Styrene use and occupational exposure in the plastics industry.
The commercial production of styrene was started in the 1930s. Currently 7 million tons of styrene a year is made worldwide by the catalytic dehydrogenation of ethylbenzene or by a process in which styrene is produced as a coproduct with propylene oxide. An estimated 62% of the styrene monomer is consumed in the manufacture of polystyrene, 12% in acrylonitrile-butadiene-styrene resins, 17% in styrene-butadiene rubber and latex, 7% in unsaturated polyester resins, and 2% in other applications. Occupational exposure to styrene occurs in monomer production and polymerization plants, during the fabrication of plastic products from monomeric or partly prepolymerized styrene, and during the transportation and handling of liquid styrene. Due to unreacted residual monomer or thermal degradation of the polymer, low concentrations of styrene can be detected during the use of plastic products. The most extensive and intensive exposure occurs in the reinforced plastics industry, in which over 200,000 workers are exposed to a styrene concentration typically ranging from 20 to 300 ppm.