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Response to “Comment on Halogenated Contaminants in Farmed Salmon, Trout, Tilapia, Pangasius, and Shrimp” Guo and Zeng (1) commented on our recently published study on halogenated contaminants in farmed salmon, trout, tilapia, pangasius, and shrimp (2), and on a news item on this article published in the same issue (3). They claim that we overlooked several Chinese studies on these contaminants in tilapia and shrimp (4–10) resulting in incorrect statements and false claims. We admit that we have overlooked most of these studies. However, these papers were not easy to find when searching in literature for publications on contaminants in farmed tilapia. We have used the search criteria “(tilapia or oreochromis) and (aquaculture or farmed or farming) and (organochlorine or pesticide or polybrominated or diphenyl)” but this did not result in hits on the references in their comment apart from one (11), to which we have referred to in our discussion on polybrominated diphenyl ether (PBDE) profiles. Even when not specifically searching for farmed tilapia, none of the papers were found (except ref 11). In addition, it was not explicitly mentioned in the title (4–10), nor in the abstract (5–7, 9, 10), nor in the keywords (4–10) that the investigated species were farmed or resulted from aquaculture. When assessing the papers more thoroughly, tables and figures from three papers (5, 7, 8) contain data on farmed tilapia. In the other cases it may be gathered from the introduction or from other parts of the paper (4, 6, 9, 10) that the studies concerned farmed fish or shrimp. A second comment is that we have not referred to a study by Meng et al. (8) which included a health risk assessment of several contaminants in farmed fish from China. This is for the same reason as mentioned above. In addition, in our study, we have estimated the relative human exposure to PBDEs, organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), dioxins, and dioxin-like PCBs and R-hexabromocyclododecane (R-HBCD) from consumption of the investigated species (2). We describe the Dutch situation with specific Dutch consumption patterns. Guo and Meng show that the earlier study (8) also included a discussion on human exposure to PCBs, PBDEs, and OCPs from fish consumption (including tilapia). However, a good comparison of their results to ours is hampered because (i) their exposure assessment describes a non-Dutch situation, whereas we focused on the Dutch situation, and (ii) their exposure assessment includes farmed fish solely from China, whereas we have included pangasius, shrimp, tilapia, trout, and salmon from different global regions. Guo and Meng find the statement of Van Leeuwen in the news item: “These levels were the lowest I had ever seen in fish samples in my professional life” misleading. However, that statement corresponds with his experience on several findings of high levels of dioxins, dioxin-like PCBs, PCBs, PBDEs, and R-HBCD in eel and many other fish species from polluted areas in The Netherlands (12, 13). Van Leeuwen did not conclude that the levels found would be lowest in the world. A fourth comment concerns the hypothesis that levels in tilapia may be low because they are omnivorous fish. We stated that “There is no comprehensive data to confirm this hypothesis” (2). Guo and Meng mentioned that ‘”this is an 7586
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untrue statement” (1) and they point toward two studies where they “have demonstrated the difference between the carnivorous and omnivorous fish in terms of accumulating OCPs and PBDEs” (1). They then provide examples of bighead carp, northern snakehead, and mandarin fish. Obviously, these examples may provide an indication, but they cannot confirm the aforementioned hypothesis, simply because they were not tilapia. Several species-dependent aspects play a role such as feeding habits and potential metabolism. Therefore, what Guo and Meng regard as a confirmation of the above hypothesis is in fact highly speculative. Their final comment concerns the presence of BDE-209 in farmed fish samples. We stated that “Such a high BDE-209 concentration has not been reported in fish before” (2). We explicitly meant “fillets of farmed fish” specifically, rather than “fish” in general. We admit we should have made this more explicit. We further stated that “The predominance of BDE-209 in farmed fish has not before been shown” (2). To our knowledge, this statement is true for several species we investigated (i.e., pangasius (Pangasius hypophthalmus) and shrimp (Penaeus monoden, Penaeus vannamei, Litopenaeus vannamei). However, we admit that in the examples of Guo and Meng (several tissues of mandarin fish, Northern snakehead, Bighead carp, golden thread, and crimson snapper) and shrimp, BDE-209 is also abundant (10, 14). Guo and Meng also referred to a study by Xiang et al. to support their comment (15), but as noted above, it is not identifiable from this publication that that study concerns farmed fish. They provide another example of high BDE-209 levels in fish (16), but this concerns wild caught fish and is again not farmed fish.
