Mobile phones, wifi and power lines
Non ionising radiation is a specific type of radiation. Most non ionising radiation has less energy than ionising radiation, this means it doesn’t have enough energy to change our cells in the same way as ionising radiation.
Non-ionising radiation is used in a wide range of communications, electronic and other devices. Different types of non-ionising radiation – such as microwaves, radio frequency waves and electromagnetic fields – are linked with different uses.
What does the evidence show about mobile phones and cancer?
So far, the scientific evidence shows it is unlikely that mobile phones could increase the risk of brain tumours, or any other type of cancer. But we do not know enough to completely rule out a risk.
In 2011, the International Agency for Research on Cancer classified mobile phones for the first time in their 'gold-standard' rating system. They said the devices could 'possibly' cause cancer in humans (group 2B), but there wasn't enough evidence to come to a clear conclusion. Read what we said at the time on our Science Update Blog.
What does the evidence say?
There have been many studies looking for a possible link, but a lot of them are small or have problems with their design. However there have been a few larger studies that, while they also have some problems, help to give us a clearer idea of where the evidence is pointing.
The IARC decision in 2011 was mainly based on the results of two sets of studies - research conducted by the Swedish Hardell group and a very large international study called InterPhone - but it's important to remember that IARC didn't feel this was enough hard evidence to come to a decision.
The Hardell studies suggest a link between using a mobile phone and a few specific types of brain tumour, particularly in heavier users. The InterPhone study, which included over 6,000 people across 13 countries, largely found no link between mobiles and brain tumours, apart from in the ten percent of people who used their phones the most - but this could be explained by problems with the study design.
Each of these studies has its own drawbacks, and they are also both case-control studies, that are less reliable as they ask patients and people without the disease to remember back over time about how and when they used mobile phones. But they may not be able to accurately remember the details about their phone use. And, more importantly, some people's answers may be subconsciously affected by their beliefs about mobile phones and cancer. Brain tumours could also affect study participants' memory or cause other symptoms, like effects on hearing, that could affect mobile phone use.
There is a more reliable type of study, known as a cohort study, which instead asks people about their habits and then follows them up over a period of time to see who develops a particular disease and then looks for patterns. There have been two notable cohort studies on mobile phones and brain tumours published since the IARC meeting.
The largest study so far on mobile phones and cancer is part of the Million Women Study and included around 790,000 women. It found no link between use of mobile phones and brain tumours or 18 other types of cancer. There was also no increased risk for most types of brain tumour, including the two most common (glioma and meningioma). But they did see a raised risk of one rare type of brain tumour (acoustic neuroma) for women who had used mobile phones for at least five years. But in an update to the findings, based on including another two years of data in their analysis, there was no longer a raised risk of acoustic neuroma.
And a Danish cohort study based on mobile phone subscriber data, which looked at over 420,000 people, found no link between mobile phones and any type of cancer including acoustic neuroma, other brain tumours and leukaemia.
Interestingly, a case-control study on acoustic neuroma from a different Swedish group, published in 2014, suggested that people who use mobile phones are more likely to notice symptoms of acoustic neuroma, such as hearing loss, and be diagnosed. So mobile phone use could increase the chance of having the disease detected but not affect the chance of developing it in the first place.
Research in this field is still ongoing and we will continue to look for any new evidence.
Mobile phones and cancer rates
The use of mobile phones has skyrocketed since the 1980s. If mobile phones increase the risk of brain tumours, more and more people should now be developing them.
But the numbers of new brain tumour cases have not changed very much. For example in the UK, the rate of brain tumours has changed very little in the past decades - and the very small increase we have seen is thought to be due to better data collection. However, brain tumours can take many years to develop, so it is possible that incidence rates would only start rising after more time.
Is the radiation from mobile phones dangerous?
There still aren't any good explanations for how mobile phones could cause cancer. The radiofrequency electromagnetic radiation they transmit and receive is very weak. This radiation does not have enough energy to damage DNA, and cannot directly cause cancer.
