The city of San Francisco has approved an ordinance that will require cell phone retailers to warn customers about the dangers of cell phone radiation, the Los Angeles Times reported on Thursday. The ordinance, which was passed in a 10-1 vote, asks that phone retailers “post general warnings” about risks. It’s unclear what exactly will be required of the retailers, and researchers have flip-flopped on whether or not there are any real risks associated with mobile wireless devices. On May 31st, the World Health Organization published a report that said cell phones are “possibly carcinogenic,” but The Economist fired back shortly after and said there’s no way the devices cause cancer. A second group wrote published a separate report in an issue of Environmental Health Perspectives and argued there is evidence “increasingly against the hypothesis that mobile phone use can cause brain tumors in adults.” A similar law was passed last year that required cell phone makers to publish specific absorption rate (SAR) figures on boxes of cell phones, but the CTIA sued before the law took effect.