Polybrominated diphenyl ethers and their methoxylated metabolites in anchovy (Coilia sp.) from the Yangtze River Delta, China

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1 Environ Sci Pollut Res (2010) 17: DOI /s z AREA 6 ENVIRONMENTAL ANALYSES AND MONITORING RESEARCH ARTICLE Polybrominated diphenyl ethers and their methoxylated metabolites in anchovy ( sp.) from the Yangtze River Delta, China Guan-yong Su & Zi-shen Gao & Yijun Yu & Jia-chun Ge & Si Wei & Jian-fang Feng & Feng-yan Liu & John P. Giesy & Michael H. W. Lam & Hong-xia Yu Received: 1 May 2009 / Accepted: 24 August 2009 / Published online: 25 September 2009 # Springer-Verlag 2009 Abstract Background, aim, and scope Polybrominated diphenyl ethers (PBDEs) and their metabolites are toxic to animals, and concentrations of the PBDEs metabolites can exceed those of the parent materials. But no information was available on concentrations of PBDEs metabolites in the lower Yangtze River in the region around Jiangsu Province of China, which is heavily urbanized and industrialized area. The aims of this study were to determine whether PBDEs and their methoxylated PBDEs (MeO-PBDEs) were accumulated in sp. in this area and to investigate the potential sources for these two kinds of brominated organic pollutants. Materials and methods Samples of four species of anchovy were collected from eight sites in the lower Yangtze River, Responsible editor: Alvin L. Young Electronic supplementary material The online version of this article (doi: /s z) contains supplementary material, which is available to authorized users. G.-y. Su : Z.-s. Gao : Y. Yu : S. Wei : J.-f. Feng : J. P. Giesy : H.-x. Yu (*) State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing , China Yuhx@nju.edu.cn Y. Yu Changzhou Environmental Monitoring Center, Changzhou , China J.-c. Ge : F.-y. Liu Freshwater Fisheries Research Institute of Jiangsu Province, Nanjing , China J. P. Giesy Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada Taihu Lake, and Hongzehu Lake. Concentrations of 13 PBDEs congeners and eight methoxylated PBDEs were determined by use of organic solvent extraction, followed by gas chromatography and mass spectrometry. Results and discussion The frequencies of detection for PBDEs and MeO-PBDEs were 92% and 53%, respectively. Concentrations of PBDEs ranged from not detected (ND) to 77 ng/g lipids (ND 3.8 ng/g wet weight). Concentrations of MeO-PBDEs in anchovy ranged from ND to 48 ng/g lipids (ND 8.2 ng/g wet weight). The PBDE concentrations in anchovy from the Yangtze River Delta were similar to or less than those reported for other species from other locations around the world, while the concentrations of MeO-PBDEs were comparable to or slightly less than those J. P. Giesy Department of Zoology, Michigan State University, East Lansing, MI, USA J. P. Giesy : M. H. W. Lam Centre for Coastal Pollution and Conservation, Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong SAR, People s Republic of China J. P. Giesy State Key Laboratory of Marine Environmental Science, College of Oceanography and Environmental Science, Xiamen University, Siming Nanlu 422, Xiamen, Fujian , People s Republic of China

2 Environ Sci Pollut Res (2010) 17: reported in other studies. This is the first report of MeO- PBDEs in biota of China. Conclusions The results of this study as well as those of other studies suggest that PBDEs in anchovy are primarily of synthetic origin and released by human activities, while MeO-PBDEs in anchovy are primarily from nature as natural products from the sea instead of metabolism of PBDEs in anchovy. Keywords GC/MS. Polybrominated diphenyl ethers. Methoxylated polybrominated diphenyl ethers. Fish. China 1 Background, aim, and scope Several species of anchovy (genus ) are economically important in the Yangtze River Delta, China. There are few differences in morphology among these species, but they differ in their life histories, especially in their migratory patterns. The estuarine tapertail anchovy ( ) and tapertail anchovy ( mystus) are economically important species in the Yangtze River