Reviews

Mobiles on the brain

"The Mobile Mystery," Panorama, BBC1, Monday 24 May, 10 05 pm

   Media attention has once again focused on alleged links between use of mobile phones and an increased risk of brain tumours. Panorama used two case histories to illustrate the possible damaging effects of these proliferating "essentials." One patient developed "band-like" headache, mood swings, and memory problems, and the other patient developed a brain tumour.

Also, two as yet unpublished studies from Sweden and the United States were reported to support the alleged link between mobile phone use and brain tumours. Details were sketchy about both studies. In the first, Dr Lennart Hardell from the Orebro Medical Centre in Sweden reported a retrospective analysis of 200 patients who had developed brain tumours. The patients were asked about their use of mobile phones. Panorama suggested that Dr Hardell had found almost 2.5 times the expected rate of brain tumours in phone users. In fact, he stated that there was no significant increase in tumours overall but that there seemed to have been a 2.5-fold increase in numbers of brain tumours in certain areas of the brain. These areas were related to the side of the head where the antenna of the mobile phone was located during phone use.

These are interesting findings, but there are many pitfalls in drawing conclusions from them. The numbers of patients were small, and we weren't told whether the areas were predetermined or decided post hoc. The retrospective nature of the study may have led to reporting and recall bias. Patients presumably knew the side of the head on which their tumours were located and may therefore have been more likely to suggest that it coincided with the ear used most often when using a mobile phone. No information was given on whether a dose-response relation existed regarding phone use or type.

Dr George Carlo, head of the Carlo institute, a $25m research body "funded by the mobile phone industry" to perform independent research in the United States, also spoke of unpublished data that he has submitted to the Food and Drug Administration. He suggested that microwaves from mobile phones may cause damage to DNA and may increase the risk of brain tumours in rats (but only on the right side). He argued that manufacturers can no longer responsibly suggest that there is no problem with mobile phones and asked the industry for millions of dollars for more research.

(Credit: IMPACT) View larger version (85K): [in this window] [in a new window]   Mobile users need not rush for a hard hat

Three other researchers were interviewed in the programme. One, who had examined the effects of microwaves on rat brains and had found some DNA breaks, argued that the results suggested that microwaves had some effect on brain. However, the work was later repeated with slightly different methodology, and no damage was found.

Other research suggesting potential benefits of mobile phone use were usedperhaps bizarrelyby the programme makers as evidence that deleterious effects may also occur. An investigation of the effect of mobile phone emissionsin which rats were exposed to emissions for two hours a day for their lifetimehad found, if anything, a decrease in the number of brain tumours. This was taken to suggest that there was "some biological effect." The mobile phone company involved was castigated for not renewing funding for the research and for keeping the results secret. Dr Alan Preece from Bristol University studied reaction time in 36 mobile phone users and found improved reaction times; results that were again interpreted as showing some interference with brain function.

What is known about the radiation produced by mobile phones? They emit 1000 times less radiation than an x ray scan and emit only during conversation. The skin and skull absorb half of the energy, and the remaining half may reach the brain and then be converted to heat. The UK National Radiological Protection Unit has set a safety limit of emission of radiation for mobile phones of 10 Watts/kg (specific absorption rate). Panorama's own research, commissioned from the National Physical Laboratory, of seven mobile phones to examine the emission levels showed that the phone judged to be the "worst" (Nokia 2110, with a specific absorption rate of 0.44) was more than 20 times below the recommended safe level, whereas the "best" was 500 times below the recommended safe levels (Motorola Star Tac 70, specific absorption rate 0.02). Panorama highlighted the 20-fold difference between the best and the worst and suggested that companies let the public know of the levels of emissions of various phones.

The programmedespite the holes in the scienceis likely to cause widespread concern. Currently, one in four people in the United Kingdom and half a billion people worldwide use a mobile phone. However, the large numbers already using mobile phones provide one source of reassurance. If there was a link between mobile phones and brain tumours we would be experiencing a dramatic increase in the incidence of primary brain tumours in the young and working population in developing countries. No such increase has yet been identified in people aged under 65.

What advice is currently reasonable to give to mobile phone users? Mobile phone companies could inform consumers of the emission of radiation from their mobile phones, irrespective of whether there was any health risk, and leave consumers to make up their own minds on how important this is. "Hands-free systems" reduce emissions to the skull by 90%, and their use would seem reasonable (with the added bonus of reducing the number of road traffic accidents). Microshields designed to protect the head will reduce emissions by 80%again, their use would be harmless if not beneficial.

Reducing mobile phone use would also reduce contact with microwave emissionsand make life quieter for us all. These are all issues of personal choice rather than of public health, because all the mobile phones tested for the programme fell well within current recommended radiation limits and there is no evidence that extremely low emissions are better than low emissions.

Any link between mobile phones and brain tumours remains to be proved. Very large and careful epidemiological studies would be required to clarify the issue or provide estimates of attributable risk. Panorama failed to provide this level of evidence.

Robin Grant, consultant neurologist. 

Department of Clinical Neurosciences, Western General Hospital, Edinburgh