- Email: [email protected]
Contamination by organochlorine compounds in the edible tissue of four sturgeon species from the Caspian Sea (Iran)
Chemosphere 73 (2008) 972–979
Contents lists available at ScienceDirect
Chemosphere journal homepage: www.elsevier.com/locate/chemosphere
Contamination by organochlorine compounds in the edible tissue of four sturgeon species from the Caspian Sea (Iran) Seyed Vali Hosseini a,b,*, Reza Dahmardeh Behrooz c,d, Abbas Esmaili-Sari c, Nader Bahramifar c, Seyed Mehdi Hosseini e, Reza Tahergorabi f, Seyed Fakhreddin Hosseini g, Xesús Feás h a
Department of Fisheries, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, P.O. Box 46414-356, Noor, Mazandaran, Iran Department of Fisheries and Environmental Sciences, Faculty of Natural Resources, University of Tehran, P.O. Box 31585-4314, Karaj, Tehran, Iran c Department of Environmental Sciences, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, P.O. Box 46414-356, Noor, Mazandaran, Iran d Department of Environmental Sciences, Faculty of Natural Resources, Zabol University, Zabol, Sistan and Baluchestan, Iran e Department of Environmental Sciences, Engineering and Technical Faculty, Allame Mohaddes Noori-Institute of Higher Education, P.O. Box 451-46415, Noor, Mazandaran, Iran f Department of Fisheries, Islamic Azad University, Tehran, North Branch, P.O. Box 19737-33583, Tehran, Iran g Department of Fisheries, Islamic Azad University-Lahijan Branch, P.O. Box 1616, Lahijan, Guilan, Iran h Departamento de Química Analítica, Nutrición y Bromatoloxía. Facultade de Veterinaria. Universidade de Santiago de Compostela, E-27002 Lugo, Galiza, Spain b
a r t i c l e
i n f o
Article history: Received 6 April 2008 Received in revised form 9 June 2008 Accepted 10 June 2008 Available online 25 July 2008 Keywords: Pollution Organochlorine Sturgeon Caspian Sea Iran
a b s t r a c t This study focused on accumulation of organochlorine compounds (OCs), including dichloro-diphenyltrichloroethanes (DDTs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and polychlorinated biphenyls (PCBs) accumulation in the muscle of four sturgeon (Persian sturgeon, Acipenser persicus; Stellate sturgeon, Acipenser stellatus; Ship sturgeon, Acipenser nudiventris and Beluga sturgeon, Huso huso) from the southern Caspian Sea. The DDT group was prominent in all of the sturgeon muscle tested constituting almost half or more of the total organochlorine content. Contaminant concentration generally followed this order: DDTs > PCBs > HCHs > HCB. The OCs concentrations in Beluga sturgeon (H. huso) were the highest and over four times higher than in the next highest species (A. nudiventris). From an ecotoxicological point of view, the concentrations of OCs in experimental fishes do not reflect a comparatively clean and pollution-free environment; however, results from this study shown that the inflow of organic pollutants into the Caspian Sea has been reduced when compared with prior studies. Levels of measured OCs in sturgeon were relatively low, but the level of some OCs in some of the specimens tested exceeded the guidelines for food; therefore, the maximum allowable daily consumption rate for sturgeon from this watershed may be limited by DDTs and PCBs content for high risk populations. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Growth in industrial, agricultural and many other human activities caused by increasing population pressure and poor environmental controls have resulted in chemical contamination of important water bodies across the world. Among these anthropogenic pollutants, major concern has been directed to organochlorine compounds (OCs) such as polychlorinated biphenyls (PCBs) and pesticides (Sudaryanto et al., 2007) because of their persistent, bioaccumulative nature and potential toxic effects on wildlife and humans (Haynes and Johnson, 2000).
