Ecological State of the Science Report on Decabromodiphenyl Ether (decaBDE): appendix E


Appendix E: Summary of Environmental Degradation and Debromination Studies for decaBDE

(a) Photodegradation

Study Authors Type of
Study
Substance Purity Degradation Mediator Experimental Conditions Degradation
Rate
Degradation
Products
Watanabe and Tatsukawa (1987) Photo-
degradation
97% decaBDE and 3% nonaBDE Artificial UV Light Dissolved in organic solvents NR Tri- to octaBDEs; possibly brominated furans
Söderström et al. (2004) Photo-
degradation
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) Photo-
degradation
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) Photo-
degradation
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) Photo-
degradation
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) Photo-
degradation/ oxidation
NR Simulated sunlight or hydroxyl radicals Sorbed to aerosol (silicon dioxide) < 6 x 1013 cm3 molecule-1s-1 Products not determined
Bezares-Cruz et al. (2004) Photo-
degradation
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). Photo-
degradation
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). Photo-
degradation
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) Photo-
degradation
98% Artificial light Dissolved in tetrahydrofuran NR Photolysis products included hepta- to nonaBDEs as well as tri- to hexabrominated dibenzofurans
Kuivikko et al. (2006) Photo-
degradation
>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) Photo-
degradation
> 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) Photo-
degradation
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) Photo-
degradation
NR Natural sunlight Either native decaBDE in house dust or decaBDE spiked house dust 2.3x10-3/hr in spiked dust and 1.7x10-3/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) Photo-
degradation
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) Photo-
degradation
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) Photo-
degradation
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) Photo-
degradation
98% Artificial light DecaBDE (BDE209) dissolved in toluene 3x10-4/s Hepta- to nonaBDEs
Kajiwara et al. (2008) Photo-
degradation
NR Natural sunlight HIPS (high-impact polystyrene) added to toluene and DecaBDE (BDE209) (100ug/L); toluene evaporated off in dark. A subset of samples hydrated with water to examine effect on photolysis. Crushed TV casing also tested. HIPS + DecaBDE samples: 50% BDE209 reduction after 1 week.Half life of BDE209 in HIPS estimated at 51 days.

Hydrated samples showed faster degradation than nonhydrated.

No degradation in dark controls.

No degradation of BDE209 in crushed TV casing samples during 224 days of sunlight irradiation.
HIPS + DecaBDE samples: hexa to nona BDE congeners increased several-fold after 1 week exposure, then levels remained constant or decreased slightly.

At end of exposure, proportion of BDE209 of total PBDEs had decreased from 90% to 44%.

Study confirmed photolytic formation of tri- to octaBDFs. Total PBDFs increased (>40 times) by day 7 of exposure, with decreasing BDE209 (HIPS + DecaBDE samples). No debromination products measured from crushed TV casing samples.

NR - not determined or not reported.

(b) Other Abiotic Degradation

Study Authors Type of
Study
Substance Purity Degradation Mediator Experimental Conditions Degradation
Rate
Degradation
Products
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

NR - not determined or not reported.

(c) Biodegradation

Study Authors Type of
Study
Substance Purity Degradation
Mediator
Experimental
Conditions
Degradation
Rate
Degradation
Products
MITI 1992 Biode-
gradation
NR Activated sludge Aerobic conditions No degradation after 2 weeks NR
CMABFRIP (2001) Biode-
gradation
97.4% decaBDE, 2.5% nonaBDE and 0.04% octaBDE Sediment/ water system Anaerobic conditions < 1% mineralization observed over 32 weeks NR
He et al. (2006) Biode-
gradation
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 (Biode-
gradation)
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) Biode-
gradation
97.9% decaBDE, 2.1% nonaBDEs Sewage sludge + primers (1 or more of 4-bromobenzoic acid, 2,6-dibromobiphenyl, tetrabromobisphenol A, hexabromo-
cyclododecane and decabromobiphenyl)
Anaerobic conditions DecaBDE (i.e., BDE209) decreased by 30% within 238 d Rate constant of 1 x 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) Biode-
gradation
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 (biode-
gradation)
n/a WWTP Sludge NR Minimal evidence of debromination in WWTP sludge or sediments NR
Parsons et al. (2004) Reductive debro-
mination 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 debro-
mination 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 debro-
mination 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 unidentified octaBDEs and two unidentified heptaBDEs
Kohler et al. (2008) Debromination in sediments NR Natural lake sediments Field - lake sediment cores Cores show DecaBDEs appear in layers corresponding to 1970s, >30 years. Despite high persistence of Deca in sediments, study suggests environmental debromination occurs, as shown by the detection of a shift in congener patterns of octa- and nonaBDE in sediments, compared to the respective congener patterns in technical PBDE products (e.g. presence of BDE202). Suggest biotic/abiotic transformation between the release of technical products and final residues in sediment.

NR - not determined or not reported.

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