Used in public transportation, mostly private cars. Toxic flammable liquid derived mainly from coal tar. It is the simplest aromatic compound, an industrial solvent which is being replaced where possible by other compounds since it is carcinogenic. Limits for exposure at work are imposed in many countries due to concern over the incidence of leukemia. Most motor spirit specifications now put a maximum benzene content of 5%. It is the basis for all other aromatic organic molecules, for all are derived by replacing one or more of the hydrogen atoms by more complex groups