Cell phones have long been feared to increase the risk of cancer to the user. An updated study by the Danish Cancer Society dispels these apprehensions in a recent paper analyzing cancer risk among all cellular subscribers in Denmark. Overall, the team found no increased risk of cancer or tumors among subscribers relative to the general population.
The researchers looked at data from the Danish national registry, which includes health and socioeconomic data for all citizens. A number of subgroups were defined; for example, those who had been subscribers for the longest period of time and those with new subscriptions. Subgroups were also defined based on age, income levels, and whether or not the individual was a smoker.
A number of different cancers were also studied, namely central nervous system tumors and localized gliomas (tumors) on specific parts of the brain anatomy. Data was analyzed statistically to get incidence rates for different combinations of cancer types and subgroups. No correlation was found between mobile phone usage and cancer. The temporal lobe, which is subjected to the highest absorption of energy from cell phones, had no increased risk of glioma either.
Presently, no mechanisms are known to support the belief that cell phones can cause cancer, but that doesn't mean that no such mechanisms exist. "There has been some concern that there may be as yet unknown mechanisms," Aslak Poulsen, a co-author of the paper, wrote in an email to The News-Letter.
"If such mechanisms should exist, it would be a major public health issue as cell phones and other sources of radiation are becoming ubiquitous," Poulsen wrote. If a correlation were to emerge, it would likely prompt research into finding the causation, a mechanism by which cancer could develop.
Despite the seeming definitiveness of the study, there are a few limitations to consider. First, sample sizes of cell phone users were based on active subscriptions, without reference to frequency and intensity of use by the individual. Also, differences in cell phone technology over the decade-long study were not included.
"Within that period there was a shift, in the Scandinavian countries, from the analogue NMT to the digital GSM standard with a somewhat lower exposure," Poulsen wrote. NMT users having been receiving larger exposure for longer periods of time than GSM users, yet the results of the study still do not indicate a correlation. Smartphones are built on an even newer system, UMTS, with 100 times lower exposure than GSM devices. There is "much lower exposure to the head from smartphones … they are not likely to pose a higher risk," Poulsen wrote.
Future work can still be done to further verify the results. "When looking at brain tumors, even longer follow up and of course more detailed exposure data will always be desirable," Poulsen wrote. For example, the study in Denmark ignored corporate use devices, which account for a large number of users in the US.
According to the CTIA, an advocacy group for the wireless communications industry, the number of cell phone users in the US in June of 2011 was 322.9 million, greater than the population of the US itself. The study in Denmark was done on a sample size of 358,403 total users. Thus, a study of American users could classify approximately 1000 times more people, and therefore help minimize statistical errors.
