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Persistency, bioaccumulation and toxicity assessment of selected brominated flame retardants
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Brominated flame retardants (BFRs) are chemicals used in e.g. electronic equipment, textiles and plastics for the prevention of fire. Over recent decades, concern has been raised regarding some heavily used BFRs, since the levels in the environment have been increasing. In the present thesis, persistent, bioaccumulative, and toxic (PBT) properties were studied for a structurally varied set of BFRs selected to represent more than 60 organic BFRs. The studied BFRs include: 2,4,4'-tribromodiphenyl ether (BDE 28), 2,2',3,4,4',5',6-heptabromodiphenyl ether (BDE  183), decabromodiphenyl ether (BDE 209), hexabromocyclododecane (HBCD), tetrabromobisphenol A (TBBPA), tetrabromobisphenol A 2-hydroxyethyl ether (TBBPA OHEE), 2,4,6-tribromophenol (246BrPh), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), and hexabromobenzene (HxBrBz).

It is likely that soil will act as a sink for BFRs. Therefore, studies of BFRs were performed on persistence in soil, and on bioaccumulation from soil in the earthworm Eisenia fetida. Large variation in the biodegradability in soil among the tested BFRs was observed. The studied brominated diphenyl ethers (BDE 28 and BDE 209) were very persistent under both aerobic and anaerobic conditions, while 246BrPh and TBECH degraded quickly in both aerobic and anaerobic soil. The bioaccumulation in earthworm from soil was high for HxBrBz, TBECH and for tested brominated diphenyl ethers with 4-6 bromine atoms (BDE 47, BDE 99, and BDE 153). Bioaccumulation was also studied in zebrafish after dietary exposure to a mixture of BFRs. It was shown that several metabolites were formed and retained in zebrafish, which highlights the importance of also searching for and identifying persistent degradation products. Maternal transfer was shown for all BFRs present in the female zebrafish. This shows that zebrafish young (fry) are exposed to these BFRs at approximately the same concentrations as female zebrafish during the early-life stages, when fish are usually most sensitive to organic contaminants. Toxicity of individual BFRs and a BFR mixture was studied in Nitocra spinipes using a silica gel-based system. Highest toxicities were observed for BDE 28, TBBPA, and TBBPA OHEE. In the mixture toxicity study, simultaneous exposure to low concentrations (individually causing no significant effect) of six BFRs significantly affected the survival of Nitocra spinipes. The results from the PBT studies presented in the thesis and literature data were compared with the criteria for PBT classification, as set in the European REACH legislation. Further, some BFRs with physico-chemical properties similar to those of identified PBTs were suggested to be prioritized for future PBT testing.

Place, publisher, year, edition, pages
Umeå: Print & Media , 2009. , 57 p.
Keyword [en]
persistence, bioaccumulation, toxicity, biodegradation, biotransformation, PBT, read across, soil, earthworm, zebrafish, copepod, BFRs, polybrominated diphenyl ethers, tetrabromobisphenol A, hexabromocyclododecane, hexabromobenzene, 2, 4, 6-tribromophenol, tetrabromobisphenol A, 2-hydroxyethyl ether, 1, 2-dibromo-4-(1, 2-dibromoethyl)cyclohexane
National Category
Environmental Sciences
Identifiers
URN: urn:nbn:se:umu:diva-22528ISBN: 978-91-7264-805-0 (print)OAI: oai:DiVA.org:umu-22528DiVA: diva2:216812
Distributor:
Kemiska institutionen, 90187, Umeå
Public defence
2009-06-05, MA121, MIT-huset, Umeå Universistet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2009-05-15 Created: 2009-05-12 Last updated: 2014-03-10Bibliographically approved
List of papers
1. Biodegradation kinetics of selected brominated flame retardants in aerobic and anaerobic soil
Open this publication in new window or tab >>Biodegradation kinetics of selected brominated flame retardants in aerobic and anaerobic soil
2010 (English)In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 158, no 6, 2235-2240 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the present study was to investigate the biodegradation kinetics in aerobic and anaerobic soil of the following brominated flame retardants: 2,4,4'-tribromodiphenyl ether (BDE 28), decabromodiphenyl ether (BDE 209), tetrabromobisphenol A (TBBPA), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), 2,4,6-tribromophenol (246BrPh), and hexabromobenzene (HxBrBz). For comparison, the biodegradation of the chlorinated compounds 2,4,4'-trichlorodiphenyl ether (CDE 28), 2,4,6-trichlorophenol (246ClPh), hexachlorobenzene (HxClBz), and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) was also assessed. In aerobic soil, BDE 209 showed no significant degradation during the test period, but concentrations of the other BFRs declined, with half-lives decreasing in the following order: BDE 28 > TBBPA > TBECH > HxBrBz > 246BrPh. Declines in almost the same order were observed in anaerobic soil: BDE 28, BDE 209 > TBBPA > HxBrBz > TBECH >246BrPh. Intra- and extrapolated half-lives in soil of tested brominated flame retardants ranged from 7 days for 2,4,6-tribromorophenol to >400 days for decabromodiphenyl ether.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
brominated flame retardants, persistence, soil, temperature, sludge
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-33266 (URN)10.1016/j.envpol.2010.02.010 (DOI)000278343000032 ()20227803 (PubMedID)
Available from: 2010-04-20 Created: 2010-04-20 Last updated: 2017-12-12Bibliographically approved
2. Accumulation of polybrominated diphenyl ethers, hexabromobenzene and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) in earthworm (Eisenia fetida): effects of soil type and ageing
Open this publication in new window or tab >>Accumulation of polybrominated diphenyl ethers, hexabromobenzene and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) in earthworm (Eisenia fetida): effects of soil type and ageing
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2010 (English)In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 44, no 23, 9189-94 p.Article in journal (Refereed) Published
Abstract [en]

