When we think of harmful radiation, things like X-rays or gamma rays usually come to mind, but these types of radiation are different from mobile phone radiation in important ways. Radiation on the ultraviolet side of visible light, like those types just mentioned, has a wavelength that is short enough to alter some of the chemical properties of the objects it interacts with. It is referred to as ionizing radiation, for this reason. Non-ionizing radiation, which includes visible light, microwaves and radio waves, is typically regarded as harmless. Large amounts of it can produce a heating effect, like in a microwave oven, but no short-term damage has been linked to exposure to non-ionizing radiation.

In addition to the increased brain cancer risk, in male rats there was also “clear evidence” of a link between the radiation and malignant heart tumors and “some evidence” of a link to adrenal-gland tumors, according to the release. In mice and in female rats, however, the link between radiation and tumors was “equivocal,” or uncertain. The hierarchy, from most to least certain, of characterizations used by the NTP is: “clear evidence”; “some evidence”; “equivocal evidence”; and “no evidence.”Today’s cellphones use higher-frequency radiation that is less able to penetrate animal tissues than the radiation used in the study, the Times reports. Further, since cellphones became popular, epidemiologists have not observed an overall increase in the frequency of brain cancers known as gliomas in humans. 

Over time, the number of cell phone calls per day, the length of each call, and the amount of time people use cell phones have increased. Because of changes in cell phone technology and increases in the number of base stations for transmitting wireless signals, the exposure from cell phone use—power output—has changed, mostly lowered, in many regions of the United States (1).