The largest study till date has refuted earlier fears that link mobile phone use to brain cancer. However experts say the risk can't be ruled out.
The study of 358,403 Danish cell phone plan subscribers over 17 years found subscribers of 13 years or more faced the same cancer risk as non-subscribers. “In general, our findings are in line with most of the epidemiological research that has been conducted to date,” said Patrizia Frei of the Danish Cancer Society's Institute of Cancer Epidemiology, lead author of the study published 20th of October in the journal British Medical Journal. “They are also in line with in vitro and in vivo studies that show no carcinogenic effects on the cellular level.”
This comes just five months after a panel of experts from the World Health Organization's International Agency for Research on Cancer deemed cell phones a possible cause of cancer. More than 5 billion mobile-phone subscriptions are held worldwide, according to the International Telecommunication Union. Concerns have arisen over whether exposing the brain to radiofrequency electromagnetic fields emitted by mobile phones leads to cancer. The IARC said the fields were “possibly” carcinogenic, the same category as diesel fuel and chloroform.
While Frei's findings offer some comfort for communicators on-the-go, experts say further studies are still warranted. “Frei and colleagues' results may seem reassuring, but they must be put into the context of the 15 or so previous studies on mobile telephones and cancer,” Anders Ahlbom and Maria Feychting of the Karolinska Institute of Environmental Medicine in Stockholm, Sweden, wrote in a BMJ editorial. “Although most of these studies were also negative, there are a few exceptions.” The one exception is a 2010 study that found a slight, statistically insignificant increase in risk in a rare form of brain cancer called glioma among cell phone users.
“Most of data that shows an association between cell phones and brain cancer is very weak,” said Timothy Jorgensen, associate professor at Georgetown Lombardi Comprehensive Cancer Center. Experts say that there is a tendency for people with cancer, desperate for answers, to over-report certain behaviors like cell phone use. In this study Frei and colleagues avoided this pitfall by using Denmark's central population register, a mammoth database containing health records as well as cell phone plan details for every resident from birth to death. The register also allowed the researchers to control for education and socioeconomic factors.
“No single study is definitive,” said Dr. Peter Shields, deputy director of Ohio State University Medical Center's Comprehensive Cancer Center. “You can't say, based on this that we never have to worry. But this may end up being the best study out there.” But the study has limitations. In particular, cell phone subscriptions were used as a surrogate for use. And “having a mobile phone subscription is not equivalent to using a mobile phone,” Ahlbom and Feychting wrote.
Professor Malcolm Sperrin, Director of Medical Physics at Royal Berkshire Hospital, and Fellow of the Institute of Physics and Engineering in Medicine, said, “This study is very large in terms of the number of people involved, is large in terms of the number of usage of the phones and also has a random nature being based on the purchase of a telephone contract rather than being a sub-group. The findings clearly reveal that there is no additional overall risk of developing a cancer in the brain although there does seem to be some minor, and not statistically significant, variations in the type of cancer. This paper supports most other reports which do not find any detrimental effects of phone use under normal exposures.”
Vicky Fobel, director of MobileWise, a charity advising on mobile phone and health, said, “All this shows that this study and the press release promoting its findings are misleading the public by implying that phone users have the all clear. The study only looked at short-term use of mobile phones and by mis-analyzing the data has massively underestimated the risks. All the other studies that have looked at the long-term risks have found a link between phone use and brain tumors. This study gives false reassurance and distracts us from the important job of helping the public, especially children, to cut the risk from mobiles.”
Frei admits, “We didn't have any information on the amount of use, so we couldn't do any subanalysis on people with heavy phone use…There are still some open questions, about greater amounts of use, and about the effects on children.” “At some point, we need to start prioritizing research on things we think might cause cancer,” said Shields. “We might not have a definite 'no' for cell phones, but we can certainly have a definite 'Let's move on.'”
The research was funded by the Danish Strategic Research Council.
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