PITTSBURGH: The head of a prominent cancer research institute issued an unprecedented warning to his faculty and staff on Wednesday: Limit cell phone use because of the possible risk of cancer. The warning from Ronald B. Herberman, director of the University of Pittsburgh Cancer Institute, is contrary to numerous studies that do not find a link between cancer and cell phone use, and a public lack of worry by the FDA . Dr. Herberman is basing his alarm on early unpublished data. He says it takes too long to get answers from science and he believes people should take action now