Out of SO2,CO,O3,NO and Peroxy acetyl nitrate (PAN) primary and secondary pollutants respectively are

Objectional materials that are emitted directly into the atmosphere by identifiable sources are called primary pollutants as  SO2,SO3,CO,NO.Secondary pollutants are those which are formed in the atmosphere as a result of some chemical reactions between matter already present O3,HCHO,PAN.