BIOACCUMULATION OF DECHLORANE PLUS IN AQUATIC FOOD WEB FROM AN

ELECTRONIC WASTE RECYCLING SITE, SOUTH

Xiao-Jun Luo, ∗,1 Jiang-Ping Wu, 1,2 Ying Zhang,1 Jing Wang, 1 She-Jun Chen, 1 Bi-Xian Mai, 1

1 State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, 2China and Research Center for Environmental Engineering & Management, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China

Abstract Water, sediment and aquatic organisms were collected from an e-waste site and analyzed for Dechlorane Plus (DP). DP is detected in all the aquatic species, with concentrations of 19.1–9630 ng/g lipid wt. An enrichment of syn-DP is observed in organisms compared with abotic samples and the fraction of anti-DP was found decreased with increased trophic level. Syn-DP was significant correlated with PBDEs and PCBs in the organisms but anti-DP was not the case. Both syn- and anti-DP significantly biomagnify in the present food web, with a trophic magnification factor (TMF) of 11.2 and 6.6, respectively. The TMFs of the DP isomers are higher than those of individual congener of PBDEs, but are generally lower than PCB congeners.

Introduction Dechlorane Plus (DP), a chlorinated flame retardant chemical, has been widely used in electrical wire and cable coatings, computer connectors, plastic roofing materials, and other polymeric systems for more than 40 years (1). Despite the long commercial history of this chemical, DP has been receiving little attention compared to other wildly used flame retardants chemicals such as polybrominated diphenyl ethers (PBDEs), and is reported in the environment more recently (2). Similarly to other flame retardant chemicals, DP appears to be persistent, bioaccumulative, and potentially toxic. The detections of DP in the sediment cores (3, 4) suggest its environmental persistence. The recent detection of the DP isomers in aquatic biota and bird indicated that it is also bioaccumulative (2, 5-8). In the present study, we measured DP in water, surficial sediment and several aquatic species from an e-waste recycling site, South China. One of the objectives of this study is to investigate the levels and isomeric composition of DP in these samples. More important, the different bioaccumulation behavior of two DP isomers in food web was investigated and compared with PCBs and PBDEs based on calculated trophic magnification factors (TMFs) .The results of this study will improve our understanding on the environmental fate of DP.

Experimental Section Sample Collection. The samples analyzed in this study are the same as those in our previous papers (9, 10). Briefly, a total of 88 wild aquatic biota samples, and 6 water samples and 6 surficial sediment samples were concurrently collected from a reservoir near the e-waste recycling plant, South China (23.6021 N, 113.0785 E) in 2006. Biota samples included Chinese mysterysnail (Cipangopaludina chinensis), prawn (Macrobrachium nipponense), mud ( molitorella), (Carassius auratus), Northern snakehead (Ophicephalus argus), and water snake (Enhydris chinensi). Additionally, five mud (Cirrhinus molitorella) were collected from another reservoir 5 km away from the e-waste recycling plant, as reference samples. The sampling site, samples collection and samples pretreatment is described elsewhere (9).

* Corresponding author phone: +86-20-85290146; fax +86-20-85290706; E-mail: [email protected] (X.J. Luo).

Vol. 71, 2009 / Organohalogen Compounds page 003033 Analysis of DP. The process of extraction and cleanup of the biota samples are same with those for PBDEs, and described elsewhere (9). Water samples are filtered by the ashed glass fiber filters (Whatman, GF/F). The filtrates are passed through a glass column contained XAD mix resins to retain the organic matter. The XAD resins are first eluted by methanol and than extracted in an ultrasonic bath by methanol and dichloromethane. The suspended sediment in the water and surficial sediment are extracted and cleaned in a manner identical to that of biota samples with the exception of GPC. Stable isotope analysis of nitrogen is previously determined on biota to define trophic levels (10). DP isomers are determined via gas chromatography/negative chemical ionization mass spectrometry using a DB-5 ht capillary column (15 m length, 025 mm diameter, 0.10 μm thickness) and selective ion monitoring. The temperature program is as follows: 110 °C initial hold time of 1 min; 110–310 °C at 10 °C/min, hold for 8 min; and the source temperature is 260 °C. DP isomers are identified by comparing sample peak retention times to those of the known standard (within ± 0.1 min).

