Guest Post by Kyle Hill

I'm sure that just about everyone you know has a cell phone. Indeed, a recent Pew Internet survey found that some 75% of 12-17 year-olds now own cell phones, up from 45% in 20041. However, along with this spike in cell phone usage there has been a rise in fear over the potential risks from prolonged cell phone use. Aside from "cell-phone elbow" and increased ear bacteria, brain tumors are the most worrying of the supposed risks. This fear has been around ever since cell phones became publicly available, and the trend continues. Fears compound as the cell phone basically becomes an extension of the human head.

Despite these fears, none of the research concerning cell phones and brain cancer has shown any likely risk to your health. Furthermore, a look at the general physics involved will show how cell phones cannot plausibly cause cancer.

Dropping Fears, Not Calls

On the extreme side of cell phone radiation fears are people campaigning for the abolition of cell phones, wi-fi, and cable; on the moderate side are parents who refuse to let their children use cell phones for any extended period, or who insist that they use the speakerphone or a hands-free set instead. Where do these groups get their fear of cell phones? Can we confidently deduce, using only our common sense, that since cell phones output radiation, they must be bad for us? This is a case in which our common sense is no match for the high-powered electron microscope of science.

You may have heard a lot of things about the risks of cell phone use, and most of it is drawn from the fact that cell phones output electromagnetic radiation. When most people hear "radiation," they think of something akin to chemotherapy or the atomic bomb, without realizing that radiation is just a term that explains how energy is transferred in wave-form. This negative knee-jerk reaction allows people to continue thinking that cell phones cause cancer, chalking it up to plain common sense.

But just what kind of radiation do cell phones output? How much energy is contained in the radiation, and is it enough to cause bodily harm? These are all questions answerable by physics.

Amplitudes and Frequencies

Let's get an idea of where cell phone output lies in the electromagnetic spectrum:

Cell phones emit radiation in the form of radio-frequency waves, which puts them at the far left of the above chart. So why is this band, or frequency, of radiation unlikely to cause cancer? The answer is in the amount of energy contained in these radio-frequency waves.

Cell phones are unlikely to cause cancer because they do not emit enough energy to break the molecular bonds inside cells. Some forms of electromagnetic radiation, such as x-rays, gamma rays and ultraviolet (UV) radiation, are energetic enough to break the bonds in key molecules such as DNA and therefore generate mutations that can lead to cancer. This is called ionizing radiation. Radiation of this strength can knock electrons off molecules and atoms in your body, causing real harm. However, electromagnetic radiation in the form of infrared light, microwaves, and television and radio signals is non-ionizing, and therefore too weak to break those bonds. This is why we don't worry about radios, televisions, and microwave ovens causing cancer. Likewise, the radiation produced by cell phones is non-ionizing. Generally, anything below visible light on the electromagnetic spectrum is safe.

This does not mean that the radiation emitted from cell phones has no effect on your body. The radiation from cell phones and other electronic devices may heat molecules near the surface of the skin (think microwaves) but does not ionize them. Ionizing radiation however, which can tear molecules apart and therefore potentially damage DNA, is the greater worry, and is way beyond the power of a cell phone. We're talking about Hulk-generating radiation here, not an AT&T signal.

Non-ionizing radiation is all around you all of the time. Just turn on your radio and tune it to a static channel. All that noise and interference you hear is radiation all around you being picked up, some cosmic and some man-made, which hits you probably every second of every day. If such pervasive radiation indeed did cause cancer, we should see many more cancer patients as a result. But we do not.

Testing the Hypothesis

Compounding these conclusions drawn from physics, even the largest studies seeking to answer this question have come up negative or inconclusive. For example, in what was described as the largest study ever on the subject, Danish researchers found no evidence that the risk of brain tumors was raised among 358,403 mobile phone subscribers over an 18-year period2. Another recent study of Americans found that brain cancer rates remained stable even as cell phone use grew exponentially from 1992-20083.

Studies of the effects of exposure from 20 or more years still need to be done (because cell phones have not existed for that long). But so far, in this case, one can safely say that it is very unlikely that cell phones hurt the brain-with the exception, of course, of getting hit on the head with one.

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Learn much more about how cell phone and cancer studies are done, and how to interpret them, here.

Image credit: HowStuffWorks.com

References:

1. Lenhart, A., Ling, R., Campbell, S., & Purcell, K. (2010, April 20). Teens and Mobile Phones. Retrieved May 31, 2012, from Pew Internet: http://pewinternet.org/Reports/2010/Teens-and-Mobile-Phones/Summary-of-findings.aspx

2. Frei, P., Poulsen, A. H., Johansen, C., Olsen, J. H., Steding-Jessen, M., & Schüz, J. (2011, October 20). Use of mobile phones and risk of brain tumours: Update of Danish cohort study. BMJ. (Open access)

3. Little, M. P., Rajaraman, P., Curtis, R. E., Devesa, S. S., Inskip, P. D., Check, D. P., et al. (2012, March 8). Mobile phone use and glioma risk: comparison of epidemiological study results with incidence trends in the United States. BMJ. (Open access)

Bio:

Kyle Hill is currently working as a research assistant at Marquette University in Milwaukee, Wisconsin, where he graduated magna cum laude with a bachelor's degree in Environmental Engineering and is now pursuing a master's degree in Communication with a focus on science, health, environment, and sustainability. His research is focused on how personal motivations and website characteristics affect the depth of information processing. You can follow him on Twitter under the name @Sci_Phile.