* Corresponding author. Present address: Area de Tecnología de los Alimentos, Depto de Química Analítica, Nutrición y Bromatología, Facultad de Veterinaria, Universidad de Santiago de Compostela, E-27002 Lugo, Galiza, Spain. Tel.: +98 912 6049868 (mobile); fax: +98 122 6253499. E-mail address: [email protected] (S.V. Hosseini). 0045-6535/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2008.06.036
Chlorinated organic compounds, due to their chemical persistence and lipophilicity, have a tendency to accumulate up the food chain. Therefore, human exposure to these pollutants occurs mainly from eating food (Tüzen, 2003; Kiviranta et al., 2004; Coelhan et al., 2006; Bocio et al., 2007). Seafood usually contains residues of PCBs, as well as other environmentally persistent OCs, and is often considered to be a major source of intake of those contaminants for humans (Falandysz et al., 2004). Therefore, it is important to determine how these compounds are distributed in fish, as this provide important information for assessing possible health risks and may also provide an incentive to improve water quality. Fish are a suitable indicator organism for environmental pollution monitoring because they can absorb and concentrate pollutants in different tissues directly from the water and also through their diet, thus enabling the assessment of the transfer of pollutants through the trophic web. Data on the presence and distribution of organic and metal contaminants in fish and espe-
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
cially edible fish species are important not only from an ecological perspective, but also from a human health perspective (Boon et al., 2002), even if the fish used for biological monitoring are not normally consumed as food. The Caspian Sea is the biggest land-locked body of water bordered by five countries: Azerbaijan, Iran, the Russian Federation, Kazakhstan and Turkmenistan. It has five major inlet rivers but no outlets and acts as a watershed reservoir for the region. The key biological issues in recent years relate to the decline of the fisheries and caviar harvesting, the massive mortality among seal populations and the introduction of invasive species in the Caspian Sea. There are several important fisheries in the Caspian Sea, but the greatest emphasis has always been placed on the sturgeons. The Caspian Sea has six commercially valuable sturgeon species, four of which produce 90% of the world’s caviar. Several anthropogenic factors, including both land-based and offshore pollution, threaten the survival of all fisheries, but especially sturgeon populations in the Caspian Sea (de Mora and Turner, 2004). Among these, chemical contamination seems to be one of the most significant factors influencing the population of sturgeons in the Caspian Sea (Ivanov, 2000; Pourkazemi, 2006). Many potentially toxic contaminants released into the Caspian Sea are lipophilic and insoluble in water. These properties increase their availability for uptake and accumulation by aquatic organisms. Previous investigations have demonstrated the occurrence of OCs in fishes from the Caspian Sea (Kajiwara et al., 2003; de Mora and Turner, 2004; de Mora et al., 2004; Shokrzadeh and Ebadi, 2006). The life history of sturgeons may leave them particularly vulnerable to the effects of bioaccumulative pollutants. As opportunistic bottom feeders, these fish frequently come in contact with sediments that could contain sediment-adsorbed hydrophobic pollutants. Furthermore, sturgeons are particularly long-lived animals (up to 100 years in the wild) that take 5–30 years to reach sexual maturity (Billard and Lecointre, 2001). These characteristics put the sturgeons at a high potential risk for accumulating persistent organic and inorganic contaminants in their tissues. Therefore, sturgeons were chosen as the target fish for this study due to their elevated risk for bioaccumulation of persistent contaminants. The objectives of this study were to understand the present status of contamination and the specific accumulation of OCs in the muscle of four species of sturgeons in the Caspian Sea (persian sturgeon (Acipenser persicus), stellate or sevruga sturgeon (Acipenser stellatus), ship sturgeon (Acipenser nudiventris) and beluga sturgeon (Huso huso) and to compare these values with guidelines for human consumption and to previous studies. These results would be important for a number of reasons: (1) provide more information about organochlorine concentrations in this aquatic ecosystem of the Caspian Sea, (2) predict possible food safety risk to humans from consumption of Caspian Sea sturgeons, and (3) provide baseline data that could predict the risk of persistent contaminants for the health of these fish, several species of which are considered to be threatened with extinction.
2. Materials and methods 2.1. Sampling, preparation and storage The Fisheries Organization of Iran has divided the whole area of the southern Caspian Sea (within Iranian waters) into five sturgeon fishery zones. Forty eight sturgeon samples (12 specimens from each of four species) were collected from one of the important sturgeon fishery zones (Babolsar station-E 36° 420 2600 N 52° 380 3500 in Mazandaran Province, Iran; Fig. 1) during January, 2007. This fishing station receives fish from all of Mazandaran Province (approximately 320–345 km of shoreline) and is the largest stur-
973
Fig. 1. Map of the Caspian Sea showing the area of sample collection. Babolsar sturgeon fisheries, Mazandaran catch area.
