Jumat, 27 Juni 2008

Cell Phones and Brain Cancer

First, someone says (again) that cell phones may cause brain cancer. Then the FDA reports that there is no convincing evidence that cell phones are a health risk. (See “Experts Revive Debate Over Cellphones and Cancer”, The New York Times online, June 3, 2008.) What’s a consumer to believe?

This is a good example of the limitations of the scientific method, and why it is sometimes hard to know the truth. Regarding the first statement, yes, cell phones may cause brain cancer (and then again, they may not.) As for the second statement, it is true that there is still no scientifically convincing evidence that cell phones are a health risk. (but again, that doesn’t mean they aren’t!)

Why is it so hard to find the truth? First, brain cancers are so rare that one would have to study literally hundreds of thousands of people. Second, to do the scientific study properly, a controlled study would need to be done in which the lives of hundreds of thousands of people would have to be strictly controlled. It can’t be done. Third, no one has used cell phones for 50 years, so potential long-term effects won’t show up for awhile. And fourth, modern phones emit much less energy than the older models did.

What can we do? We can study those few patients with brain cancer and ask questions – questions about health habits, including past cell phone use. Self-reports by patients are notoriously unreliable, of course, so it may take hundreds of such studies before we consider the evidence “convincing”. We don’t need to panic, but we need to be watchful of the changing state of knowledge regarding cell phones and cancer.

You might remind your students that a similar question came up in the 1950s when smoking was actively encouraged – does smoking cause lung cancer? Who could have known that nearly sixty years later the rates of lung cancer in persons over 65 would be more than five times the rates of that same age group in 1950?!

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