Results and Discussion DP Levels. Concentration of DP in biota, water and sediments are given in Table 1. The total DP concentrations in the collected organisms varied from 12 to 9600 ng/g lipid wt. The average concentrations of DP are 0.80 ng/L, 3930 ng/g dry wt (dw) and 7590 ng/g dw in the dissolved phase of water, suspended particles and surficial sediment, respectively (Table 1). DP was detected in all mud carp samples from the e-waste recycling site. However, it was only detected in one of the five reference samples. Meanwhile, the concentrations of DP in the contaminated mud carps are 3–159 times greater than the reference mud carps. These results suggested that the DP pollution in the e-waste recycling site was due to the primary e-waste recycling activities.

To date, few studies reported DP levels in aquatic species. Hoh et al. (2) recently analyzed DP in archived fish (walleye) from Lake Erie and found the levels of DP in the range of 0.14–0.91 ng/g lipid wt. Tomy et al. (5) reported mean concentrations of DP between 0.035 and 0.82 ng/g lipid wt in fish from Lake Winnpeg and 0.015 and 4.41 ng/g lipid wt in Lake Ontario. These concentrations were 1 – 4 orders magnitude lower than those in the present studies. Most of studies which reported DP levels in sediments were within the Northern American Great Lakes region (2, 10, 16) so far. Levels of DP in the sediment of the present study are more than one order magnitude higher than the highest concentration reported in sediment (586 ng/g dw) from Lake Eire, America (4). The elevated levels of DP in the environmental media from the e-waste recycling site also indicates that release from the e-waste may be an important source of DP in China, as assumed by Ren et al. (11).

Isomeric Ratios. The fraction of anti-DP (fanti), defined as the concentration of the anti-DP divided by the sum of concentrations of syn- and anti-DP, are calculated for the abotic samples and the organisms (Table 1). Sediments have a mean fanti values of 0.72±0.01, which are close to the values in DP commercial product (fanti = 0.75–0.80) (2). This suggests that the main source of sedimentary DP is commercial DP added in the electronic products. It is interesting to found that the fanti values (mean of 0.72) in sediments were apparently in between the water (mean of 0.66) and the suspended particles (0.84). One likely explanation for this observation is that more syn-DP than anti-DP enters into dissolved phase of water during partition process due to different octanol-water partition coefficients. It was reported that the two isomers had different aqueous solubility at 207 ng/L and 572 ng/L (4), but no information was provided as to which isomer exhibited which solubility. However, other factors such as isomer-selective microbial degradation and biota uptake can also result in different fanti values among water, suspended particles and sediment in the present study.

With the exception of two Chinese mysterysnail samples in which syn-DP was below the LOQ, most of the samples have smaller fanti values than those in surficial sediments (Table 1), meaning an enrichment of syn-DP. This is in line with those observed in several fish species from Grate Lake region (5). The higher assimilation efficiency and lower depuration rate of syn-DP relative to anti-DP, as documented in juvenile rainbow trout (Oncorhynchus mykiss)

Vol. 71, 2009 / Organohalogen Compounds page 003034 administrated DP isomers (12), may account for the low fanti values. The fanti values (0.65–0.74) in the prawn was close to those in surficial sediment, which might be relate to its benthic habitat and polyphagia food habit. Additionally, the absence of the biotranformation for anti-DP in prawn may also contribute to this observation as prawn is thought to have low metabolic capabilities for PBDEs and PCBs (9). In contrast, northern snakehead, occupied the highest trophic level in the present food web, have the lowest fanti values (0.09–0.20), which were much lower than those in sediments. Interestingly, significant negative correlation is found between fanti values and trophic level of the species (p < 0.05) (Fig 1). This finding indicates that organisms with higher trophic positions may have higher metabolism capacities for anti-DP, and/or have higher uptake efficiencies for syn-isomer compared to anti-isomer. Higher fanti values in species with higher trophic positions were also found in aquatic organisms from Lake Winnipeg (Canada), but no clear trends between fanti values and TL were observed in these biota (5). Up to date, no information exists on the biodegradation (metabolism) of DP in organisms. A photogradation of DP conducted by Sverko et al (4) has demonstrated that anti-DP degrade more readily than the syn-DP. The relatively low anti-DP fraction observed in the present study and other report (2) implied, like photogradation, that anti-DP might metabolize more readily than the syn-DP in biota. The structural conformation of anti-DP in which the four interior carbons on the cyclooctane make it more susceptible to biological attack than syn-DP, as noted by Hoh et al(2).

