Hexabromocyclododecane

Abstract

Hexabromocyclododecane (HBCD) has been produced as a commercial mixture since the 1960s and is currently used as a flame retardant added to thermal insulation foams and textiles. The HBCD commercial mixture is made up of 16 possible stereoisomers with three predominating diastereomers: alpha, beta, and gamma (α-, β-, and γ-HBCD, respectively). Releases of HBCD in the environment are detected globally and are increasing in certain regions. HBCD, with α-HBCD being the dominant isomer, has been found to be widespread in humans and wildlife. Evidence supports the classification of HBCD as persistent, bioaccumulative, and toxic, which also undergoes long-range environmental transportation. HBCD is a nuclear receptor agonist, an endocrine disruptor, and a hepatotoxicant, and it causes developmental neurotoxicity in laboratory animals and wildlife. Few human studies have investigated effects of HBCD, and no studies with HBCD stereoisomers could be found. Due to its persistence, bioaccumulation, long-range transport, and toxicity profile, HBCD has been nominated for inclusion as a persistent organic pollutant under the UN Environment Programme's Stockholm Convention on Persistent Organic Pollutants.