Some studies have found a possible link. For example, several studies published by the same research group in Sweden have reported an increased risk of tumors on the side of the head where the cell phone was held, particularly with 10 or more years of use. It is hard to know what to make of these findings because most studies by other researchers have not had the same results, and there is no overall increase in brain tumors in Sweden during the years that correspond to these reports.

A decline in male sperm quality has been observed over several decades.[11][12][13] Studies on the impact of mobile radiation on male fertility are conflicting, and the effects of the radiofrequency electromagnetic radiation (RF-EMR) emitted by these devices on the reproductive systems are currently under active debate.[14][15][16][17] A 2012 review concluded that "together, the results of these studies have shown that RF-EMR decreases sperm count and motility and increases oxidative stress".[18][19] A 2017 study of 153 men that attended an academic fertility clinic in Boston, Massachusetts found that self-reported mobile phone use was not related to semen quality, and that carrying a mobile phone in the pants pocket was not related to semen quality.[20]
There are ongoing worries about whether cellphones can give you cancer — especially brain cancer, since our phones spend so much time near our faces. It’s true that cell phones do emit radiation. But it’s radiofrequency radiation, which is much lower energy than the ionizing radiation you’d get from an X-ray, or, say, nuclear fallout. Ionizing radiation can cause DNA damage that can eventually lead to cancer. But the radiofrequency radiation from a cellphone doesn’t work that way — and today’s results support that.
Let’s be honest, we’re addicted to our smartphones. According to an ABC news report, the average person checks their phone 150 times per day, not to mention the other 15 hours per day it sits in your pocket. It’s also nothing new that cell phones emit Electromagnetic Fields/Radiation (EMF/EMR) when it’s glued to the side of our head more than 22 times per day. 
Pong’s research indicates that badly designed cell phone cases can partially block a phone’s antenna, making the device work harder to transmit signals. Due to gaps in the FCC’s cell phone regulations, a phone worn right next to the body and enclosed by a case that obstructs the antenna could expose the user to more radiation than the FCC’s legal limit.
In March, however, a peer-review panel of 11 experts from industry and academia voted to advise the agency that it should raise the confidence level from “equivocal evidence” to “some evidence” of a link between cellphone radiation and brain tumors in male rats. (The female rats did not show evidence of a link between the radiation and such tumors.) Two panel members, Lydia Andrews-Jones of Allergan and Susan Felter of Procter & Gamble, proposed the risk upgrade.
In theory, men may be more vulnerable to cellphone radiation’s effects on fertility than women. Sperm cells are made and stored in testicles, whereas egg cells are stored in ovaries. And the location of these two organs means that sperm and eggs have different levels of protection from radiation. Testicles sit outside of the abdomen, which makes them more sensitive to radiation. And, well, a phone often sits in your front pocket.

In June, at a meeting of scientific counselors to the toxicology agency, Donald Stump, one of the members, worried that the study “will be vulnerable to criticism that it was conducted using outdated technology.” The challenge, he added, is how to move forward with experiments that are large enough to be significant yet nimble enough to keep pace with the rapidly evolving devices.

Also noteworthy is that the studies evaluated radiation exposures in different ways. The NTP looked at “near-field” exposures, which approximate how people are dosed while using cell phones. Ramazzini researchers looked at “far-field” exposures, which approximate the wireless RF radiation that bombards us from sources all around us, including wireless devices such as tablet and laptop computers. Yet they generated comparable results: Male rats in both studies (but not mice or female animals) developed schwannomas of the heart at statistically higher rates than control animals that were not exposed.
I did a lot of research prior to purchasing and came down to this one as the best/most tested and proven option. Happy with the cover. I don’t have a way to actually test the efficacy of it but it’s a quality product otherwise. I haven’t dropped it but there’s enough room around the edges that it seems like it would have a good cushion to blunt the impact when I do. I’d recommend trying it if you like the looks of It.

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.

