Congener-Specific Polychlorinated Biphenyls in ... - Springer Link

Arch. Environ. Contam. Toxicol. 47, 551–560 (2004) DOI: 10.1007/s00244-004-3214-y

A R C H I V E S O F

Environmental Contamination a n d Toxicology © 2004 Springer ScienceⴙBusiness Media, Inc.

Congener-Specific Polychlorinated Biphenyls in Cetaceans from Taiwan Waters C. C. Chou,1 Y. N. Chen,1 C. S. Li1 1

Department of Veterinary Medicine, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 106, Taiwan

Received: 8 October 2003 /Accepted: 10 April 2004

Abstract. During 2000 to 2001, a total of 73 blubber samples from 13 species of stranded or accidentally captured cetaceans were collected from Taiwan coastal waters for polychlorinated biphenyl (PCB) analysis. After homogenization, saponification, liquid–liquid extraction, and silica-gel solid-phase extraction, PCB concentrations were determined by gas chromatography/mass spectrometry. Total concentrations of 19 PCB congeners (⌺PCBs) were between 0.23 ␮g/g lipid weight of Risso’s dolphin to 33.73 ␮g/g lipid weight of rough-toothed dolphin. Pentachlorobiphenyls, hexachlorobiphenyls and heptachlorobiphenyls were the predominant PCB congeners species. PCB153 was the most abundant congener in all samples. The PCB153/⌺PCBs consistently comprised between 20% to 30% of all congeners. The toxicity measured as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) were from 2.7 pg/g lipid weight of finless porpoise to 2,900 pg/g lipid weight of rough-toothed dolphin. PCB 118, a mono-ortho congener, was the largest contributor to TEQs. PCB concentrations and TEQs were higher in mature male than in immature male animals but were inconsistent in female animals because of a possible transferring of PCBs from maternal cetaceans to their offsprings during gestation and lactation. Stranded cetaceans had significantly higher PCB levels than by-catch cetaceans because of their higher lipid consumption during starvation or illness. From the collected samples, we also found that cetaceans from Taiwan waters had relatively lower PCB concentrations and TEQs than those from high-latitude areas.

Polychlorinated biphenyls (PCBs) are a group of man-made mixtures that consist of a total of 209 congeners and that have been widely used in industries in the past. These PCBs have good stability and a lipophilic nature and are easily bioaccumulated in marine food chains. Odontocete cetaceans are top predators in the marine ecosystem, possess low metabolic activity toward PCBs, and are susceptible to the accumulation and toxicity of PCBs (Kannan et al. 1993; O’Shea and Brownell 1994; Tanabe et al. 1988). PCBs are the suspected etiology in health concerns including altered physiologic per-

Correspondence to: C.C. Chou; email: [email protected]

formance of the endocrine system (Brouwer et al. 1989), decreased reproductive efficiency (Reddy et al. 2001; Reijnders 1994; Troisi et al. 1998), neurotoxicity (Tilson and Kodavanti 1998), and immunosuppression (Lahvis et al. 1995; Troisi et al. 1998). The relationship between PCB contamination in oceans and cetacean mass stranding is under suspicion (Aguilar and Borrell 1994; Guitart et al. 1996; Kannan et al. 1993; Kuehl and Haebler 1995; Watanabe et al. 2000). Therefore, studies on PCB levels and their distribution patterns may elucidate contamination status and environmental impacts on coastal waters. High urbanization and industrialization in Taiwan has led to the buildup of significant environmental pollutant burdens during the last decades. Manufacture of PCBs was banned in 1988 in Taiwan, but the majority of PCBs were still present in transformers or in other machinery. Because these systems are not well maintained, the accidental release of PCBs into the environment will continue to increase. A high diversity of cetaceans exists in Taiwan waters including 6 species of baleen whales and 22 species of toothed whales (Chou 1994). However, no formal study has been conducted on PCB levels in cetaceans from Taiwan coastal waters. Thus, in the current study, samples from stranded or accidentally caught cetaceans in Taiwan coastal waters were collected to analyze the concentrations of 19 individual PCB congeners. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) were applied to assess the toxic potential of coplanar PCBs. Apart from amplifying the PCB-congeners distribution and toxicologic impacts on cetaceans, the influences of biologic factors such as age, sex, reproductive status, and species differences between the stranded and accidentally caught individuals were evaluated as well.

