STATS ARTICLES 2011
Cell phones as (non) Cancerous as Coffee, Firefighting?
Trevor Butterworth, June 3, 2011
The World Health Organization assembled an advisory committee on the health risks of cell phones, the result is confusion.
Once again, a scientific claim is making world headlines before the study in which it is embedded is published. After convening an expert committee to pore over the existing research on cell phone usage and cancer, the International Agency for Cancer Research (a part of the World Health Organization) announced that it had
“classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (Group 2B), based on an increased risk for glioma, a malignant type of brain cancer1, associated with wireless phone use.”
This meant that cell phone usage was “possibly” carcinogenic in the same way that coffee is “possibly” carcinogenic. Other 2B carcinogens include caffeic acid, which is present in many vegetables, and, interestingly, being a firefighter. Does that mean we should avoid coffee, give up vegetables, and ban firefighting?
Of course not.
Virtually no-one thinks coffee is, realistically, a carcinogen. Sure, 72 percent of the naturally occurring chemicals in roasted coffee produce tumors in rodents. But these only happen at extremely high doses, as that indispensable font of common sense, the Carcinogenic Potency Project at UC Berkeley, points out; it is simply impossible to replicate this kind of dose through drinking coffee. On the other hand, how does one quantify occupational exposures as a firefighter?
This would seem to be the key problem with using the IARC classification list as a way of communicating risk to the public: it says nothing about exposure. “Possible” has become the new gold standard of precautionary thinking, driving public health communication; but it is, by definition (impossibly) vague.
Geoffrey Kabat, Senior Epidemiologist at Albert Einstein College of Medicine, and a specialist in cancer epidemiology offered several points of caution about over-interpreting the IARC’s classification – or, in other words, why we should be cautious about being overly precautious. “Look at the Scandanavian countries,” he says, “where they have excellent cancer registries for the whole population and where cell phone use became widespread relatively early, compared to other countries: they have not found increased rates for different types of brain tumors.”
Second, there is, he says, “no known mechanism whereby RF/microwave radiation could induce or promote cancer -- it does not have enough energy to knock electrons out of atoms and thereby damage DNA and other cellular molecules.”
Because the IARC issued its statement before it published its paper, we are only able to guess at the quantitative evidence driving their decision, but the reference to the risk for glioma, a type of brain tumor, strongly suggests that the committee relied on the INTERPHONE Study Group paper published last year.
This study looked at odds ratios (OR): the odds for getting cancer if you ever used a cell phone regularly, divided by odds for getting cancer if you never used one regularly. But the results of this study were clearly baffling, even to the authors. Overall, regular users of mobile phone had significantly reduced risks for glioma and meningioma. Only in the small group of users (highest tenth) , whose recalled cumulative call time was >1640hours, was there a modest increase in risk of glioma (but not meningioma). The authors went to great lengths to caution against giving a causal interpretation to this result, in view of the biases and uncertainties inherent in the study.
And a strong dose of caution is needed because this kind of study relies on recall data. Do people accurately recall how much time they spend on the phone? More importantly, do people with brain cancer recall things differently than people without it?
The IARC said they couldn’t ignore this study’s findings, which leaves an the impression that they put more weight on them than its authors did, while giving, in effect, less weight to an expansive and thorough 2009 review of review of the epidemiology by the International Commission for Non-Ionizing Radiation Protection. Again, the failure to publish their detailed study at the same time as they released their conclusion makes assessing the IARC’s reasoning difficult.
Right now the decision to announce cell phone use a “possible carcinogen” seems incautiously precautious. Either way, if you are a heavy cell phone user, you can eliminate this hypothetical risk with a real Bluetooth headset.