Fact sheet: Hexachlorobenzene

From: Public Services and Procurement Canada

Discover a list of a contaminant's important chemical properties, how it will react in the environment, main sources of contamination related, and a brief overview of health and safety issues.

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General information

CAS number

118-74-1

Molecular formula

C6Cl6

Formula weight

284.8 g/mol

Family

Chlorobenzenes

Properties (at room temperature where applicable)

Compound properties list
ParameterValueComment
Melting/boiling point228 0CSolid
Relative density2.05Sinks in water
Vapour pressure1 x 10 -5 mm HgVery low volatility
Vapour density0N/A
Solubility in water0.01 mg/LVery low solubility
Henry's law constant1 x 10-3atm·m3/molModerately volatile when dissolved
log Koc (Depending on soil or sediment characteristics)2.7 - 6.0*Strong adsorption to organic matter

Environmental behaviour

At 20 0C, hexachlorobenzene is a solid with very low volatility and solubility. Once it is dissolved, it is moderately volatile and adsorbs strongly to organic matter. When present in the soil, it volatilizes and dissolves very slowly. In the dissolved phase, hexachlorobenzene can reach the water table or drain into a waterway, where it will be diluted, before partially volatilizing. Fragments of hexachlorobenzene can also be carried into waterways where they will be deposited at the bottom and dissolve very slowly. Once the source has been removed, the adsorbed phase will take a long time to disappear, slowly liberating contamination in either the gaseous or dissolved state. The resulting plumes (gaseous and dissolved) are generally small in size.

Health and safety

In Canada, hexachlorobenzene is considered "toxic", as defined under Paragraph 64(a) of CEPA 1999, and has been added to Schedule 1.

Principal resources

Hexachlorobenzene has not been used commercially in Canada since 1972. Hexachlorobenzene may enter the environment from incomplete combustion of chlorinated compounds including mirex, kepone, chlorobenzenes, pentachlorophenol, PVC, polychlorinated biphenyls and chlorinated solvents.

In addition, hexachlorobenzene may enter the environment as a reaction by-product in the production of carbon tetrachloride, dichloroethylene, hexachlorobutadiene, trichloroethylene, tetrachloroethylene, pentachloronitrobenzene and vinyl chloride monomer. Hexachlorobenzene is a fungicide formerly used as a seed treatment, especially on wheat to control the fungal disease bunt. It has been banned globally under the Stockholm Convention on Persistent Organic Pollutants.

References

Environment Canada. 2009. CEPA Environmental Registry: Toxic Substances List-Updated Schedule 1 as of December 27, 2006. (Viewed December 2013)

Environment Canada. 2009. Management of Toxic Substances: Hexachlorobenzenes (QCB). (Viewed December 2013)

Montgomery, John H. 2007. Groundwater Chemicals, Desk Reference, Fourth Edition, CRC Press, Taylor and Francis Group, Florida, U.S.A.

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