For almost as long as people have had cellphones, scientists have been debating whether the now-ubiquitous devices cause health effects.
More than a decade ago, the U.S. government set in motion a study to help answer the question. Its initial findings were released this week. The researchers said the findings were significant enough that they felt the urgency to release the results before the entire study was complete.
The study found “low incidences” of two types of tumors—one in the brain and one in the heart—in male rats that were exposed to the kinds of low-level radio waves that are emitted by cellphones.
The researchers, as well as scientists not involved in the study, said it was still too soon to draw sweeping conclusions about whether cellphones cause cancer.
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“Much work remains to be done to understand the implications, if any, of these findings on the rapidly changing cellular technologies that are in use today,” said John R. Bucher, the associate director of the Department of Health and Human Services run National Toxicology Program, which conducted the study. Yet “we felt it was important to get the word out.”
Scientists pointed out some of the studies’ unusual findings: Tumors weren’t observed in female rats exposed during the tests. And rats that were exposed to radio-frequency energy lived longer than the control group, which had no exposure.
“There is a long way to go from the findings reported here…and a finding that radio-frequency [electromagnetic radiation] is a human carcinogen,” said Jonathan Samet, a professor at University of Southern California who was chairman of the World Health Organization committee that in 2011 determined cellphones were possibly carcinogenic.
The report was released late Thursday night after some of the study’s conclusions began to leak to the media. More than half of the 74-page document was scientific reviewers’ responses to the findings.
Michael Lauer, deputy director for extramural research at the National Institutes of Health, whose review of the results were included with the findings, said he couldn’t support the study’s conclusions. “The higher survival with [radio-frequency radiation], along with the prior epidemiological literature, leaves me even more skeptical of the authors’ claims,” he wrote.
The researchers said it wasn’t uncommon for toxicology studies to find results in one sex but not the other. “It’s often not explainable, but it’s not unusual,” Dr. Bucher said. “It is very difficult to explain why something doesn’t happen.”
Dr. Bucher said between 70% and 80% of the people who reviewed the results before its release felt there was a significant association. “This is not a universal conclusion as you can tell by the reviewers’ comments,” Dr. Bucher said. “Overall, we feel that the tumors are in fact likely to be related to the exposures.”
Wireless carriers and phone manufacturers deferred questions to a trade group called CTIA, which said it was reviewing the findings. In a statement, the CTIA said numerous international and U.S. organizations “have determined that the already existing body of peer-reviewed and published studies shows that there are no established health effects from radio frequency signals used in cellphones.”
This month, a survey of brain cancer rates in Australia reported no increase since the introduction of mobile phones there almost three decades ago, a result found in other countries, too.
“Given the lack of evidence for an increased incidence of brain tumors in the population in recent decades, I do not expect health agencies to react very strongly to these findings,” said Kenneth Foster, a professor of bioengineering at the University of Pennsylvania. “But they certainly will examine them carefully.”
Devra Davis, founder of advocacy group Environmental Health Trust, disagreed. “If we treat this as we did the early studies on passive smoking, asbestos, or hormone replacement therapy and wait for more proof of human harm before taking steps to reduce exposures our grandchildren will pay the price,” Dr. Davis said. “The absence of an epidemic of brain cancer at this time is not proof of the safety of cellphones.”
The Federal Communications Commission, which administers cellphone safety standards in the U.S., said it had been briefed on the results. In 2013, the agency said it would examine its safety standards to see whether they needed updating, though it has yet to make any changes.
“Scientific evidence always informs FCC rules on this matter,” a spokesman said. “We will continue to follow all recommendations from federal health and safety experts including whether the FCC should modify its current policies and RF exposure limits.”
The NTP study was designed to expose rats to levels of cellphone radiation that could be considered similar to what humans may experience by using a cellphone at maximum power.
The tumors were found in rats that were exposed to levels below the current U.S. exposure limits of 1.6 watts per kilogram. Tumors were also found in rats that had been exposed to levels above legal limits, but not high enough to cause the animals to heat up, researchers said.
A key element of the debate is what the biological mechanism might be that is causing the health effect. Until now, the only widely agreed upon way radio-frequency energy impacted humans was through heating tissues. Unlike X-rays, or other types of radiation, cellphones operate at frequencies that don’t affect cells or destroy DNA.
‘The results suggest that there may be no safe level of exposure to cell phone or wireless radiation.’
If the rats weren’t exposed to enough radio-frequency radiation to heat cells, yet still had health effects, the question is what mechanism might be causing that.
There also didn’t appear to be an increased risk based on increased exposure in the rats. That could mean radio-frequency energy isn’t the direct cause—or it could mean that the amount of exposure isn’t the determining factor.
“The results suggest that there may be no safe level of exposure to cell phone or wireless radiation,” said Joel Moskowitz, director of the Center for Family and Community Health at the University of California at Berkeley who has been an outspoken proponent of the idea that cellphones cause health effects. “We should encourage government and industry to take measures to reduce our exposure to wireless radiation.”
The NTP said it was unlikely that other similar studies could be conducted, given the size and scale of this one. Another factor is that new cellular technologies, such as high-speed LTE networks, weren’t around when this study first began in 2005. It plans to release the complete study results by the fall of 2017.
“We are aware of the fact there is certainly not an increase in brain cancer rates in the U.S. over the course of time,” Dr. Bucher said. “And this may well be because the current cellphone use is safe. This is an issue that we continue to look at.”
Ryan Knutson at email@example.com