geon fishery zone in Iran. The specimens were caught using Gill nets with the standardized mesh and dimensions set by the Iran Fisheries Research Organization. These fish were selected from among the daily catch during two week sampling period. The biological characteristics of the samples including total length and weight were recorded (Table 1), then individuals were sacrificed and processed (gutted, washed and cut to pieces) on site in high hygienic conditions. Bioaccumulation of OCs species was evaluated in muscle as this constitutes an integrated measure of exposure over long periods of time. From each harvested fish, two pieces of dorsal muscle (15 ± 1 cm) were taken immediately posterior the head and close to insertion of the dorsal fin and were wrapped in aluminum foil. Samples were placed into plastic bags and transported in an insulated box with a suitable quantity of flaked ice (the ice/fish tissue ratio was 3:1, w/w) to the laboratory. Fish tissues were brought to the laboratory within 1.2 h of sacrifice. The same day any skin and backbone material was removed and the pooled sample was divided in two portions. Then samples were packaged in polyamide bags (S-gruppen, Vinterbro, Norway) with an O2 transmission rate of 30 cm3/m2/24 h at 23 °C at 0% relative humidity. Pouches were nitrogen flushed and heat-sealed using a BOSS model N48 vacuum sealer (BOSS, Hamburg, Germany) and kept in a freezer at 18 °C before chemical analysis (within two weeks). All equipment and materials used for sample collection, transportation, and preparation were free from contamination. The chemical analysis was begun the day after completing of the sampling. 2.2. Determination of OCs 2.2.1. Standard materials, reagents and methods High purity acetone, pentane, n-hexane and dichloromethane (quality for residue analysis grade) were used as the solvents for
974
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
Table 1 Biometry and lipid content of sturgeon fishes from the Caspian Seaa Species A. persicus
A. stellatus
A. nudiventris
H. huso
a b c
Mean ± SD Min–max Median Mean ± SD Min–max Median Mean ± SD Min–max Median Mean ± SD Min–max Median
Body length (cm)
Body weight (kg)b
Lipid (%)c
149 ± 16.6 117–171 155 114 ± 12.1 93–132 117 106 ± 15.5 81.3–128 108 188 ± 24.1 138–217 194
17.2 ± 2.95 12.1–22.4 17.2 7.51 ± 1.52 5.35–10.3 7.35 15.8 ± 2.72 10.8–19.1 16.5 52.4 ± 6.94 40.5–61.6 52.6
12.6 ± 2.58 8.03–15.5 12.6 5.19 ± 1.67 2.90–7.64 4.99 4.80 ± 1.28 2.11–6.80 4.85 5.72 ± 1.87 3.07–8.46 6.08
Mean value is expressed as arithmetic mean ± standard deviation. The weight of the eviscerated fish. The lipid contents were based on the fillets (%wet wt.).
cleaning glassware and for extraction (lipid, PCBs and OC). Sulfuric acid (95–98%) was used to hydrolyze the muscle tissue and to enhance lipid extraction. Silica gel 60 (63–230 mesh) was activated at 200 °C for 24 h and deactivated by addition of 3% distilled water and was applied in the cleanup process. Anhydrous sodium sulfate was dried for 4 h at 130 °C and used to remove trace levels of water in the extracts. All standards (PCB 28, 52, 101, 138, 143, 153 and 180; o,p0 - and p,p0 -isomers of DDT, DDE and DDD; a-, b- and c-isomers of HCH and HCB) were purchased from Ehrenstorfer Inc. (Augsburg, Germany) and all chemicals were purchased from Merck Inc. (Darmstadt, Germany). Glass wool and all glassware were rinsed with acetone before use. Determination of six indicator PCB congeners (IUPAC Nos.: 28, 52, 101, 138, 153 and 180), and selected organochlorine pesticides (OCPs, the o,p0 - and p,p0 -isomers of DDT, DDE and DDD, hexachlorobenzene (HCB) and the a-, b- and c-hexachlorocylohexanes (HCHs) in thawed fish samples was performed as described by Coelhan et al. (2006) with slight modification. Samples were thawed in a refrigerator (Yakhsaran, Tehran, Iran) at 5 ± 1 °C for approximately 12 h before analysis and then were ground in a commercial meat grinder (twice) with stainless steel blades using a 4 mm diameter plate (SAYA, Model: Promeat W-1800, Tehran, Iran). Homogenized fish (20 g) was mixed with 100 g of anhydrous sodium sulfate and put in a glass column (50 cm 2.5 cm i.d.) and left for 4 h in dark cabinet. The extraction of lipid was performed with 200 ml of pentane–acetone mixture (2:1, v/v) in 4 h. Then the solvent was evaporated using a rotary evaporator (Heidolph WB 2000, Kelheim, Germany) and was purged with ultra pure nitrogen gas and lipid recovered. The lipid concentration was determined gravimetrically and expressed as a percentage of wet weight. Extracted lipid (1 g) was dissolved in 10 ml of n-hexane and placed into a centrifuge tube with a