LinkDr. Herberman is a highly respected cancer center director, which is why I can't help but wonder just what on earth he was smoking when he decided to do this. It strikes me as being rash in the extreme; the announcement even admits that the published data do not support a link between cell phone use and brain tumors. This is alarmism that, I suspect, even Revere would have a hard time supporting, because it goes far beyond the published evidence and is based on "early unpublished data." Scaring the nation based on "early unpublished data" is irresponsible in the extreme. Why did Dr. Herberman do it?
The question of whether cell phones cause or contribute to the development of brain tumors is not as easy a question to answer as one might think. First, there is the issue of biological plausibility. Radiowave energy at the power level used by most cell phones, is not ionizing, and our understanding of cancer is that, in general, ionizing radiation is what is required for radiation to cause or contribute to cancer. That does not mean that there isn't a potential mechanism by which non-ionizing radiation can cause cancer that we don't know about yet, but it makes hypothesis that cell phone radiation causes brain cancer less plausible. Too, we can actually test radiofrequency radiation in the same power range used in cell phones on cells in cell culture in order to determine whether exposure to such radiation can cause changes associated with malignant transformation. There is one confounding effect that has to be controlled for in such experiments (but is not always), namely that radiofrequency radiation interacts with water in order to heat it. Still, there are no compelling studies showing any specific effect of radiofrequency radiation on cells to induce changes associated with malignant transformation, at least none that I'm aware of. Animal studies are prone to the same sorts of problems as cell culture studies, but even so there is no good quality animal data that I'm aware of implicating cell phone radiation in the formation of cancer. On a basic science basis, there doesn't appear to be strong evidence of a plausible mechanism or effect.
That brings us to epidemiological studies. For us to consider any epidemiological to be support for the hypothesis that cell phones cause brain cancer, there must be a few key results. First, there must be an increased incidence of brain cancer in cell phone users. It's even more convincing if there is some sort of dose-response phenomenon. In other words, there should be an increasing risk of cancer with increasing cell phone use. Other results that also support the hypothesis would be tumors correlated with proximity. In other words, do people who primarily use their left hand to hold their phones to their ears tend to get tumors primarily on the left and people who primarily hold their phones with their right hand tend to get tumors primarily on the right? Finally, there should be a plausible lag time between exposure and tumor development consistent with known lag times for cancer, say 10-20 years, and some specificity. In other words, does exposure to cell phone radiation correlate with certain types of tumors and not others? There are other aspects of the results of a study that can more strongly support the hypothesis that cell phones cause brain cancer, but these are the main ones.
In general, however, getting "clean" data from an epidemiologic study of cell phone use that can support a strong enough correlation to suggest causation is very difficult. In order to correlate cell phone use with an increased incidence of brain tumors, it's necessary somehow to be able to reliably quantify cell phone usage. This presents a big problem. It's generally not possible to continuously observe people with their cell phones for years on end and obtain objective measurements. Another way is to ask people how much they use their cell phones, but memories are unreliable, and such methods are very prone to recall bias in the form of people with brain tumors being more likely to remember their cell phone use as having been heavy. That's not even counting trying to control of the number of potentially confounding factors, such as heavy cell phone use being associated with certain jobs or, especially for 10-20 years ago when cell phones were far less common, with higher socioeconomic status. Then there's the shift in technology from analog to digital in the early 2000s, which changed the power and frequencies used.
More after the jump.
Printer-friendly format
Email this thread to a friend
Bookmark this thread
(1000+ posts)
Send PM |
Profile |
Ignore
