- Email: [email protected]
Hexabromocyclododecane (HBCD) flame retardant in the environment, biota and humans: Sterioisomeric paradox
Abstracts / Toxicology Letters 196S (2010) S1–S36
relating between the effects of single substances and their mixtures. In experimental rat tests, different biochemical parameters were used as criteria for assessment of mixture toxicity, while in Daphnia magna and Stenocypris werneri we used immobilization following exposure to toxicants. In both cases, interaction was expressed in terms of “additive”, “potentiatian” and “antagonism”; based on the numerical value of the estimated “Interaction Indices”. In mixtures contained pesticides and heavy metals, their interactive toxicity based on alteration in some biochemical parameters in rat’s sera, was accounted to “antagonism” for the majority of the tested combinations. On the other side, the results of joint action estimated by cotoxicity factor (TF) method, in Daphnia and Stenocypris bioassays, showed an agreement with the results of “concentration addition (CA) method” accounting to 93–100% and 79% with “independent action (IA) method”. Therefore, the TF model, as a simple method, was suggested to assess the interactive toxicity of binary mixtures having either similar or dissimilar mode of action, as well as to be used in conjunction with the methods based on CA and IA models. Also, by using a novel Daphnia—bioassay method, it was possible to assess the potential toxicity of mixtures of contaminants (e.g., pesticides and heavy metals) in vegetables, and to categorize toxic hazards in six definite ratings. doi:10.1016/j.toxlet.2010.03.147 HBCD as a Replacement Flame Retardant; Another POP S27-1 Hexabromocyclododecane (HBCD) complex chemistry: Detection and analytical methods A. Covaci 1 , M. Abdallah 2 , L. Roosens 1 , S. Harrad 2 University of Antwerp, Belgium, 2 University of Birmingham, United Kingdom
1
An overview of the analytical methodologies for the determination of HBCD isomers, including sample preparation and instrumental approaches, is presented. HBCD isomers have been measured recently in a variety of matrices including biological tissues, environmental samples, and textiles. Traditionally, HBCD has been determined via GC-ECNI/MS. However, GC techniques have a number of serious limitations, such as interconversion of the HBCD isomers above 160 °C, degradation in dirty injection systems or above 240 °C, and weaker structural identification in ECNI/MS. In contrast, alpha-, beta- and gamma-HBCD isomers can be separated easily using reversed-phase liquid chromatography and determined by mass spectrometry (LC–MS/MS). Furthermore, HBCD stereoisomers can be resolved on an enantioselective LC column. Isomer-specific data are useful to establish profiles and to understand the sources, distribution and fate of individual isomers. Two additional isomers (delta-HBCD and epsilon-HBCD) have been isolated from technical products with delta-HBCD identified recently in fish. However, LC–MS analysis is prone to ion suppression resulting in decreased sensitivity. This problem is avoided by thorough sample clean-up to remove interfering components and by using 13C-labelled and 2Hlabelled HBCDs as internal standards to compensate for potential variations in sensitivity during and between sample runs. The comparability of results obtained using GC–MS or LC–MS has been investigated in a few studies, but results are inconclusive due to substantial variation in the methodologies employed and in the type of samples analysed (fish, dust). Until now, only a limited number of intercalibration studies have been performed for HBCD. Laboratories were able to determine satisfactorily total
S33
HBCD in marine samples (RSD < 35%). However, determination of low HBCD concentrations should be improved. There is also a need for environmentally relevant reference materials certified for HBCDs that can be used for method validation. doi:10.1016/j.toxlet.2010.03.149
