For the second time in less than a month, an international cancer research group has aired its concerns about the cancer-causing potential of radiofrequency electromagnetic fields (RF-EMF) emitted by cell phones and other devices.
The International Agency for Research on Cancer (IARC) affirmed its classification of RF-EMF as “possibly carcinogenic to humans,” following the recommendations of a panel convened in May to assess available information on RF-EMF and cancer.
In a summary published online in The Lancet Oncology, the IARC singled out cell phones for particular attention, as the World Health Organization did last month following the IARC panel’s week-long meeting in Lyon, France.
“Holding a mobile phone to the ear to make a voice call can result in high specific RF energy absorption-rate (SAR) values in the brain, depending on the design and position of the phone and its antenna in relation to the head, how the phone is held, the anatomy of the head, and the quality of the link between the base station and phone,” the authors wrote.
“When used by children, the average RF energy deposition is two times higher in the brain and up to 10 times higher in the bone marrow of the skull, compared with mobile phone use by adults. Use of hands-free kits lowers exposure to the brain to below 10% of the exposure from use in the ear, but it might increase exposure to other parts of the body.”
In its summary, the panel discussed some of the evidence that persuaded members of the committee to support the IARC reclassification of RF-EMF as a category 2B carcinogen, which includes progestins and certain anti-epileptic drugs. Class 2B is the next step up from “not classifiable” in the IARC classification system for carcinogens because of inadequate evidence.
Exposure to RF-EMF in the frequency range of 30 kHz to 300 GHz is almost unavoidable in a society that is increasingly dependent on electronic devices and equipment that generates RF-EMF.
Sources of RF-EMF include personal devices (such as cell phones and Bluetooth-enabled products), occupational sources (such as induction heaters and high-powered pulsed radar), and environmental sources (such as mobile-phone base stations, broadcast antennas, and certain medical devices).
The panel, comprising 30 scientists from 14 countries, reached a consensus on the classification of RF-EMF after an extensive review of scientific studies and other evidence.
Epidemiologic evidence appeared to carry the sway. For example, a large multicenter INTERPHONE case-control study evaluated the association between cell phone use and various types of brain tumors (Int J Epidemiol 2010; 39: 675-694). A pooled analysis of 2,708 glioma cases and 2,972 controls showed that, overall, there was almost a 20% lower risk of glioma among cell phone users.
However, an analysis limited to heavy cell phone users resulted in an odds ratio of 1.40 for cases versus controls.
The panel also cited a Swedish case-control study involving 1,148 glioma cases and 2,438 controls (Int J Oncol 2011; 38: 1465-1474). Among other results, the study showed an association between increasing cell-phone use and the odds ratio for the brain cancer.
The panel found “limited evidence” of RF-EMF carcinogenicity in more than 40 studies of preclinical models. Similarly, studies examining mechanisms of carcinogenesis provided “only weak mechanistic evidence relevant to RF-EMF-induced cancer in humans.”
The authors of the summary acknowledged some division over the adequacy of the evidence they reviewed. However, the 2B classification for RF-EMF had strong support.
“In view of the limited evidence in humans and animals, the Working Group classified RF-EMF as ‘possibly carcinogenic to humans,’” they wrote in conclusion. “This evaluation was supported by a large majority of Working Group members.”
The group’s findings will be described in detail in volume 102 of IARC Monographs.