In the present study the accumulation potentials in earthworms (Eisenia fetida) of selected brominated flame retardants (BFRs) were investigated. The tested BFRs, including polybrominated diphenyl ethers (PBDEs), hexabromobenzene (HBB),and1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), were found to be bioavailable to Eisenia fetida, and they accumulated in the earthworms. To our knowledge, this is the first published study to address the bioaccumulation potential of TBECH in terrestrial biota. Aging the soil resulted in decreased accumulation of TBECH, HBB, and PBDEs with six or less bromine atoms. However, no effect of soil aging was seen for BDEs 183 or 209, possibly due to their low mobility in soil. The use of different soils (artificial OECD soil and two natural Swedish soils) also affected the degree of accumulation in the worms. The results indicate that use of the generally accepted standard OECD soil may overestimate accumulation of organic contaminants by earthworms, due to high bioavailability of the contaminants and/or weight loss of the worms in it. Further, the accumulation of selected PBDEs and HBB was compared to the accumulation of their chlorinated analogues. Brominated compounds accumulated to the same or a lesser extent than their chlorinated counterparts.

Identifiers
urn:nbn:se:umu:diva-22527 (URN)10.1021/es1023288 (DOI)000284523400064 ()21028802 (PubMedID)
Available from: 2009-05-12 Created: 2009-05-12 Last updated: 2017-12-13Bibliographically approved
3. Maternal transfer of brominated flame retardants in zebrafish (Danio rerio).
Open this publication in new window or tab >>Maternal transfer of brominated flame retardants in zebrafish (Danio rerio).
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2008 (English)In: Chemosphere, ISSN 0045-6535, Vol. 73, no 2, 203-8 p.Article in journal (Refereed) Published
Abstract [en]

In many species reproduction and embryonic development have been shown to be sensitive to environmental contaminants. Understanding embryonic exposure to environmental contaminants is thus highly important. In this study concentrations of brominated flame retardants (BFRs) were measured in zebrafish eggs after parental exposure for 42 days via the diet. Zebrafish were exposed to two doses of eleven structurally-diverse BFRs. Eight BFRs were detected in the female zebrafish and maternal transfer to eggs was evident for all eight compounds. The highest concentrations in eggs were observed for hexabromocyclododecane (HBCD) and 2,4,4′-tribromodiphenyl ether (BDE 28), followed by 2,2′,3,4,4′,5′,6-heptabromodiphenyl ether (BDE 183) and tetrabromobisphenol A 2,3-dibromopropyl ether (TBBPA DBPE). Five potential BFR metabolites were tentatively identified in female fish and maternal transfer was observed also for these compounds. The lipid adjusted concentrations in eggs were significantly higher than the concentrations in female fish for several of the BFRs. Further, the results showed a generally higher transfer in the lower exposure level and also indicated a dependency on the physico-chemical properties of the compounds.

