Primary & Secondary pollutant

A primary pollutant is an air pollutant emitted directly from a source.

A secondary pollutant is not directly emitted as such, but forms when other pollutants (primary pollutants) react in the atmosphere.

Examples of a secondary pollutant include ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight; NO2, which is formed as NO combines with oxygen in the air; and acid rain, which is formed when sulfur dioxide or nitrogen oxides react with water.

Source: GreenFacts

Ozone

Deutsch: Primär- und Sekundärschadstoffe
Español: Contaminantes primarios y secundarios
Français: Polluants primaires et secondaires

Respiratory Diseases

Nitrogen Dioxide

Evaluation of endocrine disruptors

State of the European Environment

Phosphate resources