Pong’s research indicates that badly designed cell phone cases can partially block a phone’s antenna, making the device work harder to transmit signals. Due to gaps in the FCC’s cell phone regulations, a phone worn right next to the body and enclosed by a case that obstructs the antenna could expose the user to more radiation than the FCC’s legal limit.
Want to let people know that cellphones cannot be used in certain areas without an embarrassing confrontation? These decals are suitable for putting up in schools, restaurants, theaters, stores, taxicabs, busses, trains, hospitals, offices, homes or any other place that's appropriate for a cellphone-free zone. High quality decals measure 3½" by 3½". Nice strong adhesive, simply peel and stick.
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.