Based on health considerations the concentration of benzene in drinking water should not
exceed 0.001 mg/L.
Benzene is a clear, colourless-to-yellow liquid and highly flammable aromatic hydrocarbon. It is presentin petroleum products such as motor fuels and solvents, and motor vehicle emissions constitute the mainsource of benzene in the environment. Benzene occurs naturally in crude oil and coal and is an additive and a by-product of oil-refining processes. It constitutes approximately 1-2% of unleaded gasoline by volume (US DHHS, 2011). Tobacco smoke is another significant source of exposure (WHO, 2010). It also occurs in natural gas and emissions from volcanoes and forest fires.
Human exposure to benzene occurs primarily through inhalation (WHO, 2010). When released to surface waters, benzene rapidly volatilises to the air (WHO, 2010). Benzene is not persistent in surface water or soil and either volatilises to air or is degraded by bacteria under aerobic conditions (WHO, 2010). For water contamination, benzene is therefore of most concern in groundwater. Benzene can also occur in foods and drinks as a product of the reaction between benzoate and ascorbic acid, and has been found in soft drinks in the UK at concentrations as high as 0.028 mg/L (FSA, 2006).
Benzene is also used widely as an industrial solvent by the chemical and pharmaceutical industries in theproduction of styrene/ethylbenzene, cumene/phenol and cyclohexane. The use of benzene as a solvent has been greatly reduced in recent years. Unlike other petroleum hydrocarbons such as ethylbenzene, toluene and xylene the odour threshold for
benzene is relatively high at 10 mg/L (WHO, 2003). ADWG 2011