There's been a lot of chatter about cell-phone use leading to brain cancer. But
that conversation may be nearing its termination, unless Scandinavian skulls provide protection against radio-frequency electromagnetic radiation that other ethnic groups lack.
A study reported Dec. 3 in the Journal of the National Cancer Institute drew a lot of media attention last week. The study looked at nearly 60,000 men and women aged 20-79 years who were diagnosed with brain tumors in Denmark, Finland, Norway, and Sweden between 1974 and 2003. That huge study sample and very long study period were made possible thanks to these countries' penchant for precise medical records.
The study concludes that no meaningful increase in brain tumors occurred during that lengthy period that could be credibly attributed to cell phone use, whose toll - if there were one - would have been expected to become noticeable in later years when cell-phone use became as ubiquitous as indoor plumbing.
A few comments:
1) Data mining digs up a fair amount of fool's gold. Some - and only some - earlier epidemiological studies showed relatively weak associations between cell phones and brain cancer, or one or another form of leukemia, or whatever. Notably, studies showing an association between cell-phone use and X failed to show an association with Y or Z, while studies finding a link between cell-phone use and Y found no link to X or Z, etc. Lesson: If you comb through data from a large study long enough, you're bound to find some kind of "link." That's the nature of random noise. Accepted scientific practice is to specify in advance the relationship you're looking for, than see if you get it, rather than just sift through the results until you stumble on a quirky one.
2) Extraordinary claims require extraordinary evidence. All scientists agree that ionizing electromagnetic radiation at ultraviolet or higher frequencies (including X-rays) has enough power to break bonds that tie electrons to atomic nuclei, creating ions - that's why these frequencies are known as "ionizing radiation" - and that this can cause chemical damage to living tissue. No one has ever explained how low-frequency radiation, incapable of disrupting such bonds, can cause damage unless there's enough of it to heat tissue to a dangerous temperature. Cell phones don't emit nearly enough radiation to do that.
3) Advances in diagnostic technology lead to increases in observed frequencies of whatever you're diagnosing. In this case, there was an overall upward trend, between 1974 and 2003, of about 0.5% per year in diagnosed brain tumors. The study's authors note that:
The introduction of computed tomography in the mid-1970s and magnetic resonance imaging in the mid-1980s improved the detection of brain tumors and possibly resulted in different diagnostic approaches for common symptoms of brain tumors such as headache or dizziness.
Steady improvements in diagnosis go a long way toward explaining the fairly steady increase in observed incidence of brain cancer, which does not track with the relative explosion in cell-phone use in the 1990s.
None of which means you won't get creamed by a semi while careening down Highway 280 at 96 mph blabbing into that little block of plastic. That risk is real.
Photo by Noah Sussman
