There is increasing evidence for the existence of a class of problems which are only recognizable as significant long after the causative actions have been taken. Adverse effects become manifest long after an apparently beneficial activity has become well established. The social costs of activities decades earlier, largely in ignorance of their potential consequences, suddenly become a source of great anxiety, especially when the extent of the phenomena is as yet poorly understood and denied by certain groups of experts. The problem creates unpredictable levels of anxiety when some new initiative (possibly without negative side effects) can be argued to be potentially the source of some future problem, as in the case of the recently questioned introduction of artificial sweeteners into diet soft drinks.
Examples include: appearance of cancers from exposure to very low concentrations of carcinogenic materials long after the period of that exposure; asbestos, for which the latency period may extend over much of a human life span; the emergence of lung cancer as the consequence of smoking many years before; the spread of toxic wastes into groundwater; the emergence of resistant pesticides and pathogens following cumulative years of pesticide use; recognition of the implications of increasing concentrations of carbon dioxide in the atmosphere.