Long-awaited data from an international study have shown no evidence of increased risk of brain tumors associated with mobile phones, except in people who have the most exposure. But design flaws of the Interphone study, which is partly industry funded, suggest that the latest results cannot be taken to mean that cell phones and brain cancer are unrelated, critics say. "I'm not telling people to stop using the phone. I'm saying that I can't tell you if cell phones are dangerous, but I can tell you that I'm not sure that they are safe," said Dr. Devra Davis, professor of preventive medicine at Mount Sinai Medical Center in New York. The study itself, to be published Tuesday in the International Journal of Epidemiology, acknowledged that the findings were not definitive and called for more research. But Daniel Krewski, professor of epidemiology at the University of Ottawa in Ontario and one of the Interphone collaborators, said the study went to "great lengths to make sure that the results were scientifically sound."