Benzene occurs naturally in volcanoes, forest fires, some plants and animals. Benzene is present in crude oil.
Benzene is one of the world's major commodity chemicals. Its primary use is in the production of other chemicals, predominantly plastics and styrene, cumene (for various resins), and cyclohexane (for nylon and other synthetic fibers). Benzene is an important raw material for the manufacture of synthetic rubbers, gums, lubricants, dyes, pharmaceuticals, and agricultural chemicals.
Benzene is a natural component of crude and refined petroleum. The mandatory decrease use of lead in gasoline has led to an increase in the aromatic hydrocarbon content of gasoline to maintain high octane levels and antiknock properties. In the United States, gasoline typically contains less than 2% benzene by volume, but in other countries the benzene concentration may be as high as 5%.
Benzene is an excellent solvent. It is used in paints, thinners, inks, adhesives, and rubbers. Benzene was an important component of many industrial cleaning and degreasing formulations, but is now been replaced by less toxic toluene chlorinated solvents and mineral spirits. Although benzene is no longer added in significant quantities to most commercial products, traces of it may still be present as a contaminant.
Workers in industries that make or use benzene may be exposed to high levels of this chemical. These industries include the rubber industry, printing industry, pesticide production, detergent production, solvent production, paint and varnish production, waste management, oil refineries, chemical plants, shoe manufacturers, petroleum processing industries, steel workers, laboratory technicians, fire fighters, emergency response organisations and gasoline station employees.
In 1987, OSHA estimated that about 237,000 workers in the United States were potentially exposed to benzene. It is not known if this number has changed since then.
Although benzene exposure normally occurs in the workplace, there have been many instances of industrial discharge, disposal of benzene containing products and gasoline leaks from underground storage tanks that have allowed benzene into our soil and water supplies. Increased levels of airborne benzene can often be associated with local industries, such chemical manufacturing, petrochemical processing and coke oven emissions. People living around hazardous waste sites, petroleum-refining operations, petrochemical manufacturing sites, or gas stations may be exposed to higher levels of benzene in air.
Major sources of environmental benzene include automobile exhaust fumes and cigarette smoke. Areas of heavy vehicular traffic may have higher airborne levels. Cigarettes have been found to release between 50 and 150 micrograms of benzene per cigarette, so smoking and second-hand smoke are important sources of exposure to benzene. Second hand smoke can be a major source of benzene exposure among non- smokers.
In almost all cases, benzene levels inside residences or offices are higher than levels outside and still higher in homes with attached garages and those occupied by smokers. Seasonal variations also affect benzene levels, with higher levels found in the fall and winter when buildings are less well ventilated.
Some consumer household products, such as glues, cleaning products, detergents, art supplies, and paint strippers, contain benzene. In addition we regularly see news about the discovery of benzene in bottled water, soft drinks and food.