A two-year government study has found a small increase in two types of cancer in male rats exposed to the kind of radiation that cell phones emit. Given the ubiquity of cell-phone usage, the implications of the findings are substantial, if they are replicated in humans.
Scientists have investigated a possible link between cell phones and cancer for decades, and come up with mixed results. A huge study in Australia that was released this month tracked the incidence of brain cancer from 1982 to 2012 and compared it to cell-phone usage, which went from nonexistent to 90 percent of the country’s population during that time. Even accounting for a lag time of 10 years from the first exposure to radiation, the study found no rise in cancers associated with cell-phone usage. Previous studies with a similar design have also failed to find a link.
The latest work (PDF), released online late Thursday, complicates matters. Researchers at the U.S. government’s National Toxicology Program spent two years exposing 2,500 rats and mice to varying levels of radiation emitted by two wireless protocols commonly used in cell phones, GSM and CDMA, at frequencies of either 900 megahertz or 1900 megahertz. The results on rats were the only ones released. The study found a small increase in the incidence of glioma, a brain cancer, and schwannoma, a tumor found in the heart in male rats. Female rats and rats that were exposed in utero showed no increased incidence of tumors.
In 2011, the World Health Organization characterized cell phones as a group 2B carcinogen, due in no small part to a 2007 Interphone study that suggested heavy cell-phone users were at 40 percent higher risk of glioma than other groups. But the 2B classification is a bit confusing, as it includes the pesticide DDT and car exhaust, but also coffee and pickled vegetables. The official line is that being lumped in group 2B means cell phones are “possibly carcinogenic to humans.”
Some of the caveats to the latest study make things even less clear: the male rats exposed to cell-phone radiation actually lived longer than the control group, for example. Opinions also appear to differ depending on whom you ask. Ron Melnick, a former researcher at the NTP who ran the project until he retired in 2009, told the Wall Street Journal, “Where people were saying there’s no risk, I think this ends that kind of statement.” The National Institutes of Health, meanwhile is withholding judgment, releasing a statement emphasizing the lack of evidence of cancer risk found in previous studies.
So where does that leave us, the everyday cell-phone users? In just about the same place as we were before the work came out. As of now there’s no reason to doubt the veracity of the NTP study, and it will probably trigger a new round of debate on the issue. But the weight of evidence is not in agreement with this small signal that has been found in rats. Until similar results are replicated in people, there isn’t a great deal to worry about.