By Catherine Clabby

Results from high-dollar, long-term studies on cell phone radiation risks unveiled in Research Triangle Park this month prompted reassuring news around the world.

“Do Cellphones Cause Cancer? Maybe, in Some Rats, Anyway,” NBC News online pronounced. “No Need to Hang Up,” counseled The Hindu in India.

All that is accurate. Exposing lab animals frequently to radiofrequency radiation turned up no evidence that the devices billions of people carry in purses and pockets increased their risk of getting cancer.

For one, the radiation levels used in the testing were much higher than what today’s cell phones emit. For another, the test subjects were animals, not us.

But there is a twist: The studies found that very frequent, intense doses of the type of radiation cell phone create produced tumors in the hearts of some male rats. And those tumors were similar to brain tumors previously reported in some studies of people who were frequent cell phone users.

“Our results are interesting to me in that they show there is a biological response. We think they are a real response,” said John Bucher, a senior scientist with the National Toxicology Program, the federal outfit in Research Triangle Park that staged the studies.

Jeffrey Shuren, director of the FDA’s Center for Devices and Radiological Health, released a statement last week stressing that the NTP findings are not evidence that today’s cell phones can hurt people.

“[W]e have not seen an increase in events like brain tumors. Based on this current information, we believe the current safety limits for cell phones are acceptable for protecting the public health,” said Shuren, whose agency encouraged NTP to study health effects from cell phone radiation nearly two decades ago due to concerns over limited evidence of increased brain tumor risks.

Wide exposure

If cell phones or related technology today or tomorrow posed health risks to people, that would be a massive public health concern.

Mobile phone technology has colonized the planet. In the United States, the number of people using mobile phones is at least 265 million; the World Health Organization has counted 6.9 billion subscribers worldwide.

But scientists who watch this topic closely say their understanding of potential risks from cell phone radiofrequency radiation is not yet conclusive. Current radiation limits are based on preventing acute injury from heat phones can produce.

NIEHS' campus in Research Triangle Park.
NIEHS’ campus in Research Triangle Park. Photo courtesy: NIEHS

The International Agency for Research on Cancer, affiliated with the World Health Organization, in 2011 classified electromagnetic fields produced by mobile phones as possibly carcinogenic to humans. That was after some epidemiological studies that found increased risk for glioma, a malignant type of brain tumor, and acoustic neuroma, a non-cancerous tumor among frequent cell phone users.

The NTP studies, which cost $25 million, were designed to explore exposure risks in animals, in more systematic ways than earlier lab studies. NTP funded the construction of special testing chambers in Chicago that exposed the full bodies of rats and mice for as long as two years to varying intensities of precisely emitted 2G and 3G frequencies and modulations used in voice calls and texting today.

Exposure levels ranged from 1.5 to 6 watts per kilogram in rats, and 2.5 to 10 W/kg in mice. The lowest rates in the rat studies equalled the highest level the FCC allows from cell phones today, though phones don’t operate in ways that produce radiation that strong, Bucher stressed. Early cell phones did because they needed hefty signals to reach far fewer cell towers.


The new findings, which independent experts will assess March 26–28 at the National Institute of Environmental Health Sciences in RTP, could point scientists to additional needed research, Bucher said.

The heart tumors detected in some rats developed from Schwann cells, a type of peripheral nervous system cell that surrounds and supports nerve cells. Schwann cells, it turns out, are a type of glial cell. The brain tumors cited in the older epidemiological studies were gliomas (malignant) and acoustic neuromas (non-malignant) tumors that begin in glial cells too.

Future studies could probe just how exposure influences the creation of tumors on molecular scales, for instance. They could also help reveal thresholds at which this type of radiation may be unsafe.

“Cell phone technologies are constantly changing, and these findings provide valuable information to help guide future studies of cell phone safety,” Bucher said.

But who will pay?

Jonathan Samet, dean of the Colorado School of Public Health, led the international panel of scientists that labeled cell phone radiation a “possible” human carcinogen.

“This is something people are now exposed to through their lives everywhere on the planet. We have to understand if there is any risk,” Samet said.

The NTP findings, he said, are more evidence that the radiation can have  biological effects, which some critics of such studies have said is impossible because the signals were not strong enough.

A veteran of leading National Academy of Sciences panels that have explored risks from particulate pollution in air and risks from nanoscale materials, Samet said finding funding is one barrier that must be overcome.

One model could be the Health Effects Institute, founded in 1980. It is funded by U.S. Environmental Protection Agency and the global motor vehicle industry to independently research health effects from air pollution.

“The bottom line is we can’t write a clean bill of health for this. Therefore we need to better understand what this situation means,” he said.

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Catherine Clabby (senior environmental reporter) is a writer and editor. A former senior editor at American Scientist magazine, Clabby won multiple awards reporting on science, medicine and higher education...

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