A federal health panel on Thursday reported “higher confidence” that male rats can get cancer from heavy doses of cellphone radio waves.
No such cancer link was found in female rats, or in mice of either sex. And the small percentage of male rats that developed cancer were zapped with super-high doses of radiation — up to four times higher than what a 2G or 3G cellphone emits to a person.
“We do think the tumor responses here are real,” said senior scientist of the National Toxicology Program (NTP) John Bucher, speaking on a telephone briefing to reporters. However, “these are far higher cellphone radiation levels than people typically receive.” (The study did not test radiation levels of newer 4G or 5G cellphones.)
Many population studies of everyday use of cellphones by people have found no link to cancer. About 95% of Americans own some kind of cellphone, up from 62% in 2002. In that time, studies have shown flat or declining rates of cancer in the brain, the part of the body most exposed to cellphone radiation.
Part of the US National Institutes of Health, the NTP released a draft of the report in 2016. With the final report, the group found increased certainty — moving from “some” evidence to “clear” evidence — of a tumor link to heavy doses of cellphone radiation, at least in male rats.
Overall, the study found low rates — in the 2% to 3% range — of brain, heart, and adrenal gland tumors in 90 male rats dosed with nine hours a day of cell phone exposure for two years, starting in the womb. Two years of life for a rat is thought to be the equivalent of 70 for a person. Similar high doses to female rats, and male or female mice, produced at most equivocal evidence for causing such tumors.
“I would be very cautious about linking cellphones to cancer,” American Cancer Society Chief Medical Officer Otis Brawley told BuzzFeed News. Rates of brain tumors like the ones seen in the NTP study rats has been flat for 40 years among people, he noted, despite increasing cellphone use and much better brain scans that should detect tumors missed before.
“I don’t think cellphones cause cancer, but if they do, it’s clear they are killing a lot more people due to distracted driving than that way, or anything else,” he said.
The researchers did not have an explanation for the sex difference in the results, except they suspect the larger male rats simply absorb more radiation than smaller creatures. Whether the radiation triggers DNA damage or simply increased heating of the rats from the doses triggered the tumors was also unclear.
What’s more, the male rats in the study actually lived longer, on average, than their undosed counterparts despite having higher tumor risks, because they suffered lower rates of kidney disease.
“If I’m making a short call, I don’t have any hesitation about holding the cellphone to my ear,” said Bucher, asked about his own cel phone use. For longer calls, he uses earbuds “to increase the distance between the cellphone and my body.”
The NTP team has briefed the Federal Communication Commision and the FDA, which requested the study after the World Health Organization raised questions about cellphone safety in 2011.
“Cellphones will not be outlawed. However, the more we know about the biological effects, the safer we should be able to make them,” medical epidemiologist Richard Stevens of the University of Connecticut School of Medicine told BuzzFeed News. More studies of people are needed before making sensible risk recommendations, he added, which will take some time.
“As with all things in modern life, the question is whether the risks outweigh the benefits.”