is any substances released to the environment that threaten health or damage vegetation if present in sufficient concentration. The major pollutants emitted as a result of man’s industrial activity (largely through the combustion of fossil fuels) are: sulfur oxides - predominantly sulfur dioxide (SO2) — nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons (HC), and particulates. Such pollutants have a relatively short residence in the atmosphere before being removed by natural scavenging processes. SO2, for example, has an atmospheric residence time of about four days. There has thus been no evidence of a global buildup of these pollutants. In a given locality, however, pollutants can reach high concentrations in the atmosphere, causing respiratory ailments, as well as inhibiting growth of vegetation, turning soil acid, eroding masonry in buildings, and corroding metals.

Also see emissions (automotive), emissions (stationary source).