What that study about cell phones causing cancer in rats really proves

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When scientists released findings last week from a $25 million rat study suggesting a potential link between cell phones and cancer, it was like dumping lighter fluid onto a slow-burning fire. For decades, both scientists and consumers have clung to suspicions that our phones are not merely anxiety-inducing distractions, but little death machines deceptively packaged in rose-gold brushed aluminum. This new study—the largest and most comprehensive of its kind—seemed to offer some kind of proof that the threat of our phones was real.


"It's the moment we've all been dreading," Mother Jones wrote. The findings, The Wall Street Journal wrote, were "explosive."

It wasn't long before a wave of stories urging us to see beyond the hype followed, offering a methodical debunking of each and every piece of confounding scientific data.

"No one has proven that cellphones cause cancer," wrote The Washington Post. "In fact, most research suggests otherwise!"

The truth of what this new research proves, though, exists in an uncomfortable in-between: researchers did not prove definitively that the radiation caused by our phones causes cancer, but the evidence they present suggests that the link between the two is not so easily debunked. Instead, it indicates that there are more questions to be asked before that question can be answered definitively at all.

In the study released online last Thursday, researchers at the National Toxicology Program chronically exposed rodents to levels of radiation intended to emulate the levels that those of us humans with a heavy smartphone habit might experience. Throughout their two-year lifespans, the rats were hit with radiation nine hours a day. Researchers studied multiple groups of 90 rats, exposing each to different levels of radiation, ultimately finding that as the thousands of rats in the study were exposed to more intense radiation, more developed brain and heart cancer. It was a riff on a classic experiment used frequently to study possible carcinogens in humans.

The concern that our phones might cause cancer stems from the impact that we know certain types of radiation can have on the body. We know that one type of radiation, ionizing radiation, like x-rays, causes cancer by damaging DNA. But conventional scientific wisdom holds that the less powerful non-ionizing radiation—what's emitted by your phone, your microwave and the lightbulbs in your house—does not. The question is whether that wisdom holds up in a world where we keep our phones in our hands or our pockets all of the time, constantly bathing our bodies in low-level radiation. And if non-ionizing radiation can cause cancer, just how much of that radiation does it take?


The research presented by the NTP is compelling. So far, the evidence for either side of the argument has been wildly conflicting and inconclusive. In the NTP study, scientists showed that certain populations of rodents exposed to radiation experienced increased rates of cancer while those in the control group did not.

"There had been so many studies before that had pretty consistently not shown elevations in cancer," David Carpenter, director of the Institute for Health and the Environment at the University at Albany told Scientific American. "In retrospect the reason for that is that nobody maintained a sufficient number of animals for a sufficient period of time to get results like this.”


On the other hand, the data also included many confusing findings that seem to muddle the impact of those results. Dr. Aaron Carroll, a professor at the Indiana University School of Medicine, did a close reading of the study and pointed out many things that should trigger skepticism. For one, elevated levels of some kinds of cancer were found in male rats, but not female rats, though both groups were subjected to the same radiation. And in male rats, there was only a statistically significant increase in brain cancer for rodents hit with one type of signal, called CDMA signals, but not the other, though in the real world CDMA signals emit less radiation.

And the most confusing result of all: those rats exposed to the potentially cancer-causing radiation lived longer than their peers in the control group, which did not develop cancer at all. This find is the most problematic. It suggests that the control group rats perhaps did not live long enough to develop cancer at typically occurring rates, suggesting a potential false positive. (It's worth noting that the researchers published only part of the data online prior to peer-review, after it was leaked online last week.)


"Cell phones are UBIQUITOUS in the United States. If they were causing cancer, we would expect to see rates of cancer going up, right? That’s not what we’re seeing," Carroll, a well-known cellphone-cancer skeptic, wrote. "They’ve been decreasing since the late 1980’s."

Joel Moskowitz, the director of the Center for Family and Community Health at Berkeley and a zealous advocate for the dangers of cellphone radiation, told me that many of those issues might be easily explained by information not included in the parameters of the study—perhaps those radiation-exposed rats lived longer, for example, because of other behavioral changes brought on by the radiation, like eating less (one thing which has been proven to extend life in rodents).


"This study is probably as close to definitive that we're going to get," Moskowitz told me. "It's a proof of concept."

The only thing that is actually definitive is that the long-term effect of our phones on our bodies is still a complete unknown. This new study offers only one small bit of data to assist in unraveling the great mystery of the biological impact of phones on humans. Moskowitz pointed out just how far we are from a definitive answer—the signal types studied in this research represent technology that is quickly becoming out of date. Even if researchers had proved that 2G cell signals can cause cancer, that does not mean that 3G or 4G or 5G signals do.


"We need to find out if 4G or 5G signals are less or more harmful and if there is a safe amount of exposure," he said. "That is the only way we can regulate the industry to make cellphone use safer."

We live in a world where the FCC’s legal limits for the amount of radiation a phone is allowed to emit haven’t been updated since 1996, when the technology we used was different and we used our phones far less often. We know only what we don't know, and, generally speaking when it comes to health what you don't know is a threat. In recent years, this lack of knowledge has led the World Health Organization and European Environmental Agency, to both publicly state that the potential health impacts of phones should be explored. On the iPhone, among the legal disclaimers, there is a warning advising consumers to limit “RF exposure” by carrying their phone at least five millimeters away from their face.


With our phones, there is equal danger in fear-mongering and in being too quick to debunk. Our phones have become a nameless boogeyman, one which inspires both fear and derision that the fear is unfounded.

It is a confusing line to walk. That is why that at the same time the NIH funded this research, it updated the website of the National Cancer Institute to reassure the public that despite the recent study, the "only consistently observed biological effect" of cellphone radiation "in humans is tissue heating."


"The body of published peer-reviewed evidence to date suggests that cell phone radiation is not carcinogenic," an NIH spokesperson told me via e-mail. "The study that was released last week contained preliminary findings that have not been peer reviewed."

What the NTP study showed us is that there are many more questions we should be asking, many more variables to study.


There is, of course, one easy solution to all this: we could all just spend a little less time with our phones.