The long-awaited results of a $25 million National Institutes of Health study on the effects of cellphone radio frequency radiation exposure on animals is out, and the results are mixed. They showed a higher risk of tumors, DNA or tissue damage and lower body weight in some groups of rodents, but no obvious ill effect in others, and no clear implications for human health.
John Bucher, a senior scientist involved in the 10-year study, was cautious in his interpretation of the results in a conference call with journalists on Friday. Given the inconsistent pattern of the findings, the fact that the subjects were rats and mice rather than people, and the high level of radiation used, he said he could not extrapolate from the data to potential health effects on humans.
"At this point we don't feel that we understand enough about the results to place a huge degree of confidence in the findings," he said.
Bucher also said that, "I have not changed the way I use a cellphone, no."
The study by the National Toxicology Program is believed to be the most comprehensive assessment of the health effects of such radiation on rats and mice and involved 3,000 test animals. A draft report was released on Friday for public comment and peer review, in advance of an external expert review on March 26-28. Among other things, reviewers will examine whether some of the results might be statistical noise.
The issue of cellphone radiation's impact on human health is one that has been hotly debated for years. In 2010, the Federal Communications Commission came under fire after it dropped a long-standing recommendation that consumers buy phones with lower radiation emissions. And in 2015, the city council in Berkeley approved a disclosure ordinance that directed sellers to let buyers know of the risk of carrying devices too close to their bodies. The CTIA, which represents the wireless industry, has sued, saying the warnings are "ill-informed" and violates retailers' First Amendment rights.
The strongest finding in the new study involved male rats - but not female rats or male or female mice - which developed tumors in the nerves surrounding their hearts. Researchers also saw increases in damage to heart tissue in both male and female rats. If these results are confirmed, Bucher said, they appear to suggest that this type of radiation could be a "weak" carcinogen.
The male rat tumors were so-called malignant schwannomas. Based on limited research that shows a potentially elevated risk of schwannomas near the brain in people, the International Agency for Research on Cancer currently lists radio-frequency fields as "possibly carcinogenic to humans."
The new NIH study showed tumors in rats and mice in other parts of the body - the brain, prostate, liver and pancreas - but the scientists said it was unclear if these were related to the radiation.
The experiment involved placing rats and mice into special chambers and exposing them to different levels of radiation that mimic 2G and 3G phones, which were standard when the study was launched, for 9 hours a day. Bucher emphasized that even the lowest levels used in the study were much higher than the maximum exposure even a frequent cellphone user would get. While the United States has transitioned to 4G, 4G-LTE and 5G networks in recent years, the 2G and 3G frequencies are still used in voice calls and texting.
In addition to cancer, the study looked at other health effects such as evidence of tissue damage from the heat of cellphones, DNA damage and changes in body weight. They said they some tissue and DNA issues but "we don't feel sufficient understanding to comment on their biological significance."
For example, Bucher said, "The patterns of damage to brain in tissues in these animals are not particularly consistent with tumor outcomes."
As for the weight issue, they saw changes in newborn rats and their mothers when exposed to high levels at the time of pregnancy and lactation. But they said the study was not designed to tease out whether this was a direct effect on the babies or if it impacted how the mothers cared for their young.
"We don't have any idea really," Bucher said. On the other hand, he added, the babies did grow to normal size.
Some health and environmental groups immediately seized on the findings as more evidence of the dangers of cellphones. The Environmental Working Group's Olga Naidenko, a senior science adviser, for instance, in a news release said the study "should raise alarms for policymakers and awareness for all Americans."
The CTIA had a different interpretation, pointing out that when partial results of the same study were released in 2016 numerous international and U.S. health organizations "maintained their long-standing conclusion that the scientific evidence shows no known health risk due to the [radio-frequency] energy emitted by cellphones."
The response from the Food and Drug Administration, which commissioned the study in the first place, was more muted.
Jeffrey Shuren, director of the FDA's Center for Devices and Radiological Health, said in a statement that the agency's preliminary understanding of the results "is that the study found mostly equivocal, or ambiguous, evidence that whole body radio-frequency energy exposures given to rats or mice in the study actually caused cancer in these animals." He noted some additional unusual findings in the study, and said his team is continuing to assess them, but emphasized that based on all available scientific information the agency does not believe there are adverse health effects in humans caused by cellphone radiation.
"Even with frequent daily use by the vast majority of adults, we have not seen an increase in events like brain tumors," he said. "Based on this current information, we believe the current safety limits for cellphones are acceptable for protecting the public health."