Critics like author Devra Davis (Disconnect: The Truth About Cell Phone Radiation, What the Industry Has Done to Hide It, and How to Protect Your Family) theorize that manufacturers' warnings are themselves evidence of harmful effects. Don't let the research scare you. The jury is still out on whether cell phones can cause physical harm to their users. They do admit, however, that longitudinal studies (long-term) might reveal unforeseen hazards to users' health.
Robert Cleveland Jr., formerly of the FCC, says that "The companies want to legally protect themselves." As there is no conclusive evidence of their effects, perhaps companies just don't want to be liable if and when mobile consumers start experiencing a disproportionate cancer rate.
The problem is that the FCC's SAR limit (1.6 watts of frequency per kilogram of body mass), was derived under conditions different from real-world use. The 1.6 watts per kilogram cutoff was determined with the device in a holster, no closer than 2.5 cm to the body. This means that most users, who put their phones in their pockets, are exposing themselves to more than the recommended amount of radiation.
John Walls of CTIA said that "Because they test at the waist in the holster, any reference to use guidelines or advice incorporates the buffer the holster provides." Manufacturers like Research In Motion include a warning to the user that they should use only an approved holster in order to remain compliant with the FCC guidelines.
It's still unclear whether users should be concerned about cell phone radiation. The FDA admits that there may be dangers, and recommends using a headset, and holding the device away from the body. It is likely that companies are only recommending such procedures to avoid litigation should future research reveal harmful effects.
Then again, maybe we should err on the side of caution and use holsters.
source: TIME via Yahoo!News