Since the onset of electrification in the late 19th century, electromagnetic fields of various kinds and strengths have become a constant feature of the environment. But could they be bad for us?
Mobile phones, Wi-Fi routers, wireless phones, hair dryers, washing machines, TVs, radio receivers, overhead power lines, mobile phone basestations – though invisible, electromagnetic fields from various sources in the early 21 century are virtually omnipresent. And as with all non-natural occurrences in the environment, scientists have wondered whether the electromagnetic fields modern-day humans have to live with could actually affect their health.
Living in a microwave
“There are two known mechanisms where high-level fields have known biological effects,” says Professor Anthony Barker, a clincal scientist at the Department of Medical Physics and Clinical Engineering of the Royal Hallamshire Hospital Sheffield and chairman of a policy advisory group of the Institution of Engineering and Technology (IET), which has recently published a position statement on Biological Effects of Low-Level Electromagnetic Fields, such as those induced by overhead power lines or mobile phones.
“High-powered radio transmitters, for example, warm you up. They deposit thermal energy in the tissue, like a microwave oven, that’s also a radio-frequency transmitter exposing things you want to cook to an electromagnetic field,” Prof Barker explains, emphasising that although thermal effects of electromagnetic fields have long been known, they are insignificant in everyday life.
“Mobile phones are, in effect, little radio-transmitters, but they only transmit about a quarter of a Watt. The basestations with which the handsets communicate typically transmit some tens of Watts of energy, which is still very low,” says Prof Barker.
At the other end of the spectrum of omnipresent electromagnetic fields is the 50Hz power frequency field capable of inducing currents in the body by what’s called the Faraday law of electromagnetic induction. “The body is sensitive to electric currents of those sorts of frequencies – you can stimulate nerves and muscles with them for example,” says Prof Barker.
The technique is frequently used in medical applications. However, as Prof Barker says, to achieve neural stimulation, the strengths of electromagnetic fields used have to be several thousands of times greater than those commonly present in the environment.
But could the long-term exposure to rather weak fields possibly cause any harm?
Small-scale versus large scale
Since the early 2000s, a Swedish research group led by Kjell Hansson Mild, from Umea University, and Lennart Hardell, from Örebro University, has published several studies suggesting regular long-term use of mobile phones could substantially increase the risk of developing several types of brain tumours.
According to the group’s results, not only do heavy mobile phone users face higher risk of developing acoustic neuroma (a benign growth on the acoustic nerve) and glioma, the tumours also tend to be bigger and located on the side of the brain where the user presses the phone to his head.
In 2011, the International Agency for Research on Cancer classified radio-frequency electromagnetic fields, such as those induced by mobile phones, as possibly carcinogenic, saying that more research needs to be done in the area as existing evidence was not sufficient.
Other studies have suggested a possible connection between mobile phones and low sperm count in men or neuro-degenerative disorders such as Alzheimer’s disease. Depression, suicides, miscarriages, migraine and many other conditions have also been linked to the use of mobile phones.
However, with first large-scale long-duration studies concluding towards the end of the last decade, the momentum started swinging back in favour of these revolutionary communication gadgets.
The Interphone study, published in 2010, spanning a decade and covering 13 countries, came up with surprising results.
Among the survey’s participants, of which 7,416 were brain cancer patients, the data revealed that regular and moderate mobile phone users actually tend to have lower incidences of brain cancer than non-users. Only those who spend more than 30 minutes a day with a mobile phone pressed to their ear seem to have an increased risk of developing a brain tumour. Scientists were bewildered by such a contradiction.
“The consensus seems to be that the Interphone study doesn’t show a smoking gun,” says Prof Barker, who, together with his colleagues from the IET’s Biological Effects Policy Advisory Group (BEPAG), has reviewed about 600 scientific papers covering the health effects of mobile phones and other sources of electromagnetic fields in the everyday environment that have been published in the past two years.
“There is another type of analysis which is being increasingly carried out, which I personally find rather persuasive, and that’s the time series analysis,” Prof Barker says. “Basically, you can look at the incidence of brain tumours year on year just by looking at national registries of health, which exist in many countries.There have been several recent studies doing that, looking specifically at the brain tumour incidence rate over the past 15 years and those papers seem to show that there is no increase in the incidence of brain tumours.”
This type of analysis presumes that with the widespread use of mobile phones, an increase of brain tumours, if existent, should be noticeable in general population health data. However, these studies report unchanging incidences of brain tumours from before mobile phones were used up to the present time.
Childhood leukaemia and overhead power lines
Similarly, contradictory results have come from studies researching the connection between childhood leukaemia and overhead power lines that too cause environmental electromagnetic fields.
Several epidemiological studies conducted over the past decades have shown twice as high incidence of leukaemia in children growing up near overhead power lines. Those results, although not pointing to a causal relationship, have prompted the International Agency for Research on Cancer to categorise low-frequency electromagnetic fields (those induced by the overhead power lines) as possible carcinogens.
However a recent major study from an Oxford-based group has shown no such correlation in the data for the past 20 years.
“This paper shows something quite remarkable what has never been shown before,” says Profr Barker. “It shows that yes, there was increased incidence of childhood leukaemia in the 1960s and 1970s near power lines, but it was much less in the 1980s and by the time we got to the 1990s, the increased risk of childhood leukaemia appears to have completely vanished.”
Does it mean humans adapted to living within the omnipresent electromagnetic fields since the 1960s? Or where the past studies simply wrong?
“The only explanation currently on the table is that it might have been due to population changes,” Prof Barker suggests. “The incidence of childhood leukaemia varies in different socio-economic classes and it may be that there have been changes in the population type that used to live under power lines in the past compared with those that live under them now. There is no evidence to support this at present but it is the most plausible hypothesis to explain the results this latest paper has reported.”
Less money for health-effects research
So is there a reason to worry? Should we ditch our mobile phones, switch off Wi-Fi and favour cable-based Internet? Should we move away from the vicinity of mobile basestations and overhead power lines if we want to keep our children safe and stay healthy?
Prof Barker says that in the light of the existing evidence, the risks of developing health conditions as a result of an exposure to low electromagnetic fields are negligible compared with, for instance, the very real risks of crossing a street.
“As scientists, we have spent many years trying to determine whether there is a problem and we haven’t been able to persuade ourselves that one exists, so I think we would all be better off if we concentrate more on avoiding established risks than worrying about whether owning a mobile phone or living under overhead power lines is bad for us.”
One interesting finding came out of the latest IET statement on Biological Effects of Low-Level Electromagnetic Fields. As some of the major studies concluded with negative results, governments seem to be less keen to invest in further research. Consequently, the number of large-scale well-funded studies decreases.
“The studies that are published in the literature that my committee reviews are increasingly coming from small, not necessarily well funded groups, that have done small-scale studies and published usually positive results showing that there is an effect,” Prof Barker says.
“It’s quite interesting, because if you look at the literature, the large studies with major funding, that have done very detailed work, and done it very carefully, show negative results while small studies, that are done quickly, nearly always seem to show positive results. So it could be that the quality of the literature in this area is deteriorating somewhat as the major studies stop appearing and lots of little smaller studies replace them. “
For the full 2014 IET Position Statement on Biological Effects of Low-Level Electromagnetic Fields click here.