Ethylbenzene is an organic compound found in small amounts in air, water, and soil, and it is also present in coal tar and petroleum. It's a byproduct in many hydrocarbon-based compounds, such as gasoline and paints as well as insecticides and tobacco. Synthetic ethylbenzene production works by interaction of the chemicals benzene and ethylene. The compound then goes through ethylbenzene dehydrogenation, which breaks it down into hydrogen and styrene. Styrene is an oily liquid that also can be extracted from a natural source, styrax trees, and is used to make polystyrene, a form of plastic shaped into foam packaging, plastic cutlery, and more.
Over 1,000,000 pounds (453,592 kilograms) of ethylbenzene are produced in the United States every year, and it is used in six major industries, including a wide array of consumer products and building materials. Its use in furnishings is considered a major source of indoor air pollution. Production of the chemical is also targeted towards the manufacture of synthetic rubber and as a component of aviation fuels.
Toluene is another chemical byproduct of ethylbenzene styrene manufacturing. Uses for toluene are as an octane booster in gasoline and in other types of plastics, such as polyurethane for upholstery and mattresses. The alkylation process involved in producing ethylbenzene also results in an excess quantity of benzene and benzene-related compounds being produced than what is required to produce styrene. These compounds are fed back into the production cycle through alkylator and transalkylator reactor vessels.
Gasoline contains around 2% by weight of ethylbenzene, and the chemical itself smells like gasoline. Since it easily evaporates from gasoline and other sources into the air, it's a common ingredient in smog in large metropolitan cities. Though the human sense of scent can detect ethylbenzene concentrations in the air in as little as two parts per million, the Environmental Protection Agency (EPA) in the US has not classified its airborne contamination as a carcinogen.
Health effects from ethylbenzene exposure are suspected to be significant because it is so widespread in modern society. It evaporates from chemicals such as varnishes, spray paints and adhesives, and is present in fumes from car exhaust, gasoline, and tobacco smoke. Exposure levels are the key factor in determining risk, with short-term adverse effects being respiratory problems and effects on coordination and thinking processes. Long-term exposure to the chemical has shown it to be carcinogenic and to cause kidney and liver damage.