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Once a mainstay of panicked internet fodder, there aren't many headlines about cell phones and brain cancer these days. Though the COVID-19 pandemic has overtaken many hot healthcare topics, there's likely more to it in this case, experts said.

Perhaps people have simply lost interest and are unlikely to give up their phones even if there was an association between radiofrequency radiation (RFR) and cancer. Or maybe limitations on research have stifled conversations.

Another possibility is that, while animal studies have been of concern to some experts in the field, others believe studies in humans have all but eliminated their worries. Still others explain that of the many risks for cancer, cell phone use just isn't one of them.

Even so, there are still areas of research that could be ripe for future findings, such as cell phone use in children, and the move to 5G. Also, the public health lessons from cell phones and brain cancer may prove beneficial beyond the research itself.

To help sort out whether people may still need to be concerned about cell phones and the risk of cancer, MedPage Today caught up with several experts familiar with the research and the potential considerations going forward.

"It's becoming more of a quiet area," said Emanuela Taioli, MD, PhD, of the Icahn School of Medicine at Mount Sinai in New York City. "It was very intense and controversial 5 to 10 years ago."

One reason for the drop-off is that a number of the large studies that were being conducted were showing no real association between cell phone use and brain cancer, she added.

Notably, the Interphone Study by the International Agency for Research on Cancer was conducted in 13 countries and in 2011 of brain cancer from cell phone use.

Other large-scale studies have included a nationwide cohort study in Denmark that found that cell phones , as well as the U.K. Million Women Study, which also concluded that cell phone use under usual conditions .

When those studies were launched, there was interest in conducting large-scale research that would cost many millions of dollars, because, even if the risk was small, "since we are all exposed, the public health relevance would be really high," Taioli said.

In those early days, there was a lot of concern, she noted. Phones would produce heat, and that was considered a potential sign of radiation entering the body.

Scientists worried what the overall effect would be down the line, she said. However, years later, the results from a number of studies, as well as the fact that incidence of may have contributed to waning interest.

Of note, research involving cell phone use is inherently hard to conduct.

So much of it relies on self-reporting, Taioli explained. It also involves trying to directly measure the use of the cell phone while it's against the head, she said. Other questions include whether the cell phone is pointed at another organ, how many hours a day the phone is directly against the head, and how long the phone has been used in that way.

Though Timothy Rebbeck, PhD, of the Dana-Farber Cancer Institute and Harvard T.H. Chan School of Public Health in Boston, concurred with certain limitations of large human studies, he said he believes experts in the field view the issue as largely settled.

"My take on it is, when you get to a certain level of human data ... the risk that might be conferred by cell phone use is so small," he noted.

There are experts who prefer animal studies because they argue that the epidemiological studies in people have limitations that may prevent researchers from seeing certain outcomes, he acknowledged.

Leeka Kheifets, PhD, of the UCLA School of Public Health in Los Angeles, pointed out that while epidemiological studies don't really point to a risk, there have been animal studies that were "a bit worrisome."

The National Toxicity Program that high exposure to RFR was associated with clear evidence of tumors in the hearts of male rats, as well as some evidence of tumors in the brains and adrenal glands of male rats.

"To better understand the biological basis for the cancer findings reported in the National Toxicology Program's earlier cell phone radiofrequency radiation studies, the NIEHS [National Institute of Environmental Health Sciences] built smaller RFR exposure chambers that have the ability to use a broader range of frequencies that will allow scientists to evaluate newer telecommunications technologies. Studies are being conducted to test the performance and operations of the smaller exposure chambers," wrote a spokesperson for the NIEHS in an email to MedPage Today.

As far as timing, "some technical issues were identified with the exposure system, and this delayed the start of both the mouse and rat studies," the spokesperson added. "Some pilot studies in the newly constructed systems have now been completed, and manuscripts are being developed to share the findings. One of the first papers being developed will focus on the exposure system being used for the studies."

Kheifets also noted that it may be important to study the effects of the move to 5G, and how that may affect exposure with more towers and more information being transmitted.

Despite this, Rebbeck said there are others who continue to hold that what is seen in animal models does not reflect what is seen in humans.

Limitations similarly exist in the study of pesticides and chemical exposure -- it can be difficult to measure in people, he noted. However, with cell phone studies, enough of them have been well done, and "we can be pretty sure that there isn't anything that we're missing," he added.

"I think that we can make a policy or public health decision that cell phones don't cause cancer based on the summary of the evidence," Rebbeck said.

Moreover, messaging on the topic is crucial to help put it all in perspective, he continued. It's important to consider the things that really matter when it comes to cancer risk, such as smoking.

There are things people can do -- cancer screening, prevention, and vaccines -- that "really make a big difference," he said. "If you're worried about cancer, there are many other things that you can do to reduce your cancer risk that are real."

Another area of study that hasn't been thoroughly examined is cell phone use in children, experts said.

"They are more vulnerable in general," Taioli noted. "General radiation for diagnostic x-rays, we try to avoid them in kids because the organs are developing."

Children from a very young age now have exposure to cell phones, she said. And that in and of itself may be worth studying.

One thing that all of the experts agreed upon is that much of the concern over cell phones and brain cancer has been all but erased. It's certainly not often that any of them see people with phones pressed up against their head anymore.

Between head/earphones and text messaging, cell phone use as society once knew it has virtually disappeared.

The switch may be more important from a public health perspective than meets the eye, Taioli said.

"This is an example where people adopted a healthier behavior without having official direction or guidance," she noted. "But people just by reading and looking at each other, they introduced a healthier way of using the phone. I can't think of another example of this in the field."

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