The widespread use of mobile phones has generated public concern over possible health implications related to the devices' radiofrequency signals and electromagnetic fields. The controversy centers on whether prolonged cell phone usage increases a person's risk for brain cancer. On one side of the debate, many scientists assert that the phones' electromagnetic radiation cannot lead to carcinogenic mutations in the body, supporting their reasoning with basic physics principles. The opposing view cites mix epidemiologic findings; some studies conclude a mild association between cancer and cell phone use, while other show no carcinogenic effect from the devices.
Cell phones emit electromagnetic radiation in order to communicate with distant mobile service towers. Because body tissues absorb some of this radiation during regular phone use, there is concern as to whether these signals could cause any serious health problems. Tissues located close to a phone's antenna, such as the face, jaw, brain, and hands, are under particular scrutiny by the scientific community. 
Some forms of electromagnetic radiation, including x-rays, gamma rays, and ultraviolet (UV) radiation, have been implicated in causing cancer. Known as ionizing radiation, these waves are energetic enough to break bonds in DNA and create genetic mutations. Resulting DNA mutations in oncogenes, tumor suppressor genes, and DNA repair genes may then lead to uncontrolled cell growth. Common examples of ionizing radiation's health concerns include UV exposure from the sun, which causes melanoma and other forms of skin damage, and medical imaging x-rays, which are associated with higher cancer risk. 
In contrast, other types of electromagnetic radiation are non-ionizing, so they do not carry enough energy per quantum to remove an electron from an atom or molecule. These waves are too weak to break DNA and other important biochemical bonds. Examples include infrared, microwaves, and television and radio signals. 
What kind of radiation is emitted by cell phones? Cell phones operate at less than 0.001 kJ/mole, sending low-power microwaves to transmit communication signals. Electromagnetic radiation is considered ionizing at an energy greater than 480 kJ/mole. Thus, mobile devices are 480,000 times weaker than the cancer-causing waves and their electromagnetic radiation are not carcinogenic. 
Epidemiologic data supports both sides of the cell phone-as-a-carcinogen debate. It is important to note that although some studies showed an association between tumor growth and mobile phone use, correlation does not imply causation and confounding factors may have skewed results. A randomized, interventional study would resolve questions over cause and effect, but conducting such a study is not feasible due to scale and timeframe. Several notable studies are outlined below.
A 2010 case-control study in the International Journal of Epidemiology evaluated the correlation between cell phone use and risk of brain cancer. The study looked at about 5000 glioma and miningioma cases plus matched controls in 13 countries. The odds ratio (OR) of ever having used a mobile phone regularly was reduced for glioma [OR 0.81; 95% confidence interval (CI) 0.70-0.94] and meningioma (OR 0.79; 95% CI 0.68-0.91), indicating participation bias or other confounding factors. The authors of the study also evaluated the risk of cancer at a time greater than 10 years after first phone use, finding no statistical difference between the cases and controls (glioma: OR 0.98; 95% CI 0.76-1.26; meningioma: OR 0.83; 95% CI 0.61-1.14). The authors concluded, "Overall, no increase in risk of glioma or meningioma was observed with use of mobile phones." 
A 2009 review in Surgical Neurology was a meta-analysis of 11 long-term epidemiologic studies looking at prolonged cell phone usage and the development of an ipsilateral brain tumor. Results of the study indicated that, "using a cell phone for greater than 10 years approximately doubles the risk of being diagnosed with a brain tumor on the same side of the head as that preferred for cell phone use". These findings were statistically significant for glioma and acoustic neuroma, but not for meningioma. 
A retrospective cohort study in the Journal of the National Cancer Institute in 2000 compared all cell phone users in Denmark (420,095 total) during 1982-1995 with the Danish Cancer Registry. No statistically significant increases in cancer risk were found for cell phone users compared to controls, including those cancers anatomically close to the ear-jaw-head region where phones are placed during use. Results showed no increase of standardized incidence ratio (SIR) for cancers of the brain or nervous system (standardized incidence ratio = 0.95; 95% CI = 0.81 to 1.12) or of the salivary gland (SIR = 0.72; 95% CI = 0.29 to 1.49) or for leukemia (SIR = 0.97; 95% CI = 0.78-1.21). Authors also showed, risk for cancer did not vary by duration of cellular telephone use, time since first subscription, age at first subscription, or analogue vs. digital phone use. 
While a few epidemiologic studies concluded increased risk for brain cancer with cell phone use, evidence behind this correlation is contradictory. Physics demonstrates that cell phones do not have enough energy to produce the ionizing radiation that causes carcinogenic mutations in DNA, although there may be other reasons for the described increased cancer risk in these studies. The behavioral effects of cell phone use, such as social, cognitive, sleep, eating, and exercise patterns; thermal effects and cranial heating; and confounding factors for these types of studies, such as recall or publication bias, are future areas to look into as a possible reasons behind these epidemiologic findings.
© Claire Durkin. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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