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,
Environmental impact of the coal industry the environment. While these substances are trace impurities, enough coal is burned that significant amounts of these substances are released. During combustion, the reaction between coal and the air produces oxides of carbon, including carbon dioxide (CO, an important greenhouse gas), oxides of sulfur (mainly sulfur dioxide, SO), and various oxides of nitrogen (NO). Because of the hydrogenous and nitrogenous components of coal, hydrides and nitrides of carbon and sulfur are also produced during the combustion of coal in air. These include hydrogen cyanide (HCN), sulfur nitrate (SNO) and other toxic substances. SO and nitrogen oxide react in the atmosphere