Trophic magnification factors (TMFs). A regression analysis was made between trophic levels and the lipid-normalized concentrations (ln-transformed) of DP in organisms from the food web in the present study (Figure 2). The trophic level was determined by stable isotopes of nitrogen and given in our previous publication (10). Northern snakehead was diverged from the general trend predicted by linear regression equation, which maybe due to its high metabolic capacity for DP, as discussed above. Thus, we excluded this species from the food web when discuss the food web biomagnification of DP. The lipid normalized concentrations of syn-DP, anti-DP and total DP significantly increased with increasing trophic level, and their TMF values were 11.3, 6.5, and 10.2, respectively (Fig 2). This indicated that DP was significant biomagnifying throughout the entire food web. The TMF of syn- DP (11.3) was almost two times of that of anti-DP, suggesting that the biomagnifications poterntial of syn-DP was higher than that of anti-DP in the present food web (Fig 2).

Biomagnification of DP has also been reported in food webs from Lake Ontario and Lake Winnipeg, but the results were very different from the present study (5). No significant relationships between trophic level and concentration were found for both isomers in Lake Ontario food web. The anti-isomer was observed biomagnification in a Lake Winnipeg food web with a TMFof 2.54 (p = 0.04); which was two times lower than the value in the present study (6.5). However, syn-DP was found to dilute with increasing trophic level in Lake Winnipeg food web. This is entirely opposite to our finding..It is very difficult to explain the discrepancies between two studies based on the present data. Various factors including the food web composition, the assimilation efficiency of DP in the food web components, and even extrinsic conditions such as water temperature and environmental DP levels may lead to the different trophic biomagnification potentials of DP isomers among food webs. Further studies, especially for the metabolism of DP in organisms, were warranted to investigate mechanisms of DP biomagnification in different food web.

Comparing DP with PCBs and PBDEs. Our earlier works reported the bioaccumulation of PCBs and PBDEs in the same food web (9, 10). This provides an opportunity to compare the bioaccumulation behavior of DP isomers with those of PCBs and PBDEs. The syn-DP was found to significantly correlated with PCBs and PBDEs in the biota samples (p < 0.001), after removed an outlier, associated with a mud carp containing the highest level of DP, (Fig 3). However, this is not the case for anti-DP. This observation suggests that syn-DP may have similar bioaccumulation behavior with PBDEs and PCBs, while anti-DP may have a different behavior in biota. The stereoselective metabolism of anti-DP throughout the entire food web may lead to its different behavior in biota.

BDE47, BDE100, and BDE154 and most of PCB congeners were reported significant biomagnifications in the present food web (10). To make an identical food web composition, the TMFs for PBDEs and PCBs were recalculated after removed the northern snakehead from the food web. 11.3, which is approximate 5 times higher

Vol. 71, 2009 / Organohalogen Compounds page 003035 than that of total PBDEs (2.3), but similar to the value of total PCBs (11.1). The results suggest that trophic biomagnification of total DP is greater than total PBDEs but is comparable to total PCBs. Comparing the TMFs of DP isomers with those of individual congeners of PCBs and PBDEs in the same food web, it shows that TMFs of syn-DP and anti-DP are higher than all the PBDE congeners, but are generally lower than those highly recalcitrant PCB congeners (Fig 4). The greater food web biomagnification potential of DP isomers relative to PBDEs is likely due to the fact that PBDEs are much easier to be metabolized compared to DP isomers in the species of high trophic positions. PBDEs are demonstrated to be metabolized in several fish species (13), however, none of the possible metabolites of DP is found in lake trout exposed to DP (12), although anti-DP is suspected to be metabolized in certain fish species (2, 12). Most PCB congeners have log KOW at the range of 5 and 8, while DP have a log KOW of 9.43. The much higher KOW is likely to account for the lower food web biomagnification potential compared to PCBs, because chemicals with log KOW between 5 and 8 generally have the highest biomagnification potential in top-level predatory fish, while the biomagnification potential of compounds with logKOW greater than 8 dramatically decreased (10).