estuary. Recent human influences, including over-fishing and water pollution, have resulted in a sharp decrease of the natural population of these species. The lake anchovy ( ) is the primary species in Taihu Lake. The population of this species is rather robust, and more than 15,000 tons are harvested every year. The shortjaw tapertail anchovy ( brachygnathus) is a species in Hongzehu Lake. Recently, heavy metal pollution and organic pollution have been reported in the Yangtze River Delta (Mueller et al. 2008; Chen et al. 2004; Yang et al. 2008), but concentrations of inorganic and organic pollutants had not been previously characterized in anchovies, which are important components of the diet of the densely populated Yangtze River Delta. Polybrominated diphenyl ethers (PBDEs) have been widely used in many products as flame retardants (Covaci et al. 2003), which has resulted in their release into the environment. There have been many reports of concentrations of PBDEs in the environment where they can be found in wildlife (de Wit 2002; Hale et al. 2001; Pettersson et al. 2004) and humans (Akutsu et al. 2003; Noren and Meironyte 2000; Johnson-Restrepo et al. 2005; Bi et al. 2007). In China, PBDEs were detected in many media (Guo et al. 2008; Bi et al. 2006; Chen et al. 2007; Chen et al. 2006a; Jin et al. 2008; Wurl et al. 2006). PBDEs are even ubiquitous in aquatic (freshwater fishes, shrimps, and crabs) from the lower Yangtze River (Gao et al. 2009). PBDEs can be transformed to various metabolites by animals (Marsh et al. 2006; Qiu et al. 2007). PBDEs and their metabolites are toxic to animals (Darnerud et al. 2001; McDonald 2002), and concentrations of the PBDEs metabolites can exceed those of the parent materials (Pettersson et al. 2004). These metabolites such as some hydroxylated PBDEs (OH-PBDEs) and methoxylated PBDEs (MeO-PBDEs) can even cause endocrine disrupting effects (Canton et al. 2005; Canton et al. 2006). These facts make scientists pay increasing attention to PBDEs and their metabolites. The Yangtze River Delta, located in East China, is a major production center for chemicals, textiles, and electronics, some of which use large amounts of flame retardants such as PBDEs. The annual production and consumption of PBDEs in this area have led to PBDE contamination of sediments (Chen et al. 2006b; Shen et al. 2006) and aquatic biota (Xian et al. 2008). No information was available on concentrations of PBDE metabolites in the lower Yangtze River in the region around Jiangsu Province, which is a heavily urbanized and industrialized area. In this study, different species of anchovies ( sp.) were collected from the Yangtze River Delta, and concentrations of 13 major PBDEs congeners and eight MeO-PBDEs metabolites were measured. Structures of 21 target compounds were given in the Electronic supplementary material (Figure S1). The main objectives of this study were to (1) determine whether PBDEs and their MeO-PBDEs were accumulated in sp. in this area, (2) to determine profiles of relative concentrations of PBDEs and MeO-PBDEs in sp., and (3) to investigate the potential sources for these two kinds of brominated organic pollutants. 2 Materials and methods Sampling Specific sampling locations included Haimen (L-1), Nanjing (L-2), Jingjiang (L-3), and Taicang (L-4) from the lower Yangtze River; Sanshanhu (L-5), Pingtaishan (L-6) and Jiaoshan (L-7) from Taihu Lake; and Hongzehu Lake (L-8). Samples of four species of anchovy, including estuarine tapertail anchovy (sampling location: L-1, L-2, and L-3), tapertail anchovy (sampling location: L-4), lake anchovy (sampling location: L-5, L-6, and L-7), and shortjaw tapertail anchovy (sampling location: L-8), were collected from April to August 2007, from eight sites in the lower Yangtze River, Taihu Lake, and Hongzehu Lake (Fig. 1). Anchovies were transported to the lab in frozen condition and were maintained intact at 20 C until dissected for subsequent identification and quantification of PBDEs and MeO- PBDEs. Details of the samples are given in the Electronic supplementary material (Table S1). Identification and quantification of PBDEs and MeO- PBDEs Concentrations of individual PBDEs and MeO-PBDEs were determined by use of organic solvent

