Male rats exposed to very high levels of the kind of radiation emitted by mobile phones developed tumors in the tissues around their hearts, according to a draft report by US government researchers on the potential health risks of the devices.
Female rats and mice exposed in the same way did not develop tumors, according to the preliminary report from the US National Toxicology Program (NTP), a part of the National Institute of Environmental Health Sciences.
The findings add to years of research meant to help settle the debate over whether cellphone radiation is harmful.
However, NTP scientists and the US Food and Drug Administration (FDA) were quick to say the findings could not be extrapolated to humans and that current safety limits on mobile phone radiation are protective.
The 10-year, $25 million studies - the most comprehensive assessments of health effects and exposure to radiofrequency radiation in rats and mice to date - do raise new questions about exposure to the ubiquitous devices.
In the studies, about six per cent of male rats whose entire bodies were exposed to the highest level of mobile phone radiation developed schwannomas - a rare type of tumor - in nerve tissue near their hearts, while there were no schwannomas in animals that were not exposed to radiation.
“The intriguing part of this is the kind of tumors we saw were similar to tumors noted for quite some time in some epidemiological studies in heavy duty cellphone users,” John Bucher, a senior scientist with NTP, said in a telephone interview. “Of course, these were in the nerves in the ear and next to the brain, but the tumor types were the same as we saw in the heart.”
Dr Otis Brawley, chief medical officer of the American Cancer Society, noted that the studies were negative for common tumors.
“These draft reports are bound to create a lot of concern, but in fact they won’t change what I tell people: the evidence for an association between cellphones and cancer is weak, and so far, we have not seen a higher cancer risk in people,” he said in a statement on Twitter.
Brawley said if mobile phone users are concerned about this data in animals they should wear an earpiece.
Unlike ionizing radiation such as that from gamma rays, radon and X-rays, which can break chemical bonds in the body and are known to cause cancer, radiofrequency devices such as cellphones and microwaves emit radiofrequency energy, a form of non-ionizing radiation.
The concern with this type of radiation is that it produces energy in the form of heat, and frequent exposure against the skin could alter brain cell activity, as some studies have suggested.
In the NTP study, rats and mice were exposed to higher levels of radiation for longer periods of time than what people experience with even the highest level of mobile phone use, and their entire bodies were exposed all at once, according to the draft report.
Mobile phones typically emit lower levels of radiation than maximum levels allowed, the draft report said.
NTP, a part of the National Institutes of Health, will hold an external expert review of its complete findings from these rodent studies on March 26-28th.
Dr Jeffrey Shuren, head of the FDA’s radiological health division, said there is not enough evidence to say mobile phone use poses health risks to people.
“Even with frequent daily use by the vast majority of adults, we have not seen an increase in events like brain tumors,” he said in a statement. “We believe the current safety limits for cellphones are acceptable for protecting the public health.”
Nevertheless, the findings are potentially a concern for device makers, especially the world’s three biggest smartphone sellers, Apple Inc, Korea’s Samsung Electronics Co Ltd and China’s Huawei Technologies.
The CTIA, the trade association representing AT&T Inc, Verizon Communications Inc, Apple Inc, Sprint Corp, DISH Network Corp, and others, said on Friday that previous studies have shown mobile phone RF energy emissions have no known heath risks.
“We understand that the NTP draft reports for its mice and rat studies will be put out for comment and peer review so that their significance can be assessed,” the group said.
Samsung and Apple did not immediately respond to requests for comment. – Reuters