Can cellphone radiation cause cancer in humans? There’s no scientific consensus on this issue, but there is “some evidence” that exposure to radiation equivalent to that emanating from 1990s-era cellphones is associated with brain tumors in male rats, according to results of a US National Toxicology Program (NTP) study released last week (November 1).
“The exposures used in the studies cannot be compared directly to the exposure that humans experience when using a cell phone,” John Bucher, a senior scientist at the NTP, a government program within the department of Health and Human Services, says in a press release. “In our studies, rats and mice received radio frequency radiation across their whole bodies. By contrast, people are mostly exposed in specific local tissues close to where they hold the phone. In addition, the exposure levels and durations in our studies were greater than what people experience.”
Rats were exposed to radiation with a frequency of 900 megahertz, typical of the cellphones in use when the study was conceived in the 90s, for about nine hours per day for two years, The New York Times reports. The lowest levels of radiation used in the study were equivalent to the maximum exposure a phone can cause and still receive federal regulatory approval; the highest levels to which the animals were exposed were four times that.
Two to three percent of irradiated male rats developed malignant gliomas, compared with none of the rats in the unexposed control group, the Times reports.
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.
Today’s report, the final one, was about a decade in the making and is the last of several versions that have been released since preliminary results were presented in May 2016. It represents the consensus of NTP scientists and a group of external reviewers, according to the release. In the future, the NTP plans to conduct studies in smaller exposure chambers and to use biomarkers such as DNA damage to gauge cancer risk. These changes in the experimental setup should mean that future studies will take less time.
Even though this study does not report a risk to humans, people who want to lower their radiation exposure can do so by using headphones and holding phones farther from the body, CNN notes.