Answer
An example of a positive externality is the benefit to health of others after an individual gets a vaccination.
An example of a negative externality is pollution from coal burning power stations.
Work Step by Step
An externality is a benefit or cost that accrues to a third party outside of a market exchange. A vaccination generates extra health benefits for others who come into contact with a vaccinated person. Pollution is a negative externality because it creates costs (health and climate change) for the environment and people beyond sellers and purchases of coal-generated power.
