Environ. Sci. Technol. 2008, 42, 6378–6384
Temporal Trends, Congener Patterns, and Sources of Octa-, Nona-, and Decabromodiphenyl Ethers (PBDE) and Hexabromocyclododecanes (HBCD) in Swiss Lake Sediments M A R T I N K O H L E R , * ,† M A R K U S Z E N N E G G , † CHRISTIAN BOGDAL,† ANDREAS C. GERECKE,† PETER SCHMID,† NORBERT V. HEEB,† MICHAEL STURM,‡ HEINZ VONMONT,† HANS-PETER E. KOHLER,‡ AND WALTER GIGER‡ Empa, Swiss Federal Laboratories for Materials Testing and ¨ berlandstrasse 129, 8600 Dübendorf, Switzerland, Research, U and Eawag, Swiss Federal Institute of Aquatic Science and ¨ berlandstrasse 133, 8600 Dübendorf, Switzerland Technology, U
Received October 12, 2007. Revised manuscript received December 14, 2007. Accepted December 17, 2007.
With the recent ban of pentabromodiphenyl ether (technical PentaBDE) and octabromodiphenyl ether (technical OctaBDE) mixtures in the European Union (EU) and in parts of the United States, decabromodiphenyl ether (technical DecaBDE) remains as the only polybrominated diphenyl ether (PBDE) based flame retardant available, today. The EU risk assessment report for DecaBDE identified a high level of uncertainty associated with the suitability of the current risk assessment approach for secondary poisoning by debromination of DecaBDE to toxic lower brominated diphenylethers. Addressing this still open question, we investigated concentrations and temporal trends of DecaBDE, NonaBDE, and OctaBDE congeners in the sediments of Greifensee, a small lake located in an urban area close to Zürich, Switzerland. PBDE appeared first in sediment layers corresponding to the mid 1970s. While total TriHeptaBDE (BDE-28, -47, -99, -100, -153, -154 and -183) concentrations leveled off in the mid 1990s to about 1.6 ng/g dw (dry weight), DecaBDE levels increased steadily to 7.4 ng/g dw in 2001 with a doubling time of 9 years. Hexabromocyclododecanes (HBCD) appeared in Greifensee sediments in the mid 1980s. They are an important class of flame retardants that are being used in increasing amounts, today. As was observed for DecaBDE, HBCD concentrations were continuously increasing to reach 2.5 ng/g dw in 2001. Next to DecaBDE, all 3 NonaBDE congeners (BDE-208, BDE-207, and BDE-206) and at least 7 out of the 12 possible OctaBDE congeners (BDE202, BDE-201, BDE-197/204, BDE-198/203, BDE-196/200, BDE205, and BDE-194) were detected in the sediments of Greifensee. Highest concentrations were found in the surface sediments * Corresponding author phone: +41 44 823 4334; fax: +41 44 821 6244; e-mail:
[email protected]. † Empa, Swiss Federal Laboratories for Materials Testing and Research. ‡ Eawag, Swiss Federal Institute of Aquatic Science and Technology. 6378
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with 7.2, 0.26, 0.14, and 1.6 ng/g dw for Deca-, Nona-, Octa-, and the sum of Tri-HeptaBDE, respectively. While DecaBDE and NonaBDE were found to increase rapidly, the increase of OctaBDE was slower. Congener patterns of Octa- and NonaBDE present in sediments of Greifensee did not change with time. Consequently, there was no evidence for sediment mediated longterm transformation of PBDE within the observed time span of almost 30 years. Despite the high persistence of DecaBDE, 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. The OctaBDE congener BDE-202 was detected in sediments, representing a transformation product that is not reported in any of the technical PBDE products. Comparison of OctaBDE congener patterns in sediments with OctaBDE congener patterns from known sources reveals that (i) they were distinctively different from the congener patterns in technical PBDE products and (ii) that they were similar to the OctaBDE patterns in house dust and photodegradation products of DecaBDE, suggesting contributions from these sources.
