Comments Now playing: Watch this: The FCC has also been criticized for not updating its cellphone safety standards since 1996. Critics say the levels should be reviewed based on the latest wireless technology. The agency uses a value known as a SAR, or specific absorption rate, to determine if devices can be safely sold in the US. The SAR measures the amount of power that’s absorbed in the body per given mass. While the FCC hasn’t updated its SAR level recommendations in nearly 25 years, others have reviewed the limits. In March of this year, the engineering group IEEE recommended the safety levels remain about the same as they have been since 1996.The bottom line is that we still can’t conclusively say whether 5G poses a health risk. To help you get a better handle on the issue, CNET has put together this FAQ.What’s the issue with cellular signals?Radiation is the emission of energy from any source. That means that even heat that comes from your body counts as radiation. But some forms of radiation can make you sick. We can organize types of radiation by their levels of power on the electromagnetic spectrum. Bigger wavelengths with lower frequency are less powerful, while smaller wavelengths at higher frequencies are more powerful. This spectrum is divided into two distinct categories: ionizing and non-ionizing. Ionizing radiation, which includes ultraviolet rays, X-rays and gamma rays, are the harmful forms. The energy from ionizing radiation can pull apart atoms, and it’s known to break the chemical bonds in DNA, which can damage cells and cause cancer. This is why the FDA warns against having unnecessary X-rays. It’s also why exposure to the sun can cause skin cancer.The electromagnetic spectrum is broken up into two categories: ionizing and non-ionizing. The high-frequency millimeter wavelengths that are expected to be used for some 5G deployments are in the non-ionizing category. CNET Non-ionizing radiation has lower frequencies and bigger wavelengths. It doesn’t produce enough energy to break apart the chemical bonds of DNA. Examples include radio frequency, or RF, radiation such as FM radio, TV signals and cellphones that use traditional 3G and 4G service. Microwave and millimeter wavelength radiation, which is one of the key blocks of spectrum that 5G service will use, is also considered non-ionizing (as is visible light) and doesn’t produce the kind of energy that directly damages cells. Common devices, such as Wi-Fi routers, garage door openers, airport security scanners and walkie-talkies, use lower-frequency microwaves.Does this mean that cellphone radiation doesn’t cause cancer?It’s complicated. Some experts suspect that the radiation from these devices could damage cells via another biological mechanism, such as oxidative stress in cells, which leads to inflammation and has been found to cause cancer, diabetes and cardiovascular, neurological and pulmonary diseases. Out of the thousands of studies that have been conducted over the past two decades, the results are mixed. Most of the studies published so far on the use of traditional cellphone service in the RF range haven’t found a link with the development of tumors, according to the American Cancer Society. But the group concedes that the majority of these studies had significant limitations, which leaves some doubt. 5G is an emerging technology that hasn’t really been defined yet. Michael Wyde, toxicologist Activists fear radiation from 5G wireless service could be dangerous to public health. And they want more research done before carriers deploy the technology. NurPhoto 5G promises lightning-fast speeds and the ability to power new technologies like self-driving cars and advanced augmented and virtual reality experiences. But an undercurrent to all of the things we can do with 5G is concern about what 5G can do to us. Mobile carriers throughout the world are racing to deploy this fifth generation of cellular technology. And the biggest cellphone makers are also readying their 5G handsets. President Donald Trump has made it clear that the US must not fall behind other nations, like China, in the effort to develop and roll out the technology. But not everyone believes the US should be pushing full steam ahead.There are concerns that the very high-frequency spectrum known as millimeter wavelengths used in early deployments to make 5G a reality could pose adverse health effects for the public. Samsung, LG, Motorola: How soon can we expect 5G phones? Cellphones and cancer: 9 things you should know right now 5G is coming but not everyone is happy about it How 5G pits big carriers and government against small towns 5G Related stories Still, neither the Environmental Protection Agency nor the National Toxicology Program has formally classified RF radiation as cause of cancer. But in 2011 the World Health Organization’s International