The guidelines, issued last week, note that “some laboratory experiments and human health studies have suggested the possibility that long-term, high use of cell phones may be linked to certain types of cancer and other health effects.” These include brain cancer, tumors of the acoustic nerve and salivary glands, lower sperm count, headaches and effects on learning, memory, hearing, behavior and sleep.
Several studies have investigated the other health effects (other than cancer) of mobile phone usage on human health. Hypotheses connecting mobile phone use to effects such as headaches, fatigue, sleep disorders, memory, vision or hearing impairment, have not been proven in established studies. A connection with reduced fertility has also not been scientifically proven.
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. 
Limited to rats only, the Ramazzini study tested three doses expressed as the amount of radiation striking the animal’s bodies: either 5, 25 or 50 volts per meter. The exposure measures therefore differed from the absorbed doses calculated during the NTP study. But the Ramazzini scientists also converted their measures to W/kg, to show how the doses compared with RF limits for cell phones and cell towers set by the FCC and the International Commission on Non-Ionizing Radiation Protection; they ranged down to a 1,000 times lower. The exposures began when the rats were fetuses and continued for 19 hours a day until the animals died from natural causes.

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.
Using a speaker/personal speakerphone or earplug (not wireless) during conversation - distancing the mobile phone from the user’s body reduces his exposure to the radiowave radiation. Therefore, keep the mobile phone at a distance from the body (do not carry it on the body, such as in the belt, pocket or on a neck strap). Obviously, reducing the amount and duration of calls on the mobile phone is another simple measure to reduce exposure.
Can cellphone radiation cause cancer in humans? There’s no scientific consensus on this issue, but there is “some evidence” that exposure to radiation equivalent to that emanating from 1990s-era cellphones is associated with brain tumors in male rats, according to results of a US National Toxicology Program (NTP) study released last week (November 1). 
Forward your cell phone to landlines whenever you are at home, then power off the cell phone without missing a call. Biological effects can be related to both strength of cell phone radiation dose and duration of exposure, so consider whether or not your communication is urgent. Remember: Use a corded home landline (not a home cordless phone, because cordless phones use electromagnetic microwave technology just like cell phones). Most cordless phone base stations constantly emit microwave radiation regardless whether or not any connected handset is in use. The cordless phone handsets also emit microwave radiation. Corded landlines have no radiation emissions and are the best choice.
The Working Group indicated that, although the human studies were susceptible to bias, the findings could not be dismissed as reflecting bias alone, and that a causal interpretation could not be excluded. The Working Group noted that any interpretation of the evidence should also consider that the observed associations could reflect chance, bias, or confounding rather than an underlying causal effect. In addition, the Working Group stated that the investigation of risk of cancer of the brain associated with cell phone use poses complex methodologic challenges in the conduct of the research and in the analysis and interpretation of findings.
Radiofrequency radiation is a form of electromagnetic radiation. Electromagnetic radiation can be categorized into two types: ionizing (e.g., x-rays, radon, and cosmic rays) and non-ionizing (e.g., radiofrequency and extremely low frequency, or power frequency). Electromagnetic radiation is defined according to its wavelength and frequency, which is the number of cycles of a wave that pass a reference point per second. Electromagnetic frequencies are described in units called hertz (Hz).