Introduction Brominated diphenylethers such as decabromodiphenyl ether (technical DecaBDE), octabromodiphenyl ethers (technical OctaBDE), and pentabromodiphenyl ethers (technical PentaBDE) are chemicals that are used as flame retardants for plastics and textiles. In 2001, the market demand for technical DecaBDE was 56 100 tons, corresponding to over 80% of the total demand for polybrominated diphenylethers (PBDE), worldwide (1). Widespread use, high chemical stability, high lipophilicity, and bioaccumulation potential of some PBDE have led to an increasing contamination of the environment, wildlife, and humans (2–4). Brominated diphenylethers can cause adverse physiological effects, both in vitro and in vivo, including endocrine disruption and interference with neurobehavioral development (5, 6). This includes thyroid hormone disruption by the NonaBDE congener BDE-206 (7) and induction of developmental neurotoxic effects in mice by the NonaBDE congener BDE206 and the OctaBDE congener BDE-203 (8). PentaBDE and OctaBDE products were banned in 2004 by the European Union (EU) as well as by the states of Maine, Hawaii, Michigan, Washington, Oregon, Illinois, Maryland, and New York. Following the ban of these two products, DecaBDE has received more interest, since it remains the only diphenyl-ether-based brominated flame retardant available. The EU risk assessment report for technical DecaBDE (9) states that “. . .there is a high level of uncertainty associated with the suitability of the current risk assessment approach for secondary poisoning and the debromination issue. The combination of uncertainties raises a concern about the possibility of long-term environmental effects that can not easily be predicted”. As a matter of fact, several research groups have reported evidence for environmental debromination of DecaBDE (UV radiation (10-14), microbially mediated transformation (15, 16), metabolism in fish (17, 18) and abiotic transformation (19). Emissions of DecaBDE occur upon production and processing, as well as from use and disposal of flame retarded products, reflected by increasing environmental concentrations of DecaBDE. Incineration, recycling technology, as well as sewage sludge and e-waste disposal and recycling schemes were identified to be of highest relevance for emission reduction (20). 10.1021/es702586r CCC: $40.75
2008 American Chemical Society
Published on Web 02/13/2008
Currently, little is known on the long-term stability of DecaBDE in the environment. There are concerns that the globally increasing DecaBDE burden might act as a source of lower brominated diphenylethers (secondary poisoning). As shown previously (21), lake sediments provide a versatile historical archive of persistent environmental contaminants, settled to the lake bottom while adsorbed to particulate matter. In this study, we report on the fate of DecaBDE and the origin of its debromination products trapped in lake sediments within the last three decades.
Experimental Section Sampling. A sediment core (GR03–3) from the deepest point (31 m) of Greifensee, a small eutrophic lake (surface area 8.49 km2) located 10 km east of Zürich (Switzerland) was collected on April 25, 2003. The sediment core (diameter 6.3 cm) was cut into 1 cm slices that were freeze-dried, weighed, and stored in glass jars in the dark. Sediments were dated by measuring the 137Cs activity by γ-ray spectrometry (137Cs markers: 1954/1963 atmospheric nuclear weapons testing; 1986 Chernobyl accident) and by counting of annual varves that are well visible in sediments of Greifensee. Excellent agreement was found when comparing both dating methods. Sedimentation rates were between 0.25 and 0.34 