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What Is Benzene Found In?

Benzene is an aromatic hydrocarbon, or "arene," with th chemical formula C₆H₆. Although similar to aliphatic hydrocarbons in only consisting of the two elements, carbon and hydrogen, the chemistry of the aromatics is considerably different .

Benzene is the best known of the Huckel series, in which a planar (flat) ring contains (4n+2) п electrons housed above and below that plane and the framework of the atoms. With n = 1, or 4n+2=6, benzene is also called [6]-annulene (annulus = ring-shaped). The discovery of benzene's structure by August Kekulé represents a fascinating chapter of chemical history.

  1. Coal Tar

    • Benzene's first important source was from coal tar, from which it was isolated in 1845 by Charles Mansfield. Coal tar is a viscous brown to black liquid derivative produced during the carbonization of coal to coke and other products. Coal tar can be distilled to produce "coal tar creosotes" or "volatiles" with "coal tar pitch residue" being left behind. This, then, was a major source of benzene. Today, benzene is commonly made from petroleum products. It is among the top 20 chemicals in production volume.

    Typical Uses

    • Benzene was once dissolved in gasoline to enhance octane number. It was also a commonly used solvent, however, many such uses have been discontinued since the discovery it was both carcinogenic and compromised disease resistance. Today, benzene is used to manufacture plastics, resins, dyes, fabrics and pesticides.

    Undesirable Exposure

    • Benzene is somewhat soluble in water, and can be found in some above ground and even underground water sources. Some occurs in gasoline. Benzene is even a product of volcanic activity. It is found in cigarette smoke. Most unfortunately, traces of benzene have even been persistently found in breast milk.

      The leading source of unwanted benzene is industrial processes, including underground storage tank leaks.

    Hazards

    • Besides being a source of cancer, benzene has been identified with some forms of leukemia, lymphoma and other blood diseases. Of course, there are the usual hazards of respiration, ingestion, inflammability and skin absorption. See a relevant material safety data sheet (MSDS) for precautionary measures.

    Governmental Reevaluation

    • The Occupational Safety and Health Administration's (OSHA) permissible exposure limit currently stands at 1 PPM (parts per million). Evidence from overseas indicates serious illness can result even at that low level. For that reason, the American Conference of Governmental Industrial Hygienists (ACGIH) has recommended a change to 0.5 PPM threshold limit value (TLV), whereas the National Institute for Occupational Safety and Health (NIOSH) has set a recommended exposure limit (REL) of 0.1 PPM.

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