A toxic substance found in hydrocarbons that is also classified as a volatile organic compound. Xylene is a colorless, sweet-smelling, highly-flammable gas that occurs naturally in petroleum and coal tar. It is one of the top 30 chemicals produced in the United States in terms of volume. Xylene is used as a solvent and in the printing, rubber, and leather industries. It is also used as a cleaning agent, a thinner for paint, and in paints and varnishes. It is found in small amounts in airplane fuel and gasoline. Xylene can harm the liver, and the nervous and renal systems.