CNN Explains: Cell phones and radiation
02:29 - Source: CNN

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High cell phone radiation exposure is tied to rare tumors in male rats in a government study

More research is needed to determine whether similar findings would emerge in humans

CNN  — 

Cell phone radiation and a potential link to cancer risks have left consumers and scientists alike scratching their heads since mobile phones became widely used in the 1990s.

Some studies have failed to show a link between radio frequency from cell phones and certain health problems, such as increased risks of tumors, while others suggest the opposite.

Now, two much-anticipated reports released Friday by the US Department of Health and Human Services’ National Toxicology Program add to the cell phone conundrum.

The comprehensive research reports detail findings from two large animal studies – one in rats and one in mice – that link high levels of cell phone radiation to some evidence of carcinogenic activity in male rats, including a rare type of tumor called a schwannoma in their hearts. There were no such significant findings in the female rats.

Similarly, no significant findings emerged in the mouse study, according to the reports.

The studies were a part of the National Toxicology Program’s 10-year, $25 million assessment of radiation exposure and potential health effects.

“One of the things that we found most interesting about our findings was that the malignant schwannomas – even though they occurred in the heart and not in the head of these animals – were in fact schwannomas,” said John Bucher, a senior scientist at the National Toxicology Program and one of the authors of the reports.

“These experimental animal studies are but one approach to understanding whether exposures to radio-frequency radiation pose a risk to human health,” he said, adding that studies are continuing at the National Toxicology Program to examine changes on the molecular level in tissue samples from the rodents.

He added, “I have not changed the way I use a cell phone.”

Although tumors and biological changes were found among rodents in labs, it remains unclear whether similar findings would emerge in humans, and more research is needed, Bucher said.

The US Food and Drug Administration notes that cell phones emit low levels of radio-frequency energy that are non-ionizing and thus not considered strong enough to permanently damage biological tissue including DNA.

Cell phone safety confusion and controversy

The National Toxicology Program studies involved about 3,000 rodents in all, Bucher said.

The animals were exposed to radio-frequency radiation levels equal to and higher than the highest level currently allowed for mobile phone emissions. The researchers tracked the health of the animals from in utero to two years after their birth.

A 2-year-old rat would be somewhat comparable to a 70-year-old human, Bucher said.

The researchers divided the rodents into two groups based on radio-frequency radiation levels, low or high, and exposed their entire bodies to radio-frequency radiation for 10-minute increments totaling to about nine hours a day over the two-year period.

“It’s important to consider the magnitude of the exposures to the animals in these studies in relation to what one might typically receive from using a cell phone,” Bucher said. “The lowest energy level of the radio-frequency radiation we studied was similar to the highest level currently permitted for cell phone emissions.”

Among the male rats, the researchers found tumors in about 6% of those in the highest radiation exposure group, Bucher said. That percentage “exceeded the mean historical incidence (0.8%), and exceed the highest rate observed in a single historical control group (2%) of completed peer reviewed studies,” the researchers wrote.

The researchers also found that the male rats in the high-exposure group appeared to live longer than the other rats, but more research is needed to determine why and how that may be relevant to the study results.

Overall, the findings “don’t go much further than what we have reported earlier,” he said.

In 2016, the National Toxicology Program released preliminary data indicating that high levels of cell phone radiation increased brain tumor growth in male rats.

Yet “after reviewing all of the data from these studies, the evidence for increased malignant schwannomas in the hearts of male rats is the strongest cancer finding in our study,” Bucher said.

“In our complete evaluation, we again had a lower level of certainty that small increases in the numbers of male rats with tumors in the brains were associated with e