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Volatile organic compounds (VOCs) are chemical compounds that have a high vapor pressure and low water solubility. The group includes a wide range of carbon-based molecules, such as aldehydes, keytones, cyclic compunds and long-chain carbon.
Common examples of VOCs include paint thinners, dry cleaning solvents, and some constituents of petroleum fuels (eg. gasoline). VOCs are sometimes accidentally relased into the environment, where they can become ground-water contaminants. Vapors of VOCs escaping into the air can also contribute to air pollution.
Many VOCs found around the house, such as paint strippers and wood preservatives, contribute to Sick building syndrome because of their high vapor pressure. The United States EPA has found concentrations of VOCs in indoor air to be 2 to 5 times greater than in outdoor air. During certain activites indoor levels of VOCs may reach 1,000 times that of the outside air.
VOCs are an important outdoor air pollutant. In this field they are often divided up into the separate catagories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which can contribute to enhanced global warming. Within the NMVOCs, Benzene is a suspected carcinogen and can lead to leukaemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses. It is also known that trees are effeicient emitters of VOCs.
VOCs also react with nitrogen oxides in the air in the presence of sunlight to form ozone. Although ozone is beneficial in the upper atmosphere because it protects humans and animals from exposure to dangerous solar radiation, it poses a health threat in the lower atmosphere by causing respiratory problems.
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