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Draft: State of the Science Report on the Bioaccumulation and Transformation of Decabromodiphenyl Ether
- Summary
- List of Figures
- List of Tables
- List of Acronyms and Abbreviations
- 1: Introduction
- 2: Evidence for Bioaccumulation
- 3: Evidence of Transformation
- 4: Summary and Conclusions
- 5: Key Uncertainties and Data Gaps
- 6: References
- Appendix A.1 - Biota Concentration Data
- Appendix A.2 - Biota Concentration Data
- Appendix B - Bioaccumulation, Biomagnification and Trophic Magnification Data
- Appendix C - Selection of Log Kow for QSAR Modelling of decaBDE
- Appendix D - Model Input Parameters for BAF-QSAR and Terrestrial Biomagnification Model Predictions for decaBDE Transformation Products
- Appendix E - Summary of environmental degradation and debromination studies for decaBDE
- Appendix F - Structural Diagrams for DecaBDE and DecaBDethane
Appendix E - Summary of environmental degradation and debromination studies for decaBDE
| Study Authors | Type of Study | Substance Purity | Degradation Mediator | Experimental Conditions | Degradation Rate | Degradation Products |
|---|---|---|---|---|---|---|
| NR - not determined or not reported. | ||||||
| Watanabe and Tatsukawa (1987) | Photodegradation | 97% decaBDE and 3% nonaBDE | Artificial UV Light | Dissolved in organic solvents | NR | Tri- to octaBDEs; possibly brominated furans |
| Söderström et al. (2004) | Photodegradation | Traces of octa- and nonaBDEs | Natural sunlight and artificial UV light | Sorbed to thin layer of silica gel, sand, soil or sediment | NR | Reductive debromination with products including primarily hexa- to nonaBDEs; tetra- and pentaBDFs |
| Jafvert and Hua (2001) | Photodegradation | 98% | Artificial and natural sunlight | Sorbed to hydrated surfaces of glass and silica sand particles, humic acid-coated silica particles, and glass surfaces in contact with aqueous solutions | 12-71% degradation over 60-72 h | Identification of debromination products was largely inconclusive, although there was some evidence of the formation of hexa- to nonaBDEs. |
| Hua et al. (2003) | Photodegradation | NR | Artificial sunlight or natural sunlight | Precipitated onto quartz glass, silica particles and humic acid-coated silica particles; hydrated | 44-71% degradation over 60-72 h; humic acid slowed the rate of decaBDE decay | Small amounts of nona- and octaBDE |
| Palm et al. (2003) | Photodegradation | NR | Artificial xenon lamps | Dispersed in organic solvents | Half-life ~ 30 minutes | Three isomers of nonaBDE formed, then six isomers of octaBDE, then debromination to several isomers of heptaBDE, and finally to trace amounts of hexaBDE. Approximately 75% of decaBDE degradation followed a pathway of debromination while the products of the remaining 25% could not be determined. |
| Palm et al. (2003) | Photodegradation / oxidation | NR | Simulated sunlight or hydroxyl radicals | Sorbed to aerosol (silicon dioxide) | < 6 × 1013 cm3 molecule-1s-1 | Products not determined |
| Bezares-Cruz et al. (2004) | Photodegradation | NR | Natural sunlight | decaBDE dissolved in hexane | 99% reduction in the decaBDE concentration in as little as 30 minutes | Products ranging from tri- to nonaBDEs were observed. |
| Eriksson et al. (2004). | Photodegradation | 98% decaBDE | Artificial UV light | Organic solvents / water mixtures | 4´10-4/s in the methanol/water mixture (half-life ~ 0.5 hr), 6.5 × 10-4/s in methanol (half-life ~ 0.3 hr), 8.3 × 10-4/s in pure tetrahydrofuran (half-life ~ 0.23 hr) | 3 nonaBDEs, at least 7 octaBDEs, 8 heptaBDEs and small amounts of hexaBDEs |
| Eriksson et al. (2004). | Photodegradation | 98% decaBDE | Artificial UV light | Water / humic acid mixture | 3 × 10-5/s in water with humic acid (half-life ~ 6.4 hr | 3 nonaBDEs, at least 7 octaBDEs, 8 heptaBDEs and small amounts of hexaBDEs |
| Geller et al. (2006) | Photodegradation | 98% | Artificial light | Dissolved in tetrahydrofuran | NR | Photolysis products included hepta- to nonaBDEs as well as tri- to hexabrominated dibenzofurans |
| Kuivikko et al. (2006) | Photodegradation | >98.3% | Natural sunlight | Dissolved in iso-octane; modelling to determine rates in ocean | Half-life of 0.03 days in iso-octane Predicted half-lives in the Baltic Sea of 0.02 days (surface) and 1.2 days (mixing layer) and in the Atlantic Ocean of 0.09 days (mixing layer) | NR |
