Volatile Organic Compounds

The term volatile organic compounds (VOCs) refers to carbon-containing compounds that exist as gases or that vaporize easily. Some examples of VOCs are benzene, formaldehyde, toluene, xylene, hexane, ethylbenzene, 1,3-butadiene, and a group of compounds known as polycyclic aromatic hydrocarbons (PAHs).

The vast majority of VOCs are hydrocarbons, often represented by the chemical formula RH, where R may represent either an alkyl or an aryl group.

Volatile organic chemicals are released during a number of industrial and manufacturing operations.

For example, 1,3-butadiene is an important raw material in the manufacture of synthetic rubber: During manufacture small amounts of the chemical escape into the air.

Formaldehyde is a raw material used in the manufacture of a variety of building materials, such as phenol-formaldehyde and melamine resins.

Many household products, such as cleaning products, varnishes, waxes, paints, and organic solvents, contain VOCs, which vaporize and escape easily into the atmosphere when they are used. For this reason, VOCs often build up indoors.

About 40 percent of all VOCs released into the atmosphere are from on-road vehicles, an additional 32 percent from solvent use and evaporation, about 12 percent from combustion operations, and the remaining 17 percent from a variety of other sources.

Because they tend to build up indoors and to react with and damage living tissue, VOCs constitute an important element in the special problem of indoor air pollution.

Exposure to low concentrations of VOCs produces a number of annoying but relatively benign symptoms, such as irritation of the eyes, nose, throat, and respiratory system; headache, fatigue, dizziness, and nausea; visual problems; impairment of memory and other thought processes; and skin reactions.

Some VOCs, such as benzene, formaldehyde, perchloroethylene, and derivatives of xylene and toluene, pose more serious concerns in that they have been found to be carcinogenic. Long-term exposure to these compounds may, therefore, pose a serious health risk.