teflon lined screw cap. The sample was centrifuged (Labfuge 200, Heraaeus, Germany) at 3000 rpm for 5 min. The lipids remaining in solution were removed by reaction with 10 ml of concentrated sulfuric acid several times. Afterwards, the sample was placed into an oven at 60 °C to complete the degradation of lipids (2 h) and, subsequently, centrifuged at 3000 rpm for 5 min. The hexane phase was reduced to 0.5 ml with a gentle stream of ultra pure nitrogen gas using an evaporator set (Zymark, Turbo VapÒ evaporator, Serial No: TV9907N8675, Hopkinton, MA, USA) at 30 °C and passed through a Pasteur pipet packed with 1 g of silica gel. Before applying the sample extract to the silica gel to recovery OCs, the column was washed with 5 ml n-hexane. OCs was fractionated with 8 ml n-hexane (fraction 1) and 7 ml n-hexane/dichloromethane (1:1, fraction 2). Fraction 1 contained PCBs, HCB, p,p0 -DDE. HCHs, o,p0 - and p,p0 -DDD, o,p0 - and p,p0 -DDT, and o,p0 -DDE were found in the fraction 2.
To correct for variability due to injection conditions and correct for extraction recovery, 15 ll of an internal standard of PCB 143 and e-HCH was added to each 20 g sample of fish prior to the first extraction. In addition, procedural blanks were analyzed simultaneously with the fish samples to check for interferences or contamination from solvents and glassware. The concentrations of OC were expressed on a lipid weight basis unless otherwise specified. The electron-capture detector (ECD) response was calibrated using a standard mixture containing 18 compounds including 10 OCPs and 6 polychlorinated biphenyls and 2 internal standards. 2.2.2. Quantification The cleaned-up extraction was analyzed by gas chromatography (GC) using a Dani 1000 gas chromatograph (Monza, Italy) equipped with a 63Ni ECD. The GC system was equipped with a slightly polar – DB-5 capillary column (60 m 0.25 mm i.d., 0.25 lm film thickness) from J&W Scientific (Folsom, CA, USA). Helium was used as the carrier gas at a flow rate of 2 ml/min and nitrogen up gas at a flow rate of 42 l/min. The operating conditions were: split open after 30 s, temperature program: 100 °C (hold 1 min), 10 °C/min to 240 °C (hold 1 min), 3 °C/min to 260 °C (hold 1 min), 20 °C/min to 300 °C (hold 10 min). Injection port temperature: 250 °C, detector temperature: 300 °C and injection volume was 1 ll. The GC analysis of the cleaned-up extractions was performed in triplicate. The chromatographic data were digitally recorded and processed by the Clarity Chromatography Software (DataApex, Prague, Czech Republic). 2.2.3. Quality assurance and recovery Multi-level calibration curves were created for the quantification. Good linearity (r2 > 0.998) was achieved for tested intervals that included the whole concentration range found in the samples. Recovery tests were performed to check the efficiency of the residue analysis method for the estimation of pesticide residues in the substrate analyzed during the study. Spiking was done at two levels, 0.4 and 0.8 mg/kg. A method blank sample was included in each batch of 12 samples to monitor the contamination. The results showed all OCs blanks were below the detection limits. The method’s limits of quantification (LOQ) for individual PCBs were between 0.03 and 0.09 ng g1 lipid wt. and for OCPs between 0.01 and 0.2 ng g1 lipid wt. for all compounds tested. The recovery rate of OCPs was between 94% and 110% and for the PCBs, it was between 99% and 110%. Each analyte was identified by a comparison of its relative retention time to the peaks from the calibration standards. Quantification was based on a comparison with calibration curves in the concentration range of 0.03, 0.1, 0.3 and 0.6 ppm. The calibration lines of the standards were slightly quadratic for almost all compounds and quantification was made by a peak-by-peak height comparison and a calibration curve (point-to-point) for each analyte. Peak heights of all analytes were in the range of the calibration line. Samples with higher peaks were diluted. The analyses of OCs were performed at the Department of Environment of Tarbiat Modares University, Noor, Iran. 2.3. Statistical analysis The results are expressed as the geometric mean ± standard deviation. The data were tested for homogeneity of variances at a significance level of P < 0.05 and probability values less than 0.05 were considered as statistically significant (one-way ANOVA). Correlation coefficients were used for determination of the correlation between lipid content of each species and contaminant levels. Excel and SPSS version 13.5 (SPSS Inc., Chicago, IL, USA) were used for data manipulations and statistical analysis.
