Smartphones have become so ubiquitous that they're almost an extension of ourselves. So some new results from a long-awaited study sound pretty scary: researchers from the US National Toxicology Program found that cell phone radiation was potentially linked to a slight increase in the risk of certain types of cancer, in rats.
But the study comes with some major caveats—and only represents a partial release of the team's results. (More are coming in 2017, as the study is ongoing.) In other words, it isn't time to panic, because there is not yet an indication that these specific findings apply to humans who use mobile phones, of which there are many. The World Health Organization estimates there are 6.9 billion mobile phone subscriptions worldwide.
The study exposed groups of 90 male rats—thousands in all—to the same type of 900 MHz radiofrequency radiation (RF) that's commonly used in North American cell networks. The animals started their exposure as five-day-old fetuses in the womb, and the electromagnetic bath continued nine hours a day, for up to two years.
"This is far from a settled area"
Our normal cell phone use focuses the RF on a small portion of the head, but these animals faced exposure to a uniform field across their entire bodies, for their entire lives. They were literally bathed in it.
The study looked at three different intensities: 1.5 watts per kilogram; 3 watts per kilogram and 6 watts per kilogram. Meanwhile, the average exposure to our own heads when using a cellphone is about 1.6 watts per kilogram, according to study author John Bucher, who addressed reporters' questions about this work on Friday.
By the end of the experiment, 3.3 per cent of the rats in the lowest radiation category developed malignant gliomas, a type of brain tumour. The same result was seen in the medium-dose group. Interestingly, among the rats receiving the highest dose, only 2.2 per cent developed the tumours. In the control group receiving no radiation exposure, none of the animals developed gliomas.
The rats exposed to RF in all three exposure categories also showed a slight increase in a rare type of heart tumour, called a schwannoma, from 2.2 percent in the lowest exposure category to 5.5 percent in the highest. None of the control animals (the group that was not deliberately bathed in radiation) developed schwannomas.
Study authors say the increase in cancers seen in the rats exposed to RF is statistically significant, and that their data was reviewed by top experts in the field. But they aren't giving any explanation for why this increase in cancer was seen.
"We have a variety of studies that are either planned or proposed that might get at some of the molecular issues," said Bucher, associate director of the National Toxicology Program.
"Cell phone radiofrequency radiation has been studied for many, many years in a variety of different exposure scenarios. This is far from a settled area. But the new technologies that we are able to apply to these kind of studies now and in the future will help us understand the mechanistic underpinnings if in fact these tumours are related to RF radiation."
The study is drawing criticism. Although Bucher told reporters that the majority of the peer reviews of this work passed muster, one reviewer, Dr. Michael Lauer of the National Institutes of Health, wrote in the manuscript that he does not accept the findings and that the increase of cancer rates was attributable to "false positives," among other issues he took with the work.
Bucher believes that this study has value, if only to further the discussion about the potential cancer-causing properties of cell phone radiation. Without a doubt, it's an area that's calling out for more research.
As for whether we should all ditch our phones, the best approach for now seems to be wait and see. (The WHO offers ways to limit exposure, including by using a hands-free device.) Bucher says he doesn't plan on changing his own cell phone use, even though he told reporters he's only on his handset for an hour a day. "That may change after this," he said.
Correction: An earlier version of this piece said that the radiation "gave" rats cancer, but a causal link has not been established. The piece has been updated to reflect this.