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.
But this study also has some drawbacks. First, it is based only on whether or not people had a cell phone subscription at the time. It didn’t measure how often these people used their phones (if at all), or if people who didn’t have a subscription used someone else’s phone. There are also limits as to how well this study might apply to people using cell phones today. For example, while the cell phones used at the time of the study tended to require more power than modern cell phones, people also probably used the phones quite a bit less than people use their phones today.
A 2010 review stated that "The balance of experimental evidence does not support an effect of 'non-thermal' radiofrequency fields" on the permeability of the blood-brain barrier, but noted that research on low frequency effects and effects in humans was sparse.[4] A 2012 study of low-frequency radiation on humans found "no evidence for acute effects of short-term mobile phone radiation on cerebral blood flow".[5][6]
Our recommendation is to reduce your exposure from wireless sources. We advocate what’s referred to as the Precautionary Principle. Basically, this means that because there’s research, lots of it actually, saying the energy that powers our cellphones (RF radiation) could be causing health concerns like tumors and cancer. We ought to take care when using our cell phones and all devices that emit RF, using them mindfully.
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. 
Experts suggest that mobile phone users can take a number of precautions to reduce any possible health risks. Almost all agree that the best step is to keep mobile phone conversations short and to a minimum. Many believe that so-called hands free kits reduce the risks by cutting the amount of electromagnetic radiation entering the brain. They also recommend that users buy phones with external aerials so that it is as far away from the head as possible when in use. Similarly, it is believed that phones with a long talk time are more efficient and produce less powerful emissions. Users are also advised against buying handsets with a high “SAR” value, which means it emits more radiation.

The main difference between our product and other radiation shields available on the internet is simple. OUR PRODUCT WORKS. We are the only cell phone radiation shield that provides full testing on our product by a leading SAR testing lab, IMST which tested the cell phones in the now famous ABC News 20/20 report, and publish these SAR Shield radiation tests on our website for everyone to scrutinize. In 2002 the US government tested various shields, and found that many did not work. The FTC then sued several makers of radiation blockers including, Wave Scrambler, Safety Cell and SafeTshield. This action was taken after Good Housekeeping Institute found that 5 shields did not reduce the radiation they claimed, these five shields were Wave Scrambler by Rhino International, Radiation Free Shield, Wave Shield by Interact Communications, Safe-T-Shield by SV1 Inc, and Safety Caps by Safety Cell. It is easy to say a product reduces radiation, but why don’t our “competitors” publish these results so we can actually see the claims they make are real?
The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO). Its major goal is to identify causes of cancer. The IARC has classified RF fields as “possibly carcinogenic to humans,” based on limited evidence of a possible increase in risk for brain tumors among cell phone users, and inadequate evidence for other types of cancer. (For more information on the IARC classification system, see Known and Probable Human Carcinogens.)
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.
For now, it’s probably better not to spend too much of your time worrying: you’re surrounded by cellphone signals, Wi-Fi signals, and all other kinds of radio frequency radiation day in and out — not just when you put your phone up to your face. And until the evidence suggests otherwise, all of this is still considered less of a cancer risk than eating red meat (which you shouldn't freak out about that much either).
Generally speaking, the near-field refers to the RF field close to the antenna and the far-field is the RF field further away from the antenna. Often times when you use your cell phone, your body is often located in the near-field (one wavelength or less) of the cell phone antenna. It is especially concerning when you hold your phone next to your head or wear it on your body as you can be exposed to very intense near-field radiation from the phone.
2. Our products are designed to provide an anti-radiation barrier between the device and the body. This way, the devices are still usable and able to send and receive signal out of the non-shielded side while shielding the EMF away from the body. Because of this, you will only see a reduction in EMF levels on the shielded side of the device. The test you have conducted shows the highest levels from anywhere around the device.
In subsequent analyses of Interphone data, investigators addressed issues of risk according to specific location of the tumor and estimated exposures. One analysis of data from seven of the countries in the Interphone study found no relationship between brain tumor location and regions of the brain that were exposed to the highest level of radiofrequency radiation from cell phones (9). However, another study, using data from five of the countries, reported suggestions of an increased risk of glioma and, to a lesser extent, of meningioma developing in areas of the brain experiencing the highest exposure (10).
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