Two types of air pollutants: primary vs secondary Primary pollutants: released directly from sources Examples: CO, So2, NOX Secondary pollutants: formed through chemical reactions of the primary pollutants and the constituents of the unpolluted atmosphere in the air. Example: 03Two types of air pollutants: primary vs. secondary • Primary pollutants: released directly from sources – Examples: CO, SO2, NOx • Secondary pollutants: formed through chemical reactions of the primary pollutants and the constituents of the unpolluted atmosphere in the air. – Example: O3