Research finds no higher risk of brain tumors among cellphone users

One of the most exhaustive studies of its kind to date, in which more than 800,000 women in the United Kingdom participated, has indicated that there is a similar risk of developing a brain tumor among those who use cellphones and those who do not. The work, carried out by scientists from Oxford University and the International Agency for Research on Cancer (IARC), has added further weight to several previous studies that suggest the normal use of cellphones does not cause tumors of any kind.

More than 5.3 billion people own a cellphone, according to the GSM Association. The devices, which emit electromagnetic fields, were classified a decade ago by IARC as “possibly carcinogenic” after a suspected increased risk of glioma – a malign cerebral tumor – was detected in a study involving 5,000 patients. However, it was only a suspicion. The World Health Organization (WHO) noted that “to date, it has not been confirmed that cellphone use has adverse health effects.”

The latest study used data from The Million Women Study, an Oxford University initiative that recruited one of every four UK women born between 1935 and 1950, with the initial objective of breast cancer research. Following almost 15 years of follow-up, the study’s authors have found that 0.42% of participants developed a brain tumor, with similar numbers recorded among cellphone users and people who have never owned one. Neither did scientists detect any significant differences in the risk of glioma, meningioma, acoustic neuroma or any other tumors supposedly linked to the use of wireless devices, such as those of the eye or the pituitary gland.

Only 18% of participants in the study said they spend more than half-an-hour a week talking on their cellphones, making it almost impossible to draw conclusions over the risk among people who spend considerably longer on their devices, says epidemiologist Joachim Schüz, co-author of the study and a member of IARC. “Given the lack of evidence among intensive users, it remains a good precautionary approach to recommend users reduce unnecessary exposure to cellphones,” Schüz told EL PAÍS.

The investigation, which was published on March 30 in the Journal of the National Cancer Institute, explains that radiofrequency electromagnetic fields – those emitted by mobile devices – can penetrate the head by several centimeters. The principal effect of this is, simply, surface heating of the skin. The paper did not detect any increased risk of tumors in the temporal and parietal lobes of the brain, the areas potentially most exposed to these electromagnetic fields. The tumors observed in the study, furthermore, were distributed as much on the left side of the brain as the right, despite the majority of people using their right hands when on the phone.

The authors also note that emissions from devices on the market today are “substantially lower” than among older generations of cellphones. “On balance, a very heavy user of today is unlikely to accumulate the same RF-EMF exposure as a modest user of the first two wireless generations,” the paper concludes.

Memory bias

One of the advantages of the new work is that it is prospective: the follow-up and the questions asked about cellphone use started before any tumors were reported. Until now, retrospective studies were more common, in which people diagnosed with cancer calculated their daily cellphone use over the course of their lives. In these early studies, there was the risk of so-called memory bias: patients with cerebral tumors tend to exaggerate their cellphone usage, because they can believe that it is the cause of their diagnosis. In the new study, the participants tallied their daily cellphone usage by answering two sets of questions, set in 2001 and 2011. In the most recent questionnaire, 75% of women aged between 60 and 64 used cellphones.

“These results back the evidence, which is ever-more abundant, that cellphone use under normal conditions does not increase the risk of brain tumors,” Oxford University statistical programmer Kirstin Pirie said in a statement.

The study does not include children or teenagers, but its authors point out that two months ago the results of an international investigation called MOBI-Kids – which analyzed the potential connection between cellphone use and the risk of brain tumors in young people in 14 countries – were released. The study, coordinated by epidemiologist Elisabeth Cardis, Research Professor in Radiation Epidemiology at the Global Health Institute in Barcelona, also found no evidence of a link.