Alpha hexachlorocyclohexane (alphaHCH)

Alpha-HCH is one of the five stable isomers of technical HCH, a pesticide formerly used in agriculture. In general, HCHs are among the most studied pesticides with respect to their environmental fate and effects (Breivik et al., 1999).


Alpha-HCH by itself is not intentionally produced or available on the market. Instead, alphaHCH is produced as a part of technical HCH which is used as an insecticide or as an intermediate chemical in the manufacturing of lindane (enriched HCH). Currently no production data on technical HCH have been reported, whereas manufacture of lindane still takes place (IHPA, 2006).

HCH is manufactured by photochemical chlorination of benzene which leads to the formation of mainly five stable HCH isomers. The yields of different isomers vary due to technical differences in the production process. The reported ranges are:

  • alpha-HCH : 55-80%,
  • beta-HCH: 5-14%,
  • gamma-HCH: 8-15%,
  • delta-HCH: 6-10%; and
  • epsilon-HCH:1-5%.

Human Health Impacts

In humans, breathing toxic amounts of alphaHCH can result in blood disorders, dizziness, headaches, and possible changes in the levels of sex hormones in the blood. These effects have occurred in workers exposed to HCH vapors during pesticide manufacturing. People who have swallowed large amounts have had seizures; some have died. Animals that have been fed alphaHCH have had convulsions. All HCH isomers can produce liver and kidney effects. HCH isomers are changed by the body into other chemical products, some of which may be responsible for the harmful effects. Long-term oral administration of alphaHCH or technical-grade HCH to laboratory rodents has been reported to result in liver cancer.

The US Department of Health and Human Services (DHHS) has determined that HCH (all isomers) may reasonably be anticipated to cause cancer in humans. The International Agency for Research on Cancer (IARC) has classified HCH (all isomers) as possibly carcinogenic to humans. The US-EPA has classified alphaHCH as a probable human carcinogen.

More information




Adapted from US Agency for Toxic Substances and Disease Registry Toxicological Profile (PDF) and the Stockholm Convention Draft Risk Profile (PDF)

Hatfield Consultants The World Bank funded by the Canadian POPs Trust Fund through the      
Canadian International Development Agency
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