The impact of primary pollutants on the oxidation reactivity of the troposphere

Man-made emissions to the atmosphere impact local and global air quality an d have resulted in significant changes in the oxidation properties of the t roposphere at least in the northern hemisphere over the last 50 years. A br ief overview is given of the impact, direct and indirect, that primary poll utants have on the oxidation reactivity or the so-called oxidation efficien cy of the troposphere. The important roles played by ozone and the hydroxyl radical, CO and methane are emphasised. Several important problem areas ar e highlighted.