An example of a point source.

A localized, discrete, and fixed contaminant emission source, such as a smokestack or waste discharge pipe. Since point sources are usually easily identified, their discharges of pollution can be monitored readily. Point sources are distinguished from nonpoint sources and mobile (or vehicular) sources and historically were the first to receive emission controls. Some point sources release exceptionally large quantities of contaminants. For example, a smelter in Sudbury, Ontario, was for many years the largest single source of sulfur dioxide in North America, emitting several million tons of pollutants annually through a smokestack over 1,247 ft (380 m) tall.