Cell phones emit radio waves, which are a form of radiation.The amount of radio frequency energy getting into the body and brain is expressed by a measurement called Specific Absorption Rate (SAR). The level of exposure varies further depending on several factors, including cell phone traffic at the time, distance from the nearest cell tower, the size of the handset and how close the phone is to your head.

Research about cell phones’ carcinogenic effects contradict one another so it is currently impossible to draw ironclad conclusions. But one Swedish study that followed young people using mobile phones for 10 years calculated a 400% increase in brain tumors.

San Francisco just became the first city in the country to pass legislation requiring cell phone retailers to display radiation levels. And if your phone was made in the last two years, you can find out about its SAR — Locate the phone’s FCC ID number, which is usually located on the back of the phone, and fill in the info on this site: http://www.fcc.gov/oet/ea/fccid