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The National Toxicology Program (NTP), a federal, interagency program whose goal is to safeguard the public by identifying substances in the environment that may affect human health, released two technical reports on Friday, 2 February 2018 on high-exposure radiofrequency (RF) radiation (cell phones) in rodents.

Bottom line: At most, the results suggest that RF energy is a weak carcinogen. The studies did not address human health risks, but the present results suggest that they would be quite low at realistic exposure levels. These levels were much higher than levels of cell-phone emissions allowed for humans. Given the evidence reported, current cell-phone limits adequately protect the public.

There was a significant amount of data generated and it will take time for the various health agencies to review and come to any conclusions. For the most part, results showed that higher exposure does not cause additional gliomas (tumors in the brain and spinal cord), yet showed an increase in tumors in tissues surrounding nerves in the hearts of male rats (but not female rats). Additionally, there were no health effects in the mice studied. Researchers mentioned at the briefing that the male rats in the high-exposure group lived longer than the other rats. They said more research is needed to determine why and how that may be relevant to the study results.

At the briefing, the investigators also emphasized the equivocal nature of the findings, meaning it was unclear if any of these tumor increases were related to RF radiation. The study showed no clear dose-response relationship, which suggests that the exposure did not directly cause the increase in tumors.

The relevance of the findings to humans is unclear. The exposure levels used in the study (1.5-6 W/kg) were well above whole-body exposure limits for humans (0.08 and 0.4 W/kg). The exposure levels to the rats were thermally significant, capable of inducing thermoregulatory changes in the animals. At this time, the researchers said it is not known how to assess the relevance to humans of the findings in the rats.

The International Agency for Research on Cancer classifies RF radiation from cell phones as a "possible" human carcinogen, meaning that the evidence supports some level of suspicion but is not strong enough to say the RF exposure "probably" or "actually" causes cancer.

The results of the NTP study need to be assessed by health agencies in the context of many other studies that have already been published. The study results may increase the level of suspicion that RF energy causes cancer, but it is not clear at present how large of an effect they will have on health agency conclusions about the matter.

To view the press release, click here.

Links to other stories on this topic:

Statement from Jeffrey Shuren, MD, JD, director of the FDA's Center for Devices and Radiological Health

Los Angeles Times: "Radiation From Cellphones Is Not Hazardous to Your Health, Government Scientists Say"

Fast Company: "Government Research Shows Link Between Cell Phone Radiation and Tumors in Rats"

Wall Street Journal (may require login): "Why the Largest Study Ever on Cellphones and Cancer Won't Settle the Debate"

The Washington Times: "High Cell-Phone Radiation Causes Tumors in Rats, but Humans Should Be Safe: Researchers"

Reuters: "High Levels of Cellphone Radiation Linked to Tumors in Male Rats: U.S. Study"

The Week: "Scientists Finally Agree That Your Phone Won't Give You Cancer"