Our results demonstrate that both syn- and anti-DP have significant biomagnification potentials in aquatic food web. The food web biomagnification potential of DP is higher than those of PBDEs but is lower than that of PCPs. More work should be done on the bioaccumulation of DP in aquatic and terrestrial food web, and on the toxic effects to the wildlife.

Acknowledgements We thank Dr Yong Luo from Sun Yet-Sen University, China for assistance in samples collection. This work was supported by the National Science Foundation of China (Nos 20897012, 40873074), the National Basic Research Program of China (No.2009CB421604).

Reference 1. OxyChem. Dechlorane Plus Manual. Ver: 7-27-07. 2. Hoh, E.; Zhu, L.;Hites, R. A. Environ. Sci. Technol. 2006; 40: 1184-1189. 3. Qiu, X.; Marvin, C. H.;Hites, R. A. Environ. Sci. Technol. 2007; 41: 6014-6019. 4. Sverko, E.; Tomy, G. T.; Marvin, C. H.; Zaruk, D.; Reiner, E.; Helm, P. A.; Hill, B.;McCarry, B. E. Environ. Sci. Technol. 2008: 42: 361-366. 5. Tomy, G. T.; Pleskach, K.; Ismail, N.; Whittle, D. M.; Helm, P. A.; Sverko, E.; Zaruk, D.;Marvin, C. H. Environ. Sci. Technol. 2007; 41: 2249-2254. 6. Ismail, N.; Gewurtz, S. B.; Pleskach, K.; Whittle, D. M.; Helm, P. A.; Marvin, C. H.;Tomy, G. T. Environ. Toxicol. Chem 2009: 28: 910-920. 7. Gauthier, L. T.; Hebert, C. E.; Weseloh, D. V.;Letcher, R. J. Environ. Sci. Technol. 2007: 41:4561-4567. 8. Gauthier, L. T.;Letcher, R. J. Chemosphere 2009: 75: 115-120. 9. Wu, J. P.; Luo, X. J.; Zhang, Y.; Luo, Y.; Chen, S. J.; Mai, B. X.;Yang, Z. Y. Environ. Int. 2008; 34:1109-1113. 10. Wu, J. P.; Luo, X. J.; Zhang, Y.; Yu, M.; Chen, S. J.; Mai, B. X.;Yang, Z. Y. Environ. Pollut. 2009; 157: 904-909. 11. Ren, N.; Sverko, E.; Li, Y. F.; Zhang, Z.; Harner, T.; Wang, D.; Wan, X.;McCarry, B. E. Environ. Sci. Technol. 2008; 42: 6476-6480. 12. Tomy, G. T.; Thomas, C. R.; Zidane, T. M.; Murison, K. E.; Pleskach, K.; Hare, J.; Arsenault, G.; Marvin, C. H.;Sverko, E. Environ. Sci. Technol. 2008; 42: 5562-5567. 13. Stapleton, H. M.; Letcher, R. J.; Li, J.;Baker, J. E. Dietary accumulation and metabolism of polybrominated diphenyl ethers by juvenile carp (Cyprinus carpio). Environ. Toxicol. Chem. 2004; 23: 1939-1946.

