We now have evidence that cell phone radiation can cause cancer in male rats. It is not cause for concern yet, as we are waiting for recommendations from the FDA and others. As always with these kinds of studies, the rats were exposed to a lot of radiation over two years. The original federal studies from the US National Toxicology Program, which uses labels to suggest how strong the evidence is, labeled the evidence "equivocal." That's the second lowest on the scale that the NTP uses, meaning there wasn't enough evidence to really make a connection. After the studies went through peer review, however, the committee upgraded the studies from "equivocal" to "clear" evidence. Clear evidence means they believe there is a provable link. This is the first study that's ever shown this.