Materials and Methods Field Sampling From 2000 to 2001, a total of 73 blubber samples from 13 cetacean species were collected including 19 samples from stranded cetaceans and 54 others from those accidentally caught by commercial fishing nets in Taiwan coastal waters. The samples comprised 37 male and 36 female animals. Samples from stranded animals came from the coasts of 14 counties in Taiwan and including live and dead stranded.

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Samples of by-catch came mainly from waters near Penghu and Hualien with the collaboration of local fishermen (Fig. 1). The developmental stage of each cetacean was classified as either mature or immature based on the reference data for the body length in different cetacean species, the statuses of reproductive organs, and tooth wear (Ridgway and Harrison 1994, 1999). Blubber samples were collected near the front end of the anterior dorsal fin with a stainless steel knife and then were wrapped and sealed with aluminum foil and stored at ⫺20°C until analysis. Species, sampling location and date, cause of death, condition of carcasses, body length and girth, sex, blubber thickness, tooth eruption, and other gross findings were recorded for each specimen. Decomposed samples were excluded from analysis for lipid contents and PCB concentrations in blubber because these may have decreased progressively with time after direct exposure to the sun (Borrell and Aguilar 1990).

Chemical Analysis Blubber samples were cut into fine pieces and weighed precisely for the determination of PCBs and also for the percentage of hexaneextractable lipid content (HEL%). The preparation steps for the analysis of PCBs were modified from the Standard Methods of the Environmental Protection Agency (NIEA 1991). Briefly, 5 g blubber was homogenized with 100 ␮L recovery standard PCB 112 (4 ␮g/mL) and 30 mL ethanol for 5 minutes and then saponificated with 60 mL 1 mol/L NaOH/EtOH from 50°C to 100°C for 60 minutes until the sample was digested completely. After cooling to 50°C, 50 mL nhexane was added, and the solution was transferred to a separatory funnel containing 30 mL ultra-pure water. After liquid–liquid extraction, the separated hexane layer was added to anhydrous Na2SO4, and the water layer was subjected to liquid–liquid extraction with 50 mL hexane twice. The above hexane layers were pooled and evaporated to 2 mL and then underwent a cleaning process with 5 mL 5% fuming sulfuric acid. The mixture was vortexed for 1 minute, stood still until two layers separated, the hexane layer collected, and 1 mL n-hexane added to the lower layer and vortexed again. This step was repeated three times. The pooled solution was applied to a solid-phase extraction column containing 1 g silica gel (J. T. Baker, Phillipsburg, NJ) for further cleaning. PCBs were eluted from the column with 15 mL n-hexane at 2 mL/min under a pressure of 254 mmHg. Finally, the collected eluate was concentrated to 500 ␮L using a stream of nitrogen before analysis. To determinate HEL%, 5 g of the same blubber sample was ground with 15 g anhydrous sodium sulfate and 50 mL n-hexane three times. The combined solution was concentrated to 10 mL by rotary vacuum evaporator and transferred to an aluminum pan. The solution was evaporated at 100°C and weighed several times until the residue dried to a constant weight, then HEL% was calculated. For PCB analysis, 1 ␮L of concentrate was injected splitless into a Hewlett-Packard 6890 gas chromatograph (GC) equipped with an HP 5972 mass spectrometer (MS). A 60-m RTX-5MS capillary column (0.25-mm inside diameter, 0.25 ␮m film thickness) was used for chemical separation. Oven temperature was programmed at 150°C and maintained for 1 minute, increased by 6°C/min to 240°C and held for 1 minute, increased to 255°C at 1°C/min and held for 3 minutes; and finally increased by 10°C/min to 300°C and held for 5 minutes. The total elapsed time was 44.5 minutes. Based on the reported abundance and toxicities, the following 19 PCB congeners (Chem Service, West Chester, PA) were analyzed: 28, 52, 66, 77, 101, 105, 118, 126, 138, 149, 153, 156, 157, 169, 170, 180, 183, 187, and 189. PCB112 was used as a recovery standard. Final concentrations were calculated by using PCB103 as the internal standard; only recovery rates ⬎ 70% were accepted, and the results were not corrected by individual recovery. Identification of individual PCB congeners was confirmed by retention time and mass spectrum under

