PrintThe pollutants that are emitted directly from a combustion process are called “primary pollutants.” When emitted into the atmosphere, these primary pollutants combine with other reactants and form “secondary” pollutants.
An example of a secondary pollutant would be ozone. When hydrocarbons are emitted, and they react with NOx in presence of sunlight, they form ozone. Health and environmental effects of secondary pollutants are discussed in the next section: Global and Regional Effects of Pollutants.
