The American Cancer Society (ACS) states that the IARC classification means that there could be some risk associated with cancer, but the evidence is not strong enough to be considered causal and needs to be investigated further. Individuals who are concerned about radiofrequency exposure can limit their exposure, including using an ear piece and limiting cell phone use, particularly among children. (5)
Whether you call them cell phones, smart phones or mobile devices, it seems like everyone has one. According to the wireless telecommunications industry, the U.S. now has an estimated 300 million mobile subscribers, compared to 110 million subscribers a decade ago. The increase in cell phone use has generated concern about possible health risks related to radiofrequency electromagnetic fields from this technology, and a market for shields as possible protection against the radio waves the phones emit. The Federal Trade Commission (FTC), the nation's consumer protection agency, has some practical tips to help you avoid scams and limit your exposure to electromagnetic emissions from your cell phone.
The World Health Organization states that "A large number of studies have been performed over the last two decades to assess whether mobile phones pose a potential health risk. To date, no adverse health effects have been established as being caused by mobile phone use."[2] In a 2018 statement, the FDA said that "the current safety limits are set to include a 50-fold safety margin from observed effects of radiofrequency energy exposure".[3]
Rats were exposed to radiation with a frequency of 900 megahertz, typical of the cellphones in use when the study was conceived in the 90s, for about nine hours per day for two years, The New York Times reports. The lowest levels of radiation used in the study were equivalent to the maximum exposure a phone can cause and still receive federal regulatory approval; the highest levels to which the animals were exposed were four times that. 
Great article. I learned several things that I will put into use with my electronic technology. Thank you. There are numerous EMF/EMR blockers that you can stick on your cell phones, computers, (even microwave ovens for people who still use these). Each brand I’ve researched has the same goal but they’re all different. Are some brands more effective than others? If you can recommend some good brands, I would appreciate your advice. What are good features to look for when selecting the EMF blockers?
(Some common flaws in these studies: The summaries of the evidence weren’t comprehensive, the researchers often didn’t look at the quality of the studies they found, and they failed to do other simple things that would limit bias from creeping in. They also relied on case-control studies, a poor method to determine causality — more on that soon.) So we didn’t include these eight reviews in our analysis.

Parents and consumer advocacy groups occasionally capture attention for voicing concerns about cellphones and other types of non-ionizing radio-frequency radiation exposure, such as the energy emitted from wifi routers in schools. In some cases, they have exaggerated what we know about the risks to kids, and rarely note that cellphones are also just one of many radiation sources we all live with. (Even the Earth itself, the air we breathe, and the sun and stars in our galaxy constantly give off radiation.)

Several studies that will provide more information are under way. Researchers from the Centre for Research in Environmental Epidemiology in Spain are conducting another international case–control study—Mobi-Kids—that will include 2000 young people (aged 10–24 years) with newly diagnosed brain tumors and 4000 healthy young people. The goal of the study is to learn more about risk factors for childhood brain tumors.
Just as inevitably, worries about brain cancer spawned a market for products that supposedly protect cell phone users. For $62, you can order a Delta Shield, a thin polyester patch that contains a microchip that allegedly renders cell phones harmless. Users are instructed to place the patch on their cell phone battery. The similar BIOPRO Cell Chip, sold online for $35, attaches to the outside of the phone. The penny-size WaveShield 2000 Gold, selling for about $25, fits on the earpiece.
There were no biological hypotheses tested in the study. It was therefore only a numbers game. Ignored were mechanisms of disease found in other studies of cell phone radiation effects, including genetic damage, blood-brain barrier leakage, and disrupted intercellular communication. The study did not discuss any research supporting the notion that cell phones could cause problems in users.
"On the same [IARC] scale that said phone use was possibly carcinogenic, smoking is at the highest level. They are class 1 carcinogens; that's beyond doubt, they definitely do cause cancer ... There's an absolute difference between substances, where the evidence says that there is no doubt about the fact that they cause cancer, compared to mobile phones, where they say it is still possible because the data over ten years use still isn't in."

I really want to caution you to be careful of any "expert" or EMF blogger recommending anti-radiation filtering cases, stickers that attach to the phone or necklaces to "ward off" EMF.  I get it, when I first realized 25 years ago that I was sensitive to electromagnetic energy and then later, when I understood that without a doubt, man made electromagnetic radiation has a biological effect on my body, I wanted an easy fix.  I tried the shielding materials and cases and I just did not feel any better.  Then I bought meters to see if the energy changed and I actually noticed what the California Department of Health now says and it's what the FTC and FCC post warnings about:  "Some shielding materials can make exposures worse". So please, be careful and read on for what you can do to avoid electromagnetic radiation exposure.
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Most of the research is attributed to "SPSU," which is presumably St. Petersburg State Polytechnic University, and some of the research, it is suggested, was conducted at the Kirov Military Medical Academy, though it's unclear why a military academy would conduct clinical research on civilian cell phone radiation. The names of the scientists who conducted these studies are conspicuously absent, as are any published results.
Another part of the INTERPHONE study compared more than 1,000 people with acoustic neuromas to more than 2,000 people without tumors, who served as matched controls. As with gliomas and meningiomas, there was no overall link between cell phone use and acoustic neuromas. There was again a suggestion of a possible increased risk in the 10% of people who used their cell phones the most, but this was hard to interpret because some people reported implausibly high cell phone use, as well as other issues.

A full featured desktop or wall mount corded telephone (no microwaves) combined with a special ultra low EMF headset. You get all the benefits of a normal telephone without putting yourself close to the strong magnetic fields associated with the handset, speakerphone, or phone base. The special headset cord is about 3 feet long and uses a plastic tube to carry the sound to your ear. Absolutely no electronics, wires or magnets are near your ear. Cord provides distance from telephone base and traditional handset, convenient mobility, and can be extended up to 15 feet with option extension cord, sold separately (see below). Tested and approved by Less EMF Inc., dramatic field reduction when the headset is used. Although pictured as white, our current stock is a black phone.
The effect of mobile phone radiation on human health is a subject of interest and study worldwide, as a result of the enormous increase in mobile phone usage throughout the world. As of 2015, there were 7.4 billion subscriptions worldwide, though the actual number of users is lower as many users own more than one mobile phone.[1] Mobile phones use electromagnetic radiation in the microwave range (450–3800 MHz and 24-80GHz in 5G mobile). Other digital wireless systems, such as data communication networks, produce similar radiation.
Educate yourself about the RF sources in your home, and replace the devices that you can with non-wireless alternatives, and replace the wireless connections that you can with wired ethernet or other cord/cable connections. Note: most wireless devices can connect non-wirelessly, sometimes an easy-to-find adaptor accessory is required to use cords/cables.
The CERENAT study, another case–control study conducted in multiple areas in France from 2004 to 2006 using data collected in face-to-face interviews using standardized questionnaires (18). This study found no association for either gliomas or meningiomas when comparing regular cell phone users with non-users. However, the heaviest users had significantly increased risks of both gliomas and meningiomas.