“This is by far—far and away—the most carefully done cell phone bioassay, a biological assessment. This is a classic study that is done for trying to understand cancers in humans,” says Christopher Portier, a retired head of the NTP who helped launch the study and still sometimes works for the federal government as a consultant scientist. “There will have to be a lot of work after this to assess if it causes problems in humans, but the fact that you can do it in rats will be a big issue. It actually has me concerned, and I’m an expert.”

But others beg to differ. Earlier this year 190 independent scientists representing 39 countries (including the United States) appealed to global health organization to strengthen cellphone guidelines and ensure the public be “fully informed about the potential health risks from electromagnetic energy.” These scientists, who have collectively authored more than 2,000 papers on the topic, add to a growing number of prominent experts and government agencies around the world who are holding up a caution sign for consumers — particularly when it comes to kids.

Bottom line: if you’re carrying your phone in your pocket, sock, bra or anywhere against your body, the manufacturers can't guarantee that the amount of radiation you're absorbing will be at a safe level. Distance is your friend.

“Phones are transmitting radiation so long as they are connected to the Internet or connected to Wi-Fi, and even if you're not talking on your phone, your phone is talking to the tower,” Dr. Devra Davis, a former White House senior health adviser, said

Be aware that your phone is, in essence, always transmitting. Experts suggest that if you plan to watch a movie on your device, download it first, then switch to airplane mode while you watch in order to avoid unnecessary radiation exposure.

“Children are not little adults,” Dr. Gisela Mercada-Deane, chair of radiology at the American Academy of Pediatrics, said. “The amount of radio frequency that children will be exposed by the time they are our age [an adult] is exponential to the amount of radiation, radio frequencies that we ourselves are being exposed to in a lifetime.”