975
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
3. Results and discussion The levels of organic contaminants in sturgeon are shown in Table 2. Organochlorine contaminants were detected in all samples. Considerable variation was observed in OC levels among species (P < 0.05). Contaminant levels generally followed this pattern: DDTs > PCBs > HCHs > HCB with a mean value of 1780 ng g1 lipid wt. for total organochlorines. Furthermore, the highest concentration of OCs which was found in H. huso (P < 0.05), suggested their higher potential to accumulate persistent organic pollutants, following by A. nudiventris, A. persicus and A. stellatus (Fig. 2). DDT and related compounds were found at moderate to high levels with large variations in concentration across species for P the samples tested. DDT concentrations averaged 1 1260 ± 2480 ng g lipid wt. and in H. huso, was five times higher than the next highest specie (A. nudiventris). For the DDT components measured, p,p0 -DDE was found in the highest level in all fish muscle with values ranging from 254 in A. stellatus to 2840 ng g1 lipid wt. in H. huso (mean: 606 ng g1 lipid wt.). In all tested fish species, the residues were found in the order of DDE, DDD and DDT. This is in agreement with the results of other authors (Ruus et al., 1999; OSPAR, 2000; Szlinder-Richert et al., 2008). p,p0 -DDE was dominant because p,p0 -DDE is the metabolite of p,p0 -DDT (Li et al., 2008a, b; Muir et al., 2003) and generally is the most bioaccumulative and persistent among the isomers in abiotic and biotic components of the aquatic ecosystems (Aguilar,
1984; Andersen et al., 2001). A number previous studies have proved that p,p0 -DDE was the major DDT residue in aquatic species (Naso et al., 2005; Sapozhnikova et al., 2005). The high proportion of DDE in the analyzed samples suggested that this compound may either still be in use in countries around the Caspian Sea or is highly persistent in the soils or sediments in the Caspian Sea and surrounding area. Also, the ratio of DDE/DDT ranged between 2.50 and 3.28 in the studied sturgeons (Table 2). It was remarkably higher than to the ratio found in Herring (Clupea harengus), Spart (Sprattus sprattus), Cod (Gadus morhua), Flunder (Platichtys flesus) and Salmon (Salmo salar) by Szlinder-Richert et al., (2008) and in Common carp (Cyprinus carpio), Goldfish (Carassius auratus), Nile tilapia (Oreochromis niloticus), Catfish (Clarias lazera) and Chinese softshell turtle (Pelodiscus sinensis) by Li et al. (2008a, b) in the southern Baltic Sea and Gaobeidian Lake in China (ranged 0.18– 0.74 and 0.50–0.88, respectively). In addition to some cases mentioned in above, these results suggesting new input of DDE and reflecting the fact that may be some illegal agricultural practices implying fresh input of DDE still occur in Iran or other countries around the Caspian Sea. But one must not forget that somewhat of these differences can be related to the higher size and age of our studied fish with mentioned species. P P In marine mammals, a ratio of p,p0 -DDE/ p,p0 -DDTs ( p,p0 0 0 0 DDTs = p,p -DDT + p,p -DDE + p,p -DDD) below 0.6 has been considered to reflect a fresh DDT exposure (Aguilar, 1984). In the present study this value was above 0.6 only for A. stellatus (Table 2).
