beta-HCH

Alpha-hexachlorocyclohexane (alpha-HCH) is a major by-product (65-70%) in the manufacture of lindane (> 99% gamma-HCH). Its solubility in water is low, but it is very soluble in organic solvents such as acetone, chloroform, and xylene. It is a solid with a low vapour pressure. It is an environmental pollutant. Alpha-HCH is a stereoisomer of gamma-structure HCH, the active ingredient of lindane (> 99% gamma-HCH). It differs in the spatial orientation of the hydrogen and chlorine atoms on the carbon atoms. Alpha-HCH can be determined separately from the other isomers by gas chromatography with electron capture detection and other methods after extraction by liquid/liquid partition and purification by column.

An organochlorine pesticide of moderate mammalian toxicity which is degraded slowly in the environment and can accumulate in mammalian tissues.

Alpha- and beta-HCH have been used in mixtures with gamma-HCH (as "HCH" or "fortified HCH") in agriculture and in wood protection.

Alpha-HCH does not occur naturally. It is released to the environment as a result of the use of technical-grade HCH and the inappropriate disposal of the residue resulting from the purification of lindane. Alpha-HCH is basically a by-product (and impurity) in the manufacturing of lindane (> 99% gamma-HCH). Technical-grade HCH, which is synthesized from benzene and chlorine in the presence of ultraviolet light, consists of: 65-70% alpha-HCH 7-10% beta-HCH 14-15% gamma-HCH (lindane) approx. 7% delta-HCH approx. 1-2% epsilon-HCH approx. 1-2% ther components. Purification of lindane produces a residue, consisting almost entirely of non-insecticidal HCH isomers (mainly alpha- and beta-), which can be used as an intermediate for the production of trichlorobenzene and other chemicals. Alpha- and beta-HCH have been used in mixtures with gamma-HCH (as "HCH" or "fortified HCH") in agriculture and in wood protection.

Small amounts of alpha-hexachlorocyclohexane (alpha-HCH) may result from the isomerization of lindane (gamma-HCH) upon exposure to sunlight. Release of alpha-HCH to the environment probabaly occurs mainly from the use of technical hexachlorocyclohexane as a pesticide. When released to water, alpha-HCH is not expected to volatilize or hydrolyze extensively. Release of alpha-HCH to the soil will most likely result in slow leaching to groundwater. Slow volatilization may also occur. Alpha-HCH entering the atmosphere, by analogy to lindane, may be subject to rain-out and dry deposition. The estimated half-life for the reaction of alpha-HCH with hydroxyl radicals in the atmosphere is 1.63 days. Biodegradation may occur slowly in aerobic surroundings and is expected to occur rapidly and extensively under anaerobic conditions. Alpha-HCH has been reported to photodegrade in water in spite of the lack of a photoreactive center, but photolysis is not considered to be a major process in its environmental fate. Alpha-HCH will bioconcentrate slightly in fish and other aquatic organisms. Monitoring data indicate that alpha-HCH is a contaminant in air, water, sediment, soil, fish and other aquatic organisms, foods, and humans. Human exposure results primarily from food.

Evidence for Carcinogenicity: CLASSIFICATION: B2; probable human carcinogen. BASIS FOR CLASSIFICATION: Dietary alpha-HCH has been shown to cause increased incidence of liver tumors in five mouse strains and in Wistar rats. HUMAN CARCINOGENICITY DATA: Inadequate.

EPA Method 508
EPA Method 608
EPA Method 617
EPA Method 625
EPA Method 8080A
EPA Method 8081
EPA Method 8250A

[1] Lide, D.R., Editor (2003) Handbook of Chemistry and Physics. 84th Edition, CRC Press, Boca Raton, Florida.

[2] Mackay, D., Shiu, W.Y., Ma, K., Lee, S.C., (2006) Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals, Second edition, Taylor and Francis, Boca Raton, Florida

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[4] US EPA. [2009]. Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.00]. United States Environmental Protection Agency, Washington, DC, USA

[5] IPCS: Intox Databank, http://www.intox.org/databank/index.htm

[6] ATSDR: Agency for toxic substances and disease registery, http://www.atsdr.cdc.gov/

[7] TOXNET: TOXikology Data NETwork TOXNET - http://toxnet.nlm.nih.gov/

[8] IRZ: Integrovaný registr znečišťování životního prostředí (IRZ) : http://www.irz.cz/