In the studies, the researchers looked at a whole slew of health outcomes (like offspring survival, bodyweight changes, and body temperature changes), but importantly, they also looked at brain tumors, including gliomas. They exposed the animals to radio frequency radiation for up to nine hours a day over two years, and then examined more than 40 tissues in each animal. And they had a control group that wasn’t exposed to radiation for comparison.
A study by the Corporate EME Research Laboratory and Motorola Florida Research Laboratories tested 9 different cell phone radiation shields, 5 of which claimed to block 99% of cell phone radiation. The other 4 shields tested claimed to emit a reverse radiation that would cancel out the harmful radiation from cell phones. The study found that all of the radiation shields had no effect on the amount of radiofrequency radiation a cell phone user is exposed to from their phone.[2]
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.

Wherever you come out on the cellphone and cancer question, one thing is clear: How we live with cellphones, along with our exposure to the radiation they emit, has changed dramatically over the past several decades. That has policy implications; it’s something regulators, researchers, and cellphone companies need to pay attention to. In that context, a few things should happen:
SafeSleeve products are not tested by an FCC-approved lab. They have grossly mislead consumers. They only had tested one piece of material they claim is in their products. The consumer is given no proof that any of SafeSleeve products reduce any type of radiation. Do not bother testing their products with an RF meter because accurate testing requires a special lab that costs thousands of dollars. That’s why SafeSleeve has never had their products tested.

Epidemiology studies investigating cell phone use patterns with human cancer risk have produced inconsistent results. Some studies enrolled people who already had tumors with suspected links to RF radiation, such as gliomas, acoustic neuromas and salivary gland tumors. Researchers compared the self-reported cell phone use habits of the cancer patients with those of other people who did not have the same diseases. Other studies enrolled people while they were still healthy, and then followed them over time to see if new cancer diagnoses tracked with how they used cell phones. All the epidemiology studies, however, have troubling limitations, including that enrolled subjects often do not report their cell phone use habits accurately on questionnaires.
It might be invisible to the naked eye, but electric and magnetic fields (EMFs), including electromagnetic radiation, are everywhere these days, and chances are it’s taking a major toll on your health. High-tech devices including your mobile phone, laptop, tablet, and wearable tech like the Apple Watch® all generate a near-continuous source of unseen pollution that can be stressful and toxic to your cells. If your goal is to be as healthy as possible, it’s important to address the issues that cell phone radiation and other technology create.
Safe Cell was successfully tested by an Independent laboratory. The Shielding Effectiveness test as a cell phone radiation protection shield, was conducted by The California Institute of Material Sciences which results proved that "Safe Cell possesses Shielding Effectiveness in the cell phone test frequency range 0.800 GHz to 10.525 GHz". (click here to view the full test report)
Consumers should utilize an air tube headset as a safer alternative to wired headsets or in-ear Bluetooth headsets, use the speaker feature and keep phones away from your body unless there is RF radiation shielding between the wireless device and cell phone users body.  When carrying a phone on your body it’s highly recommended to use either an RF Safe flip cover radiation shielded phone case or pocket shield to deflect excessive radiation away.
DefenderShield Cellphone Radiation Case also claims independent testing and says in their website: That a "sophisticated layering of separate non-toxic, human safe materials processed for maximum radiation blocking efficiency. Each material has unique and targeted radiation-shielding characteristics designed to work in unison to eliminate all radiation emissions from 0 to 10 GHZ and Defender Shield technology refracts, conducts and finally absorbs all these potentially harmful emissions."  In this demonstration, the radiation level measured when DefendeShield case was on is still quite a bit above the level of exposure that I would recommend. I personally do not recommend-holding a phone with a shielding case to your head as the DefenderShield website shows a young woman doing as she demonstrates the product. 
There's a lot of talk in the news these days about whether or not cell phones emit enough radiation to cause adverse health effects. The concern is that cell phones are often placed close to or against the head during use, which puts the radiation in direct contact with the tissue in the head. There's evidence supporting both sides of the argument.
EWG urges the FCC to include third party-produced cases and accessories in its cell phone testing policies to ensure that they do not compromise cell phone function and do not prevent a cell phone from complying with the Commission’s exposure limits. Manufacturers should publish the radiation data for a given phone when used directly next to the body and when used with the cases most commonly sold for a specific model.
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.

From the FCC website: "The FCC ID number is usually shown somewhere on the case of the phone or device. In many cases, you will have to remove the battery pack to find the number. Once you have the number proceed as follows. Go to the following Web address: Once you are there... Enter the FCC ID number (in two parts as indicated: 'Grantee Code' is comprised of the first three characters, the 'Equipment Product Code' is the remainder of the FCC ID). Then click on 'Start Search.' The grant of equipment authorization for this particular ID number should appear. The highest SAR values reported in the equipment certification test data are usually included in the comments section of the grant of equipment certification."
Jump up ^ Repacholi MH, Lerchl A, Röösli M, Sienkiewicz Z, Auvinen A, Breckenkamp J, d'Inzeo G, Elliott P, Frei P, Heinrich S, Lagroye I, Lahkola A, McCormick DL, Thomas S, Vecchia P (2012). "Systematic review of wireless phone use and brain cancer and other head tumors". Bioelectromagnetics (Systematic review). 33 (3): 187–206. doi:10.1002/bem.20716. PMID 22021071.
Though some findings were reassuring, others do raise concerns. Specifically, three of the studies—one from Sweden, another from France, and a third that combined data from 13 countries—suggest a connection between heavy cell-phone use and gliomas, tumors that are usually cancerous and often deadly. One of those studies also hinted at a link between cell phones and acoustic neuromas (noncancerous tumors), and two studies hinted at meningiomas, a relatively common but usually not deadly brain tumor.

Just take a moment and think about how much you’re using your phone every single day. Answering calls, discussing plans, talking about your day with friends, playing games, watching videos and using apps, only scratch the surface of how much you’re actually using your phone. You might even have it by your bedside or on your nightstand when you go to bed at night. It’s time you stopped exposing yourself to dangerous EMF radiation and protected yourself from the dire consequences of using an unshielded smartphone or tablet.
Researchers have carried out several types of epidemiologic studies in humans to investigate the possibility of a relationship between cell phone use and the risk of malignant (cancerous) brain tumors, such as gliomas, as well as benign (noncancerous) tumors, such as acoustic neuroma (tumors in the cells of the nerve responsible for hearing that are also known as vestibular schwannomas), meningiomas (usually benign tumors in the membranes that cover and protect the brain and spinal cord), and parotid gland tumors (tumors in the salivary glands) (3).