Table 2 Concentrations of organochlorines in muscle tissue of sturgeons from the Caspian Sea (ng g1 lipid wt.) Compound
Acipenser persicus
Acipenser stellatus
Acipenser nudiventris
Huso huso
Grand average
pp0 -DDE
375a (141–2120) 136 (81–242) 121 (63–237) 60.3 (34–91) 38.1 (28–53) 56.3 (41–75) 6.41 (4.9–14) 21.1 (17–48) 5.72 (4.6–14) 8.71 (4.1–29.3) 17.5 (11–97) 22.7 (16–115) 68.6 (36–432) 105 (63–738) 58.6 (39–160) 71.5 (43–395) 33.2 634 789 344 2.50 0.59 0.67 1170
254 (96–781) 80.5 (23–231) 78.7 (36–213) 39.7 (21–76) 27.1 (17–43) 44.2 (24–81) 4.52 (3.4–11) 19.8 (15–39) 4.33 (3.2–9.1) 7.39 (3.7–24) 13.09 (6.1–81) 16.1 (8.6–81) 43.1 (13.8–186) 70.9 (24–324) 51.9 (21–217) 39.5 (17–146) 28.6 413 524 234 2.72 0.61 0.66 794
501 (186–2080) 123 (71–1230) 264 (47–1810) 65.6 (34–180) 49.5 (25–98) 74.2 (29–154) 4.22 (3.1–7.3) 14.9 (9.1–31) 3.69 (2.2–9.1) 7.98 (4.1–19) 34.7 (23–140) 32 (19–160) 83.8 (31–910) 118 (81–759) 69.4 (34–475) 107 (69–815) 22.8 888 1080 445 3.28 0.56 0.69 1550
2840 (361–2050) 913 (285–2330) 979 (318–3162) 416 (198–663) 120 (76–193) 471 (275–864) 6.73 (5.6–16) 22.6 (19–46) 8.77 (6.3–17) 12.7 (5.4–38) 72.5 (33–197) 68.5 (41–185) 151 (94–812) 261 (191–1850) 188 (137–1110) 208 (120–1640) 38.1 4740 5740 950 3.17 0.60 0.85 6740
606 ± 1240
pp0 -DDT pp0 -DDD 0
op -DDE op0 -DDT op0 -DDD
a-HCH b-HCH
c-HCH HCB PCB 28 PCB 52 PCB 101 PCB 138 PCB 153 PCB 180 P HCH P 0 pp -DDTs P DDTs P PCBs P P DDEs/ DDTs P pp0 -DDE/ pp0 -DDTs P P DDTs/ OCs P OCs a
Geometric mean (Min–max).
187 ± 400 222 ± 419 89.9 ± 180 49.7 ± 41.9 96.5 ± 206 5.35 ± 1.28 19.3 ± 3.33 5.32 ± 2.25 8.98 ± 2.39 27.5 ± 27.2 29.9 ± 23.1 78.2 ± 46.1 123 ± 83.9 79.3 ± 64.4 89.0 ± 73.1 29.9 ± 6.41 1030 ± 2060 1260 ± 2480 429 ± 316 2.92 ± 0.367 0.58 ± 0.21 0.71 ± 0.08 2560 ± 2800
976
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
Fig. 2. Relative amounts of organochlorine compounds in sturgeons (12 samples per each species) collected from the Caspian Sea.
Kajiwara et al. (2003) showed a ratio above 0.6 for different species of sturgeon (A. persicus, A. gueldenstaedtii, A. stellatus, A. nudiventris and H. huso) from the Caspian Sea in 2003. In addition, Coelhan et al. (2006) reported values of 0.24–0.70 for this ratio for 13 species of fish from the Marmara Sea in Turkey. With regard to DDT and its metabolites, a maximum residue limit (MRL) for fish has not yet been established, while in some food products of animal origin (meat, milk and eggs), the European Union (UE) has recommended a tolerance limit of 1000 ng g1 of lipid, for the sum of p,p0 -DDT, p,p0 -DDE, p,p0 -DDD and o,p0 -DDD (Decreto Ministeriale 19 maggio, 2000). On the basis of this standard, with the exception of H. huso, the other species were below the proposed value. This finding is in agreement with results reported for different fish species from the Caspian Sea, including Rutilus frisii kutum, Clupeonella delicatula, Mugil auratus and Vimba vimba (Shokrzadeh and Ebadi, 2006). There has been no definitive source established for the source of DDTs into the Caspian Sea. However, considering these observations it is probable that some DDT is still being used in the Caspian Sea watershed. Fish lipid content can substantially influence the bioaccumulation of organochlorine compounds. However, the correlation between lipid content and DDT contaminant levels was inconsistent. The highest and lowest correlation coefficients were observed in A. stellatus (r = 0.894) and A. nudiventris (r = 0.410), respectively. The expected relationship between lipid content and lipophilic contaminants was probably not seen due to the limited number of fish tissues examined. Despite this limitation, the differences observed here may reflect other confounding factors including individual migration pattern and/or food habit, body size, sex, age and regional differences besides the lipid concentration. Total HCH levels were between 22.8 and 38.1 ng g1 lipid wt. for all species. In all of the fish muscle tested, b-HCH, a persistent isomer of technical HCHs, was the dominant isomer (Table 2). The reason for higher levels b-HCH might be that a-HCH can be isomerized into b-HCH, which is more persistent with respect to microbial degradation and also has a lower volatility and may show high