Gabriel Bell at Slate rounds up scientific opinion on the dangers of radio frequency radiation. The Federal Drug Administration, the World Health Organization, the Centers for Disease Control, the Mayo Clinic, the American Cancer Society, the European Commission Scientific Committee on Emerging and Newly Identified Health Risks and other scientists say that high levels of electromagnetic frequencies may not be good for humans, but there is no evidence that the EMF frequencies from cell phones pose any sort of physical risk. Still, with all those scientists on one side of the issue, last week the California Department of Public Health took the other side and issued a series of guidelines on "reduc[ing] exposure to radio frequency energy from cell phones." California's health department now says, "research suggests long-term, high use" of the cell phones "may impact human health." California did not mention anything about humans being bombarded by FM radio signals, baby monitors, Wi-Fi routers, or any of the hundreds of other radio frequencies that humans encounter every day. Of course, most people don't keep transistor radios in their pockets anymore. But many people do carry car door openers in a pocket in their pants that beam electronic signals. Those are weak signals, but most cell phones also emit less than a watt of power. Many AM radio stations send out 50,000-watt signals. Microwaves, can clearly do damage to human tissue, but are a different part of the radio spectrum. So far, the International Agency for Research on Cancer is about the only respected scientific organization saying that the radio waves produced by cell phone use are "possibly carcinogenic to humans."