Better Information Needed

That's partly because most research on radio frequency energy has focused on short-term exposure of the entire body, the report said. There are long-term studies currently under way, but "it will likely be many more years before a definitive conclusion can be reached on whether mobile phone emissions pose any risk to human health," according to the GAO, the investigative arm of Congress.

Until the research offers clear answers, Americans need better information, the report said.

"In the short term, millions of consumers will be required to make their own judgments," said Rep. Ed Markey, the Massachusetts Democrat who requested the study with Democratic Sen. Joseph Lieberman of Connecticut.

Based on what they know, people could decide to make shorter calls or use a headset and hold the device away from their body, Lieberman said, pulling out the earpiece he attaches to his wireless phone. Some may conclude that the risk is negligible and not change their behavior.

The lawmakers recommended that the Federal Communications Commission and the Food and Drug Administration set up a Web site and call center to make it easier for consumers to look up the radiation level of their particular phone model.

Major manufacturers have started including such information voluntarily inside their phone packaging. The FCC has information on its Web site, but consumers need the individual phone's ID number to look up the radiation level.

Information Too Technical

Information provided by the agencies on cell phones also can be written too technically for average consumers or not contain the latest available research, the GAO said. That's a source of concern because the industry passes along information from both the FCC and FDA to consumers with its products.

"We rely on government information," said Jo-Anne R. Basile of the Cellular Telecommunications and Internet Association, the leading industry trade group. "We would welcome the government updating it on a regular basis and putting it in consumer-friendly terminology."

The government also should clean up its process for determining whether cell phones comply with radiation limits, the GAO said. Currently, manufacturers test their own phones in various positions, and submit data to the FCC.

The type of equipment used, a small change in the position of the phone or even the way technicians mix fluid that's used for testing can cause variations in results, the GAO said. The FCC, in conjunction with engineering organizations, is working to standardize testing procedures to reduce the variables. Still, a phone's actual radiation level could fall between 30 percent above or below the amount a company reports in its test results.