Mobile Phones and Cancer
The World Health Organization's IARC classifies radiofrequency fields, including those emitted by mobile phones, as possibly carcinogenic to humans.
Mobile phones emit nonionizing electromagnetic fields (EMFs) within the mid-frequency range of 1.9 and 2.2 GHz.1There has been concern that mobile phone use may increase the risk of cancer because EMFs may be absorbed by tissues, and the use of mobile phones is rapidly increasing.2
Although the World Health Organization's International Agency for Research on Cancer (IARC) classifies radiofrequency fields, including those emitted by mobile phones, as Group 2B — possibly carcinogenic to humans — the data regarding the risk of cancer remain uncertain and controversial.3Interpretations of the current data vary according to the organization or agency, with many US agencies stating either the data are not conclusive or no causal link has been established between mobile phone use and cancer.2To further, and hopefully more definitively, determine whether there is an increased risk of cancer with mobile phone or other wireless technology use, the large, prospective cohort study COSMOS is following nearly 300,000 adults for 20 to 30 years.4Similarly, the MOBI-Kids study is assessing the effect of EMF exposure on children and adolescents.5
The current data primarily include case-control studies. Controversy is present, however, as a result of study designs, potential biases, and interpretations of statistical outcomes. Moreover, a clear pathophysiologic link in animal or in vitro studies has not been established, with recent studies finding that EMF exposure does not result in micronuclei formation, a marker of chromosomal instability, or changes in DNA integrity.6-8
The INTERPHONE Study
The INTERPHONE case-control study was conducted in 13 countries and included adults aged 30 to 59 from geographic areas expected to have the longest duration and highest concentration of mobile phone use.9Participants included 2708 cases of glioma and 2409 cases of meningioma diagnosed between 2000 and 2004 and a total of 5634 matched controls. Mobile phone use was ascertained by face-to-face or paper interviews with the patient or a proxy.
Overall, mobile phone use was not associated with an increased risk of glioma or meningioma — instead, a protective effect was found with an odds ratio (OR) of 0.81 (95% CI, 0.7-0.94) and 0.79 (95% CI, 0.68-0.91), respectively. The authors indicated, however, that the reduced ORs may be a result of participation bias or methodological limitations, such as prodromal symptoms, timing of interviews, and confounding factors. There was no association for those who first used a mobile phone more than 10 years ago.
Individuals with the highest cumulative mobile phone use of 1640 hours or more demonstrated an increased risk for glioma (OR, 1.40; 95% CI, 1.03-1.89), but not meningioma.9Another analysis of the INTERPHONE data included modeling to determine the radiofrequency exposure of participants, which demonstrated that the OR for glioma increased with increasing total cumulative specific energy, with an OR of 1.91 (95% CI, 1.05-1.90) at the highest exposure level.10For ipsilateral tumors, at least 10 years of mobile phone use significantly increased the risk for glioma with an OR of 2.80 (95% CI, 1.13-6.94). Another analysis also found that the intracranial location of gliomas was skewed toward where participants reported their preferred location to be for mobile phone use.11
Given that the results of the INTERPHONE study were not clear and the investigators reported limitations that could have affected the data, controversy followed with different interpretations by experts in the field.12This led to additional analyses that focused on adjusting for some of these limitations, such as a study of Canadian participants from the INTERPHONE study that showed a higher OR of 2.2 (95% CI, 1.3-4.1) of glioma when researchers adjusted the data for selection and recall biases.13Several studies conducted since INTERPHONE attempted to reduce bias or included different populations in the control versus mobile phone user groups.
However, an analysis of glioma incidence from the Surveillance, Epidemiology, and End Results (SEER) program found that the rates of glioma remained nearly unchanged between 1992 and 2008 (-0.02% per year; 95% CI, -0.28%-0.25%).14Low-grade gliomas decreased by -3.02% per year (95% CI, -3.49% to -2.54%), but temporal gliomas increased by 0.73% (95% CI, 0.23%-1.23%). The authors concluded that if mobile phone use was associated with gliomas, a much greater increase in incidence should have been found. They noted that the relative risk of glioma from INTERPHONE is consistent with the slight decrease in incidence of glioma in this study, but not the overall reduction when INTERPHONE compared users versus never users.