At a glance
| Chemical family | Organochlorine — cyclodiene insecticide |
| CAS number | 76-44-8 |
| Classification | IARC Group 2B (possibly carcinogenic to humans); Stockholm Convention Annex A (elimination); Canada SOR/2025-270 prohibited |
| Where you encounter it | Legacy termite treatments in building foundations; household dust and indoor air in pre-1988 homes; food chain (dairy, meat); breaks down to heptachlor epoxide, which is more persistent |
| Sleep micro-environment relevance | Not in any modern product. Like chlordane, applied directly to foundations for termite control and persistent in indoor environments for decades. Heptachlor epoxide found in indoor air and dust |
Regulatory & certification status
| European Union | POP Regulation (EU) 2019/1021 — banned. Original dirty dozen Stockholm POP. Regulatory |
| United States | EPA cancelled virtually all uses (1988). CERCLA hazardous substance. California Proposition 65 listed (cancer). Regulatory |
| Canada | Prohibited under the Prohibition of Certain Toxic Substances Regulations, 2025 (SOR/2025-270), in force 30 June 2026. Regulatory — Canada authority |
| International | Stockholm Convention Annex A (elimination) — original dirty dozen POP. IARC Group 2B (possibly carcinogenic). Regulatory — International authority |
What it is
Heptachlor is a chlorinated cyclodiene insecticide named for its seven chlorine atoms. It was widely used for subterranean termite control and soil-insect treatment, often in combination with chlordane. In the environment, heptachlor converts to heptachlor epoxide — a more persistent, more bioaccumulative metabolite that retains biological activity. IARC classified heptachlor as Group 2B (possibly carcinogenic) based on sufficient evidence of carcinogenicity in animals (liver tumours) and inadequate evidence in humans. The combination of persistence, bioaccumulation, and possible carcinogenicity led to its inclusion in the Stockholm Convention dirty dozen.
Where it shows up in bedding
Heptachlor was not used in bedding products. Like chlordane and aldrin, it was applied to building foundations for termite control, creating a reservoir of contamination that can persist for decades. Heptachlor and its metabolite heptachlor epoxide have been detected in household dust and indoor air of treated homes years after application. During sleep, dust ingestion and inhalation contribute to exposure. Food-chain bioaccumulation (dairy, meat) is the primary exposure route for the general population.
Citations
- IARC (1991). Heptachlor. IARC Monographs Vol. 53. Source Peer-reviewed
- ATSDR (2007). Toxicological Profile for Heptachlor and Heptachlor Epoxide. Source Regulatory
- Government of Canada. Prohibition of Certain Toxic Substances Regulations, 2025 (SOR/2025-270). Source Regulatory
Frequently asked questions
What is heptachlor epoxide?
Heptachlor epoxide is the primary breakdown product of heptachlor. It is more persistent and more bioaccumulative than the parent compound. Environmental monitoring for heptachlor contamination typically measures heptachlor epoxide because the parent compound converts relatively quickly. Both are regulated together under the Stockholm Convention.
How is heptachlor different from chlordane?
Heptachlor and chlordane are closely related organochlorine insecticides — heptachlor is actually a component of technical-grade chlordane. Both were used for termite control, both persist in household dust, and both are dirty dozen Stockholm POPs. Chlordane was more widely used and is more commonly detected in indoor environments.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-07-07. If you find a factual error, contact us.