S27-2 Hexabromocyclododecane (HBCD) flame retardant in the environment, biota and humans: Sterioisomeric paradox R. Letcher Government of Canada, Canada 1,2,5,6,9,10-Hexabromocyclododecane (HBCD) is a brominated flame retardant (BFR) that is incorporated into a wide range of consumer products to delay the ignition of combustion and thus suppress flammability. A main application is the incorporation of HBCD in polystyrene foam boards used for thermal insulation by the construction industry. HBCD ranks among the largest massproduced BFRs worldwide, with a recent global demand reported to be ∼17,000 metric tons/year. Four technical mixtures of HBCD are currently available for commercial use and are comprised of three major sterioisomers, alpha-HBCD (∼10%), beta-HBCD (∼9%) and gamma-HBCD (∼81%), and minor impurities of other stereoisomers. These structural isomers of HBCD can also possess chirality and thus the number of isomers is even larger. Since HBCD is an additive flame retardant, it is thus pre-disposed to leaching out of commercial products, which leads to contamination and subsequent HBCD accumulation and persistence in the environment. The potential for HBCD to accumulate in organisms and biomagnify within a food web was initially observed in fish and lower aquatic organisms, with subsequent evidence of bioaccumulation in top feeding fish, birds and mammals including humans. Stereoisomer-specific processes have been shown to result in, e.g., the preferential accumulation of the alpha-isomer in biotic samples relative to the dominance of the gamma-isomer in commercial HBCD mixtures. Recent studies have demonstrated that the betaand gamma-HBCD are significantly metabolized in vitro and in vivo assay while the alpha-isomer was not, where isomer-specific (metabolic) biotransformation is the most likely explanation for almost exclusive accumulation of alpha-HBCD in biota. The present study will review and summarize the current state-of-knowledge with respect to stereoisomer-specific presence, bioaccumulation, fate and toxicokinetics of HBCDs in biota and their food webs including in humans, mammals, birds and fish, as well as results from captive studies with HBCD-dosed animals. doi:10.1016/j.toxlet.2010.03.150
S27-3 Different HBCD stereoisomers are metabolized differently H. Hakk Biosciences Research Laboratory, United States The requirement of flame retardancy in most consumer products has resulted in a vast array of chemical compounds that unfortunately have toxic effects and are environmental pollutants. Hexabromocyclododecane (HBCD) is an additive brominated flame retardant applied to extruded and high-impact polystyrene foams (<2.5% by weight) used as thermal insulation in buildings, and HBCD is the only suitable flame retardant for these appli-
relating between the effects of single substances and their mixtures. In experimental rat tests, different biochemical parameters were used as criteria for assessment of mixture toxicity, while in Daphnia magna and Stenocypris werneri we used immobilization following exposure to toxicants. In both cases, interaction was expressed in terms of “additive”, “potentiatian” and “antagonism”; based on the numerical value of the estimated “Interaction Indices”. In mixtures contained pesticides and heavy metals, their interactive toxicity based on alteration in some biochemical parameters in rat’s sera, was accounted to “antagonism” for the majority of the tested combinations. On the other side, the results of joint action estimated by cotoxicity factor (TF) method, in Daphnia and Stenocypris bioassays, showed an agreement with the results of “concentration addition (CA) method” accounting to 93–100% and 79% with “independent action (IA) method”. Therefore, the TF model, as a simple method, was suggested to assess the interactive toxicity of binary mixtures having either similar or dissimilar mode of action, as well as to be used in conjunction with the methods based on CA and IA models. Also, by using a novel Daphnia—bioassay method, it was possible to assess the potential toxicity of mixtures of contaminants (e.g., pesticides and heavy metals) in vegetables, and to categorize toxic hazards in six definite ratings. doi:10.1016/j.toxlet.2010.03.147 HBCD as a Replacement Flame Retardant; Another POP S27-1 Hexabromocyclododecane (HBCD) complex chemistry: Detection and analytical methods A. Covaci 1 , M. Abdallah 2 , L. Roosens 1 , S. Harrad 2 University of Antwerp, Belgium, 2 University of Birmingham, United Kingdom
1
