Berkeley lawmakers voted this week to require cellphone retailers to provide customers with a notice on the potential health hazards of carrying their device too close to their bodies, making the progressive California city the first in the nation to have wireless warnings if the law is allowed to go into effect in July.

"It's an important right-to-know issue," said Berkeley mayor Tom Bates, who voted in favor of the measure. "It's really just a note of caution."

Currently, most wireless-capable devices such as smart phones carry FCC-mandated safety recommendations on how close to the skin the devices should be kept. It's suggested that users keep most models at a distance of 5 to 25mm to limit radiation exposure to safe levels.

But those notices are often buried deep inside manuals and online instructions, leaving most consumers unaware they even exist.