Fig. 1. Map showing the major sampling sites of cetaceans in Taiwan waters from 2000 to 2001 and the geography of nearby countries the total-ion scan mode. Trace quantification was performed in the selected ion-monitoring mode. The cluster ions were monitored at m/z 186, 256, and 258 for trichlorobiphenyls; at m/z 222, 290, and 292 for tetrachlorobiphenyls; at m/z 256, 324, and 326 for pentachlorobiphenyls; at m/z 290, 360, and 362 for hexachlorobiphenyls; and at m/z 326, 394, and 396 for heptachlorobiphenyls, respectively. All data collected were processed using HP G1701 BA MS ChemStation and Enviroquant software. The results reported, herein referred to as “⌺PCBs,” refers to the sum of the concentrations (ng/g) of PCB congeners in the wet sample weight or extractable lipid weight.

Quality Assurance and Control To ensure adequate quality assurance and control, the method blank, solvent blank, certified calibration standards, internal standard, recovery standard, matrix spike sample, and triplicate analyses were applied in the study. The recoveries of PCB112 standard added in each analyzed sample were 70% to 116%, and those of matrix spike samples were from 75% of PCB77 and PCB156 to 104% of PCB180. The methods of the limit of detection (LOD) and the limit of quantitation (LOQ) described by Skoog and Leavy (1992) were used. The LOD and LOQ was defined as 3 times and 10 times the standard deviation of measured values for samples (n ⫽ 10) spiked with the analyte amount. The LOD of target PCB congeners ranged from 3.36 pg (PCB52) to 14.91 pg (PCB180) and the LOQ from 11.21 to 49.71 pg. Only the method and solvent blank below the instrument’s LOD were accepted to exclude the interference of alien contaminant. Every identified peak was evaluated against standards to assess relative retention time (⫾ 0.05 minutes) and the confirmation ions (⫾ 20%).

Statistical Analysis Results were analyzed using SAS 6.12 and Microsoft Excel 2000 including linear regression and one-way analysis of variance (p

Congener-Specific PCBs in Cetaceans

⬍0.05). Duncan multiple-range test and general linear model procedures were also applied to differentiate PCB concentrations among the species.

Results and Discussion Percent Hexane-Extractable Lipids (HEL%) and Total of 19 PCB Congeners (⌺PCBs) The HEL% of blubber from by-catch samples was similar among individuals of the same species but showed significant differences between different species (Table 1). The lowest lipid content (28%) was found in Risso’s dolphin, and the highest lipid content (95%) was found in dwarf sperm whale. Significant differences also existed between different species of stranded individuals. However, stranded cetaceans had a wide variety of lipid contents within the same species. For example, the HEL% in stranded rough-toothed dolphin ranged from 0.76% to 27%. Comparing the HEL% of the same species, stranded cetaceans were significantly lower than by-catch cetaceans in Risso’s dolphin, pantropical spotted dolphin, and finless porpoise but not in Fraser’s dolphin (p ⫽ 0.62). These findings suggested that stranded cetaceans consumed more lipids during stranding because of starvation or disease. The ⌺PCBs ranged from 0.09 to 8.29 ␮g/g wet weight and 0.24 to 21.26 ␮g/g lipid weight for by-catch cetaceans and from 0.10 to 5.63 ␮g/g wet weight and 0.51 to 33.73 ␮g/g lipid weight for stranded cetaceans (Table 1). The PCB residue levels in the blubber fluctuated strictly parallel to the changes in the contents of the sample. For example, the blubber from one stranded rough-toothed dolphin had the highest PCB concentration of 33.73 ␮g/g by lipid weight but only 0.26 ␮g/g by wet weight for its minute lipid content (0.76%). Therefore, quantification of pollution concentrations normalized by HEL% was more reliable and comparable. In our study, the stranded samples had significantly higher total PCB residue levels than by-catch samples that were apparently affected by lipid consumption.

