Well, the cleanup in general might not be, but the levels they probably want it at are. Even a slight decrease in the level you want it reduced to massively inc

Well, the cleanup in general might not be, but the levels they probably want it at are. Even a slight decrease in the level you want it reduced to massively increases the cost of the cleanup. In theory they would find a compromise position (for an acceptable concentration in the environment) between the theoretical risk of a low level of the contaminant and the cost and effort of the cleanup.