Creosote mixed with coal-tar creosote, or fortified with pentachlorophenol. Water-gas-tar creosote is also derived from petroleum oil or shale oil, but by a different process; its distilled during the production of water gas. The tar is a by-product resulting from enrichment of water gas with gases produced by thermal decomposition of petroleum. Of the creosotes derived from oil, it is practically the only one used for wood preservation. It has the same degree of solubility as coal-tar creosote and is easy to impregnate into wood. Like standard oil-tar creosote, it has a low amount of tar acids and tar bases, and
Coal tar to squamous cell carcinoma. The International Agency for Research on Cancer lists coal tars as Group 1 carcinogens, meaning they directly cause cancer. Both the U.S. Department of Health and Human Services and the state of California list coal tars as known human carcinogens. Coal tar causes increased sensitivity to sunlight, so skin treated with topical coal tar preparations should be protected from sunlight. The residue from the distillation of high-temperature coal tar, primarily a complex mixture of three or more membered condensed ring aromatic hydrocarbons, was listed on 28 October 2008 as a substance of very high concern by