Styrene (ethenylbenzene) is a commercially important chemical used in the production of polymers, copolymers, and reinforced plastics. Exposure mainly occurs in industries and operations using styrene, and industrial sources are the most likely cause of general population exposure. Other potential sources of general population exposure include motor vehicle exhaust, tobacco smoke, and other combustion/pyrolysis processes. Low-level exposure of the general population can occur through the ingestion of food products packaged in polystyrene containers.