3 636 Environ Sci Pollut Res (2010) 17: Fig. 1 Collection locations of anchovy E Sample locations Cities L-8 N Hongzehu Lake Yangtze River L-2 Nanjing L-3 L N Taihu Lake Changzhou L-7 Wuxi L-5 L-6 Suzhou L-1 Shanghai extraction, followed by gas chromatography and mass spectrometry (GC/MS). After measuring the length and weight of individual fish, the edible fillet was taken out of the fish. The fillet was freeze-dried and homogenized. Approximately 2.0 g of dry sample, to which surrogate standard 13 C-BDE-139 (Wellington Laboratories, Canada) was added was Soxhlet-extracted with a mixture of dichloromethane and hexane (V/V=1:1) for 24 h. The extract was concentrated by rotary evaporation and lipid content was determined gravimetrically. The extract was dissolved in dichloromethane and hexane (V/V=1:1) and acidified with 5 ml H 2 SO 4 to remove the fat. PBDEs and MeO-PBDEs were back-extracted with a total of 30 ml dichloromethane and hexane (V/V=1:1) in three separate 10 ml extractions. The organic solvent containing PBDEs and MeO-PBDEs was concentrated and passed through a silica gel column for further clean up. The silica gel column was packed with glass-wool, activated silica gel (0.25 g), 44% (w/w) acid silica gel (1.0 g), silica gel (0.25 g), and anhydrous sodium sulfate (0.30 g) from bottom to top in a disposable Pasteur pipette. The fraction containing PBDEs and MeO-PBDEs was eluted with 13 ml hexane followed by 10 ml dichloromethane. The eluate was concentrated by rotary evaporation and further concentrated to near dryness under a gentle nitrogen flow. A known amount of 13 C-PCB- 178 (Cambridge Isotope Laboratories, USA) was added as the internal injection standard and made up to 100 μl with hexane prior to GC/MS analysis. Concentrations of 13 PBDEs and eight MeO-PBDEs were determined by use of a GC/MS (Thermo Finnigan Polaris Q, USA) coupled with an Agilent DB-XLB column (15 m 0.25 mm 0.25 μm, USA) in two separate runs. The mass spectrometer detector was operated in electron impact ionization (EI) mode. Samples and standards were analyzed in both SIM and MS/MS mode. Quantification and qualification were processed by SIM and MS/MS modes in a single analysis. The selected ions (m/z) in SIM mode, precursor ion, and product ions selected in MS/MS mode for each chemical were based on the mass spectrum of the standard solution. Detailed information about the SIM ion, precursor ion, and product ions were given in the Electronic supplementary material (Table S2). The individual PBDEs, in order of retention times, included BDE-17, 28, 71, 47, 66, 100, 99, 85, 154, 153, 138, 183, and 190, The eight target MeO- PBDEs included 2 -MeO-BDE-28, 2 -MeO-BDE-68, 6-MeO-BDE-47, 4 -MeO-BDE-49, 2 -MeO-6 -Cl-BDE-68, 6-MeO-BDE-90, 6-MeO-BDE-85, and 6-MeO-BDE-137, in order of retention times. Identification of specific PBDEs and MeO-PBDEs was performed by comparing relative retention times versus internal standard and product ions in MS/MS mode with the standard chemicals. The limit of detection (LOD) was defined as the concentration that would result in a signal-to-noise ratio of 3. LOD based on 2.0 g of dry sample and instrument sensitivity, varied from

4 Environ Sci Pollut Res (2010) 17: congener to congener, from to 0.11 ng/g dry weight. Concentrations less than the LOD were assumed to be not detected in calculating summary statistics. Quality assurance/quality control One procedural blank was run with every batch of six to ten samples to assess potential sample contamination. The laboratory blanks demonstrated that the sample analysis was free from background contamination. Therefore, concentrations were not corrected for background. Recoveries of 13 C 12 -BDE-139 surrogate standard in blanks and samples ranged from 100.2% to 136.3% and from 65.6% to 122.7%, respectively. Recoveries of the 13 PBDEs and eight MeO-PBDEs in initial and ongoing recovery samples ranged from 74.4% to 94.5%. Method performance in spiked samples was