Definition - What does Secondary Pollutants mean?
Secondary pollutants are defined as pollutants in our environment that are formed when other primary pollutants interact with the atmosphere. Unlike primary pollutants, which are air, water or soil pollutants that are emitted directly from a particular source, secondary pollutants pollute our environment indirectly and are not emitted from a source, but are activated or synthesized by other pollutants as they are emitted.
Safeopedia explains Secondary Pollutants
The most commonly known secondary pollutants are certain gases that are synthesized by photochemical reactions in our lower atmosphere. The primary pollutants that cause the creation of these gases are nitrogen oxide gases and hydrocarbons. These chemicals participate in photochemical reactions driven by ultraviolet light on sunny days and this results in secondary pollutants, such as ozone, in our atmosphere.