Agency for Research on Cancer classified RF radiation as “possibly carcinogenic to humans” after studies suggested links to a specific type of brain tumor. But the agency also acknowledged that the evidence is limited. Just for reference, coffee and pickled vegetables are in the same “possibly carcinogenic” category as RF. “There is some evidence from epidemiological studies and other research on the biological effects that electromagnetic radiation could cause cancer,” said Jonathan Samet, a pulmonary physician and epidemiologist and the dean of the Colorado School of Public Health, who chaired the IARC’s committee in 2011. “But the whole body of evidence is not strong.” As a result, the committee couldn’t say for certain that cellphones are safe, but it couldn’t say they’re unsafe, either. Samet said more high-quality research is needed on how non-ionizing radiation, such as RF, might cause changes in cells.Last year, the National Toxicology Program also published final results of its decade-long study on rats, which found a link between exposure to high levels of 2G and 3G cellphone radiation and cancerous heart tumors in male rats. The study also found that the exposed rats outlived other rats that hadn’t been exposed to any radiation. In April, the Belgian government halted a 5G test in Brussels over concerns that radiation from the base stations could be harmful. Members of Parliament in the Netherlands are also calling on the government to take a closer look at 5G. Switzerland is taking steps to monitor 5G’s impact on people. In the US, New Hampshire is considering establishing a commission to study the health effects of 5G networks. Several leaders in Congress have written to the Federal Communications Commission expressing concern about potential health risks. And in Mill Valley, California, the city council blocked the deployment of new 5G wireless cells.These kinds of worries aren’t new. Consumers for years have been anxious about possible health effects of radiation in everything from microwaves to cellphones, prodded by claims that radio airwaves cause brain cancer, reduced fertility, headaches in children and other illnesses. My constituents are worried that should this technology be proven hazardous, the health of their families and value of their properties would be at serious risk. US Rep. Thomas Suozzi 5G and your health 13 Photos Mobile The deployment of new 5G networks, which requires many more small cell towers to be deployed much closer to where people live, work and go to school, is reigniting those fears. Lawmakers and policy makers throughout the world are starting to put on the brakes. The Food and Drug Administration and the FCC say there’s nothing to be worried about. Most studies haven’t found a link between radio frequency signals from cellphones or cell towers and disease, the agencies say. But in 2011, the World Health Organization said cellphones might cause some brain cancers, leaving open the possibility that a link exists between cancer and cellphone radiation. Critics say the safety of using millimeter wavelength for 5G technology hasn’t been tested and more information is needed before the US and the rest of the world race to deploy these next-generation networks. Share your voice Tags 4:36 It’s still unclear what, if anything, this means for human cellphone radiation exposure and cancer. Researchers involved in the studies noted that the exposure levels of the rats couldn’t be compared with exposure that humans experience since the rats received RF radiation across their entire bodies at intensity levels that were four times higher than what’s allowed for cellphones. Meanwhile, human exposure to RF radiation is localized to the head and is at lower power levels. Those researchers also acknowledged that these studies can’t tell us much about the effects of 5G.”5G is an emerging technology that hasn’t really been defined yet,” said Michael Wyde, lead toxicologist on the studies. “From what we currently understand, it likely differs dramatically from what we studied.” The phone industry maintains that there are no harmful effects from cellphone radiation, including 5G.”Radiofrequency energy from wireless devices and networks, including 5G, hasn’t been shown to cause health problems, according to the consensus of the international scientific community,” the wireless industry association CTIA said in a statement. The group has put together this FAQ on cellphone radiation and possible health effects. Does 5G pose greater health risks to people?The concerns about 5G are similar to the concerns about 2G, 3G and 4G, the earlier generations of wireless service. In fact, 5G in the US is expected to use some of the same frequency bands that previous generations of wireless have used, including low-band 600MHz frequencies as well as midband spectrum in the 2.5GHz, 