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.
Jeff is worried that using a cell phone is dangerous because of electromagnetic radiation. Leo says that there's no evidence at all that one could get brain cancer from a cell phone.The theory is sensible because electromagnetic radition can damage human cells, but it's in proportion to power output and cell phones are just too low power to do that. People don't really use smart phones as actual phones anymore, anyway. They use them as handheld computers.