The effort to calm fears was not successful. There are 10 million users of cellular phones in America, and by the end of the week phone companies and retailers thought they were all calling with questions. On Wall Street last Friday, Motorola’s stock dropped by nearly $5, and shares in McCaw Cellular, the largest cellular-phone operator, fell by more than $3.

Cellular phones with built-in transmitters emit high-frequency radio waves. Researchers have found that some radio waves cause biological changes, but it is not known whether they are harmful. Several scientists said last week that more research is needed, and the Cellular Telecommunications Industry Association agreed. It wants Washington to appoint a scientific commission to review the risks-“if only to reassure those [who] … have been misled.”