Creosote from both oil shale and petroleum, and are known as oil-tar creosote when derived from oil tar, and as water-gas-tar creosote when derived from the tar of water gas. Creosote also has been made from pre-coal formations such as lignite, yielding lignite-tar creosote, and peat, yielding peat-tar creosote. The term creosote has a broad range of definitions depending on the origin of the coal tar oil and end use of the material. With respect to wood preservatives, the United States Environmental Protection Agency (EPA) considers the term creosote to mean a pesticide for use as a wood preservative meeting the
Coal tar the European Chemicals Agency. The exact mechanism of action is unknown. Coal tar is a complex mixture of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds. It is a keratolytic agent, which reduces the growth rate of skin cells and softens the skin's keratin. Coal tar is produced through thermal destruction (pyrolysis) of coal. Its composition varies with the process and type of coal used – lignite, bituminous or anthracite. Coal tar contains approximately 10,000 chemicals, of which only about 50% have been identified. Components include polycyclic aromatic hydrocarbons (4-rings: chrysene, fluoranthene, pyrene, triphenylene, naphthacene, benzanthracene, 5-rings: picene, benzo[a]pyrene, benzo[e]pyrene,