However, there have been some studies that have shown that rats can develop a specific type of brain tumor, called a schwannoma, if they're subjected to prolonged radiofrequency radiation. These studies examined thousands of rats and mice, and exposed them to a variety of radiations — everything from "near-field" (which is what you get holding a phone to your ear) to "far-field" (which is what you get walking through everyone's Wi-Fi signals at Starbucks).

The pacemaker studies were a harbinger of bad things to come. Results showed that cell phones do indeed interfere with pacemakers, but moving the phone away from the pacemaker would correct the problem. Amazingly, the industry was extremely upset with the report, complaining that the researchers went off target. When Dr. Carlo and his colleagues published their findings in the New England Journal of Medicine in 1997,11 the industry promptly cut off funding for the overall program. It took nine months for the FDA and the industry to agree on a scaled-down version of the program to continue going forward. Dr. Carlo had volunteered to step down, since he was clearly not seeing eye-to-eye with the industry, but his contract was extended instead, as no one wanted to look bad from a public relations standpoint.
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)
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. 
The phone is placed in various positions on the head and body, including held to both ears, and all measurements are taken and reported to the FCC when the manufacturer is seeking approval. However, it should be noted that only the very highest SAR values for each type of radiation are included in final consideration for compliance with the FCC’s guidelines.
If not, then how can the seller claim that the reported effects on cell cultures, muscle strength testing, plants, skin heating, or other biological effects are due to electromagnetic changes (see for example)? Electromagnetic field characteristics are well known and easy to measure. If there is truly an electromagnetic change, that change will be easy to detect and measure.
Studies in people: Another type of study looks at cancer rates in different groups of people. Such a study might compare the cancer rate in a group exposed to something like cell phone use to the rate in a group not exposed to it, or compare it to what the expected cancer rate would be in the general population. But sometimes it can be hard to know what the results of these studies mean, because many other factors that might affect the results are hard to account for.
What the study showed: Self-reported cell phone use was not associated with an increased risk of glioma, meningioma, or non-central nervous system tumors. Although the original published findings reported an association with an increased risk of acoustic neuroma (14), this association disappeared after additional years of follow-up of the cohort (15).

A few other health concerns have been raised about cell phone use. One has been whether the RF waves from cell phones might interfere with medical devices such as heart pacemakers. According to the FDA, cell phones should not pose a major risk for the vast majority of pacemaker wearers. Still, people with pacemakers may want to take some simple precautions to help ensure that their cell phones don’t cause a problem, such as not putting the phone in a shirt pocket close to the pacemaker.

SafeSleeve was founded in California by two Engineering graduates (University of Cal Poly San Luis Obispo) Cary and Alaey, with a desire to make a difference. They wanted to develop a product to help simplify, protect, and enhance the lives of their increasingly busy, tech dependent peers, family and friends. This is apparent in the highly efficient and useful, yet stylish designs and branding of SafeSleeve products. 
Homeopathic remedies, credit cards and passports with chips, and electronic equipment can all be compromised by exposure to electromagnetic fields. The EMP Can™ is a great air-tight way to store these items and protect them from outside EMF influences including low grade EMP. Shields both radiofrequency and magnetic fields by 95% or more. All metal construction, nice wide mouth and quick-close latch keep contents secure.

Don’t rely on a “radiation shield” or other products claiming to block RF energy, electromagnetic fields, or radiation from cell phones. According to the U.S. Federal Trade Commission, products that interfere with the phone’s signal may force it to work harder and emit more RF energy in order to stay connected, possibly increasing your exposure. It is best to use wired solutions to reduce RF rather than rely on an untested  product.
Radiation is all around us. Power lines, appliances, and electronic devices all emit electromagnetic frequencies. One source that many of us keep close, perhaps too close, are cell phones, tablets, and other mobile devices. They all use radio frequency (RF) electromagnetic energy, a form of non-ionizing radiation, to communicate. Research has shown that this type of radiation is not benign or harmless to the human body, especially children. Exposure to cell phone and Wifi radiation has been linked to fatigue, dizziness, mental fog, and even worse. As a result, the demand for products that reduce exposure to device radiation is on the rise. In fact, "How can I protect myself from cell phone radiation? What do you recommend?" is a question we get all the time. So, to help, I wanted to offer my thoughts on five products I've found that I believe are worth a look if you're interested in reducing your exposure to cell phone and mobile device radiation.
The company's "Researches" page, for example, states that "Aires Technologies are more than 12 years (sic). For this period there have been conducted a number of studies on mechanisms of coherent transformers that effect on physical, chemical, technological and biological processes (sic). The studies were carried out in close collaboration with leading research and academic institutions."
Today’s report, the final one, was about a decade in the making and is the last of several versions that have been released since preliminary results were presented in May 2016. It represents the consensus of NTP scientists and a group of external reviewers, according to the release. In the future, the NTP plans to conduct studies in smaller exposure chambers and to use biomarkers such as DNA damage to gauge cancer risk. These changes in the experimental setup should mean that future studies will take less time.
Generally, the Ministry of Health adopts the instructions of most international entities, recommending to follow the “precautionary principle” regarding mobile phone use. The instructions of the Ministry take into account the technological need of the population in Israel, along with the measure of precaution necessary according to the recent scientific information in order to balance between the population’s needs and the preservation of its health.
In 2011, the International Agency for Research on Cancer (IARC), a component of the World Health Organization, appointed an expert Working Group to review all available evidence on the use of cell phones. The Working Group classified cell phone use as “possibly carcinogenic to humans,” based on limited evidence from human studies, limited evidence from studies of radiofrequency radiation and cancer in rodents, and inconsistent evidence from mechanistic studies (4).
In the US, a small number of personal injury lawsuits have been filed by individuals against cellphone manufacturers (including Motorola,[28] NEC, Siemens, and Nokia) on the basis of allegations of causation of brain cancer and death. In US federal courts, expert testimony relating to science must be first evaluated by a judge, in a Daubert hearing, to be relevant and valid before it is admissible as evidence. In a 2002 case against Motorola, the plaintiffs alleged that the use of wireless handheld telephones could cause brain cancer and that the use of Motorola phones caused one plaintiff's cancer. The judge ruled that no sufficiently reliable and relevant scientific evidence in support of either general or specific causation was proffered by the plaintiffs, accepted a motion to exclude the testimony of the plaintiffs' experts, and denied a motion to exclude the testimony of the defendants' experts.[29]

