The energy of electromagnetic radiation is determined by its frequency; ionizing radiation is high frequency, and therefore high energy, whereas non-ionizing radiation is low frequency, and therefore low energy. The NCI fact sheet Electromagnetic Fields and Cancer lists sources of radiofrequency radiation. More information about ionizing radiation can be found on the Radiation page.
Another animal study, in which rats were exposed 7 days per week for 19 hours per day to radiofrequency radiation at 0.001, 0.03, and 0.1 watts per kilogram of body weight was reported by investigators at the Italian Ramazzini Institute (35). Among the rats with the highest exposure levels, the researchers noted an increase in heart schwannomas in male rats and non-malignant Schwann cell growth in the heart in male and female rats. However, key details necessary for interpretation of the results were missing: exposure methods, other standard operating procedures, and nutritional/feeding aspects. The gaps in the report from the study raise questions that have not been resolved.
I love this case. However, I don't understand what happens to the radiation that must collect under the case; isn't there a burst of radiation when the case is opened? I posted this question but the answers were from people who hadn't thought of that issue; they didn't have the answer, except for one who theorized that the radiation is slowly leaking out the top, bottom, and sides. I assume the case keeps radiation off the hand that holds the case with the phone in it, which is great, but I do wonder about the stored radiation when, for example, I'm listening to a podcast with the case closed, then open it later.

According to Dr. Devra Davis, who wrote Disconnect: The Truth About Cell Phone Radiation, cell phones are dangerous because they emit erratic signals capable of disrupting resonance and DNA repair. As long as your cellular phone is on, it sends out radiation intermittently. Even if you don’t take your phone out of your pocket all day, it continues to expose you to radiation. Dr. Joseph Mercola, founder of recently wrote an excellent article on the dangers of cell phones and provided common sense ways we can protect ourselves and our family from the electromagnetic radiation it emits.
We began by getting a baseline of ambient RF in the room at the location of our testing. We then recorded a baseline of the cellphone RF while on an active call with no case. And finally, we measured the reduction in that baseline (still on the active call) using a variety of different cases and RF reducing products – all at the same set distance from the phone.
The perfect way to shield your ears. Comfortable enough to sleep in, and stylish enough to wear in public. High shielding performance silver stretch fabric gives excellent radiofrequency and microwave shielding. Made of double thickness 2" wide 71% polyamide + 29% elastomer fiber. Ideal for cellphone shielding or any other activity when you need to shield your ears and forehead. Thin enough to fit under a hat or helmet. Durable and unwrinkleable, washable too (no bleach). Silver provides anti-bacterial properties and suppresses odor. Folds small for easy transport. Pretty Silver color.
When you make a phone call, just flip the shielded front cover down when you put the phone against your head. It’s that simple. By keeping the shielded front cover closed while against any part of your body, a barrier is created to protect from a broad spectrum of potentially harmful cell phone radiation emissions, yet won’t affect signal quality. You can use your cell phone with a higher sense of safety by simply keeping the shielded flip cover between your body and radiation-emitting source.
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.
Launched at the U.S. Food and Drug Administration’s request 10 years ago, the NTP study dosed rats and mice of both sexes with RF radiation at either 1.5, 3 or 6 watts of radiation per kilogram of body weight, or W/kg. The lowest dose is about the same as the Federal Communications Commission’s limit for public exposure from cell phones, which is 1.6 watts W/kg. The animals were exposed nine hours a day for two years (about the average life span for a rat), and the exposures were cranked up steadily as the animals grew, so the absorbed doses per unit body weight remained constant over time.

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.

Until the FCC establishes testing procedures that fully correspond to real-world cell phone use and reviews its radiation standards to ensure that they are fully protective for all users, including young children, EWG advises phone users to adopt these simple measures to minimize radiation exposure: Use a headset, keep the phone away from the body and text rather than talk.  
None of the three cases contain metallic parts, which are known to affect SAR, but all increased the user’s radiation exposure. The effect on radiation exposure would likely vary with each of the hundreds of cases on the market, and each would have to be tested individually to come up with an exact measure. The results in Table 1, however, are believed to reflect the range of radiation increases.

The frequency of radiofrequency electromagnetic radiation ranges from 30 kilohertz (30 kHz, or 30,000 Hz) to 300 gigahertz (300 GHz, or 300 billion Hz). Electromagnetic fields in the radiofrequency range are used for telecommunications applications, including cell phones, televisions, and radio transmissions. The human body absorbs energy from devices that emit radiofrequency electromagnetic radiation. The dose of the absorbed energy is estimated using a measure called the specific absorption rate (SAR), which is expressed in watts per kilogram of body weight.