3.5GHz and 3.7GHz-4.2GHz bands. But operators, such as AT&T and Verizon, are also targeting higher frequency bands for 5G. The FCC has already auctioned off airwaves in the 24GHz and 28GHz bands. Later this year, it’ll auction off licenses in the 37GHz, 39GHz and 47GHz bands. It’s this so-called “high band” spectrum that’s of most concern, because it’ll require denser radio deployments. There’s also less research on the effects of radiation at these higher frequency bands. That said, these high-band frequencies are still non-ionizing. As stated earlier, non-ionizing radiation doesn’t have enough energy to break apart DNA and directly cause changes to cells that could lead to cancer.Enlarge Image5G networks using millimeter wave frequencies will require small towers every few blocks instead of every few miles, which some people fear will increase exposure to cell tower radiation.But if researchers discover that non-ionizing radiation can set off some other biological chain reaction, such as oxidative stress in cells, it could be relevant to 5G. There are also additional concerns specific to 5G, due to the super high-frequency millimeter wavelengths used. Because signals transmitted over millimeter waves are limited in range and can’t penetrate obstacles like walls or even leaves on trees, networks using these frequencies will require radios on every city block, versus 4G gear that transmits signals over miles. This means that 5G will require up to five times the amount of infrastructure as 3G or 4G deployments. Not only will there be more 5G radios transmitting signals, but the radios will have to be closer to you. The sheer volume of devices transmitting signals so close to people is what concerns activists and lawmakers like Rep. Thomas Suozzi, a Democrat from New York. “Small cell towers are being installed in residential neighborhoods in close proximity to houses throughout my district,” he said in a letter to the FCC earlier this year. “I have heard instances of these antennae being installed on light poles directly outside the window of a young child’s bedroom. Rightly so, my constituents are worried that should this technology be proven hazardous in the future, the health of their families and value of their properties would be at serious risk.”What do activists say?Activists point to research that they say shows cellphone radiation affects human health, and they want 5G deployments halted until the safety of these devices can be determined. Martin Pall, a professor emeritus of biochemistry and basic medical sciences at Washington State University, says the evidence is clear that cellphone radiation is dangerous. He says results from existing studies show clear links between cellphone radiation and a wide range of medical maladies from cancer to infertility to depression. “What we’re doing is destroying our health,” Pall said in an interview. He added that if 5G deployments aren’t stopped, “we [as a society] are playing around with our very survival.” Pall isn’t alone in this thinking. Social media and other online forums are filled with similar predictions. A November 2018 post on Facebook that went viral blamed the mysterious death of 300 birds in the Netherlands on 5G testing. (The test actually took place months earlier.) There’s also lots of talk in these forums about the phone industry trying to suppress data about the dangers of cellphone radiation. Forum participants say the same deceptive tactics used by the tobacco industry to hide the dangers of cigarette smoking are being used by the wireless industry. Protesters in New York City want to stop 5G deployments until the industry can prove the networks are safe. Sarah Tew/CNET Though conspiracy theories around cellphone safety have existed for years, they’ve gotten more attention lately with the hype about 5G. A New York Times article published in March noted that the Russian propaganda network RT America has been at the forefront of running stories about harm from 5G. Community groups, like the Oakmore Neighborhood Advocacy Group in the San Francisco Bay Area, have cited some of the arguments presented by Pall and others during city council meetings and other community forums while speaking out against the deployment of 5G in their neighborhoods. Lawmakers on Capitol Hill have taken notice. Sen. Richard Blumenthal, a Democrat from Connecticut, and several Democrats in the House of Representatives, including Rep. Anna Eshoo of California, are demanding the FCC demonstrate that 5G is safe. What does the science say?Experts such as Kenneth Foster, a professor of bioengineering at the University of Pennsylvania, who has been studying the health effects of radio-frequency energy for nearly 50 years, says that Pall and other 5G activists have been cherry-picking findings from studies that support their views while ignoring other