WASHINGTON, May 27 (UPI) -- Despite concerns about low levels of radiation from cellphones increasing the risk of brain cancer among the 90 percent of Americans who use the devices every day, research has not shown an actual risk -- until now.
Low levels of radiation from cellphones caused the growth of brain tumors in rats exposed to it for long periods of time, researchers in the National Toxicology Program found in a recent study.
The link between cellphone radiation and cancer in mice was referred to by at least one scientist as a "game changer," because it shows RF radiation emitted by cellphones may be carcinogenic.
Although more research is necessary -- higher rates of cancer were found only in male rats, and the length of time the rodents were exposed to radiation may be much higher than what humans are exposed to from their devices -- confirmation of the effects of cellphone radiation is a big deal.
"This is by far -- far and away -- the most carefully done cell phone bioassay, a biological assessment," Dr. Christopher Portier, the retired head of the NTP who launched the study and continues to consult for the agency, told Scientific American. "This is a classic study that is done for trying to understand cancers in humans. 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."
For the study, published in the journal bioRXiv, researchers exposed more than 2,500 rats, male and female, to the type of radiation in cellphones for nine hours every day for up to two years.
Male rats exposed to the radiation developed two types of tumors, glioma tumors in the brain and schwannoma tumors in the heart, which were similar to those identified in previous international studies. Male rats not exposed to the radiation had normal levels of cancer, as did all female rats in the study, regardless of their exposure to radiation.
The two types of tumors rats developed as they were exposed to radiation have been linked to cell phone use in humans in a previous study by the International Agency for Research on Cancer, but had not been seen in experiments with animals. In the new study, between 2 and 3 percent of rats developed gliomas and between 6 and 7 percent developed schwannoma tumors.
The NTP says the research released this week is preliminary, and that the remainder of study data should be released sometime in 2017, STAT reported.
The early release also includes comments from researchers at the National Institutes of Health raising questions about how the study was conducted, its size and differences in results from previous studies they say may raise concerns.
"This study in mice and rats is under review by additional experts," the NIH said in a statement to Consumer Reports. "It is important to note that previous human, observational data collected in earlier, large-scale population-based studies have found limited evidence of an increased risk for developing cancer from cell phone use."