Cries of alarm are raised so often over new risks, that policy makers are frustrated by their inability to distinguish real hazards from false alarms. Which warnings deserve costly governmental solutions? Which should be provisionally ignored? There exists an excellent collection of over 40 case studies of public warnings about alleged hazards from the period 1947-1973. These can now be re-evaluated, with the hindsight of two or more decades, to see which of these warnings were valid and which were not. The cases can then be searched for hallmarks that distinguish the true warnings from the false alarms. Hallmarks that are identified can be used to help evaluate new warnings.