Factors Affecting PCB Levels PCBs are highly lipophilic, and they accumulate in blubber with age and may be transferred to offspring during gestation and lactation (Ridgway and Reddy 1995). Once transferred to offspring, PCBs concentrate in the adipose tissue of calves because of their relatively low lipid content. Hence, no difference was found in PCB levels of mature or immature female animals in this study. Corpora albicantia was used to evaluate the reproductive history of cetaceans. In general, female cetaceans with more corpora albicantia experienced more reproductive history. Samples from four pregnant cetaceans and five lactating cetaceans were noted in this study. The levels of PCBs were low in these cetaceans compared with others in the same species. However, because records of corpora albicantia from each female cetacean were incomplete, the results were thus inconclusive. Samples from mature male cetaceans had higher PCB levels than immature male animals. In mature male animals, the PCB

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residues of bottlenose dolphin were higher than those from Fraser’s dolphin, Risso’s dolphin, pantropical spotted dolphin, and finless porpoise in the by-catch group. For samples from stranded cetaceans, only pygmy killer whale and rough-toothed dolphin had fresh mature male samples suitable for comparison; the PCB concentrations from rough-toothed dolphin were higher than those from pygmy killer whale. The habitats of cetaceans’ prey may play an important role in the determination of PCB levels among species. According to Tanabe et al.’s study (1988), cetaceans inhabiting waters far from human activities have higher PCB concentrations than coastal and terrestrial mammals. PCBs have been banned for two decades, and particulate PCBs can be transported by atmospheric pathways and eventually settle down to the deep base of the ocean (Travis and Hester 1991). Thus, we propose that cetaceans feeding on prey from deep waters far from land have PCB levels higher than those that hunt prey in coastal and neritic areas. In this study, accidentally caught mature male bottlenose dolphin had higher PCB concentrations than those of mature male finless porpoise, likely because the primary diets of bottlenose dolphin were epipelagic and mesopelagic fishes, whereas those of finless porpoise were neritic and demersal prey species (Wang 2003). Pygmy killer whales were distributed over the tropical latitude areas (Wang 2003) and frequently dive to depths of 3,000 m to 4,000 m and 20 km away from the coast in eastern Taiwan waters (Yeh 2000). This oceanic species, seldom entering the shallow and coastal areas, mainly ate large deep oceanic fishes and cephalopods such as salmons and enoploteuthid squids (Wang 2003) and also had relatively higher PCB concentrations. PCB concentrations in blubber from adult male cetaceans of the same reported species from 1976 to 1999 were chosen for comparison with our results (Table 2). Although the numbers of congeners reported in most of the literature are greater than those in our study, the PCB congeners in this study were selected based on their reported frequency and abundance in marine mammal tissues per previous studies. Thus, the collected PCBs might represent the majority, and a total concentration variation within one order of magnitude was considered as having no variation. Extremely high PCB levels were noted in striped and bottlenose dolphin in mass mortalities of morbillivirus infection in the Mediterranean Sea (Corsolini et al. 1995; Kannan et al. 1993). The mobilization of lipid increased PCB levels in blood, which then led to increased susceptibility to infection because of liver lesions (Aguilar and Borrell 1994). In our study, stranded cetaceans had significantly higher PCB concentrations than by-catch cetaceans that were apparently affected by lipid consumption. However, there was no direct link between PCB levels and any specific disease. Cetaceans from Taiwan’s coastal waters had PCB levels similar to those of Australia and South Africa in the southern hemisphere including species of bottlenose dolphin, Risso’s dolphin, and dwarf sperm whale (de Kock et al. 1994; Vetter et al. 2001). Along the west coast of the Pacific Ocean, finless porpoise, Fraser’s dolphin, and Risso’s dolphin from Japanese waters had higher PCB concentrations than those from the eastern and southern Pacific Ocean including the coastal waters of Taiwan and the Philippines (Prudente et al. 1997; Minh et al. 2000; Tanabe et al. 1987). This implied that cetaceans inhabiting temperate and cold

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Table 1. Lipid contents and PCB concentrations of by-catch and stranded cetaceans Species

Stage/Sex

Bottlenose dolphin (Tursiops truncatus)

By-catch Immature male Mature male Immature females Mature females Total By-catch Immature male Stranded Mature male By-catch Immature male Immature female Mature females Total Stranded Mature male Immature females Total By-catch Immature males Mature males Immature female Mature females Total Stranded Mature females Stranded Mature male By-catch Immature male Mature males Immature females Mature females Total Stranded Mature female Stranded Mature male Mature female Female fetus Total Stranded Mature female By-catch Immature males Mature male Immature females Mature females Total Stranded Mature male Immature female Total Stranded Mature males Mature females Total By-catch Immature female By-catch Immature male