| Kuivikko et al. (2006, 2007) | Photodegradation | > 98.3% | Natural sunlight | Dissolved in iso-octane; modelling to determine rates in ocean | Half-life of 0.03 days in iso-octane; mixing zone half-lives of 1.8 days (Baltic Sea) and 0.4 days (Atlantic Ocean) | Mixing zone half-lives of 1.8 days (Baltic Sea) and 0.4 days (Atlantic Ocean), which were the same for both decaBDE concentrations |
| Ahn et al. (2006a) | Photodegradation | 98% | Artificial light and natural sunlight | Sorbed to montmorillonite, kaolinite, organic-carbon-rich natural sediment (16.4% OC content), aluminum hydroxide, iron oxide and manganese dioxide | For artificial light, half-lives ranged from 36 to 178 days For natural light, half-lives for montmorillonite, kaolinite and sediment were 261, 408 and 990 days, respectively (negligible degradation on other matrices) | Identified products for kaolinite and montmorillonite exposed to sunlight included nonaBDEs (BDE208, -207 -206), octaBDEs (BDE197, -196) as well as small amounts of tri- to heptaBDEs |
| Stapleton and Dodder (2006) | Photodegradation | NR | Natural sunlight | Either native decaBDE in house dust or decaBDE spiked house dust | 2.3 × 10-3/hr in spiked dust and 1.7 × 10-3/hr in natural dust, corresponding to half-lives of 301 and 408 h in sunlight, respectively | Spiked dust: lower brominated PBDEs including hepta-, octa- and nonaBDE congeners; 54% of the degradation products were not identified |
| Gerecke (2006) | Photodegradation | 98% | Natural sunlight | decaBDE (BDE209) sorbed to kaolinite. Irradiated dry or in water | Half-lives of 76 and 73 minutes were determined for dry and wet conditions, respectively; dependent on light penetration | Lower brominated PBDEs (under dry conditions); unidentified products (under wet conditions) |
| Stapleton (2006b) | Photodegradation | NR | Natural sunlight | Either native decaBDE in house dust or decaBDE spiked house dust | Half-life for decaBDE was estimated at 216 h | Three nonaBDEs, six octaBDEs and one heptaBDE. Mass balance analysis of decaBDE determined that approximately 17% of the original decaBDE was unaccounted for, suggesting the formation of alternative (unidentified) products or volatilization of lower brominated PBDEs |
| Hagberg et al. (2006) | Photodegradation | NR | Artificial light | decaBDE (BDE209) dissolved in toluene | NR | Mono- to hexa-substituted PBDFs; the majority of the products were tetra- to hexaBDFs; lower brominated PBDEs not monitored |
| Barcellos da Rosa et al. (2003) | Photodegradation | 98% | Artificial light | decaBDE (BDE209) dissolved in toluene | 3 × 10-4/s | Hepta- to nonaBDEs |
| Study Authors | Type of Study | Substance Purity | Degradation Mediator | Experimental Conditions | Degradation Rate | Degradation Products |
|---|---|---|---|---|---|---|
| NR - not determined or not reported. | ||||||
| Keum and Li (2005) | Reductive debromination | NR | decaBDE (i.e., BDE209) reducing agents - zerovalent iron, iron sulphide, and sodium sulphide. | Dissolved in ethyl acetate | Up to 90% transformation of decaBDE after 40 d | Stepwise debromination with mono- to hexaBDE congeners present after 40 days (started with higher brominated PBDEs) |
| Li et al. (2007) | Reductive debromination | Commercial DE-83R decaBDE (> 97%, Great Lakes Chemical) | Nanoscale zerovalent iron | Dissolved in acetone, distilled water added. 25 ± 0.5°C | Half-life was 2.5 h | Stepwise debromination to form tri- to nonaBDEs |
| Rahm et al. (2005) | Hydrolysis (nucleophilic aromatic substitution) | NR | Reaction with sodium methoxide | Dissolved in methanol | Half-life for the hydrolysis reaction was 0.028 h | NR |
| Ahn et al. (2006b) | Metal oxide-mediated debromination | 98% | Birnessite | Sorbed to birnessite in THF:water and water:catechol systems | THF:water - >75% transformation of decaBDE in 24 h Catechol:water - degradation only observed for highest concentration of catechol (15% degradation over 23 days) | In THF:water -nonaBDEs (BDE207, -208), octaBDEs (BDE196, -197), heptaBDEs (BDE183, -190 and eight unknowns), hexaBDEs (BDE138, -153, -154 and five unknowns), pentaBDEs (BDE99, -100, -118 and one unknown), and tetraBDEs (BDE49, -47, -66). Not determined for water:catechol |
| Study Authors | Type of Study | Substance Purity | Degradation Mediator | Experimental Conditions | Degradation Rate | Degradation Products |
|---|---|---|---|---|---|---|
| NR - not determined or not reported. | ||||||