concentrations in fish (Andersen et al., 2001; Kouras et al., 1998; Li et al., 2008a, b; Manirakiza et al., 2002; Rajendran et al., 2005). Previous researchers have noted that b-HCH is the main congener in fish from the Caspian Sea, making up more than 60% of the HCH burden (Kajiwara et al., 2003; Wang et al., 2007). Similar to the DDT residues, the highest concentrations of HCHs were found in H. huso (38.1 ng g1 lipid wt.; Table 2). This level was comparable to or lowers than those in H. huso reported by Kajiwara et al. (2003) (20–65 ng g1 lipid wt.). Overall, the proportion of a-, bP and c-HCH to HCH concentrations in sturgeon muscle were approximately 17.8, 64.1 and 17.7%, respectively. The high proportion of a-HCH suggests recent input and/or atmospheric transport from other areas because a-HCH can be excreted easily from the
animal’s body (Willett et al., 1998). Due to its high volatility, HCHs can be detected in many matrices all over the world. Iwata et al. (1993), who investigated HCHs concentrations in the surface water from various regions worldwide, found considerable HCHs contamination in latitudes above 40°N. Considering this fact, the high a-HCH level may be related to atmospheric transport from lower latitudes. Relatively high concentrations of HCHs in the fish of the Caspian Sea may indicate extensive local use in the past of this pesticide. However, in general, the HCH concentrations in sturgeon fish in this study were not high. These observations may suggest that lack of new input of HCHs into soil and water (river) around this region. Mean concentrations of hexachlorobenzene (HCB) were relatively consistent, ranging from 7.39 ng g1 lipid wt. in A. stellatus to 12.7 ng g1 lipid wt. in H. huso. Mean concentrations of HCB in this study were lower than in the previous study by Kajiwara et al. (2003) where they reported 9.3–41 for H. huso, 7.4–9.5 for A. nudiventris, 5.2–9.9 for A. persicus and 5–9.3 for A. stellatus ng g1 lipid wt. In general, mean HCB levels of fishes in this study were higher than of fishes from other Asian countries, such as India, Thailand, Vietnam and Indonesia (<5.0 ng g1 lipid wt.; Kannan et al., 1995), but lower than in fishes from Australia (123 ng g1 lipid wt.) and China (61 ng g1 lipid wt.; Nakata et al., 2005). Although little information is available on the contamination of HCB in the Caspian Sea, it is probable from these results that HCB is still in use around the coastal waters of the Caspian Sea. Total PCB concentrations (the sum of six congeners 28, 52, 101, 138, 153 and 180) varied in the range of 234 and 950 ng g1 lipid wt., with an average value of 429 ng g 1 lipid wt. The highest concentration of PCBs was observed in H. huso, followed in order by A. nudiventris, A. persicus and A. stellatus (Table 2). In general, our results indicate that PCB contamination in sturgeons of this study is lower or of the same order as those of Kajiwara et al. (2003). Kajiwara et al. (2003) have reported mean of 700–4900, 300–850, 390–400 and 170–310 ng g1 lipid wt. for H. huso, A. persicus, A. nudiventris and A. stellatus, respectively. Considering the large number of oil wells in Kazakhstan and Azerbaijan, and the resulting industrial effluents containing PCBs and wastewater from human activities (de Mora and Turner, 2004), these impacts might have been reflected in the OC levels in this study. On the other hand, Iran is located at the southern end of the Caspian Sea where there are few oil wells. Therefore, the PCBs concentrations were lower than those from the more industrialized regions as reported by Kajiwara et al. (2003). In the former USSR, technical PCB mixtures have been produced and used in both closed and open systems, such as capacitors, sealing paste additives and plasticizers, since the 1930s (Ivanov and Sandell, 1992). The PCB levels reported here were lower than those reported for other species living in areas with a wide industrial presence, such as the Berlin rivers (1050 ng g1 wet wt.) (Fromme et al., 1999), and in moderately polluted areas, such as the Vanajavesi River in Finland (852– 1740 ng g1 wet wt.) (Tulonen and Vuorinen, 1996). The bioconcentration of PCBs in aquatic organisms correlates with the degree of chlorination, the