<unk>  is a thick dark liquid which is a by-product of the production of coke and<unk>  gas from<unk> . It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoriasis and seborrheic dermatitis (dandruff). It may be used in combination with ultraviolet light therapy. Industrially it is a railroad tie preservative and used in the surfacing of roads.<unk>  was listed as a known human carcinogen in the first Report on Carcinogens from the U.S. Federal Government.<unk>  was discovered circa 1665 and used for medical purposes as early as the 1800s. Circa 1850, the discovery that it could be used as the main ingredient in synthetic dyes engendered an entire industry. It is on the World Health Organization's List of Essential Medicines.<unk>  is available as a generic medication and over the counter. Side effects include skin irritation, sun sensitivity, allergic reactions, and skin discoloration. It is unclear if use during pregnancy is safe for the baby and use during breastfeeding is not typically recommended. The exact mechanism of action is unknown. It is a complex mixture of phenols, polycyclic aromatic hydrocarbons (PAHs), and heterocyclic compounds. It demonstrates antifungal, anti-inflammatory, anti-itch, and antiparasitic properties.
Coal tar
Asbestos
Khat
Polychlorinated naphthalene
Vinyl chloride
Dissolvable tobacco
Triphenylchloroethylene
Benzene