Dwarf sperm whale (Kogia sinus) False killer whale (Pseudorca crassidens) Finless porpoise (Neophocaenoides phocaenoides)

Fraser’s dolphin (Lagenodeiphis hosei)

Indo-Pacific Humpback dolphin (Sousa chioneusis) Pantropical spotted dolphin (Stenella attenuata)

Pygmy killer whale (Feresa attenuata)

Pygmy sperm whale (Kogia breviceps) Risso’s dolphin (Grampus griseus)

Rough-toothed dolphin (Steno bredanensis) Short-finned pilot whale (Globicephala macrorhynchus) Spinner dolphin (Stenella longirostris)

Mean ⫾ SD. Insufficient samples to determine lipid content. PCB ⫽ Polychlorinated biphenyl. a

b

Lipid (%)

⌺PCBs (␮g/g wet wt.)

⌺PCBs (␮g/g lipid wt.)

1 1 2 2 6

46 66 85 48 59 ⫾ 20a

1 6.87 4.55 2.3 3.59 ⫾ 2.91a

2.15 10.41 5.35 4.44 5.36 ⫾ 3.57a

1

95

0.2

0.21

1

22

5.63

25.25

1 1 3 5

88 82 83 ⫾ 6a 84 ⫾ 5a

2.5 0.18 1.62 ⫾ 1.16a 1.51 ⫾ 1.17a

2.84 0.21 2.02 ⫾ 1.58a 1.82 ⫾ 1.48a

1 2 3

46 73 64 ⫾ 15a

0.3 0.5 0.43 ⫾ 0.12a

0.65 0.39 0.68 ⫾ 0.05a

3 5 1 2 11

75 ⫾ 7a 53 ⫾ 9a 66 46 59 ⫾ 13a

1.66 ⫾ 0.77a 3.33 ⫾ 0.97a 0.78 1.07 2.23 ⫾ 1.33a

2.40 ⫾ 1.42a 6.41 ⫾ 2a 1.18 2.35 4.10 ⫾ 2.72a

2

52

2.38

6

1

b

–

0.29

b

78 62 ⫾ 8a 70 61 ⫾ 14a 65 ⫾ 11a

6.57 2.04 ⫾ 0.75a 2.13 1.58 ⫾ 2.48a 2.30 ⫾ 2.03a

8.42 3.25 ⫾ 0.79a 3 2.16 ⫾ 3.18a 3.28 ⫾ 2.53a

1

20

0.1

0.51

1 1 1 3

27 33 26 29 ⫾ 4a

3.96 0.78 0.32 1.68 ⫾ 1.98a

14.54 2.37 1.22 6.04 ⫾ 7.38a

1

34

5

14.8

44 ⫾ 5a 64 40 ⫾ 7a 40 ⫾ 11a 43 ⫾ 9a

1.88 ⫾ 2.51a 3.82 2.99 ⫾ 1.78a 0.73 ⫾ 0.2a 1.98 ⫾ 2.1a

1 1 2

14 13 13.5

1.25 3.14 2.2

9.33 23.26 16.48

3 2 5

17 ⫾ 14a 17 17 ⫾ 11a

1.41 ⫾ 1.41a 0.45 1.03 ⫾ 1.13a

17.01 ⫾ 15.3a 3.45 11.55 ⫾ 13.21a

1

50

2.39

4.88

1

64

0.38

0.49

N

1 4 2 4 11

9 1 4 4 18

–

4.44 ⫾ 6.47a 5.97 7.22 ⫾ 3.7a 1.58 ⫾ 1.5a 4.50 ⫾ 5.14a


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Table 2. Mean ⫾ SD of total PCB concentrations in blubber of adult male cetaceans Species

Location

Bottlenose dolphin

South Africa Italy Australia Taiwan South Africa Taiwana British Columbia, Canada Taiwan Japan Hong Kong Taiwan Off Kii Peninsula, Japan Mindanao Sea, Philippines Taiwan Hong Kong Bay of Bengal, India Taiwan Off Taiji, Japan South Africa British Columbia, Canada Italy Taiwan Southern Pacific Mindanao Sea, Philippines Bay of Bengal, India Eastern tropical Pacific Taiwana Off Sanriku, Japan South Africa Mediterranean Sea, Italy

