VOCs are volatile organic compounds. All life forms are made of organic compounds carbon-containing chemicals. Organic compounds that are easily released from solids or liquids into the air, water or groundwater as vapors or gases are called VOCs. In addition to carbon, they typically contain oxygen and hydrogen.
Some VOCs exist in the natural environment, some are man-made, and some are either natural or man-made. Fuel burning and the use of certain chemical products are common sources of the release of VOCs. According to the U.S. Geological Survey, many VOCs are contaminants of concern in drinking water because they are toxic and may cause cancer in humans.