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,
Coal mining in the United Kingdom the United States. Of the coal mined in the UK in 2016 all was from open-cast coal mines. Employment in coal mines fell from a peak of 1,191,000 in 1920 to 695,000 in 1956, 247,000 in 1976, 44,000 in 1993, and to 2,000 in 2015. Almost all onshore coal resources in the UK occur in rocks of the Carboniferous age, some of which extend under the North Sea. Bituminous coal is present in most of Britain's coalfields and is 86% to 88% carbon. In Northern Ireland, there are extensive deposits of lignite which is less energy-dense based on oxidation (combustion)