air pollutant
A substance, gaseous material or @A00176@ which has been introduced into the air (either by human activity or by natural processes) in sufficient concentration to produce a measurable effect on humans, animals, vegetation or materials (monuments, etc.): SO2, NO2, H2S, CO, @H02889@, etc.
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2172 [Terms] [Paper]