How does consumer surplus relate to marginal benefit in the presence of externalities in a market?

Consumer surplus is the difference between what consumers are willing to pay for a good or service and what they actually pay. It shows the benefit consumers receive when they buy something for less than their maximum price. Marginal benefit is the additional satisfaction or value a consumer gets from consuming one more unit of a good. When externalities, like pollution, are present, the true cost of a product might not reflect in its price, which can affect consumer surplus. For example, if a factory pollutes a river, consumers might enjoy low prices for fish, but they are not considering the negative impact of pollution, which decreases the overall marginal benefit and can lead to a lower consumer surplus in the long run.