cm y-1. The organic carbon content of the sediments was determined with a Euro EA-CNS autoanalyzer (HEKAtech GmbH, Germany) and varied between 1.4 and 5.3% (average 2.8%). The water content of the sediments was between 54 and 75%, averaging to 65%. Full details on the sediment core are given in Supporting Information Table S1. Surface fluxes, burdens, inventories, and doubling times of brominated flame retardants in sediments were calculated according to Zhu and co-workers (22). Analytical Methods. To suppress photodegradation of DecaBDE upon clean up, samples were protected from light, and the hood used for clean up was shielded with UV-filter foils that were checked for absence of brominated diphenylethers, previously. Freeze-dried sediments (6 g) were spiked with 13C12-labeled Tri-HeptaBDE (BDE-28, -47, -99, -100, -153, -154, and -183), 13C12-labeled DecaBDE (both from Cambridge Isotope Laboratories, U.S.), 81Br6-labeled HBCD (Empa, Switzerland) and extracted (Soxhlet) for 24 h with a 1:1 mixture of acetone and n-hexane. Traces of elemental sulfur were removed by gel permeation chromatography (Biobeads S-X3, 30 × 2.5 cm column, sample injection volume 5 mL, elution with 5 mL/min of a 1:1 mixture of cyclohexane/ ethyl acetate, sample collection time 18-38 min). Chromatography columns were packed with 1 g of silica gel (Kieselgel KG 60, Merck, Switzerland, previously activated at 130 °C for 12 h), 1 g of acidic silica gel (treated with 44% of concentrated sulfuric acid) and 1 g of silica gel (previously activated at 130 °C for 12 h). Concentrated extracts (0.5 mL) were transferred to the column and eluted with 50 mL of n-hexane (PBDE fraction), 25 mL of n-hexane/dichloromethane 98:2 (discarded) and 25 mL of n-hexane/dichloromethane 50:50 (HBCD fraction). The n-hexane fraction containing the PBDE was redissolved in 1 mL of n-hexane and further purified over 1 g of Alumina B-Super I (ICN Biomedicals GmbH, Germany, previously activated at 600 °C for 12 h), topped with 0.25 g of sodium sulfate, packed in a Pasteur pipet. After elution with 5 mL of n-hexane and 5 mL of n-hexane/ dichloromethane 98:2, PBDE were collected by elution with 5 mL of n-hexane/dichloromethane 50:50. Samples were concentrated, redissolved in toluene, transferred to a GC vial, adjusted to a final volume of 25 µL, and spiked with 5 ng of 13C12-labeled BDE-126 for determination of internal standard recoveries. GC analysis was carried out using a DB-1 equivalent stationary phase (PS347.5 polydimethylsiloxane, 10 m × 0.28 mm, film 0.1 µm; temperature program: 110 °C/ 1 min, 12
FIGURE 1. Concentrations of PCB and PCDD/F (34), as well as Tri-HeptaBDE, DecaBDE, and HBCD in Greifensee sediments. °C/min to 320 °C, 320 °C/ 5 min; carrier gas: hydrogen at 4 mL/min) on a HRGC MEGA 2 series gas chromatograph (Fisons Instruments, U.S.). Positive ion electron ionization mass spectra were acquired on a MAT 95 high resolution mass spectrometer (Thermo Fisher Scientific, Waltham, U.S.) in single ion monitoring mode at an ionization energy of 60 eV and a mass resolution of m/∆m of 8000. The two most abundant ions of the respective clusters were recorded: [M-2Br]+ for Hexa-DecaBDE, [M-Br]+ for HBCD, and [M]+ for Tri-PentaBDE. Quantification of Octa- and NonaBDE was based on their relative responses versus 13C12-labeled BDE183. The Tri-HeptaBDE and DecaBDE were quantified based on their 13C12-labeled analogues. HBCD was quantified based on its 81Br6 analogue. Principal component analysis was performed with “R”, a free software environment for statistical computing and graphics (23). Full details on quality assurance and on the reference materials used are given in the Supporting Information.