The authors of these studies noted that the results were preliminary and that possible health outcomes from changes in glucose metabolism in humans were unknown. Such inconsistent findings are not uncommon in experimental studies of the biological effects of radiofrequency electromagnetic radiation in people (4). Some factors that can contribute to inconsistencies across such studies include assumptions used to estimate doses, failure to consider temperature effects, and lack of blinding of investigators to exposure status.
Perhaps more importantly, what types of radiation are causing, or likely to cause, or are suspected of causing, harm to humans? Is it the “harmonics” from the transmitter? Is it the RF from the circuitry? Is it the primary frequency on which the cell phone operates? This is important to understand. If the problem is the primary frequency on which the cell phone operates then forget the case and ditch the cell phone.
When you talk, your voice is transmitted from the antenna as radio frequency radiation (RFR) between 800 MHz and 2,200 MHz. A range equal to the middle of microwave frequency and 20% to 80% of the radiation emitted is deposited in the user's head. The microwave radiation is absorbed and penetrates the area around the head, some reaching an inch, to an inch and a half into the brain. Exposure to this microwave RFR has shown to have serious health consequences. Laboratory studies have shown that radiation from cell phones expose the user to a wide range of health problems including: 
As a good thing to keep in mind, there are hundreds of thousands of people suffering from EHS in the world. Some of them live in forests, tents, and anywhere they can get away from society and EMFs because their symptoms are so bad when exposed. I have not heard one single EHS person claim that any of these types of devices work. They sure don’t for me. Most EHS sufferers are so desperate that they have researched and tried just about everything. Getting away from EMFs, or blocking them with material that does actually block them, like as a Faraday cage, is what works. And this is clearly what the scientific evidence shows. If these devices worked, that would be fabulous. One could spend $100 and be well, instead of having their life turned upside down, and in the worst cases as with some, committing suicide due to complete hopelessness and helplessness.. However, that is not the case. To further prove whether they work or not, one could wear one, and measure with a meter designed to measure EMF absorption in the body (they exist now). Has the manufacturer had this done, and is their evidence of it? An EHS person can tell without a meter anyway, but to prove to others, this might be a good idea.
The Ministry of Health Medical Administration circular (from 2002) addressed to hospital Directors, states that use of mobile phones and wireless handheld transceivers (walkie talkie) in the hospital, must on the one hand guarantee the patient’s wellbeing and safety, and on the other hand, allow the staff, the patients and their families to enjoy the service benefits. This circular outlines the areas where use of mobile phones is strictly forbidden and areas where use is permitted (while keeping an appropriate safety distance from areas where life-supporting equipment or systems are operated).

The ultra thin (1mm) RadiCushion by Cellsafe slips into the cell phone case and redirects radiation away from the face of the phone. It's available in black or white but not recommended for use with aluminum or metallic cell phone cases. Test results show a SAR reduction of 96%. A slightly thicker (2mm) RadiCushion is available for iPad and iPad mini; it adheres to the back of the device and also provides SAR reductions of 96%. Visit their website for more information or watch this independent test which shows an 80% reduction and also compares it to the BlocSock:

To check for radiowave emissions, use an RF meter with Near Field antenna. Again, position the antenna loop on the phone (because the entire antenna stem has some sensitivity, it is best to position the entire antenna over the area that will be shielded). Note carefully where the loop is positioned. Make a call and watch the readings. Notice the highest and lowest readings, and make a mental note of the "average" reading. Now, insert the shield, and repeat.

