international recommendations. Studies have found no links between computer screens and risks to health.
Microwave ovens do produce electromagnetic radiation, but most countries have manufacturing standards that specify maximum leakage levels for new ovens. This reduces leakage outside the ovens to almost non-detectable levels, and leakage also drops as you move further away from the oven.
Although some studies have suggested an association between microwave ovens and cancer, most research has found no link. A modern oven in good condition is safe to use if you follow the instructions correctly.
Cooking food in microwave ovens does not cause cancer either. However, it’s important to remember that any type of cooking can affect the nutritional value of some foods, such as fruit and vegetables. The best way to keep as many nutrients as possible in fruit and vegetables is to use very little water and to avoid overcooking them.
Exposure to radiation, asbestos, pesticides or other cancer-causing chemical substances through your occupation can be associated with a higher risk of developing cancer. It’s important to remember that this usually affects only a small number of people in very specific jobs, and that the main risk comes from heavy exposure over several years. However, most countries now have strict regulations for hazardous substances in the workplace, which means that exposure to them, and the associated health risks, have significantly reduced in recent years.
Regulation of these substances is generally more effective than individual actions. In addition, smoking often increases the risk related to occupational cancer-causing substances. Non-smoking asbestos workers are five times more likely to develop lung cancer than non-smokers not exposed to asbestos; if they also smoke, the risk factor jumps to 50 or higher. Environmental exposures also can increase the risk of lung cancer death.
Some studies have suggested that working night shifts or being exposed to artificial light at night could increase the risk of cancer, in particular breast cancer. However, many of these studies looked at breast cancer in animals, and so did not prove that shift work increases the risk of breast cancer in humans.
In 2007, the International Agency for Research into Cancer (IARC) concluded that working night shifts “probably” does increase the risk of cancer, based on the available evidence at the time. But more recently, a review of ten different studies in humans showed that night shift work is unlikely to increase your risk of breast cancer. This research also found that women working night shifts are more likely to be overweight or obese than women who don’t work night shifts – and overweight and obesity are associated with a higher risk of many cancers, including breast cancer. This may be because the working pattern of night shift workers makes it more difficult to shop for and cook healthy food, or take part in regular physical activity.
Based on all the research to date, there is not enough reliable evidence to suggest that night shift work causes breast cancer. IARC is now planning to review the evidence on shift work. In the meantime, it’s important to remember that maintaining a healthy weight, keeping active and eating a healthy diet, together with not smoking, are the most effective ways to reduce your cancer risk.