Results and Discussion Increasing Concentrations of DecaBDE and HBCD in Sediments. As shown in Figure 1, the concentrations of the lower brominated diphenyl ethers (technical PentaBDE and OctaBDE mixtures, represented by the sum of Tri-HeptaBDE congeners) are leveling off since the mid 1990s, while sediment concentrations of DecaBDE and HBCD are increasing rapidly (24). Between 1982 and 2001, DecaBDE concentrations have doubled every 9 years, reaching 7.2 ng/g dry weight (dw) in 2001, while HBCD reached a level of 2.5 ng/g dw. PBDE appeared in the sediments of Greifensee in the mid 1970s, followed by HBCD in the mid 1980s (see Figure 1). This is in line with recent data from Zegers and co-workers (25), reporting the first appearance of PentaBDE and DecaBDE in lake sediments from Western Europe in the early and late 1970s, respectively. Rapidly increasing sediment concentrations of DecaBDE have been reported by a number of groups in North America, Europe, and Japan, recently. In the sediments of the Great Lakes, Song et al. (26–28), Li et al. (29), and Zhu et al. (22) reported DecaBDE concentrations between 4.3 and 315 ng/g dw and doubling times between 5.3 and 45 y. In contrast, Zegers and co-workers (25) report concentrations seeming to decrease with time, based on the most recent layer of sediment cores from Drammenfjord (Norway), the western Wadden Sea (The Netherlands) and Lake Woserin (Germany), while Minh and co-workers (30) observed again increasing concentrations for DecaBDE (up to 85 ng/g dw) and HBCD (up to 2.3 ng/g dw) in sediments VOL. 42, NO. 17, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 3. Concentrations of DecaBDE, NonaBDE, OctaBDE, and Tri-HeptaBDE congeners (reported as the respective sums) in the sediments of Greifensee between the years 1974 and 2001. FIGURE 2. Reconstructed ion chromatograms ([M-2Br]+ ions), obtained for the purified extract of the surface sediments of Greifensee (2001), showing Octa-, Nona-, and DecaBDE congeners. of Tokyo Bay (Japan). Increasing concentrations for DecaBDE were also found by Muir and co-workers in lake sediments from the Canadian Arctic (31). Debromination of DecaBDE to NonaBDE and OctaBDE Congeners. Theoretically, 12 OctaBDE and three NonaBDE congeners may be formed by debromination of DecaBDE. Figure 2 indicates that all three NonaBDE and at least seven OctaBDE are present in the Greifensee surface sediments. Using authentic reference materials, detected congeners were identified as BDE-208, BDE-207, and BDE-206 (NonaBDE) and to BDE-202, BDE-201, BDE-197/204, BDE-198/203, BDE196/200, BDE-205, and BDE-194 (OctaBDE), respectively. Concentrations and Fluxes of Brominated Flame Retardants. Concentrations of DecaBDE, NonaBDE, OctaBDE, and Tri-HeptaBDE in sediments of Greifensee as a function of deposition time are presented in Figure 3. In 2001, sediment concentrations were 7.2, 0.26, 0.14, and 1.6 ng/g dw for Deca-, Nona-, Octa-, and the sum of Tri-HeptaBDE, respectively. In contrast to the findings of Zegers and co-workers (25), the HeptaBDE congener BDE-183, which is the main congener present in the technical OctaBDE product, has also been detected in Greifensee sediments (see Table 1). Compared to the sum of all congeners in the sample representing the year 2001, DecaBDE amounts to 78%, while the Nona-, Octa-, and Tri-HeptaBDE congeners amount to 2.8, 1.5, and 17%, respectively. Compared to the Great Lakes, where DecaBDE accounts for 95-99% of the total PBDE load (22), the relative amounts of the lower brominated diphenylethers were considerably higher in Greifensee, most likely reflecting a stronger impact of local DecaBDE sources in the Great Lakes catchment basin. Vives and co-workers (32) reported the same trends in sediments from different locations (urban vs rural) of Lake Maggiore in Italy and Switzerland. DecaBDE concentrations in Greifensee were significantly higher than those obtained by a dynamic substance flow analysis for sediments in Switzerland (20). This might be due to the urban catchment area of Greifensee and/or an underestimation of the atmospheric emissions in the substance flow analysis. In contrast to our data, the model results showed a leveling off or even a decrease (depending on the value used for the 6380