listed in the Electronic supplementary material (Table S3), and reported results were not corrected for surrogate recovery. To facilitate comparison with the results of other studies, concentrations of PBDEs and MeO-PBDEs are given normalized to both wet weight and lipid weight (Tables 1 and 2). Statistical analysis Statistical analysis was performed with the SPSS 13.0 for Windows. Spearman rank correlation was used to examine the strength of associations between different datum (including weight and length of individual Table 1 PBDEs and MeO-PBDE concentrations in anchovy (pg/g ww) (L-1) (L-2) (L-3) mystus (L-4) (L-5) (L-6) (L-7) brachygnathus (L-8) Lipid (%) BDE-17 ND ND ND ND ND 140 ND ND ND 79 BDE-28 ND 270 ND 74 ND 240 ND ND ND BDE-71 ND 330 ND 85 ND 320 ND ND BDE ND ND ND BDE-66 ND 60 ND ND ND ND 150 ND 170 ND ND BDE-100 ND 140 ND ND ND 83 ND BDE-99 ND 25 ND 59 ND 95 ND ND ND BDE-154 ND 440 ND ND 340 ND ND 190 ND ND ND BDE-153 ND 190 ND ND 46 ND ND 39 ND ND ND PBDEs ND ND ND MeO- ND 270 ND 160 ND 450 ND ND ND ND ND BDE MeO ND 2.6 ND ND 38 ND 160 ND ND BDE MeO ND 2.7 ND ND 38 ND 160 ND ND PBDEs Only chemicals with concentrations greater than the LOD are listed ND not detected, the concentration was less than the LOD

5 638 Environ Sci Pollut Res (2010) 17: Table 2 PBDEs and MeO-PBDEs concentrations in anchovy (ng/g lip) (L-1) (L-2) (L-3) mystus (L-4) (L-5) (L-6) (L-7) brachygnathus (L-8) Lipid (%) BDE-17 ND ND ND ND ND 2.4 ND ND ND 1.2 BDE-28 ND 1.9 ND 0.73 ND 4.8 ND ND ND BDE-71 ND 2.4 ND 0.98 ND 1.9 ND ND BDE ND ND ND BDE-66 ND 0.43 ND ND ND ND 3.0 ND 4.1 ND ND BDE-100 ND 1.1 ND ND ND 2.0 ND BDE-99 ND 1.5 ND 0.68 ND 1.9 ND ND ND BDE-154 ND 2.6 ND ND 6.8 ND ND 3.8 ND ND ND BDE-153 ND 1.1 ND ND 0.24 ND ND 0.79 ND ND ND PBDEs ND ND ND MeO- ND 2.4 ND 1.9 ND 2.0 ND ND ND ND ND BDE MeO-BDE ND 29 ND ND 0.55 ND 4.0 ND ND MeO ND 31 ND ND 0.55 ND 4.0 ND ND PBDEs Only chemicals with concentrations greater than the LOD are listed ND not detected, the concentration was less than the LOD fish, concentrations of individual target compounds, PBDEs, and MeO-PBDEs), though the relativity was very low between the shape of individual fish and concentrations of target compounds. Mann Whitney U nonparametric tests were used to compare the difference between/among groups. The meaning of group was shown in the last part of the discussion. 3 Results and discussion 3.1 PBDEs and MeO-PBDEs concentrations In the present study, nine out of 13 targeted PBDEs were detected and two out of eight MeO-PBDEs were detected. Four PBDEs, including BDE-85, BDE-138, BDE-183, and BDE-190, were not detected in anchovy. Similarly, six MeO-PBDEs, including 2 -MeO-BDE-28, 4 -MeO-BDE- 49, 2 -MeO-6 -Cl-BDE-68, 6-MeO-BDE-90, 6-MeO-BDE- 85, and 6-MeO-BDE-137, were not detected either. The MeO-PBDEs detected in anchovy were 2 -MeO- BDE-68 and 6-MeO-BDE-47. These MeO-PBDEs have been detected in previous studies. This is the first report of MeO-PBDEs in the biota in China. The mass spectra showed that the precursor ions of 2 -MeO-BDE-68 and 6-MeO-BDE-47, which were also their molecular ions, had a loss of BrCH 3 (M-94 + ) in the EI-MS/MS mode. These fragmentations were in agreement with the previous observations of ortho-meo-pbdes (Athanasiadou et al. 2006). The fragmentation of 2 -MeO-BDE-68 and 6-MeO- BDE-47 in EI-MS/MS mode also showed similar ion

6 Environ Sci Pollut Res (2010) 17: clusters compared with the synthesized MeO-PBDEs standard (see Figure S2). Thus, it was confirmed that the above MeO-PBDEs were detected in anchovy from the Yangtze River Delta. The frequencies of detection for PBDEs and MeO- PBDEs were 92% and 53%, respectively. PBDEs and MeO-PBDEs were not detectable in one anchovy sample (C. brachygnathus) from L-8. PBDEs were not detected in one anchovy sample (C. mystus) from L-4. MeO-PBDEs were also not detected in most individuals of C.. The detection rates of PBDEs and MeO-PBDEs were as follows: 11% (BDE-17), 42% (BDE-28), 72% (BDE-71), 94% (BDE-47), 17% (BDE-66), 58% (BDE- 100), 50% (BDE-99), 31% (BDE-154), 14% (BDE-153), 25% (2 -MeO-BDE-68), and 53% (6-MeO-BDE-47). In