The US Food and Drug Administration (FDA) has taken the unusual step of contradicting colleagues at an agency within the National Institutes of Health after they claimed that a study they conducted into the effects of radio frequency radiation (RFR) showed “clear evidence” of an association with a form of heart cancer.
Scientists from the National Toxicology Program (NTP), part of the National Institute of Environmental Health Sciences within the National Institutes of Health, issued a report on November 1 in which they said that their study clearly showed that male rats exposed to high levels of RFR developed heart schwannomas, a form of cancer that is very rare in humans.
They also said that there was some evidence to suggest that exposed male rats were at increased risk of developing tumors in the brain and adrenal glands.
John Bucher, PhD, senior scientist at the NTP, said in a release: “We believe that the link between radio frequency radiation and tumors in male rats is real, and the external experts agreed.”
The FDA reacted promptly the same day.
“After reviewing the study, we disagree, however, with the conclusions of their final report regarding ‘clear evidence’ of carcinogenic activity in rodents exposed to radiofrequency energy,” said Jeffrey Shuren, MD, JD, director of the Center for Devices and Radiological Health at the FDA.
“The totality of the available scientific evidence continues to not support adverse health effects in humans caused by exposures at or under the current radiofrequency energy exposure limits,” he continued.
“We believe the existing safety limits for cell phones remain acceptable for protecting the public health,” the FDA concluded.
Final Results From Long-term Studies
The NTP studies took more than 10 years to complete and cost $430 million.
Draft results were released in February 2018, as reported in detail at the time by Medscape Medical News. This latest announcement was a final report of the findings, disseminated in press releases and a press briefing.
The studies involved exposing male and female mice and rats to RFR with modulations that are used in 2G and 3G cell phones. These were the standard technologies in use at the time the study started (the study was nominated in May 1999).
Exposure levels were far higher than that typically experienced by humans using cell phones. The lowest level was the maximum permissible exposure for cell phone users; subsequent levels rose to four times that.
Acknowledging this, Bucher said: “The exposures used in the studies cannot be compared directly to the exposure that humans experience when using a cell phone.”
He added: “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.”
He pointed out that the whole-body exposure performed in the study is “commonly done” in studies such as these to replicate the effects seen in animal tissue exposures.
However, he echoed comments made by the NTP at the release of the draft results earlier this year, saying, “These findings should not be applied to human cell phone use.”
In the FDA announcement, Shuren emphasized that the study yielded some “unusual findings,” including that exposed male rats lived longer than unexposed rats, that only the highest energy dosage was significantly associated with the development of heart schwannomas, and that there was no true dose response.
“Researchers will need to consider all of the findings when exploring future human epidemiological studies,” Shuren said.
“We must remember the study was not designed to test the safety of cell phone use in humans, so we cannot draw conclusions about the risks of cell phone use from it,” the FDA commented.
Shuren’s statements, however, did not stop the story from taking on a life of its own.
In the United Kingdom, the Daily Mail coveredthe story with the lurid headline, “Cell phones ARE linked to cancer, landmark study finds.”
It made the claim that there was “clear evidence” of a link between heart, brain, and adrenal gland cancers “front and center,” saying that the link in male rats is “undeniable.”
The story does acknowledge, however, that the exposures were “much higher” than those seen in humans and that the evidence was “less clear” for female rats and mice of both sexes.
“Still, scientists warn that the new research suggests that men in particular should take precautions to minimize the exposure of sensitive areas to cell phone radiation,” the newspaper said.
The article notes that the study employed older technologies and that since then, 3G and 4G technologies have become industry standards.
“While newer technologies have continued to evolve, it is important to note that these technologies have not completely replaced the older technologies,” Bucher is quoted as saying. “In fact, today’s phones are very complex in that they contain several antennas, for Wi-Fi, GPS, 2G/3G bands, etc.”
The New York Times also reported the NPT study, noting that the next-generation phones “employ much higher frequencies.” They add, “these radio waves are far less successful at penetrating the bodies of humans and rats, scientists say.”
Despite the numerous caveats that accompany the findings, Bucher said in a telephone press conference that he has “never been a heavy user of a cell phone” but has become “a little more aware of my use of cell phones” since taking part in the studies.
“If I’m making a short call, I have absolutely no hesitation at all in picking up the phone and using it in a traditional manner,” he added.
“If I’m on a conference call for an hour or two, I tend to just think about using earbuds or some other way of increasing the distance between the cell phone and my body,” he said.
Anthony B. Miller, MD, PhD, professor emeritus at the Dalla Lana School of Public Health, University of Toronto, Canada, went further.
The Daily Mail quoted him as saying: “This animal evidence, together with the extensive human evidence, coupled with the rising incidence of brain cancers in young people in the US, conclusively confirms that radio frequency radiation is a Category 1 human carcinogen.”
Details of the Studies
In the NPT studies, the animals were housed in bespoke chambers with a transmitting antenna that radiated RFR fields and rotating stirrers that generated uniform exposure.
In the study, rates and mice were exposed to whole-body RFR. The rats were exposed at a frequency of 900 MHz; the mice, at a frequency of 1900 MHz. Two technologies were employed: code division multiple access (CDMA), and the Global System for Mobile Communications (GSM).
These technologies were chosen because CDMA and GSM are commonly used in the United States and Europe. There are substantial differences in their signal structure, which the researchers believed may result in different RFR exposures.
The exposure levels were 1.5 to 6 watts per kilogram for rats and 2.5 to 10 watts per kilogram for mice at periods of 10 minutes on and 10 minutes off for approximately 9 hours per day.
Exposure began in the womb for rats and at 5 to 6 weeks of age for mice. Exposure continued for up to 2 years, which equates to the majority of their natural lifespan. Incidence rates of cancer were then compared with unexposed control animals.
Michael Wyde, PhD, who was the lead toxicologist on the studies, said in a release: “A major strength of our studies is that we were able to control exactly how much radio frequency radiation the animals received — something that’s not possible when studying human cell phone use, which has often relied on questionnaires.”
The researchers found what they describe as “clear evidence” of an association between RFR exposure and malignant schwannomas in the hearts of male rates.
They also found “some evidence” of an association between RFR exposure and the development of malignant gliomas and adrenal gland tumors in male rats.
However, in female rats and in both male and female mice, the evidence as to whether there was an association between RFR exposure and the development of cancers was “equivocal.”
RFR exposure was associated with lower body weights among newborn rats and their mothers, particularly exposure to high levels of RFR during pregnancy and lactation. The animals went on to grow to a normal size.
It was also observed that lifespan was longer for male rats exposed to RFR than for unexposed rats, which Wyde suggested “may be explained by an observed decrease in chronic kidney problems that are often the cause of death in older rats.”
The NTP is building smaller exposure chambers for future studies, which will allow newer technologies to be evaluated in weeks or months, rather than years.
These studies will focus on identifying biomarkers of the potential effects of RFR exposure, such as DNA damage in exposed tissue.
The study was funded by the National Institutes of Health. The investigators have disclosed no relevant financial relationships.