Keyword
Maternal transfer, Dietary Exposure, Zebrafish, Egg, Brominated flame retardants
Identifiers
urn:nbn:se:umu:diva-10113 (URN)doi:10.1016/j.chemosphere.2008.04.033 (DOI)18514256 (PubMedID)
Note
Brominated Flame Retardants (BFRs) - Papers presented at the Fourth International Symposium, BFR2007, held in Amsterdam, The Netherlands 24-27 April 2007Available from: 2008-09-02 Created: 2008-09-02 Last updated: 2010-01-15Bibliographically approved
4. Uptake and Biotransformation of Structurally-Diverse Brominated Flame Retardants in Zebrafish (Danio Rerio) after Dietary Exposure
Open this publication in new window or tab >>Uptake and Biotransformation of Structurally-Diverse Brominated Flame Retardants in Zebrafish (Danio Rerio) after Dietary Exposure
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2009 (English)In: Environmental Toxicology and Chemistry, Vol. 28, no 5, 1035-42 p.Article in journal (Refereed) Published
Abstract [en]

Zebrafish (Danio rerio) were fed a diet containing a mixture of 11 structurally diverse brominated flame retardants (BFRs) at nominal concentrations of either 1 or 100 nmol/g for up to 42 d, followed by an elimination period of 14 d. Uptake rates and elimination constants for five of the BFRs were calculated from measurements of their concentrations in the male fish during the exposure and elimination phases. Observed uptake efficiencies were highest for 2,4,4′-tribromodiphenyl ether (BDE 28) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) and were lowest for decabromodiphenyl ether (BDE 209). Estimated half-lives for TBECH and 2,4,6-tribromophenol were short (<2 d). Four BFR metabolites were identified in the fish: 2,2′,3,4′,5′,6-Hexabromodiphenyl ether (BDE 149), 2,2′,4,4′,5,6′-hexabromodiphenyl ether (BDE 154), 2,4,6-tribromoanisole, and 1,2,4,5-hexabromobenzene. These metabolites were still present in the zebrafish after the 14-d elimination period. No relationship between the BFR concentrations in the zebrafish and their log octanol-water partition coefficient (KOW) values was found. Generally, low tendencies to bioaccumulate were observed for perbrominated and hydroxylated compounds. The observed accumulation of BFR metabolites in fish, however, shows that low concentration of a BFR does not provide, in isolation, a sound indication that the BFR poses low risks.

Keyword
Brominated flame retardants, Fish, Accumulation, Elimination, Metabolites
Identifiers
urn:nbn:se:umu:diva-11248 (URN)doi:10.1897/08-302.1 (DOI)
Available from: 2009-01-12 Created: 2009-01-12 Last updated: 2010-01-15Bibliographically approved
5. Are individual NOEC levels safe for mixtures? A study on mixture toxicity of brominated flame-retardants in the copepod Nitocra spinipes.
Open this publication in new window or tab >>Are individual NOEC levels safe for mixtures? A study on mixture toxicity of brominated flame-retardants in the copepod Nitocra spinipes.
2008 (English)In: Chemosphere, ISSN 0045-6535, Vol. 72, no 9, 1242-9 p.Article in journal (Refereed) Published
Abstract [en]

In aquatic ecosystems organisms are exposed to mixtures of pollutants. Still, risk assessment focuses almost exclusively on effect characterization of individual substances. The main objective of the current study was therefore to study mixture toxicity of a common group of industrial substances, i.e., brominated flame–retardants (BFRs), in the harpacticoid copepod Nitocra spinipes. Initially, 10 BFRs with high hydrophobicity but otherwise varying chemical characteristics were selected based on multivariate chemical characterization and tested individually for effects on mortality and development using a partial life cycle test (six days) where silica gel is used as a carrier of the hydrophobic substances. Based on these findings, six of the 10 BFRs were mixed in a series of NOEC proportions (which were set to 0.008, 0.04, 0.2, 1, and five times the NOEC concentrations for each individual BFR), loaded on silica gel and tested in a full life cycle test (26 days). Significantly increased mortality was observed in N. spinipes after six and 26 days exposure at a NOEC proportion that equals the NOECLDR value (×1) for each BFR in the mixture (p = 0.0015 and p = 0.0105, respectively). At the NOEC × 5 proportion all animals were dead. None of the other NOEC proportions caused significant negative responses related to development and reproduction. This shows that low concentrations of individual substances can cause toxicity if exposed in mixtures, which highlights the need to consider mixture toxicity to a greater extent in regulatory work.

Keyword
Environmental risk assessment, Silica gel, Crustacean, Reproduction, Development, Statistical power
Identifiers
urn:nbn:se:umu:diva-10190 (URN)doi:10.1016/j.chemosphere.2008.05.004 (DOI)18561976 (PubMedID)
Available from: 2008-08-05 Created: 2008-08-05 Last updated: 2010-01-15Bibliographically approved

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