| MITI 1992 | Biodegradation | NR | Activated sludge | Aerobic conditions | No degradation after 2 weeks | NR |
| Schaefer and Flaggs (2001) | Biodegradation | 97.4% decaBDE, 2.5% nonaBDE and 0.04% octaBDE | Sediment/water system | Anaerobic conditions | < 1% mineralization observed over 32 weeks | NR |
| CMABFRIP (2001) | Biodegradation | NR | Sediment microorganisms | Anaerobic conditions | No transformation or mineralization over 32 weeks | NR |
| He et al. (2006) | Biodegradation | 98% | Anaerobic bacteria | decaBDE (i.e., BDE209) dissolved in TCE and inoculated with anaerobic culture/medium | Degradation only observed with one culture (with S. multivorans) in which 0.1 mM decaBDE degraded to non-detectable levels over 2-month experiment | Octa- and heptaBDEs were detectable at the end of the experiment |
| Knoth et al. (2007) | WWTP monitoring (Biodegradation) | NR | WWTP sludge (primary, secondary and digested) | Field WWTP | NR | An increase in the proportion of lower brominated PBDE congeners was not observed, indicating no transformation of decaBDE during the total WWTP retention time |
| Gerecke et al. (2005) | Biodegradation | 97.9% decaBDE, 2.1% nonaBDEs | Sewage sludge + primers (1 or more of 4-bromobenzoic acid, 2,6-dibromobiphenyl, tetrabromo-bisphenol A, hexabromo-cyclododecane and decabromobiphenyl) | Anaerobic conditions | decaBDE (i.e., BDE209) decreased by 30% within 238 d Rate constant of 1 × 10-3 d-1 | 2 nonaBDEs and 6 octaBDEs. This was indicative of reductive debromination; loss of bromine from the para and meta positions |
| Gerecke et al. (2006) | Biodegradation | 97.9% decaBDE, 2.1% nonaBDEs | Sewage sludge + single primers (either 2,6-dibromophenol or 4-bromobenzoic acid) | Anaerobic conditions | Half-lives of 700 days (with primer) and 1400 days (without primer) were observed. Monitoring at an operating WWTP found that the concentration of decaBDE in sludge decreased between the influent and outlet streams. | In the experiments using a primer, decaBDE transformed slowly to BDE208. |
| La Guardia et al. (2007) | WWTP monitoring (biodegradation) | n/a | WWTP Sludge | NR | Minimal evidence of debromination in WWTP sludge or sediments | NR |
| Parsons et al. (2004) | Reductive debromination in sediments | NR | Anaerobic sediments | Anaerobic sediment suspensions in anaerobic medium Sediments collected from Western Scheldt | Significant decrease in decaBDE over 2 months; however, results are highly uncertain since similar decrease was observed in abiotic control | nonaBDEs and possibly lower brominated PBDEs |
| Parsons et al. (2007) | Reductive debromination in sediments | NR | Anaerobic sediments | Anaerobic sediment suspensions in anaerobic medium Sediments collected from Western Scheldt | No statistically significant decrease in decaBDE over 260 days | nonaBDEs detected in decaBDE-spiked samples, although degradation of decaBDE was not significant |
| Tokarz III et al. (2008) | Reductive debromination in sediments | NR | Anaerobic sediments and cosolvent-enhanced biomimetic system | Natural sediments with no detectable PBDEs collected from Celery Bog Park, West Lafayette, Indiana. PBDEs dissolved in a toluene solution added to sediments, then evaporated off. This mixture was then blended with wet sediments. Biomimetic experiment involved the use of Teflon-capped glass vials with 0.03 mM of BDE209, -99 or -47 mixed with 5.0 mM titanium citrate and 0.2 mM vitamin B12 in 0.33 M TRIZMA buffer solution containing tetrahydrofuran. | The biomimetic system demonstrated reductive debromination at decreasing rates with decreasing bromination (e.g., half-life of 18 seconds for BDE209 and almost 60 d for BDE47) In natural sediment microcosms, the half-life for BDE209 was estimated to range from 6 to 50 years, with an average of 14 years, based on observations over 3.5 years | Proposed pathway for both systems combined: BDE209 > nonaBDEs (BDE206, -207 -208) > octaBDEs (BDE196, -197) > heptaBDEs (BDE191, -184, two unknown heptaBDEs) > hexaBDEs (BDE138, -128, -154, -153) > pentaBDEs (BDE119, -99) > tetraBDEs (BDE66, -47, -49) > triBDEs (BDE28, -17) Specifically, at the end of 3.5 years, their analysis of BDE209 degradation in sediments identified BDE208, -197, 196, -191, -128, -184, -184, 138, and -128, as well as three unidentied octaBDEs and two unidentified heptaBDEs |
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