In 2012 an independent report concluded that there is no convincing evidence that being exposed to radiofrequency fields, including those from mobile phones, within the guidelines could affect somebody's health.
The UK follows a set of international safety standards, which restrict the amount of electromagnetic radiation people can be exposed to and have a very large safety margin.
What about masts and base stations?
Mobile phone masts and base stations are unlikely to increase your cancer risk. They were included in the 2012 review, mentioned above, which found no convincing evidence that the radiation they gave off could affect your health. The exposure you would get from a base station is usually at least a hundred times below international guidelines. And it is much less than the exposure you would get from a phone.
Mobile phones are a relatively recent invention. So far, studies have indicated that using these phones for about 10 years is unlikely to cause cancer. But we cannot be completely sure about their long-term effects. And there have not been enough studies looking at how mobile phone use could affect the health of children.
Research is underway to fill both of these gaps in our knowledge. Until we get a conclusive answer, the Government recommends some precautions for people who have concerns.
For example, adults using mobile phones could minimise their exposure by keeping calls short. And children under the age of 16 should only use mobile phones for essential calls.
You can read the Government recommendations in full at the NHS website.
Wi-Fi and Smart Meters
There has been some media speculation that Wireless internet (Wi-Fi) and smart meters, which can be used to record energy use in your home and transmit it back to your energy provider, could cause cancer. Smart meters and Wi-Fi both use radio waves to send information.
The radio waves produced by Wi-Fi and smart meters are very low power, much lower than those given off by mobile phones, and well within international guidelines. The evidence to date suggests exposures to the radio waves produced by smart meters and Wi-Fi do not pose a health risk.
A different type of radiation (extremely low frequency EMF) is associated with power lines. It is important to note that the type of radiation given off by power lines is different to that given off by household appliances and mobile phones.
There is little strong evidence to link power lines to adult cancers, or to most types of childhood cancer. But some studies have suggested a statistical link between exposure to magnetic fields and a higher risk of childhood leukaemia. At the moment, we don't have enough convincing evidence to be sure whether the link is real, but if it were, the impact would be small - only around 1% of childhood leukaemias.
Power lines and childhood leukaemia - the evidence isn't clear
It is difficult to carry out research into exposure to magnetic fields and risk of childhood leukaemia, and there is no clear indication of what should be measured and when. So research that puts together results from a number of different studies is useful to help get a clearer overview.
2 studies like this found that the very small number of children who were exposed to the highest magnetic fields had a higher risk of leukaemia (around one and a half times to twice the risk) than the children exposed to the lowest levels. But because the studies they were based on had very variable results, it wasn't possible to be sure that power lines or magnetic fields caused the higher risk, especially because there's no good explanation for how this might happen. However, the researchers said that problems with the studies were unlikely to be the whole explanation. Another study’s results suggested a similarly increased risk, but the result could have been a chance finding because the results weren't 'statistically significant'.
The International Agency for Research on Cancer evaluated the evidence and concluded it was 'limited'. They rated low frequency magnetic fields as a 'possible' cause of childhood leukaemia - which means that we can't rule a risk out. This conclusion was supported by a separate World Health Organisation review of the evidence.
Overall, at the moment it isn't possible to say with certainty whether or not being exposed to the highest levels of magnetic fields from power lines increases the chance of developing childhood leukaemia. There isn't a good suggestion for how magnetic fields could cause leukaemia, laboratory studies don't support a link and the results from individual studies are variable. But the studies combining several results together do seem to show a raised risk. This is likely to remain a difficult area to finally resolve.
However, even if the link seen in these studies is a real effect, the impact would be small as only around 1 to 4% of children have the highest levels of exposure. And the evidence shows that there is no noticeable increase in risk for the lower levels of magnetic fields that most people are exposed to.
For more information about power lines, EMFs and cancer, visit the UK GOV website.