When it comes to ionizing radiation — which we’re exposed to in X-rays, in CT scans, and during air travel — we know it’s powerful enough to damage the DNA, and that repeated DNA damage over time can cause cancer. That’s why, for example, you’re not supposed to get too many X-rays in your lifetime. (In case you were wondering, there’s no precise number on how many X-rays are too many — but the Food and Drug Administration suggests keeping track and avoiding any that seem unnecessary.)

A few epidemiology studies have reported higher rates of tumors inside the skull among people who use cell phones heavily for 10 years or more. Of particular concern are benign Schwann cell tumors called acoustic neuromas, which affect nerve cells connecting the inner ear with structures inside the brain. These growths can in some instances progress to malignant cancer with time. But other studies have found no evidence of acoustic neuromas or brain tumors in heavy cell phone users.
Use the speaker mode on the phone or a hands-free device such as a corded or cordless earpiece. This moves the antenna away from your head, which decreases the amount of RF waves that reach the head. Corded earpieces emit virtually no RF waves (although the phone itself still emits small amounts of RF waves that can reach parts of the body if close enough, such as on the waist or in a pocket). Bluetooth® earpieces have an SAR value of around 0.001 watts/kg (less than one thousandth the SAR limit for cell phones as set by the FDA and FCC).
I can’t count how many times I’ve heard people speculate, joke, or jokingly speculate that their cellphone might be giving them cancer. It comes from a very reasonable place of discomfort — few people understand how radiation works, we put our phones right beside our brains all the time, and technology in general often feels like it ought to be causing some sort of societal ill.
 I purchased two different color cases and I was surprised when I received it because the inner case was different than described in some of the reviews. But when I looked at the Amazon listing, I didn’t realize that the case has been updated and I’m pleasantly surprised. The inner case is a soft, flexible plastic that doesn’t seem like it would break at all. I borrowed an EMF reader from a friend and the case works as described. I’m very happy with the cases and I’m glad that I purchased one for my boyfriend too! I definitely recommend this case!
There are few if any references to actual studies in published, peer-reviewed journals that support the claim that Aires, or any other, cell phone shield actually works. The "Researches" page contains a superficially impressive list of sciencey-sounding titles and findings supposedly demonstrating the importance of using cell phone shields, all of them in Russia for some reason.
Most cellphone shielding products are designed to reduce radiation to the user while still allowing the phone to function. This means that some radiation can still get to the phone… and some radiation can still get out of the phone! But sometimes you need to completely kill the signal. The RF Kill Box is a full-metal shielding jacket with very high shielding performance.
Then there is non-ionizing radiation, which encompasses the vast majority of light we are exposed to: visible light from lightbulbs, infrared light from an oven and from people, gigahertz light from our wifi, megahertz light to/from our cell phones, and radio waves hitting our car radio. They are not harmful in small doses because one photon does not have enough energy to ionize atoms and/or break apart molecules. In very large doses, non-ionizing radiation can be harmful. For example, a visible light laser with sufficient power (at least several hundred times more than a legal laser pointer) which is concentrated in a small enough spot will burn your skin and do worse things to your eye if it gets in there. And those of us who are old enough, remember the gerbil-in-a-microwave flash animations which went viral 17 years ago [1] as a humorous (but not exactly factual) representation of what would happen if you microwaved a live rodent.
Jump up ^ For example, Finland "Radiation and Nuclear Safety Authority: Children's mobile phone use should be limited". Finnish Radiation and Nuclear Safety Authority (STUK). 7 January 2009. Archived from the original on 11 January 2010. Retrieved 20 January 2010. and France "Téléphone mobile, DAS et santé" [Mobile telephones, SAR and health] (PDF). Votre enfant et le téléphone mobile [Your child and mobile telephony]. Association Française des Opérateurs Mobiles (AFOM)[French Mobile Phone Operators' Association] et l’Union Nationale des Associations Familiales (UNAF) [National Federation of Family Associations]. 31 January 2007. Retrieved 20 January 2010.

Use a corded home phone whenever possible, to minimize the need for a cell phone. Cordless home phones emit RF, so replace cordless phones with corded home phones. One initial step is to unplug the electrical cord of the cordless phone base station when the phone is not in use, because otherwise that base station will emit RF nonstop. Note: you can plug a corded phone handset or corded headset into your VoIP connection.  
Your phone sends radiofrequency, or RF, waves from its antenna to nearby cell towers, and receives RF waves to its antenna from cell towers when you make a call or text or use data. The frequency of a cell phone’s RF waves falls between those emitted by FM radios and those from microwave ovens, all of which are considered “non-ionizing” forms of radiation. That means that—unlike radiation from a nuclear explosion, a CT scan, or a standard X-ray—the radiation from your phone does not carry enough energy to directly break or alter your DNA, which is one way that cancer can occur. (FM radios and microwaves don’t raise alarms, in part because they aren’t held close to your head when in use and because microwave ovens have shielding that offers protection.)
Most of these early studies did not find an increase in the risk for developing tumors among mobile phone users. The main problem characterizing these studies stems from the fact that the development of cancer (in particular brain tumors) takes a very long time (at least 10-20 years and up to 40 years or more), while mobile phone technology is relatively new (as aforesaid, popular use began only in the mid-90s). Hence, these studies could not demonstrate risk even if such existed.
The following is an excerpt of a typical conclusion published in a scientific journal about the links between EMFs, cell phones and health: "Epidemiologic research shows a low degree of association, inconsistency and missing dose-effect relations. A biologic mechanism of action is still debatable. No harm to human health has been shown. Conclusion: There is no scientific basis as to the harmful effects of EMFs on human health."

The FCC has yet to implement GAO’s recommendations to more closely reflect real-life use. For a narrow subset of smartphones – those sold with lanyards or straps – the FCC advises manufacturers to test phones at a distance of no more than 5 mm from the body (FCC 2014). Yet the FCC has done nothing to ensure more realistic testing of most other smartphones or to account for the widespread use of accessories such as cases, which many different manufacturers produce with both metallic and non-metallic components.

A series of studies testing different scenarios (called simulations by the study authors) were carried out using incidence data from the Nordic countries to determine the likelihood of detecting various levels of risk as reported in studies of cell phone use and brain tumors between 1979 and 2008. The results were compatible with no increased risks from cell phones, as reported by most epidemiologic studies. The findings did suggest that the increase reported among the subset of heaviest regular users in the Interphone study could not be ruled out but was unlikely. The highly increased risks reported in the Swedish pooled analysis were strongly inconsistent with the observed glioma rates in the Nordic countries (24).