anchovy, concentration of PBDEs ranged from not detected (ND) to 77 ng/g lip (ND 38 ng/g ww) with mean and median values of 18 ng/g lip (1.0 ng/g ww) and 8.6 ng/g lip (0.81 ng/g ww), respectively (Tables 1 and 2). By comparison, concentrations of PBDEs in anchovy from the Yangtze River Delta were generally less than those in biota from other locations around the world (Gao et al. 2009). Concentrations of MeO-PBDEs in anchovy ranged from ND to 48 ng/g lip (ND 8.2 ng/g ww) with the mean and median values of 9.1 ng/g lip (1.0 ng/g ww) and 2.0 ng/g lip (0.078 ng/g ww), respectively (Tables 1 and 2). Concentrations of PBDEs in anchovy were less than those reported in biota from other locations, while the concentrations of MeO-PBDEs were comparable to or slightly less than those reported from other locations, especially when compared with the wet weight concentration (see Table S3). The highest concentration was observed for 6-MeO-BDE- 47 (0.92 ng/g ww, mean values). The relatively high concentrations of the 6-MeO-BDE-47 congener in anchovy may be due to the relatively high lipid content in anchovy (Verreault et al. 2005a, b; Stapleton et al. 2006). However, the MeO-PBDEs concentrations were definitely less than concentrations of MeO-PBDEs that have been reported for some marine mammals, which can reach micrograms per gram, lipid levels (Teuten et al. 2005). 3.2 Profiles of PBDEs and MeO-PBDEs The PBDEs that were most frequently detected also contributed the highest proportion to the PBDEs. For example, BDE-47 and BDE-71 contributed more than 70% of the PBDEs. Besides these two tetra-bdes, BDE-28, BDE-100, BDE-99, and BDE-154 also were predominant congeners. After BDE-47, BDE-71 was the second most predominant PBDEs congener in anchovy. This result is different from the PBDE profiles reported for other aquatic species from other locations. The different patter observed in anchovy may be due to species-specific metabolism of anchovy. BDE-183 and BDE-190 were not detected in anchovy, which indicates that more-brominated PBDEs congeners were not readily accumulated by anchovy. Lack of heavier PBDEs might be related to the source profile or the fact that they were less soluble in water. Congeners 2 -MeO-BDE-68 and 6-MeO-BDE-47 were detected in some anchovy with concentrations of 2 -MeO-BDE-68 less than those of 6-MeO-BDE-47. The concentration of 6-MeO-BDE-47 was relatively high in anchovy from locations L-1, L-2, L-3, and L-4, in which concentrations of 6-MeO-BDE-47 were comparable or even higher than that of BDE-47 (Fig. 2). Concentrations of PBDEs congeners and MeO-PBDEs were inter-correlated. Concentrations of most PBDEs congeners were positively correlated with each other, and concentrations of the 2 detected MeO-PBDEs were also positively correlated with each other. However, concen- Fig. 2 Profiles of PBDEs and MeO-PBDEs in anchovy from the Yangtze River Delta

7 640 Environ Sci Pollut Res (2010) 17: trations of the two detected MeO-PBDEs were negatively correlated with concentrations of BDE-47. Concentration of 6-MeO-BDE-47 was also significantly negatively correlated with the concentration of PBDEs. This may be due to the lack of a metabolic origin of MeO-PBDEs from PBDEs. This fact is also supported by Vetter et al. (2001) who did not detect significant amounts of parent compounds (PBDEs) in marine mammals from northeastern Australia despite the high levels found of 6 -MeO-BDE47. Previous research has shown that there is a wide variety of naturally occurring organobromine compounds, which are produced by bacteria, fungi, plants, and animals (Gribble 2000). Both OH-PBDEs and MeO-PBDEs have been found in marine sponges and freshwater species (Kierkegaard et al. 2004). These facts suggest that MeO-PBDEs in anchovy from the Yangtze River Delta may also result from their food web in which MeO-PBDEs may be also naturally produced. 