Environ. Sci. Technol. 2008, 42, 8173–8174
Response to Comment on “Brominated Flame Retardants, Polychlorinated Biphenyls, and Organochlorine Pesticides in Captive Giant Panda (Ailuropoda melanoleuca) and Red Panda (Ailurus fulgens) from China” We appreciate Hardy and Ranken’s interest in our recent article (1) about the detection of decabromodiphenyl ethane (DeBDethane) in tissues from captive panda and thank them for their comments (2). We offer the following responses to their comments. First, they claim that DeBDethane is not readily available biologically. Therefore, our conclusion that DeBDethane can be detected in tissues might not be correct. In fact, several investigations showed that DeBDethane was found in the particle phase of the atmosphere (3), in sediment from a sewage treatment plant in Sweden (4), in tree bark from North America (5), in house dust from the United States (6), and in air near the Great Lakes (7). These results indicated that DeBDethane is widely present in the environment. The presence of DeBDethane in fish tissues from Lake Winnipeg (Canada) was first reported by Law et al. (8). This study also suggested that DeBDethane is biomagnifying within the food web with the trophic magnification factor (TMF) value up to 9.2 in a food web (white sucker f walleye). The DeBDethane shares a structure similar to another fully brominated polybrominated diphenyl ether (PBDE) congener (DecaBDE). Deca-BDE was also thought in the past to be not available biologically due to its large molecular size and low aqueous solubility, but this has been proven not true. More and more recent studies have documented that Deca-BDE can accumulate in biota, including humans. The Deca-BDE was also found in tissue samples of panda at levels 5-100 times higher than that of DeBDethane levels in most samples. Given that these two products have the similar applications, the exposure pathway to pandas for these two chemicals is likely the same. The DeBDethane is the second highest current-use additive brominated flame retardant (BFR) in China, with an increasing production ratio of 80% per year (http://www.polymer.cn/). In our following survey on the environmental samples, DeBDethane was also present in various environmental matrices (air, soils, indoor/outdoor dust, sediment, and sewage sludge) in China. Thus the presence of DeBDethane in tissue samples of panda is not particularly surprising. Recently, we conducted a study on persistent halogenated compounds (PHCs) in bird samples collected from an e-waste recycling region and the results also showed that DeBDethane was widely detected in biota samples and the concentrations of DeBDethane in piscivorous birds were higher than those in omnivorous and insectivorous birds. These investigates indicate that DeBDethane can accumulate in the ambient environment and in tissues of biota. In addition, the “absence” of DeBDethane in the environment and biological samples in most previous studies is likely due to the fact that this compound has been rarely measured via target analyses. The second concern is the analysis method. Indeed, we agree with the comment of Drs. Hardy and Ranken that the analysis of DeBDethane is difficult due to its low solubility in organic solvents. In our study, the same mixing solvent (acetone/tetrahydrofurane/toluene ) 20:30:50) as that of Kierkegaard’s study (4) was used to obtain the DeBDethane solution (30 µg/mL). Soxhlet extraction with 50% acetone in hexane was used to extract DeBDethane. This extraction 10.1021/es8020974 CCC: $40.75
Published on Web 09/27/2008
2008 American Chemical Society
solvent was the same as that used Zhu’s study (5) and Venier’s study (7) for tree bark and air particle. Kierkegaard et al. (4) used toluene/acetone (1:1) to replace hexane/acetone to extract DeBDethane from sewage sludge, sediment, and indoor air, and Stapleton et al. (6) used dichloromethane to extract DeBDethane via accelerated solvent extraction for house dust. Although different extraction methods can lead to different efficiencies of extraction, it can be concluded that DeBDethane can be extracted using the extraction method in our study (1). As part of our quality assurance criteria, we performed a separate QA/QC experiment on DeBDethane before the panda samples were analyzed. Three procedural blanks, triplicate spiked blanks, and triplicate spiked matrices were processed in the same procedure as the panda samples. The spiked blanks and spiked matrices were prepared by adding 200 ng of DeBDethane to extraction solvent and extracted tissue mixed with sodium sulfate powder, respectively. During the panda sample analysis, a procedural blank was also employed for each batch of