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half-lifetime of DecaBDE) of the concentrations in sediments since the mid 1990s. For Greifensee in 2001, the surface flux of DecaBDE reached 830 pg/(cm2 × y) in 2001, whereas the surface fluxes of NonaBDE and OctaBDE were 30 and 16 pg/(cm2 × y) in 2001, respectively. Thus, concentrations and surface fluxes of the Nona- and OctaBDE congeners were more than 1 order of magnitude below those of DecaBDE. Estimated burdens (total mass in the lake) and inventories (mass per surface area) of DecaBDE, NonaBDE, OctaBDE, Tri-HeptaBDE, and HBCD on Greifensee were in the order of 1–2 kg (19 ng/cm2) for DecaBDE, 50 g (0.5 ng/cm2) for Nona- and OctaBDE, and about 0.5 kg (5 ng/cm2) for both, Tri-HeptaBDE and HBCD. Compared to Lake Michigan (22), showing a DecaBDE doubling time similar to Greifensee (7.5 versus 9 years), DecaBDE surface flux (4.9 vs 0.83 ng/(cm2 × y) and inventory (190 vs 19.1 ng/cm2) were 6 and 10 times higher in Lake Michigan than in Greifensee, respectively. Next to DecaBDE, concentrations of Nona- and OctaBDE in sediments of Greifensee increase with time. However, while Deca- and NonaBDE concentrations were found to increase rapidly, the increase of the OctaBDE concentrations was less pronounced, as shown in Figure 3. It is likely that only parts of the predominately particle bound DecaBDE in the environment are available for photodegradation and/or microbially mediated transformation (e.g., DecaBDE located at the particle surface), limiting the extent of DecaBDE debromination. The kinetics of phototransformation of DecaBDE is strongly dependent on the matrix, as shown by Ahn and co-workers (33), reporting half-life-times for DecaBDE between 1423 d on the mineral birnessite, and 150–200 h on soil. Temporal Trends of Congener Patterns. Figures 4 and 5 show the congener patterns of Nona- and OctaBDE in sediments between 1974 and 2001, compared to the congener patterns of a typical technical Octa- and DecaBDE product. First, congener patterns of Octa- and NonaBDE observed in sediments of Greifensee are different from the Octa- and NonaBDE patterns determined in technical OctaBDE (dominated by BDE-207 and BDE-197/204) and DecaBDE (dominated by BDE-206 and BDE-196/200) coproducts. Consequently, there are biotic and/or abiotic transformation processes involved between the release of the technical products into the environment and their final residues in sediments that are responsible for the changes of congener patterns observed. Upon release from materi-
TABLE 1. Concentrations and Surface Fluxes of Brominated Flame Retardants in Greifensee Sedimentsa average year of sedimentation top layer of sample (1 cm disk) bottom layer of sample (1 cm disk) sedimentation rate [cm/y] DecaBDE [ng/g dw] BDE-206 BDE-207 BDE-208 sum NonaBDE [ng/g dw] BDE-202 BDE-194 BDE-196/200 BDE-197/204 BDE-198/203 BDE-201 BDE-205 sum OctaBDE [ng/g dw] BDE-28 BDE-47 BDE-99 BDE-100 BDE-153 BDE-154 BDE-183 sum Tri-HeptaBDE [ng/g dw] HBCD [ng/g dw] DecaBDE NonaBDE OctaBDE Tri-HeptaBDE HBCD a
2001
1995
2002 1996 1999 1993 0.34 0.34 sediment concentrations 7.2 6.7 0.12 0.075 0.070 0.046 0.076 0.041 0.26 0.16 0.011 0.010 0.008 0.001 0.022 0.023 0.033 0.036 0.039 0.031 0.024 0.020 0.003 0.004 0.14 0.12 0.031 0.027 0.74 0.64 0.51 0.51 0.098 0.11 0.056 0.073 0.064 0.081 0.079 0.121 1.60 1.60 2.5 1.8 surface fluxes [pg/(cm2 × y)] 830 600 30 14 16 11 180 140 290 160
1989
1982
1974
1990 1987 0.34
1984 1980 0.23
1976 1972 0.31
4.1 0.052 0.030 0.033 0.12 0.007 0.002 0.015 0.026 0.028 0.020 0.009 0.11 0.018 0.53 0.39 0.089 0.053 0.062 0.094 1.20 1.3 400 11 11 120 130
1.9 na na na na na na na na na na na na 0.016 0.44 0.11 0.035 0.016 0.015 0.041 0.67 0.40 110 na na 39 23
1.1 0.011 0.010 0.010 0.03 0.002 0.000 0.006 0.011 0.006 0.004 0.002 0.03 0.006 0.21 0.072 0.020 0.014 0.009 0.036 0.36 0.51 110 3 3 37 51
na, not analyzed, sample lost.
