Here's an interesting article to check out in Popular Science. It's not conclusive and needs further study, but indicates cell phone radiation isn't good for brain tissue:
http://www.popsci.com/popsci/medicine/article/0%2C12543%2C573349%2C00.html
"His team exposed 32 rats to 2 hours of microwave radiation from GSM cellphones. Researchers attached the phones to the sides of the rats' small cages using coaxial cables -- allowing for intermittent direct exposure -- and varied the intensity of radiation in each treatment group to reflect the range of exposures a human cellphone user might experience over the same time period. Fifty days after the 2-hour exposure, the rat brains showed significant blood vessel leakage, as well as areas of shrunken, damaged neurons. The higher the radiation exposure level, the more damage was apparent. The controls, by contrast, showed little to no damage. If human brains are similarly affected, Salford says, the damage could produce measurable, long-term mental deficits."