extraction to monitor the contamination in the laboratory. No DeBDethane was detected in any of the procedural blanks. The DeBDethane recoveries in triplicate spiked blanks and triplicate spiked matrices were 82.3-154.7% and 96.0-108.6%, respectively. Relative standard deviates (RSD) were 35% and 6.5%, respectively, for spiked blanks and spiked matrices. These experiment results indicated that the data present in the paper were trustworthy. The third point of your concern is what standard was used in our study. We acquired the technical DeBDethane product, SAYTEX8010, from the largest industrial-chemical market in South China, which is located at Dongpu, Tianhe district of Guangzhou (named as Guangzhou Dongpu Industrial-Chemical Market Plaza). There are numbers of stores that sell tcommercial DeBDethane products in this market. We obtained two samples of SAYTEX8010 from two stores. To determine if these two samples contained DeBDethane, approximately 100 ng of DeBDethane was injected to an Agilent 6890 gas chromatograph (GC) coupled to an Agilent 5975B mass spectrometer (MS) operating in the fullscan monitoring in EI (electron impact) ionization mode. The mass spectra and relative retention time as given in the Supporting Information (Figure S3 in ref 1) were comparable with those in Kierkegaard et al.’s study (4). Only two other small peaks were found eluted before the DeBDethane peak. This confirms that the technical DeBDethane samples we obtained predominantly contain DeBDethane and were suitable for standards to identify and quantify (at least primarily estimate) the occurrence and concentrations of DeBDethane in our tissue samples. We agree that using the technical product is not the best way to quantify the accurate concentration of chemicals because the technical product may contain impurities. But this is a general method to identify the organic contaminants in environmental samples in the early stage of investigation, for example, in the early studies on PCBs and PBDEs, the PCB technical products (Aroclors) and BDE technical products (Bromkals) have been used to identify and quantify the PCBs and PBDEs levels in environment samples. In our recent studies, a standard solution of DeBDethane purchased from Wellington Laboratories has replaced the technical product as DeBDethane standard. Hopefully, this will increase the data precision in reporting results from studies on DeBDethane in future studies. VOL. 42, NO. 21, 2008 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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Literature Cited (1) Hu, G.-C.; Luo, X.-J.; Dai, J.-Y.; Zhang, X.-L.; Wu, H.; Zhang, C.-L.; Guo, W.; Xu, M.-Q.; Mai, B.-X.; Wei, F.-W. Brominated flame retardants, polychlorinated biphenyls, and organochlorine pesticides in captive giant panda (Ailuropoda melanoleuca) and red panda (Ailurus fulgens) from China. Environ. Sci. Technol. 2008, 42, 4704–4709. (2) Hardy, M. L.; Ranken, P. F. Comment on “Brominated flame retardants, polychlorinated biphenyls, and organochlorine pesticides in captive giant panda (Ailuropoda melanoleuca) and red panda (Ailurus fulgens) from China”. Environ. Sci. Technol. 2008, 42, 8172. (3) Julander, A.; Westberg, H.; Engwall, M.; van Bavel, B. Distribution of brominated flame retardants in different dust fractions in air from an electronics recycling facility. Sci. Total Environ. 2005, 350, 151–160. (4) Kierkegaard, A.; Bjorklund, J.; Friden, U. Identification of the flame retardant decabromodiphenyl ethane in the environment. Environ. Sci. Technol. 2004, 38, 3247–3253. (5) Zhu, L.; Hites, R. Brominated flame retardants in tree bark from North America. Environ. Sci. Technol. 2006, 40, 3711– 3716. (6) Stapleton, H. M.; Allen, J. G.; Kelly, S. M.; Konstantinov, A,.; Klosterhaus, S.; Watkins, D.; Mcclean, M. D.; Webster, T. F. Alternate and new brominated flame retardants detected in
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U.S. house dust. Environ. Sci. Technol. 2008, 42 (18), 6910– 6916. (7) Venter, M.; Hites, R. A. Flame retardants in the atmosphere near the Great Lakes. Environ. Sci. Technol. 2008, 42, 4745– 4751. (8) Law, K.; Halldorson, T.; Danell, R.; Stern, G.; Gewurtz, S.; Alaee, M.; Marvin, C.; Whittle, M.; Tomy, G. Bioaccumulation and trophic transfer of some brominated flame retardants in a Lake Winnipeg (Canada) food web. Environ. Toxicol. Chem. 2006, 25, 2177–2186.
Guo-Cheng Hu, Jia-Yin Dai, and Mu-Qi Xu Key Laboratory of Animal Ecology and Conservation Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, P.R. China
Xiao-Jun Luo and Bi-Xian Mai State Key Laboratory of Organic Chemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, P.R. China ES8020974
