primary pollutant

in atmospheric chemistry
https://doi.org/10.1351/goldbook.P04838
A pollutant emitted directly into the air from identifiable sources (e.g. SO2, NO, @[email protected], etc.). Secondary pollutants, such as ozone, are generated within the atmosphere through chemical changes which occur in primary pollutants.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2208 [Terms] [Paper]