An example of an undesirable public good (or public "bad") is:

Question

Quizplus · Accepted Answer

Poor air quality is an example of an undesirable public good because it affects everyone in the area regardless of whether they contribute to its creation or not. It is a classic example of a negative externality, in which the actions of one person or group impose costs on others. While efforts can be made to mitigate air pollution, it is often difficult to assign responsibility for its creation and enforce restrictions on behavior that contribute to it, making it a difficult problem to solve.

An Example of an Undesirable Public Good (Or Public "Bad")