Short answers, pulled from the story.
Benzene is an organic chemical compound made of six carbon atoms joined in a flat hexagonal ring, each carbon holding one hydrogen atom. Because it contains only carbon and hydrogen, it is a hydrocarbon, and its continuous cyclic pi bonds make it an aromatic hydrocarbon.
Michael Faraday first isolated and identified benzene in 1825 from the oily residue left by the production of illuminating gas, giving it the name bicarburet of hydrogen. In 1833, Eilhard Mitscherlich produced it by distilling benzoic acid with lime and named it benzin.
Friedrich August Kekule proposed benzene's ring of six carbon atoms with alternating single and double bonds in an 1865 paper. He later said the ring shape came to him in a daydream of a snake biting its own tail, and in 1929 Kathleen Lonsdale confirmed the flat hexagonal ring using X-ray diffraction.
Benzene is classified as a carcinogen and a notorious cause of bone marrow failure, linked to aplastic anemia, acute leukemia, and cardiovascular disease. The American Petroleum Institute stated in 1948 that the only absolutely safe concentration for benzene is zero, and there is no safe exposure level.
Benzene is used mainly as an intermediate to make other chemicals, with more than half of production becoming ethylbenzene, a precursor to styrene for plastics like polystyrene. About 20% becomes cumene for phenol and acetone, and roughly 10% becomes cyclohexane for nylon fibers.
About 50% of all benzene exposure in the United States comes from smoking tobacco or breathing tobacco smoke. Other major sources are automobile service stations, motor vehicle exhaust, and industrial emissions, and exposure can also occur through contaminated water.