The agency now lists mobile phone use in the same "carcinogenic hazard" category as lead, engine exhaust and chloroform.
Until now, the World Health Organization has said no adverse health effects have been established. But a team of 31 scientists from 14 countries, including the United States, made the decision after reviewing peer-reviewed studies on cell phone safety.
Experts say the type of radiation coming out of a cell phone is not like an x-ray, but more like a very low-powered microwave oven. But the cell phone industry maintains there is no conclusive evidence of danger.
For now, experts suggest using a headset or speaker phone to avoid possible health risks.