The use of "hands-free" was not recommended by the British Consumers' Association in a statement in November 2000, as they believed that exposure was increased.[41] However, measurements for the (then) UK Department of Trade and Industry[42] and others for the French Agence française de sécurité sanitaire environnementale [fr][43] showed substantial reductions. In 2005, Professor Lawrie Challis and others said clipping a ferrite bead onto hands-free kits stops the radio waves travelling up the wire and into the head.[44]
Designed to be “leaky”, it permits only a fraction of the RF radiation to penetrate. Exposure to people is reduced (typically 90-99% reduction), and the device usually still works, but with a more limited range. Great for when you permanently or temporarily want to quiet microwave levels without fully turning off the source. Place it over cellphones, cordless phones, two-way radios, smart devices, even wifi routers. Sturdy metal. The two larger units have convenient handle and access holes for wire and cable pass through. Pick the sizes which meet your needs.
Specific Absorption Rate is an indicator of how much EMF radiation body tissue absorbs when you’re using a cell phone and is one way to measure and compare the harm of different devices. In this article, I wanted to provide a resource to compare and contrast the SAR levels of many popular phones and talk a bit about what Specific Absorption Rate is, and how we can use it.
Stick on anti-radiation protection shields etc are often made of metal which may block signal and prevent reliable mobile phone communications with signal towers. Mobile phones recognise the potential for a dropped signal and actually increase power to compensate. The result is a fast draining battery and an even higher radiation output as a result of using the product (an exception to this are shields that are placed in between the phone and the user as these do not impede signal to cell towers to any significant degree)
The U.S. Food and Drug Administration (FDA) notes that studies reporting biological changes associated with radiofrequency radiation have failed to be replicated and that the majority of human epidemiologic studies have failed to show a relationship between exposure to radiofrequency radiation from cell phones and health problems. The FDA, which originally nominated this exposure for review by the NTP in 1999, issued a statement on the draft NTP reports released in February 2018, saying “based on this current information, we believe the current safety limits for cell phones are acceptable for protecting the public health.” FDA and the Federal Communications Commission share responsibility for regulating cell phone technologies.
Unfortunately, however, we’ll probably never have an RCT on cellphones and cancer in humans. It’d be too difficult and too expensive to randomly assign particular levels of cellphone use to thousands of people and have them stick with those plans for enough time (we’re talking at least five years) to figure out whether certain types of phones or phone use patterns cause cancer to develop. That’s not to mention the fact it’d be nearly impossible to find a group of people willing to not use cellphones and then make sure they actually stick to their promise.

The World Health Organisation (WHO) released a fact sheet about these issues, shortly after the IARC re-classification, entitled "Electromagnetic fields and public health: mobile phones". The fact sheet points to the findings of the IARC and describes some of the known short-term and long-term effects of phone use, but ultimately, it lands on the side of where the most conclusive evidence exists:

In one type of study, called a case–control study, cell phone use is compared between people with these types of tumors and people without them. In another type of study, called a cohort study, a large group of people who do not have cancer at study entry is followed over time and the rate of these tumors in people who did and didn’t use cell phones is compared. Cancer incidence data can also be analyzed over time to see if the rates of brain tumors changed in large populations during the time that cell phone use increased dramatically. These studies have not shown clear evidence of a relationship between cell phone use and cancer. However, researchers have reported some statistically significant associations for certain subgroups of people.