A major new study provides evidence of a possible link between cellphone exposure and cancer, at least in rats — findings that are likely to spark a fierce new debate about the 21st century’s most ubiquitous tech gadget.
When researchers exposed rats to the radiofrequency radiation emitted by cellphones, they saw higher incidence of two types of cancer: malignant gliomas in the brain and schwannomas in the heart. The increased risk was relatively small, but if the findings translate to humans — still an unknown — it could have a large public health impact, given the widespread use of cellphones worldwide.
The highly anticipated, $25 million study was conducted by the US National Toxicology Program and released late Thursday.
The findings add new urgency to a decades-long debate over whether cellphones can cause cancer.
But the research doesn’t settle that debate by any means.
It comes with major caveats. The statistically significant results were limited to male rats. Dr. Michael Lauer of the National Institutes of Health’s Office of Extramural Research, who peer-reviewed the study, concluded “there were no statistically significant differences in rates of glioma or schwannomas in females.”
The male rats exposed to radiation — about 9 hours a day, 7 days a week — lived longer than a control group not exposed to radiation. The authors also noted that it was unusual that no cancers occurred in the control group in this study. The incidence of malignant gliomas in male rats — 2.2 percent to 3.3 percent — was within the range seen in non-exposed rats in previous studies, they said.
Still, the authors said that the brain and heart tumors observed in rats exposed to the radiofrequency radiation are similar to malignancies seen in some epidemiological studies of cellphone use. They say their findings “appear to support” the World Health Organization’s classification of cellphones as a possible carcinogen. (That’s the same classification given to coffee and talcum powder.)
But other population-level studies in humans have found no increased risk, and the incidence of brain cancer has not risen in recent decades as cellphone use has exploded.
Ron Melnick, who was the lead investigator on the study until he retired in 2009, said that he had seen the study’s data himself.
The data “indicated that there were increased tumor responses in the brain and the heart,” he told STAT in a phone interview before the study was released. Melnick said he was asked for his opinion after the results came in because he had been involved in designing the study.
As recently as Wednesday, the NIH said the study was still under review by unnamed additional experts.
“This study in mice and rats is under review by additional experts,” NIH said in a statement. “It is important to note that previous human, observational data collected in earlier, large-scale population-based studies have found limited evidence of an increased risk for developing cancer from cellphone use.”
The agency did not immediately respond to a request for comment on the report’s release, which followed a Wednesday leak on what researchers had found.
The researchers have more data stockpiled that they haven’t reported. They say the rest of the results from the study will likely trickle out starting in late 2017.
The new study has the potential to start a firestorm. Until now, there have been conflicting results from other research about whether cellphones cause cancer, but the general takeaway from official authorities was that there is no definitive link — as the NIH statement reiterates.
But there have been now a streak of animal studies suggesting a cancer risk, said Dariusz Leszczynski, a Finnish researcher who focuses on radiation and health and reviewed the leaked news reports of the NTP study.
“Such positive results … suggest that human health might be in some danger,” he said in an email. “The human health risk might not only be possible but it might rather be probable.”
The findings could therefore jeopardize the conventional wisdom at a time when the number of Americans who own a cellphone has exceeded 90 percent in recent years.
“None of us expected them to find anything in this study. I’ve been quoted as saying it’s a total waste of money,” said David Carpenter, director of the Institute for Health and the Environment at the University of Albany.
The results have been long anticipated. An NIH official told Congress in 2009 that the results would likely be released in 2014, but their release appeared to be prompted only by this week’s leak.
“We’ve been waiting a long time for this study, far too long for this study,” said Joel Moskowitz, director and principal investigator at the Center for Family and Community Health at the University of California, Berkeley.
Still, he added: “The debate will keep going on, I’m sure. This is not going to be the definitive study.”