Dwarf sperm whale False killer whale Finless porpoise

Fraser’s dolphin

Humpback dolphin

Risso’s dolphin

Spinner dolphin

Striped dolphin

PCBs (␮g/g wet weight) 2.93 ⫾ 4.64 743.33 ⫾ 323.47 6.88 0.25 ⫾ 0.11 0.2 40 (34–46) 5.63 39.8 27.35 (6.7–48) 0.3 51 (45–57) 6.2 (3.8–8.6) 3.33 ⫾ 0.98 30.07 ⫾ 10.62 4.6 0.29 110 (76–130) 2.72 1.7 610 2.54 0.19 (0.15–0.23) 2.5 (2.4–2.6) 2.2 (1.6–3) 0.8 0.38 37 1.11 490 ⫾ 130.54

PCBs (␮g/g lipid weight) 1646.67 ⫾ 700.38 16.06 (6.6–25.53) 10.47 0.2 44.13 (36.56–51.69) 25.25 43.55 (23.1–64) 0.65 67.1 9.39 6.41 ⫾ 2 64.67 ⫾ 28.7 7.93 127.91 5.67 1000 7.66 3.79 3.33 1.7 0.49 74 1688.33 ⫾ 707.4

Reference de Kock et al. 1994 Corsolini et al. 1995 Vetter et al. 2001 Current study de Kock et al. 1994 Current study Jarman et al. 1996 Current study Tanabe et al. 1987 Minh et al. 1999 Current study Minh et al. 2000 Minh et al. 2000 Current study Minh et al. 1999 Prudente et al. 1997 Current study Prudente et al. 1997 de Kock et al. 1994 Jarman et al. 1996 Corsolini et al. 1995 Current study Tanabe et al. 1988 Minh et al. 2000 Minh et al. 2000 Prudente et al. 1997 Current study Minh et al. 2000 de Kock et al. 1994 Kannan et al. 1993

a

Data from immature male animals. PCB ⫽ Polychlorinated biphenyl.

waters accumulated relatively higher concentrations than those from tropical waters. The reported PCB levels in sediments and waters were retrieved for environmental-exposure comparison. PCBs in the sediments of estuaries of Jiulongjiang, Minjiang, and Zhujiang in southeastern China (1.6 to 14.6 ng/g dry weight), Hong Kong (0.5 to 97.9 ng/g dry weight), and the Tanshui River of Taiwan (6.5 ng/g dry weight) were relatively lower than those of the Gulf of Mexico (2 to 134 ng/g dry weight) and the United States Pacific coast (0.1 to 2,000 ng/g dry weight) (Richardson and Zheng 1999; Yuan et al. 2001). Our study subjects—such as bottlenose dolphin, finless porpoise, roughtoothed dolphin, and humpback dolphin—which migrated between southeastern China sea, Taiwan, and Hong Kong had relatively lower PCB levels. Finless porpoise and humpback dolphin inhabit shallow waters near the coast, in river estuaries, and even in rivers. They could serve as local industrial pollution indicators in these waters. The PCB concentrations of finless porpoise and humpback dolphin from Hong Kong waters were higher than those from Taiwan waters. The highest PCB concentrations in sediments in Hong Kong were at Victoria Harbour, which was surrounded by densely populated areas and had low seawater exchange (Richardson and Zheng 1999). Although two oceanic currents pass through Taiwan and provide strong seawater

exchange, the PCB concentrations in finless porpoise and humpback dolphin were apparently influenced by the local contamination, which was higher in Hong Kong than in Taiwan.

Congener Compositions Percentage compositions of different chlorinated PCB congeners for each sample were determined. PCB153 was the most predominant congener followed by PCB101, 138, 118, 149, 180, 187, 52, 66, 105, 170, 183, and 28 in almost all species examined; however, PCB77, 126, 156, 157, 169, and 189 generally showed ⬍ 1%. In this study, the PCB153/⌺PCBs were consistently between 20% and 30% in either by-catch or stranded samples. This implied that PCB153 was the most recalcitrant chlorobiphenyl congener with regard to biotransformation in different sex, age, and species. The major PCB congeners found were pentachlorobiphenyls, hexachlorobiphenyls, and heptachlorobiphenyls. This pattern was different from that in invertebrates and lower vertebrates, in which the abundant PCB congeners were trichlorobiphenyls to pentachlorobiphenyls (Wang et al. 2000). For invertebrates and fishes, equilibrium partitioning of the parent PCB conge-