FIGURE 4. Congener patterns of NonaBDE in sediments of Greifensee between the years 1974 and 2001 (left) compared to patterns of NonaBDE in technical Octa- and DecaBDE products (right). als, PBDE congener patters may also be changed by thermal processes (transformation and/or different volatility of individual PBDE congeners). Second, the congener patterns of Octa- and NonaBDE in sediments are remarkably stable
over time. Once the congeners are buried in the sediments, no major changes were observed between 1974 and 2001 within the measurement uncertainty specified. Consequently, there was no evidence for sediment-mediated long-term transformation of these congeners within the observed time span of almost 30 years. This has been observed previously for polychlorinated biphenyls (PCB) that were studied in the same sediments (34). A closer look at Figure 5 reveals that the sediment samples contain BDE-202, an OctaBDE congener that was not present in the tested technical DecaBDE and OctaBDE products we analyzed (expect for very small amounts in the OctaBDE technical product from Great Lakes, see Supporting Information Table S2). La Guardia and co-workers (35) did not report the BDE-202 congener in the technical Penta-, Octa-, and DecaBDE products they investigated, either. There are several known processes that lead to the formation of BDE202, including photodegradation of DecaBDE (10, 11, 14), as well as biotransformation in sewage sludge (16) and fish (18, 36). As DecaBDE is the major BDE in atmospheric deposition (37), part of the BDE-202 present in lake sediments might be formed by photochemical transformation of DecaBDE on aerosols exposed to sunlight. BDE-202, however, is also present in sewage sludge. Recently, we reported the formation of BDE-202 (yet unidentified at that time) in sewage sludge by anaerobic microbially mediated transformation of the NonaBDE congener BDE-208 (16). Possible Sources of OctaBDE Congeners. To explore the origin of OctaBDE in the sediments of Greifensee, congener patterns from own data and from literature (10–12, 16, 33, 38) have been compiled, normalized to BDE-196/200 (see Supporting Information Table S2 and Figure S2) and compared to the patterns observed in the sediments of Greifensee (note: NonaBDE congener patterns were similar for all VOL. 42, NO. 17, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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FIGURE 5. Congener patterns of OctaBDE in sediments of Greifensee between 1974 and 2001 (left), compared to patterns of OctaBDE in technical Octa- and DecaBDE products (right).
