Overview
Hexabromocyclododecane is a brominated flame retardant with the CAS number 25637-99-4. Its big use was insulation foam, both the expanded and extruded polystyrene boards used in buildings, and it also appeared in some textile coatings. The substance is persistent, builds up in living organisms, and is toxic, which is why regulators moved to phase it out.
Where it is controlled
HBCDD is a persistent organic pollutant under the Stockholm Convention and the EU POP Regulation, which means its production and use are banned apart from any narrow exemptions. It is also on the REACH Authorisation list, Annex XIV, and was identified as a substance of very high concern before that listing.
Typical uses
The dominant application was flame-retarded polystyrene foam for thermal insulation. Smaller volumes went into upholstery textiles and a few electrical and electronic housings. Because the foam stays in buildings for decades, legacy material remains a concern long after the ban.
HBCDD is one of the brominated flame retardants, alongside PBB, PBDE and TBBPA. It is unusual in that it is regulated as a POP rather than only under RoHS.
Note: general educational information, not legal advice. Check the official source before relying on it.