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Fig. 2. The relative concentrations of 19 specific PCB congeners in by-catch and stranded Risso’s dolphins, finless porpoises, Fraser’s dolphins, and pantropical spotted dolphins from Taiwan waters from 2000 to 2001. PCB ⫽ polychlorinated biphenyl


557

Fig. 3. The relative concentrations of 19 specific PCB congeners in five stranded rough-toothed dolphins with decreasing HEL% (27%, 24%, 22%, 10%, and 0.76%) from Taiwan waters from 2000 to 2001. HEL% ⫽ hexane-extractable lipid percent; PCB ⫽ polychlorinated biphenyl

Fig. 4. The relative concentrations of 19 specific PCB congeners in mature male animals and one mature female pygmy killer whale and its fetus in Taiwan waters from 2000 to 2001. PCB ⫽ polychlorinated biphenyl

ners between body and the surrounding water was more important than enzymatic metabolism (Tanabe et al. 1988). Thus, the PCB patterns in invertebrates and lower vertebrates showed a higher percentage of lower chlorinated biphenyls. Different capacities in PCB metabolism also cause different PCB congener patterns in different higher vertebrates. In human beings, phenobarbital (PB)-type PCB congeners (PCB52, 66, 101, 149, 180, and 183) were metabolized preferentially, and 3-methylcholanthrene (3-MC)–type PCBs congeners (PCB77, 126, and 169) were metabolized less efficiently. In

contrast, small cetaceans only metabolized 3-MC–type inducers and had minimal metabolism for PB-type and mixed-type inducers (Tanabe et al. 1988). PB-type and mixed-type PCB congeners were at 29% and 54%, respectively in our study, and the levels of 3-MC–type PCB congeners were all ⬍ 1 ng/g wet weight. Compared with accidentally caught cetaceans, the relative concentrations of hexachlorobiphenyls and heptachlorobiphenyls to PCB153 increased and of trichlorobiphenyls to pentachlorobiphenyls decreased in stranded cetaceans. Al-

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Table 3. TEQs of non-ortho and mono-ortho PCB congeners in by-catch and stranded cetaceans from Taiwan waters from 2000 to 2001 TEQs of PCB Non-Ortho Coplanar (pg/g lipid weight) Sample Type By-catch cetaceans Bottlenose dolphin Dwarf sperm whale Finless porpoise Fraser’s dolphin Pantropical spotted dolphin Risso’s dolphin Short-finned pilot whale Spinner dolphin Stranded cetaceans False killer whale Finless porpoise Fraser’s dolphin Pantropical spotted dolphin Pygmy killer whale Pygmy sperm whale Risso’s dolphin Rough-toothed dolphin

Mono-Ortho Coplanar (pg/g lipid weight)

77

126

169

105

118

1.3 –a 0.2 0.1 0.5 0.4 – 0.1

142.4 – – – – – – –

3.9 – 8.4 4.1 5.6 17.4 4 –

36.8 0.5 2.1 9.8 7.5 10.2 14.2 1.3

34 2 9.4 22.4 18.5 31.7 42 4

– 0.1 – – 0.1 1.1 3.6 2.9

– – – – – – – –

– – – – 4.9 41.2 38.5 527.2

– 1 15.2 0.4 17.8 26.3 31.1 16.3

108.3 3.5 36.2 1.8 49.8 90.4 87.7 51.1

156

Sum

157

189

32.3 0.8 2 12.9 16.4 20.6 19.5 2

16.1 0.1 2.4 10.1 10.2 10.9 10.5 1

2 – 0.3 1.2 1.4 0.9 0.9 –

268.8 3.4 24.8 60.6 60.1 92.1 91.1 8.4

84.5 2.1 12.2 1.5 23.9 69.4 104.7 33.8

67.7 1.3 11.5 1.3 13.1 33.4 44.6 44.2

17.7 0.1 – 0.1 0.3 2.6 6.9 3.2

278.2 8.1 75.1 5.1 109.9 264.4 317.7 678.7

a

Below detection limit. PCB ⫽ Polychlorinated biphenyl. TEQs ⫽ 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents.