An overview of the analytical methodologies for the determination of HBCD isomers, including sample preparation and instrumental approaches, is presented. HBCD isomers have been measured recently in a variety of matrices including biological tissues, environmental samples, and textiles. Traditionally, HBCD has been determined via GC-ECNI/MS. However, GC techniques have a number of serious limitations, such as interconversion of the HBCD isomers above 160 °C, degradation in dirty injection systems or above 240 °C, and weaker structural identification in ECNI/MS. In contrast, alpha-, beta- and gamma-HBCD isomers can be separated easily using reversed-phase liquid chromatography and determined by mass spectrometry (LC–MS/MS). Furthermore, HBCD stereoisomers can be resolved on an enantioselective LC column. Isomer-specific data are useful to establish profiles and to understand the sources, distribution and fate of individual isomers. Two additional isomers (delta-HBCD and epsilon-HBCD) have been isolated from technical products with delta-HBCD identified recently in fish. However, LC–MS analysis is prone to ion suppression resulting in decreased sensitivity. This problem is avoided by thorough sample clean-up to remove interfering components and by using 13C-labelled and 2Hlabelled HBCDs as internal standards to compensate for potential variations in sensitivity during and between sample runs. The comparability of results obtained using GC–MS or LC–MS has been investigated in a few studies, but results are inconclusive due to substantial variation in the methodologies employed and in the type of samples analysed (fish, dust). Until now, only a limited number of intercalibration studies have been performed for HBCD. Laboratories were able to determine satisfactorily total
S33
HBCD in marine samples (RSD < 35%). However, determination of low HBCD concentrations should be improved. There is also a need for environmentally relevant reference materials certified for HBCDs that can be used for method validation. doi:10.1016/j.toxlet.2010.03.149
S27-2 Hexabromocyclododecane (HBCD) flame retardant in the environment, biota and humans: Sterioisomeric paradox R. Letcher Government of Canada, Canada 1,2,5,6,9,10-Hexabromocyclododecane (HBCD) is a brominated flame retardant (BFR) that is incorporated into a wide range of consumer products to delay the ignition of combustion and thus suppress flammability. A main application is the incorporation of HBCD in polystyrene foam boards used for thermal insulation by the construction industry. HBCD ranks among the largest massproduced BFRs worldwide, with a recent global demand reported to be ∼17,000 metric tons/year. Four technical mixtures of HBCD are currently available for commercial use and are comprised of three major sterioisomers, alpha-HBCD (∼10%), beta-HBCD (∼9%) and gamma-HBCD (∼81%), and minor impurities of other stereoisomers. These structural isomers of HBCD can also possess chirality and thus the number of isomers is even larger. Since HBCD is an additive flame retardant, it is thus pre-disposed to leaching out of commercial products, which leads to contamination and subsequent HBCD accumulation and persistence in the environment. The potential for HBCD to accumulate in organisms and biomagnify within a food web was initially observed in fish and lower aquatic organisms, with subsequent evidence of bioaccumulation in top feeding fish, birds and mammals including humans. Stereoisomer-specific processes have been shown to result in, e.g., the preferential accumulation of the alpha-isomer in biotic samples relative to the dominance of the gamma-isomer in commercial HBCD mixtures. Recent studies have demonstrated that the betaand gamma-HBCD are significantly metabolized in vitro and in vivo assay while the alpha-isomer was not, where isomer-specific (metabolic) biotransformation is the most likely explanation for almost exclusive accumulation of alpha-HBCD in biota. The present study will review and summarize the current state-of-knowledge with respect to stereoisomer-specific presence, bioaccumulation, fate and toxicokinetics of HBCDs in biota and their food webs including in humans, mammals, birds and fish, as well as results from captive studies with HBCD-dosed animals. doi:10.1016/j.toxlet.2010.03.150
S27-3 Different HBCD stereoisomers are metabolized differently H. Hakk Biosciences Research Laboratory, United States The requirement of flame retardancy in most consumer products has resulted in a vast array of chemical compounds that unfortunately have toxic effects and are environmental pollutants. Hexabromocyclododecane (HBCD) is an additive brominated flame retardant applied to extruded and high-impact polystyrene foams (<2.5% by weight) used as thermal insulation in buildings, and HBCD is the only suitable flame retardant for these appli-