FIGURE 6. Principal component analysis of OctaBDE congeners in Greifensee sediments (layer of 2001): Greifensee sediments (GS), sewage sludge (SS), house dust (HO), dust collected from a commercial airplane (HA), technical DecaBDE (DA, DB, DG) and OctaBDE (OG, OD) products, as well as UV-treated DecaBDE (kaolinite (UK), sediments (US), methanol/ water (UO), tetrahydrofuran (UT)). Details and references are given in Supporting Information Table S2. sources, therefore, no further analysis was possible). The comparison of OctaBDE congeners included dust samples (house dust and dust collected in a commercial airplane), sewage sludge, UV-treated DecaBDE (on kaolinite, sediments and in various solvents), as well as technical Octa- and DecaBDE products. A principal component analysis (Figure 6) of these data showed distinctive clusters for the technical DecaBDE and OctaBDE products, the dust samples, the UVtreated DecaBDE, and the sewage sludge samples. The congeners BDE-197/204 were prominent in dust samples, while BDE-201 and BDE-198/203 were abundant in UVtreated DecaBDE samples. In sewage sludge, prominent 6382
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congeners included BDE-202, BDE-201, and BDE-198/203 (Supporting Information Figure S2). As shown in Figure 6, the sediments of Greifensee were closest to the clusters representing the dust samples, the UV-treated DecaBDE samples and the sewage sludge samples. Thus, comparison of OctaBDE congener patterns in sediments with OctaBDE congener patterns from known sources revealed that (i) they are distinctively different from the congener patterns in technical PBDE products and (ii) that their patterns are similar to the OctaBDE patterns in house dust and photodegradation products of DecaBDE, suggesting contributions from these sources. Brominated Flame Retardants Are Emerging Persistent Organic Contaminants. Next to PBDE and HBCD, concentrations of POPs (persistent organic pollutants) such as PCB (polychlorinated biphenyls) and PCDD/F (polychlorinated dibenzo-p-dioxins and -furans) determined in the same sediments previously (34) are shown in Figure 1 (dashed lines). The effect of emission reduction measures and regulatory action has led to a significant decrease of the sediment levels of PCB and PCDD/F since the mid 1960s. Concentrations of DecaBDE and HBCD, however, are rapidly increasing today as the PCB and PCDD/F were in the mid 1950, before regulative action and emission reduction measures were established. In this respect, DecaBDE and HBCD are prime examples for emerging persistent organic contaminants. Open Questions and Implication on Regulative Action. Sediments are a final sink for PBDE and HBCD based flame retardants. While concentrations of Tri-HeptaBDE level off, DecaBDE burdens are rapidly increasing, similar to what has been seen in the 1960 for the PCBs and other “legacyPOPs” (34). It is possible that the rapid increase of DecaBDE and HBCD observed today is at least partly related to a substitution of the PentaBDE and OctaBDE products. Octaand NonaBDE congeners are present in sediments, and their congener pattern is significantly different from the congener patterns of technical Octa- and DecaBDE products. As congener patterns in the sediments of Greifensee remain constant over time (within the specified measurement
uncertainty of 10-20%), no evidence for sediment-related long-term transformation processes was found in this study, covering almost 30 years. For a substance to be considered as persistent (P) within a persistence, bioaccumulation and toxicity (PBT) assessment, data should be available to demonstrate that the substance has a half-life in fresh- or estuarine water sediments higher than 120 d. Based on our data for DecaBDE and HBCD, this is clearly the case. Despite the high persistence of DecaBDE, environmental debromination of this chemical is a relevant issue, as shown by the detection of shift in congener patterns of Nona- and OctaBDE and the occurrence of the congener BDE-202, a congener that is usually not present in technical DecaBDE and OctaBDE products. With regard to secondary poisoning by environmental debromination of DecaBDE to potentially toxic congeners, tackling the question if the increasing environmental reservoir of DecaBDE represents a significant risk will be important with respect for a decision on future regulative action.
Acknowledgments We thank Åke Bergman (Stockholm University, Sweden) for his help in identifying BDE-202 and for providing the BDE202 reference material. We also thank Anneli Pettersson (Örebro University, Sweden) for the BDE-196 and BDE-197 reference materials. Brian Sinnet, Thomas Kulbe, Alois Zwyssig, and Erwin Grieder (Eawag, Switzerland) are acknowledged for collection and dating of sediment cores and organic carbon determination. Leo Morf and Andreas Buser are acknowledged for excellent cooperation and for sharing the results of their dynamic substance flow analysis on DecaBDE. Financial support from the Swiss National Science Foundation (National Research Programme NRP50 “Endocrine Disruptors - Relevance to Humans, Animals and Ecosystems”, grant numbers 4050-066536 and 4050-066566) is acknowledged.
Note Added after ASAP Publication An error was discovered in Figure 3 of the version published ASAP on February 13, 2008. A corrected version was published on April 25, 2008.
Supporting Information Available Details on quality assurance (Figure S1), reference materials, sediment core data (Table S1), and OctaBDE congener patterns (Table S2 and Figure S2). This material is available free of charge via the Internet at http://pubs.acs.org.
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