Hexabromocyclododecane Challenges Scientists and Regulators

Hexabromocyclododecane and Hexachlorocyclohexane: How Lessons Learnt Have Led to Improved Regulation

“…Stereoisomer-specific bioaccumulation has been observed in HBCD. Like HCH, HBCD seems to undergo stereoselective processes such as biotransformation and bioisomerization in the environment, resulting in relative enrichment of different stereoisomers (Law et al, 2005;Janak et al, 2005;Heeb et al, 2008).This has been observed in the preferential accumulation of α-HBCD in relation to the much dominant γ-HBCD in the technical HBCD mixture . Differences in the water solubility of HBCD stereoisomers (48.8, 14.7 and 2.1 μg/l for α-, β-and γ-HBCD, respectively) may also be responsible for differences in the metabolism and bioaccumulation of the stereoisomers (Hunziker et al, 2004).…”

“…1), HBCD has a molecular formula of C 12 H 18 Br 6 , and is an additive brominated flame retardant (BFR) produced by bromination of 1,5,9-cyclododecatriene (Heeb et al, 2005). As a flame retardant, it is incorporated into a wide range of consumer products to resist ignition of combustion and prevent or reduce flammability, particularly in materials that are susceptible to combustion (BSEF, 2009).…”

“…As a flame retardant, it is incorporated into a wide range of consumer products to resist ignition of combustion and prevent or reduce flammability, particularly in materials that are susceptible to combustion (BSEF, 2009). Law et al (2005) described 16 possible stereoisomers of HBCD comprising 6 pairs of enantiomers and 4 mesoforms. However, technical HBCD is a mixture of 3 diastereomers: α-HBCD (10-13%), β-HBCD (1-12%) and γ-HBCD (75-89%) .…”

“…However, technical HBCD is a mixture of 3 diastereomers: α-HBCD (10-13%), β-HBCD (1-12%) and γ-HBCD (75-89%) . Like HCH, the complex stereochemistry of HBCD and the differential environmental behaviour and fate of its isomers have made chemical analysis and regulation of HBCD difficult (Law et al, 2005;Janak et al, 2005). The production of HBCD for use as a BFR in polystyrene materials commenced in the 1980s, though the chemical had been available on the market since the 1960s (EC, 2008).…”

Levels and distribution of hexabromocyclododecane (HBCD) in environmental samples near manufacturing facilities in Laizhou Bay area, East China

“…The variations were generally considered to be the results of thermal isomerization during the processing of final products and isomer-specific processes in environmental media. Rearrangement of HBCD isomers takes place at temperatures above 160 C, and decomposition occurs above 240 C. 24 The different physicochemical properties of the three isomers (e.g. thermal stabilities and photodegradation characteristics) can give rise to isomer-specific transport, partitioning, degradation and metabolism of HBCD in environmental media.…”