though significant differences of the congener percentages between stranded and by-catch samples were only found in Risso’s dolphin, the trend also existed in three other cetaceans (Fig. 2). This indicated that higher chlorinated PCB congeners were more resistant to biotransformation during lipid consumption. Five stranded rough-toothed dolphins (Fig. 3) had a wide range of lipid contents ranging from 0.76% to 27%, but they also had higher percentages of heptachlorobiphenyls (PCB170, 180, 183 and 187) than tetrachlorobiphenyls to hexachlorobiphenyls (PCB52, 101, 118, 138, and 149), which remained in blubber. According to PCB congener composition of one mother– fetus pair of pygmy killer whales, the percentages of trichlorobiphenyls to hexachlorobiphenyls, but not heptachlorobiphenyls, were higher in the calf (Fig. 4). This suggests that the lower chlorinated biphenyls, which were readily soluble in blood, accounted for a major part of the PCBs from maternal transfer through the placenta to the fetus.

The 2,3,7,8-Tetrachlorodibenzo-p-Dioxin Equivalents (TEQs) Coplanar PCB congeners are capable of binding the cytosolic aryl hydrocarbon (Ah) receptor, thus resulting in alterations in gene expression of cytochrome P450 enzymes (Safe, 1994). TEQs— using mammal-specific 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalent factors (TEFs) reported by the World Health Organization (Van den Berg et al. 1998)—were selected for toxicity assessment of non-ortho coplanar PCB77, 126, and 169 and mono-ortho coplanar

PCB105, 118, 156, 157, and 189. These dioxin-like congeners were thought to have toxic impacts on creatures in the environment (Tilbury et al. 1999). PCB126 had the highest TEFs at 0.1 and was followed by PCB169 (0.01) and PCB156 and 157 (both 0.0005). TEFs of PCB77, 105, 118, and 189 were all 0.0001. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) of by-catch cetaceans ranged from 2.7 pg/g lipid weight in finless porpoise to 413.9 pg/g lipid weight in Risso’s dolphin. Those of stranded cetaceans ranged from 3.5 pg/g lipid weight in Fraser’s dolphin to 2,900 pg/g in rough-toothed dolphin. For by-catch cetaceans, bottlenose dolphin had the highest mean TEQ of 268.8 pg/g lipid weight, and finless porpoise had the lowest mean TEQ of 24.8 pg/g lipid weight (Table 3). Because spinner dolphin and dwarf sperm whale had only one sample each, they were excluded from the comparison. In stranded cetaceans, the highest mean TEQ of 678.7 pg/g lipid weight came from rough-toothed dolphin (Table 3). TEQs were more variable than PCB concentrations, likely because of high SD in almost every cetacean species. In general, mono-ortho congener PCB118 was the major contributor and mono-ortho congener PCB156 the second contributor to toxicity in this analysis. The majority of our analysis samples had no detectable PCB126, the highest TEF in current PCB congeners. Moreover, this study showed similarly low PCB levels and TEQs in spinner dolphin compared with those found in the Philippines and India (Minh et al. 2000). Therefore, Taiwan coastal waters could be listed as a not-heavilycontaminated area.


Conclusion To our knowledge, this is the first report on residues of PCBs in cetaceans from Taiwan waters. The total concentrations of 19 PCB congeners ranged from 0.23 ␮g/g lipid weight of Risso’s dolphin to 33.73 ␮g/g lipid weight of rough-toothed dolphin. PCB153 was the most abundant congener and contributed 20% to 30% of total PCBs. Mature male animals had higher PCB concentrations than immature male animals, but there were no differences between male and female animals. PCB concentrations varied widely between female animals because of different reproductive statuses. Stranded cetaceans had significantly higher PCB levels than by-catch ones and were apparently affected by lipid consumption. The percentages of higher chlorinated biphenyls were higher in stranded cetaceans than those in by-catch cetaceans, indicating that PCB congeners with more chlorine were more resistant to biotransformation. The PCBs transferred from mother to fetus mainly consisted of the lower chlorinated biphenyls. The TEQs ranged from 2.7 pg/g lipid weight of finless porpoise to 2,900 pg/g lipid weight of rough-toothed dolphin, and PCB118 was the largest contributor. Compare with the references, cetaceans from Taiwan waters had a relatively low level of PCB concentrations and TEQs in our study.

Acknowledgments. This study was supported by a grant from the National Science Council of Taiwan (Grant No. NSC90-2313-B-002316). We thank Taiwan Cetacean Society for providing the samples.

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