What the fuck is benzene? That’s what I want to know.
Benzene is a sweet-smelling chemical compound originally derived from crude oil. Despite being a known carcinogen, benzene is still widely used in the United States: Added to gasoline, paints and rubber, it ranks in the top 20 most-produced chemicals by volume, employed mainly in the manufacture of petrochemicals—that is, chemicals derived from petroleum. Benzene can be thought of as an intermediary chemical, a gateway substance to bigger and better things. Fiddle with its molecular structure, add or subtract some carbon rings and apply heat or acid, and voilà, a miraculous petrochemical is born! Industries manufacturing plastics, resins and synthetic fiber use benzene in pre-production, and many trade recipes for dyes, lubricants, detergents, explosives, and pesticides call for it as well. Due to the chemical’s near-ubiquity in many household synthetics, concentrations of benzene indoors often exceed levels found outdoors—but unless you’re lighting the furniture on fire, you’re probably all right.
In 1825 the scientist Michael Faraday first isolated and identified benzene from illuminating gas, dubbing it “bicarburet of hydrogen”. The name “benzene” comes from “gum benzoin”, an aromatic resin created in Southeast Asia during the 15th century and exported to European pharmacists and perfumers. In 1903 an enterprising coffee merchant and Nazi sympathizer named Ludwig Roselius discovered that benzene could be used to decaffeinate coffee; his Europe-wide brand became known as Sanka (from the French “sans caffeine”) in 1907 and soon moved overseas to the States. Fortunately for everyone involved, benzene as a de-caffeinater fell out of use shortly afterward. Because of its pleasant, almost fruity smell, benzene was used as an after-shave lotion throughout the 19th century; later, in the 1920s, the chemical saw use in industrial solvents to cut grease. The addition of benzene to petrol in the 1930s was found to increase octane ratings and reduce knocking in internal combustion engines—a boon to the fast-growing automobile industry. Before tetraethyl lead took over as the primary anti-knocking additive in the 1950s, gallons of petrol would often contain several percent benzene for a smoother ride. (These days, EPA regulations state that benzene concentrations in gasoline cannot exceed 0.62 percent.)
Composed of six carbon atoms and six hydrogen atoms, benzene molecules form characteristic six-sided rings with alternating double carbon bonds. At room temperature it is a colorless, highly flammable liquid, which until the late 1970s could be found at hardware stores in quart-sized cans for “general-purpose use”. Today, the average person encounters benzene in its gaseous state. Trace amounts of benzene gas are produced by incomplete combustion, such as in volcanic eruptions, forest fires, and old two-stroke engines. Smoking tobacco is a surprisingly rich source—the average smoker inhales ten times more benzene gas in a day than those who abstain. In the U.S. it is estimated that 50 percent of the nationwide exposure to benzene is from cigarettes and second-hand smoke, compared to the 20 percent from automobiles and industrial emissions. Benzene gas evaporates quickly into the air and partially dissolves in water, often floating on top in a thin film.
Why is benzene considered toxic? After all, it’s made from oil, which was once benign plant matter. In fact, the gas is chemically unchanged when inhaled and exhaled over short periods of time, and can likewise be excreted in urine. So why the fuss? Put very, very simply, benzene is a chemical that, when oxidized in the body (via energy-producing reactions conducted in every cell) or in an internal combustion engine, produces additional forms that the body cannot readily excrete, and these forms can interact with DNA to pernicious effect. Bone marrow failure, leukemia, and several other cancers have been linked to benzene exposure, as well as numerous birth defects and chromosomal damage. Non-human animals are also susceptible. In as early as 1948, the American Petroleum Institute stated that “it is generally considered that the only absolutely safe concentration for benzene is zero.”
So there you go.