Precursor gases

• CO (Carbon Monoxide)
• NOx (Nitrogen Oxides)
• NMVOC (Non-Methane Volatile Organic Compounds)
• CH4 (Methane)  

Tropospheric ozone is toxic and is also a greenhouse gas. Methane is also a direct greenhouse gas.

External links

• Global Emission Inventory Activity (GEIA) (Global gridded emission inventories)
• GEIA NMVOC emissions per compound group (gridded, 1990 emissions based on EDGAR V20)