Radicals in the polluted troposphere

Complex reactions involving radicals occur, giving rise to secondary pollutants such as ozone, aldehydes, peroxyacetyl nitrate (PAN) and particulate matter. 

Catalytic hydroxyl radicals dominate the chemistry of the troposphere. These are formed by the following processes  

CH3C002N02, is an important constituent of photochemical smog, acting as an irritant to the eyes and respiratory system and being highly toxic to plants. 

---