3.3 Potential source of PBDEs and MeO-PBDEs In order to investigate potential sources of PBDEs and MeO-PBDEs in anchovy, samples were divided into three groups based on their location and natural history characteristics. The first group (G1) consists of C. and C. mystus samples from the lower Yangtze River (sampling locations: L-1, L-2, L-3, and L-4). Both of these species reside in the coastal area and migrate back to the Yangtze River to spawn. The second group (G2) consists of C. from Taihu Lake (sampling locations: L-5, L-6, and L-7), while the third group (G3) consists of C. brachygnathus from Hongzehu Lake (sampling location: L-8). The difference among G1, G2, and G3 is that these latter two spices reside in the lake for all their lifetime. Concentrations of PBDEs in anchovy of G2 were significantly higher than concentrations of PBDEs in anchovy classified as G1 or G3 (Mann Whitney U test; p<0.01). Concentrations of MeO-PBDEs in G1 anchovy were significantly higher than those classified as G2 or G3 (p<0.01). In general concentrations of PBDEs were higher in anchovy from Taihu Lake than those from other two regions. But concentrations of MeO-PBDEs in anchovy from the lower Yangtze River were higher than those in the other two regions. Based on this observation, it is postulated that PBDEs in anchovy from Taihu Lake are primarily from human activities around the highly populated area (such as city of Suzhou, Wuxi, and Changzhou), while MeO-PBDEs are primarily derived from natural sources in the sea instead of the metabolism of synthetic PBDEs. This hypothesis is supported by the following observations: (1) The two detected MeO-PBDEs, 2 -MeO-BDE-68 and 6-MeO- BDE-47, have both been shown to be natural products produced by marine organisms instead of by metabolism synthetic PBDEs (Teuten et al. 2005). (2) C. and C. mystus from the lower Yangtze River are migratory fishes, residing in the Yangtze River estuary and migrating back to the Yangtze River to spawn. Since they do not feed during the migration and spawning, most of their food come from the estuary and are of marine origin, rather in the river. (3) Concentrations of MeO-PBDEs in anchovy from Yangtze River (L-1, L-2, L-3, and L-4) were obviously higher than those in anchovy from Taihu Lake and Hongzehu Lake (L-5, L-6, L-7, and L-8). This result suggests that the source of MeO-PBDEs in anchovy may be from the sea. (4) C. and C. brachygnathus are non-migratory fishes which reside in Taihu and Hongzehu Lakes. Concentrations of PBDEs in C. from Taihu Lake are higher than that of other anchovies. This is in agreement with the fact that artificial pollution is, in general, higher in Taihu Lake than in other areas of the Yangtze River Delta. 4 Conclusions PBDEs and MeO-PBDEs were detected in anchovy from the Yangtze River Delta. This is the first report of MeO- PBDEs in biota of China. The PBDE concentrations in anchovy from the Yangtze River Delta was similar to or less than those reported for other species from other locations around the world, while the concentrations of MeO-PBDEs were comparable to or slightly less than those reported in other studies. The results of this study as well as those of other studies suggest that PBDEs in anchovy are primarily of synthetic origin and released by human activities around the highly populated Taihu Lake area, while MeO-PBDEs in anchovy are primarily from nature as natural products from the sea instead of metabolism of PBDEs in anchovy. Acknowledgments We are grateful to the financial supports of the National Basic Research Program of China (973 program) (No. 2008CB418102), National Natural Science Foundation of China (No ), NSFC/RGC Joint Research Grant (No and N_CityU110/05), Jiangsu Science and Technology Department (BM ), Jiangsu Ocean and Fishery Department (K2006-3) and Department of Personnel Jiangsu (07-G-028) China. Prof. Giesy was supported by the Canada Research Chair program and an at large Chair Professorship at the Department of Biology and Chemistry and Research Centre for Coastal Pollution and Conservation, City University of Hong Kong. References Akutsu K, Kitagawa M, Nakazawa H, Makino T, Iwazaki K, Oda H, Hori S (2003) Time-trend ( ) of polybrominated diphenyl ethers in Japanese mother's milk. Chemosphere 53 (6):

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