Volatile organic compounds or VOCs are relatively insignificant as direct greenhouse gases. Instead they act indirectly by helping to produce ozone in the troposphere via photochemical reactions in the atmosphere.

The bulk of VOCs are produced from natural sources, such as plants, the most important VOCs emitted by plants being isoprene and monoterpenes. Some VOC emissions also arise from the oceans and a range of man-made sources.

The term VOCs encompasses many compounds including non-methane hydrocarbons, alcohols, aldehydes and organic acids. The bulk of natural VOC emissions occur in the tropics, while man-made emissions tend to be concentrated in highly populated areas such as cities.

Human Impact

Various human activities give rise to VOCs with the most important being evaporation of petrol and diesel, such as that from spills, and the incomplete combustion of fuel. Biomass burning can also give rise to significant VOC emissions

Potential for control

As VOCs are predominantly produced by natural sources it is tempting to ignore strategies to prevent man-made VOC release. However, in the case of petrol spillages at least VOC emissions can easily be reduced. By simply avoiding overfilling petrol tanks individuals can both save themselves money and cut VOC emissions