Literature Cited (1) Guo, Y.; Zeng, E. Y. Comment on halogenated contaminants in farmed salmon, trout, tilapia, pangasius and shrimp. Environ. Sci. Technol. 2009. (2) Van Leeuwen, S. P. J.; van Velzen, M. J. M.; Swart, C. P.; van der Veen, I.; Traag, W. A.; de Boer, J. Halogenated contaminants in farmed salmon, trout, tilapia, pangasius, and shrimp. Environ. Sci. Technol. 2009, 43, 4009–4015. (3) Lubick, N. Farmed fish from top to bottom. Environ. Sci. Technol. 2009, 43, 3987. (4) Zhou, H. Y.; Wong, M. H. Screening of organochlorines in freshwater fish collected from the pearl River Delta, People’s Republic of China. Arch. Environ. Contam. Toxicol. 2004, 46, 106–113. (5) Kong, K. Y.; Cheung, K. C.; Wong, C. K. C.; Wong, M. H. The residual dynamic of polycyclic aromatic hydrocarbons and organochlorine pesticides in fishponds of the Pearl River delta, South China. Water Res. 2005, 39, 1831–1843. (6) Cheung, K. C.; Leung, H. M.; Kong, K. Y.; Wong, M. H. Residual levels of DDTs and PAHs in freshwater and marine fish from Hong Kong markets and their health risk assessment. Chemosphere. 2007, 66, 460–468. (7) Cheung, K. C.; Zheng, J. S.; Leung, H. M.; Wong, M. H. Exposure to polybrominated diphenyl ethers associated with consumption of marine and freshwater fish in Hong Kong. Chemosphere. 2008, 70, 1707–1720. (8) Meng, X. Z.; Zeng, E. Y.; Yu, L. P.; Mai, B. X.; Luo, X. J.; Ran, Y. Persistent halogenated hydrocarbons in consumer fish of China: Regional and global implications for human exposure. Environ. Sci. Technol. 2007, 41, 1821–1827. (9) Guo, J. Y.; Zeng, E. Y.; Wu, F. C.; Meng, X. Z.; Mai, B. X.; Luo, X. J. Organochlorine pesticides in seafood products from Southern China and health risk assessment. Environ. Toxicol. Chem. 2007, 26, 1109–1115. (10) Guo, J. Y.; Wu, F. C.; Mai, B. X.; Luo, X. J.; Zeng, E. Y. Polybrominated diphenyl ethers in seafood products of south china. J. Agric. Food Chem. 2007, 55, 9152–9158. 10.1021/es9021975 CCC: $40.75
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Published on Web 08/21/2009
(11) Meng, X. Z.; Yu, L.; Guo, Y.; Mai, B. X.; Zeng, E. Y. Congenerspecific distribution of polybrominated diphenyl ethers in fish of China: Implication for input sources. Environ. Toxicol. Chem. 2008, 27, 67–72. (12) Van Leeuwen, S. P. J.; Leonards, P. E. G.; Traag, W. A.; Hoogenboom, L. A. P.; de Boer, J. Polychlorinated dibenzop-dioxins, dibenzofurans and biphenyls in fish from the Netherlands: concentrations, profiles and comparison with DR CALUX (R) bioassay results. Anal. Bioanal. Chem. 2007, 389, 321–333. (13) Van Leeuwen, S. P. J.; de Boer, J. Brominated flame retardants in fish and shellfish - levels and contribution of fish consumption to dietary exposure of Dutch citizens to HBCD. Mol. Nutr. Food Res. 2008, 52, 194–203. (14) Guo, Y.; Meng, X. Z.; Tang, H. L.; Mai, B. X.; Zeng, E. Y. Distribution of polybrominated diphenyl ethers in fish tissues from the Pearl River Delta, China: Levels, compositions, and potential sources. Environ. Toxicol. Chem. 2008, 27, 576–582. (15) Xiang, C. H.; Luo, X. J.; Chen, S. J.; Yu, M.; Mai, B. X.; Zeng, E. Y. Polybrominated diphenyl ethers in biota and sediments of the Pearl River Estuary, South China. Environ. Toxicol. Chem. 2007, 26, 616–623.
(16) Wu, J. P.; Luo, X. J.; Zhang, Y.; Luo, Y.; Chen, S. J.; Mai, B. X.; Yang, Z. Y. Bioaccumulation of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in wild aquatic species from an electronic waste (e-waste) recycling site in South China. Environ. Int. 2008, 34, 1109–1113.
S. P. J. van Leeuwen,* M. J. M. van Velzen, C. P. Swart, I. van der Veen, W. A. Traag, and J. de Boer Institute for Environmental Studies (IVM), VU University, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands, RIKILT-Institute of Food Safety, P.O. Box 230, 6700 AE Wageningen, The Netherlands * Corresponding author phone: +31 20 59 89 555; fax: +31 20 59 89 553; e-mail:
[email protected]. † VU University. ‡ RIKILT-Institute of Food Safety.
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