(Some common flaws in these studies: The summaries of the evidence weren’t comprehensive, the researchers often didn’t look at the quality of the studies they found, and they failed to do other simple things that would limit bias from creeping in. They also relied on case-control studies, a poor method to determine causality — more on that soon.) So we didn’t include these eight reviews in our analysis.
So, what types of RF are these cases intended to block? If they block the frequency being used by the phone than if the blocking is complete the phone won’t work. If it’s partial than, as noted by the FCC and related in the article, the phone may attempt to compensate for the weakened signal by increasing it’s signal strength, thereby emitting higher levels of radiation itself, and reducing battery life in the process.

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.

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.
"Someone claiming they need to reduce [the safe SAR level of 2 W/kg] by 90-percent — they just have no evidence to make that claim, and they are actually playing on the fact that people will be concerned enough about the possible cancer risk, although they don't understand that there's no sufficient data yet to make a statement about an actual cancer risk," said Professor Olver.

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).