Correspondence Comment on “Halogenated Contaminants in Farmed Salmon, Trout, Tilapia, Pangasius, and Shrimp” Recently, van Leeuwen et al. (1) measured several classes of persistent halogenated contaminants (PHCs), including polychlorinated biphenyls (PCBs), polychlorinated dibenzop-dioxins and dibenzo-p-furans (PCDDs/Fs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane diastereomers (HBCDs), and perfluorinated compounds (PFCs), in farmed fish and shrimp collected from southeast Asia, Europe and South America. The authors further assessed human exposure to PHCs based on estimated Dutch consumption rates. In the same issue that van Leeuwen et al.’s work (1) was published, a news story (2) commenting on the results of van Leeuwen et al. also appeared. Apparently, van Leeuwen et al. (1) presented an interesting set of data that add to the current knowledge base about the contamination of farmed aquatic species by PHCs, whereas the news story (2) is expected to generate much attention from the global environmental science community. On the other hand, some statements, conclusions, or quotes in the article (1) and the news story (2) are inaccurate, incorrect, and even misleading. Specifically, existing data about the occurrence of PHCs in farmed aquatic species appear to have been severely overlooked, creating the impression that the issues investigated by van Leeuwen et al. have not been examined previously. There are at least five places in the published paper (1) or the news story (2) that failed to cite the results from several previous studies. First, there is a claim in the Introduction that “Almost no information is available on the contamination of farmed shrimp and new species like tilapia and pangasius” (1). This is obviously a false claim as there are abundant data available about the occurrence of OCPs and/or PBDEs in farmed tilapia (3–7) and shrimp (8, 9) in South China. Given the fact that China is the world’s largest producer of tilapia (10), assessment of exposure hazard via consumption of tilapia is simply a natural step toward proper risk management. It is also worthwhile to note that a news story published by Environmental Science & Technology in 2007 (11) highlighted the results from our previous study (7), in which 30 farmed tilapia individuals (along with 12 other fish species) were analyzed for OCPs, PBDEs, and PCBs. With such media coverage, it is quite perplexing that the tilapia data could be neglected in van Leeuwen et al.’s work. Second, the subsection titled “Comparison to Other Farmed Fish” conducted a detailed comparison of the PHC levels in salmon and two pangasius samples from different regions, but made no reference to tilapia, although tilapia data, as noted above, are more than sufficient to warrant a reasonable assessment. The last paragraph of the Results and Discussion section starts with “This is only a first estimation of the relative importance of contaminant exposure originating from new species such as pangasius and tilapia” (1). Obviously this statement was based on the unawareness of the available data as noted above, and particularly our previous study which also compared the relative abundances of OCPs and PBDEs in tilapia and human exposure due to fish consumption (7). Third, the news story (2) writes, “Tilapia, pangasius, and shrimp had much lower levels: less than 1 nanogram per gram wet 7584
9
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 43, NO. 19, 2009
weight. Van Leeuwen says, “These levels were the lowest I had ever seen in fish samples in my professional life””. This seems to be a misleading statement. The fact is, low levels (less than 1 ng/g wet weight) of OCPs, PCBs, and PBDEs have been reported in a large number of tilapia and shrimp samples we analyzed, e.g., 0.14-10.80 ng/g wet weight for DDTs, ND-0.49 ng/g wet weight for PCBs and 0.014-0.37 ng/g wet weight for PBDEs in 29 tilapia samples (7) and 0.10-52.3 ng/g wet weight for DDTs (8) and an average of 0.14 ng/g wet weight for PBDEs in 39 shrimp samples (9). Fourth, the Introduction section suggests that, because tilapia are omnivorous fish, they may contain less organic contaminants than other carnivorous fish species, and further claims that “There is no comprehensive data to confirm this hypothesis” (1). Again, this is an untrue statement. Our previous studies (12, 13) have demonstrated the difference between the carnivorous and omnivorous fish in terms of accumulating OCPs and PBDEs. For example, in tissues from three freshwater farmed fish species, bighead carp contained lower OCP concentrations than northern snakehead and mandarin fish, which was attributed to the fact that bighead carp feed on zooplankton and phytoplankton whereas northern snakehead and mandarin fish are carnivorous and at higher trophic levels than bighead carp (12). Ironically, van Leeuwen et al. (1) cited one (13) of our previous papers for comparison of the PBDE compositional profiles in farmed tilapia, but somehow failed to capture the information noted above. Finally, the statements, “The predominance of BDE-209 in farmed fish has not before been shown” and “Such a high concentration has not been before reported in fish” (the highest is 3500 pg/g wet weight), in the Results and Discussion section (1) are incorrect. In our investigation (14) on tissues (skin, gills, gastrointestinal tract liver, and muscle) from mandarin fish, northern snakehead, bighead carp, golden thread, and crimson snapper, BDE-209 was detected in 70 of the total 187 samples with a range of 0.39 to 59.9 ng/g dry weight. In addition, BDE-209 (the highest concentration is 624 ng/g lipid) was found as the major congener (the average relative abundance is 45%) in some biota samples from the Pearl River Estuary, South China (15), and extremely high concentrations of BDE-209 (the highest concentration is 138 ng/g wet weight) were also determined in wild aquatic species from an electronic waste recycling site in South China (16). Fish feeds have been identified as the main source of BDE209 in farmed fish (17). Besides fish, BDE-209 was also the most predominant constituent among all PBDE congeners measured in 39 shrimp samples with an average concentration of 0.076 ng/g wet weight as compared to 0.067 ng/g wet weight for the sum of BDE-28, -47, -66, -85, -99, -100, -138, -153, and -154 (9).
Acknowledgments This work was financed by the National Natural Science Foundation of China (nos. U0633005, 40532013, and 40821003). This is contribution No. IS-1105 from GIGCAS.
Literature Cited (1) 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, 42, 4009–4015. (2) Lubick, N. Farmed fish from top to bottom. Environ. Sci. Technol. 2009, 43, 3987. 10.1021/es9018223 CCC: $40.75
2009 American Chemical Society
Published on Web 08/21/2009
(3) 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. (4) Kong, K. Y.; Cheung, K. C.; Wong, C. K.; 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. (5) 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. (6) 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. (7) 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. (8) 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. (9) 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) State of Word Aquaculture, Technical Paper 500; FAO Fisheries: Rome, 2006. (11) Engelhaupt, E. Mixed news on Chinese farmed fish. Environ. Sci. Technol. 2007, 41, 1803–1804. (12) Guo, Y.; Meng, X. Z.; Tang, H. L.; Zeng, E. Y. Tissue distribution of organochlorine pesticides in fish collected from the Pearl River Delta, China: Implications for fishery input source and bioaccumulation. Environ. Pollut. 2008, 155, 150–156.
(13) Meng, X. Z.; Yu, L. P.; Guo, Y.; Mai, B. X.; Zeng, E. Y. Congenerspecific distribution of polybrominated diphenyl ethers in fish of China: Implications for input sources. Environ. Toxicol. Chem. 2008, 27, 67–72. (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 the 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. (17) Guo, Y.; Yu, H.-Y.; Zhang, B.-Z.; Zeng, E. Y. Persistent halogenated hydrocarbons in fish feeds manufactured in South China. J. Agric. Food Chem. 2009, 57, 3674–3680.
Ying Guo State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China and Graduate School, Chinese Academy of Sciences, Beijing 100039, China
Eddy Y. Zeng State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China ES9018223
VOL. 43, NO. 19, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
9
7585
