Data is scare on radioactivity coming from Japan 's damaged reactors . Experts need good data in building computer models to track radioactivity . But data has been hard to come by , and there are `` conflicting reports '' about damage in some of the reactors , the official said . Comment: Experts say radiation from Japan does not pose a significant health threat to the U.S .
Data is scare on radioactivity coming from Japan 's damaged reactors . Experts need good data in building computer models to track radioactivity . Comment: Experts say radiation from Japan does not pose a significant health threat to the U.S .