Vol. 71, 2009 / Organohalogen Compounds page 003036 1 TABLE 1. Concentrations of Syn- and Anti-DP Isomers in the Aquatic Species (ng/g lipid wt), Water (ng/L), and Sediments

2 (ng/g OCa) from an E-waste Recycling Site as well as Mud Carps from the Reference Site, South China

DP Sample lipid or OC (%) synP -D Panti-D Fanti

Chinese mysterysnail (n = 43, [3])c 0.59 ± 0.11d 3.17 ± 3.17 17.1 ± 5.50 0.50 Prawn (n = 7, [3]) 2.39 ± 0.32 64.1 ± 20.8 126 ± 31.6 0.68 ± 0.03 Mud carp (n = 12, [8]) 2.87 ± 0.41 496 ± 310 1210 ± 842 0.54 ± 0.07 Crucian carp (n = 18, [7]) 3.63 ± 0.71 135 ± 47.3 142 ± 68.5 0.47 ± 0.04 Northern snakehead (n = 6) 1.49 ± 0.31 225 ± 106 30.0 ± 11.9 0.14 ± 0.02 Water snake (n = 2) 1.06 ± 0.15 1060 ± 109 909 ± 605 0.41 ± 0.20 Reference mud carp (n = 6, [3]) 5.22 ± 0.78 1.35 ± 1.35 7.41 ± 7.32 0.84 Water (n = 6, [3]) － 0.27 ± 0.04 0.53 ± 0.06 0.66 ± 0.06 Suspended sediment (n = 6, [3]) 4.83 ± 0.53 13100 ± 2890 65600 ± 11400 0.84 ± 0.01 Surficial sediment (n = 6, [3]) 9.79 ± 0.75 21800 ± 2160 55300 ± 7140 0.72 ± 0.01 3 a Organic carbon. b Data from reference 9. c Number of individual samples collected, figures in parentheses indicate

4 analyses number of pooled samples when individuals were pooled. d Mean ± SE.

5

0.75

sediment Prawn

0.60

Mud carp

0.45 Crucian carp

Water snake

anti f

0.30

r = -0.86 0.15 p < 0.05 Northern snakehead

2.8 3.2 3.6 4.0 4.4 6 Trophic level

7 Figure 1. Relationship between the fraction of the anti isomer and trophic levels.

8

Vol. 71, 2009 / Organohalogen Compounds page 003037 7 syn-DP 7 anti-DP 8 Total DP Water snake Water snake Water snake 6 6 7 Common carp Mud carp Mud carp Mud carp 6 5 5 Common carp Common carp Prawn Crician carp Northern Crician carp 5 Prawn Crician carp 4 snakehead 4 Northern Prawn snakehead Northern 4 3 3 snakehead ln conc. (ng/g l.w.) ln Conc. (ng/g l.w.) ln Conc. (ng/g l.w.) Conc. ln Chinese mysterysnail 3 Chinese mysterysnail y = 2.32725x-1.58941 Chinese mysterysnail y = 2.42209x-2.63138 y = 1.87915x-0.8932 2 2 r = 0.9419, p < 0.005 r = 0.94553, p < 0.005 r = 0.90823, p < 0.05 2 2.0 2.5 3.0 3.5 4.0 4.5 2.0 2.5 3.0 3.5 4.0 4.5 2.0 2.5 3.0 3.5 4.0 4.5 9 Trophic level (TL) Trofic level (TL) Trofic level (TL)

10 Figure 2. Trophic magnification of syn-DP, anti-DP and total DP

200000

anti-DP vs PBDEs syn-DP vs PBDEs 160000 r = 0.29 r = 0.76 p = 0.14 120000 p < 0.001

80000

40000

0 3000000 syn-DP vs PCBs anti-DP vs PCBs

2400000 r = 0.14 r = 0.74 p = 0.50 p < 0.0001 1800000 Concentration (ng/glipid)

1200000

600000

0

0 600 1200 1800 6000 7000 0 600 1200 1800 2400 11 Concentration (ng/g lipid)

12 Figure 3. Polt of anti- and syn-DP versus PBDEs and PCBs. Data of PBDEs and PCBs are from literature 9.

20 DP PBDE PCB

15

10

TMFs

5

0 syn- DP anti-DP Total DP 47 BDE 100 BDE 154 BDE Total PBD 28 PCB 52 PCB 110 PCB 118 PCB 138 PCB 153 PCB 180 PCB Total PCB

13 E

14 Figure 4 Compare of TMF of DP with TMF of PCBs amd PBDEs

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