https://doi.org/10.1351/goldbook.14928
Any undesirable solid, liquid, or gaseous matter occurring, as a result of human activities, in a solid, liquid, or gaseous environmental medium and causing adverse effects.
Notes:
- "Undesirability", like toxicity, is concentration-dependent, low concentrations of most substances being tolerable or even essential in many cases.
- A primary pollutant is one emitted into the atmosphere, water, sediments, or soil from an identifiable source.
- A secondary pollutant is a pollutant formed by chemical reaction in the atmosphere, water, sediments, or soil.
- Pollutant should be distinguished from contaminant; the latter implies presence above background due to human activities; the former implies that the substance also is causing adverse effects.
See: contaminant