A major US telecommunications industry group on Friday asked a federal court to block a law requiring mobile phone makers to warn customers that the gadgets are bathing them in radiation.
The unprecedented ordinance was passed by the northern California city's elected board of supervisors in June.
CTIA-The Wireless Association filed a lawsuit in a US District Court here calling for the law to be derailed on the grounds it would confuse, not help, people shopping for mobile telephones.
In particular, shoppers must be shown estimates of how much of the radio wave radiation from each mobile phone model is absorbed into the body of the person using it.
All mobile phones sold in the United States must meet Federal Communications Commissions (FCC) standards regarding safe levels of radio wave exposure, according to the CTIA.
"The ordinance misleads consumers by creating the false impression that the FCC's standards are insufficient and that some phones are safer than others based on their radio frequency emissions," CTIA spokesman John Walls argued in a release.
He noted that the US Food and Drug Administration (FDA) has determined that available scientific evidence shows no link between health problems and mobile telephone radio waves, according to Walls.
"The ordinance contradicts the thorough review of the science by the FCC, FDA and other US and international expert agencies," Walls said.
The law is the first of its kind in the United States.
Research into whether mobile phone radiation causes cancer or other health trouble has been inconclusive.