research that contradicts or finds no link between cellphone radiation and health hazards. We need more systematic reviews of the existing research and more well-done studies focusing on health-related endpoints. Kenneth Foster, professor of bioengineering, University of Pennsylvania 58 Foster, who sits on the IEEE’s standards committee for setting radio-frequency exposure limits, acknowledges that unlike at 3G and 4G radiation levels, which have been studied for at least two decades, there isn’t as much research on the biological effects of using millimeter wavelengths for 5G service. Samet, who chaired the WHO’s 2011 committee on cellphone radiation, said it’s still too early to know based on population studies if cellphone radiation causes tumor growth in humans. He said that it took at least 20 to 25 years after cigarettes began being mass produced for epidemiologists to notice the link between lung cancer and smoking tobacco. Since widespread cellphone use is relatively recent, we could still be a number of years away before we’d see an epidemic of cancer due to cellphone radiation exposure, he said.Are there any known biological effects of signals at millimeter wavelengths?The Department of Defense sponsored some studies in the late 1990s and early 2000s looking at the use of millimeter wavelengths as a non-lethal weapon. The “active denial” technology that the military employs uses very high-frequency millimeter wavelengths, above 94GHz, to produce an intense burning sensation that barely penetrates the skin and stops when the transmitter is switched off or when the individual moves out of the beam. The IEEE and the International Commission on Non-Ionizing Radiation Protection have used this research to set safety limits for the use of 5G millimeter wave, which are well below these levels, Foster said.What do the agencies that regulate cellphone safety say?FCC Chairman Ajit Pai has said the agency places a “high priority on the safety of wireless services and devices.” He said the agency’s guidelines for RF exposure are derived from guidance from the EPA, as well as the IEEE, the International Commission on Non-Ionizing Radiation Protection and the National Council on Radiation Protection and Measurements.”The FCC relies on the expertise of health and safety agencies and organizations with respect to appropriate levels of RF exposure,” he said. “These institutions have extensive experience and knowledge in RF-related issues and have spent a considerable amount of time evaluating published scientific studies that can inform appropriate exposure limits.”The FDA, which is also responsible for ensuring the safety of cellphones, has said that it “continues to believe that the current safety limits for cellphone radio frequency energy exposure remain acceptable for protecting the public health.”Can cities and towns in the US stop the deployment of 5G?Many local governments, including several in the San Francisco Bay Area and other parts of the country, are trying to stop the 5G rollout, insisting that companies prove the technology isn’t harmful to people. But the Telecom Act of 1996 prohibits local governments from using health or safety concerns as a reason to block cellphone deployment. Experts say more research is needed to understand whether there is a health risk associated with cellphone use. Sergei Malgavko Foster said that so long as equipment makers comply with the FCC’s safety standards, the agency can’t stop deployment of 5G. And he argued there’s a good reason for that.”The regulatory system requires manufacturers of RF-emitting equipment verify compliance with FCC safety limits, not directly conduct toxicity studies,” he said. “If this were done consistently for all newly introduced devices, it would basically stop any new RF products.”In the first six months of 2019 alone, the FCC approved more than 21,000 RF-emitting devices across the entire frequency range. “None of these, I assume, have been subjected to comprehensive toxicity testing,” he said. “But all had to be shown to comply with FCC safety limits together with many other regulations.”So is 5G millimeter wave service safe?According to expert agencies and the studies conducted so far, there’s nothing to suggest 5G millimeter wave is a significant health risk. But most experts say more quality research is needed. “Everybody, including me, seems to be calling for more research on possible bioeffects of 5G,” Foster said. “But what we don’t need is more fishing expeditions and cherry-picking of the literature. We need more systematic reviews of the existing research and more well-done studies focusing on health-related endpoints.”Originally published June 20, 5 a.m. PT.Update, 12:59 p.m.: Includes additional background information regarding which spectrum 5G will use in the US and activists’ assertions that 5G is dangerous.