Benzene is a colourless liquid with a sweet odor. It is highly flammable and is formed from both natural processes and human activities. 
Benzene is widely used in the United States; it ranks in the top 20 chemicals for production volume. Some industries use benzene to produce other chemicals which are used to make plastics, resins, and nylon and synthetic fibers. Benzene is also used to make some types of rubbers, lubricants, dyes, detergents, drugs, and pesticides. Natural sources of benzene include volcanoes and forest fires. Benzene is also a natural part of crude oil, gasoline, and cigarette smoke.
Anthropogenic releases of benzene into the atmosphere result mainly from environmental tobacco smoke, automobile exhaust, automobile refuelling operations, and industrial emissions.
Benzene has a moderate water solubility of 1,78 g/l, but is highly volatile and can rapidly evaporate from surface waters to the atmosphere. It has a low adsorption to sediments or soils and will rapidly be removed from them to surface and ground water and the atmosphere. In the atmosphere it will be degraded within 8 days, in water it takes 16 days to degrade it to half of its original concentration .
The most sensitive crustaceans start dying at concentrations above 3.3 mg/l although most species tolerate concentrations above 120 mg/l, the most sensitive fish at concentrations above 4.9 mg/l, although most species tolerate concentrations above 100 mg/l. 
Concentrations in air typically range between 0.3 ppb and 159 ppb. The highest measured concentration of benzene in marine waters is 315 µg/l. 
Environmental standards and legislation