While it seems the matter has not been settled; I.E. look at Wikipedia's take, before you go on a Pavlovian reaction "Tin-Foil hat" spree:
The effect of mobile phone radiation on human health is the subject of recent interest and study, as a result of the enormous increase in mobile phone usage throughout the world (as of June 2009, there were more than 4.3 billion subscriptions worldwide). Mobile phones use electromagnetic radiation in the microwave range. Other digital wireless systems, such as data communication networks, produce similar radiation.
"The WHO has classified mobile phone radiation on the IARC scale into Group 2B - possibly carcinogenic. That means that there "could be some risk" of carcinogenicity, so additional research into the long-term, heavy use of mobile phones needs to be conducted. Some national radiation advisory authorities have recommended measures to minimize exposure to their citizens as a precautionary approach."
Also, Tetrapak DOES have Aluminum, or else they wouldn't publish this:
Me, I take no unnecessary risks.
Tetrapak boxes are made of a multi-layered carton, with Cardboard, Plastic, AND Aluminum Foil. So much so, it can be used to make a reflecting antenna for Wi-fi!
So all it takes is a Tetrapak box, to make the radiation to be reflected away from your body... And back to the Cell Phone, where it boosts the signal!
Cut, glue, cover the outer part of the carton with some colored Paper, that's it.
You can easily cut it with the typical Kitchen Scissors, those that cut Chicken, Fish, what have you...
-Either a complete box, with the exterior side, the one facing AWAY from your body, open;
-A back and sides box, as mine;
-Or just a card you put between the Cell-Phone and you!
Works fine on the pockets of any pair of Jeans, too, IF it's NOT a loose pocket model...
Otherwise the box and the Phone will be dancing away from each other.
So for a case that fits all clothing solution, make a real Box, leaving the exterior side with a Window, for you to se the screen and the phone to receive the Signal...