The reason we’re talking about cellphones and cancer — why there’s a concern here — is because they emit radiation, the invisible waves of electric and magnetic energy, of varying power, organized on the electromagnetic spectrum. You can see in the graphic below that less powerful (or lower-frequency) types of radiation are on the left, moving to the more powerful (or higher-frequency) types of radiation on the right.
So you decided you are going to use your cell phone in your car, despite all the warnings. But you have the good sense to keep it away from your head and body! This handy mount can securely hold your phone, iPod, MP3 player or GPS unit with confidence as your drive. Allows easy access and a clear view. Can be used by anyone in the car: driver, passenger, or even in the back seat. Plugs securely into a cup holder and is fully adjustable to any position. Cradle adjusts and can securely accommodate devices up 3.5 inches wide. Completely hands free. Can also be used on boats, recliners or anywhere a cup holder is waiting. You can even do his’n’hers!
1. Keep your distance. Do not keep your cell phone next to your body or in your bra. Some athletic wear companies are now making bras with cell phone pockets, as seen in the picture above. PLEASE do not put your phone in the pocket unless your phone is on airplane mode. There is evidence offered by the Environmental Health Trust to suggest that women who keep a cellular phone in their bra may develop breast cancer. Research also indicates that men who keep their cell phones on their belt or near their reproductive organs may have lower sperm counts and less sperm motility.
If you're looking for ways to limit your exposure to the electromagnetic emissions from your cell phone, know that, according to the FTC, there is no scientific proof that so-called shields significantly reduce exposure from these electromagnetic emissions. In fact, products that block only the earpiece – or another small portion of the phone – are totally ineffective because the entire phone emits electromagnetic waves. What's more, these shields may interfere with the phone's signal, cause it to draw even more power to communicate with the base station, and possibly emit more radiation.
EWG met with representatives of Pong Research and fully agrees with its business premise that cell phone cases should decrease, not increase, radiation exposure. Pong hopes to carve out a niche by selling cases that lower the phones’ radiation exposure. We anticipate that as awareness of the potential risks of cell phone radiation grows, Pong and other companies will respond by marketing cell phones and cases that offer users good communication with less radiation.
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]
Since 2001, the FCC has allowed manufacturers to test phones at a distance of up to one inch from the body to account for the use of a holster. In a 2012 report, however, the Government Accountability Office, the Congressional watchdog agency, noted that many cell phone owners actually keep and use their phones right next to the body, so these outdated testing policies could result in radiofrequency (RF) radiation exposure greater than the FCC’s legal limit (GAO 2012). The GAO report concluded:
I noticed the Blocsock hardly added any bulk to my phone, and fit comfortably in my pocket. I have a Rocketfish RF-MTVT2SP protective gel case and thankfully the phone fits the Blocsock without having to take off this case. The Blocsock is very easy to use, and is quick and easy to take out and answer the phone. Again, if you get one, make sure the size you order is right and not too tight or loose. The pouch on the Blocsock is handy when using the phone to call people so the phone can be placed in the pouch between the Blocsock and me, protecting my head from radiation while still enabling people to clearly hear me and vice versa.
Yes, the information transferred between the base unit (the phone’s stationary unit) and the wireless phone’s mobile unit is transferred as radiowave radiation. Therefore, the “precautionary principle” should also be adopted regarding wireless phones. In addition to the guidelines regarding mobile phones, the Ministry of Health recommends regarding wireless phones:
According to this sub-regulation, “a speakerphone is a device that enables use of the phone without holding it, providing that if the device is installed on the phone, the phone will be positioned in the vehicle in a stable manner that prevents it from falling”. For the regular mobile phone instrument in the vehicle, it is advisable to install an antenna outside the vehicle and not inside it, and to prefer wire connections between the phone and the speaker over use of a blue tooth.
EMF’s? Most everyone has grown up with EMF’s. It is not so much in your wifi as it is in your homes wiring. Check your walls and plugs with a meter. Also, every modern car is off the charts with EMF. Way I see it, people are living just fine. My grandmother is 86, living under power lines and house full of EMF electric wiring. She is fine. Unless I see 50% of the population dying early and having serious, serious issues, I will not panic over EMF’s
These experimental findings raise new questions as to the potential for radiofrequency radiation to result in cellular changes and offer potential avenues for further laboratory studies. Cancers in the heart are extremely rare in humans, where the primary outcomes of potential concern with respect to radiofrequency radiation exposure from cell phones are tumors in the brain and central nervous system. Schwann cells of the heart in rodents are similar to the kind of cells in humans that give rise to acoustic neuromas (also known as vestibular schwannomas), which some studies have suggested are increased in people who reported the heaviest use of cell phones. The NTP has stated that they will continue to study this exposure in animal models to further advance our understanding of the biological underpinnings of the effects reported above.