Graphic: Diego Aguirre Preferring to err on the side of caution, the San Francisco Board of Supervisors on Tuesday voted 10-1 to require cell phone makers to post notices in their stores with details on the level of radiation each model emits.

The ordinance requires retailers to post information on what is called the "specific absorption rate" (SAR) of its products. The SAR rates measure the amount of radio wave radiation absorbed into the user's body tissue.

San Francisco Mayor Gavin Newsom, who supports the ordinance, is expected to sign it into law. It would take effect in February, with a $300 fine for those found in violation. Other jurisdictions, including Maine and California, have considered similar legislation, but it appears San Francisco would be the first to enact it.

(To watch a video recording of the San Francisco Board of Supervisors' vote click here)

Some worry that prolonged exposure to cell phone radiation may cause brain cancer, although scientific studies have proven inconclusive. The most recent and most comprehensive study, conducted by Interphone and published May 17, found no increased risk for the two most common types of brain cancer.

The lack of certainty one way or the other poses a conundrum. If the government issues warnings just to be safe, it may scare consumers needlessly. On the other hand, if a risk does indeed exist, the government is obligated to alert the public of the potential harm.

The Federal Communication Commission, which regulates cell phone safety along with the Food and Drug Administration, states on its Web site "there is no scientific evidence to date that proves that wireless phone usage can lead to cancer or a variety of other health effects," but goes on to note that "studies are ongoing."

The FCC has set a standard that no cell phone sold in the United States can have a SAR in excess of 1.6 watts per kilogram.

Enterprising consumers can find SAR information on the FCC Web site, but they need to have the product's FCC ID code. San Francisco's new law would put that hard-to-find data directly in front of consumers in stores.

Not surprisingly, representatives of the cell phone industry oppose the law, citing both the existing FCC standard and the lack of definitive scientific evidence linking cell phone use to brain cancer.

John Walls, a spokesman for the Cellular Telecommunications and Internet Association, told the San Francisco Chronicle that the law "will potentially mislead consumers with point-of-sale requirements suggesting that some phones are safer than others, based on radio emissions."

That argument did not sway the lawmakers in city of San Francisco, who say it will serve the public.

"This is a modest and commonsense measure to provide greater transparency and information to consumer," Tony Winnicker, a spokesman for Mayor Newsom, told the Chronicle.