stereochemistry and lipophilicity (Bordajandi et al., 2003). Also, the chlorination pattern of the PCBs is important for the toxicity of the substance. Generally, congeners with high chlorination numbers are more difficult to metabolize and eliminate than the less chlorinated congeners (Yang et al., 2006). Of the congeners measured, PCB 138, 153 and 180 were the major contaminant congener in all samples (accounting for 26.5–30.5, 16.8–24.1 and 15.5–22.1 of the total PCB concentrations, respectively). This is not surprising since congeners 153 and 138 have a long half-life. These congeners have a particular biological interest, since they exhibit a considerable bioaccumulation starting at low trophic levels (Pruel et al., 1993) and they are toxic (Hong et al., 1998). This finding is in agreement with results reported for differ-
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
ent fish species from Marmara Sea (Coelhan et al., 2006) and the Adriatic Sea (Storelli et al., 2007). PCB 28, 52 and 101 were detected at lower concentrations following the order PCB 28 > PCB 52 > PCB 101. It is easier for lower chlorinated PCBs to pass through the body’s cell membranes than for higher chlorinated PCBs, which means that higher chlorinated PCBs have much stronger abilities of accumulation in fish samples (Bernes, 1998). As mentioned in above, because of the lipophilic nature, stability and persistence of the high chlorinated biphenyls, a higher rate of bioaccumulation is favored in studied fish than the low chlorinated ones (Borga et al., 2001). As it is known the biotransformation rate of PCBs is strongly affected by their degree of chlorination and by the position of the chlorine atoms on the biphenyl rings. The lack of unsubstituted adjacent-meta and -para positions on the biphenyl rings of the congeners 180, 153 and 138 enhance the resistance to metabolic attack by the cytochrome P450 iso-enzymes, which can metabolize the less chlorinated congeners (PCBs 28, 52 and 101) (Van den Brink and Bosveld, 2001). When considering the OCs in marine organisms suitable for human consumption, the most important aspect is their toxicity to humans. In this way, the European Union has set PCB standards with directive 1999/788/CE which permits a maximum content of 200 ng g1 lipid basis, calculated as the sum of the concentrations of the seven ‘‘target” congeners (PCBs 28, 52, 101, 118, 138, 153 and 180) in meat, poultry and derived products (Commission of the European Communities, 1999), but not in fish. In our study, as shown in Table 2, the mean PCB concentrations exceeded the above-mentioned limit. Furthermore, in Germany, a maximum residue limit exists for 6 individual PCB indicators (SHmV, 2003). For each PCB 138 and 153 congener, the maximum allowed concentration for marine fish is 100 ng g1 fresh weight, while the limit for PCBs 28, 52, 101 and 180 is 80 ng g1 fresh weight. On the basis of this, with the exception of the 138 congener, the other measured concentrations are clearly below these limits for all fish samples analyzed. There has been a European proposal to impose a limit of 8 pg TEQ/g fresh weight in fish, i.e., for the sum of the dioxins and dioxin-like PCBs (EC, 2005). For DDTs and HCHs, the residual concentrations are proposed as 2000 and 5000 ng g1 wet wt, respectively in China (Chen et al., 2002). The detected levels of DDTs and HCHs were below these guidelines in the present study. Over 60% of the total organochlorine contamination is due to the DDT components (Fig. 3). While the usage of DDTs in agriculture has been banned in Iran since 1983 (Çok et al., 1999), nothing is known about its illegal use. Another explanation may be inputs from the other countries around the Caspian Sea (Senthil-kumar et al., 2001). Confirmation of this assumption could be done by measuring the DDTs in local species at several points in the Caspian Sea. Taken as a whole, the organochlorine contamination in the sample analyzed was high, but it is significantly lower than in previous
977
samples (Kajiwara et al., 2003). Also, Wang et al. (2007) demonstrated a decline in PCB and DDT levels and a more recent decline in HCH levels in sturgeon caviar from the Caspian Sea. Still, it is not surprising to find declining trends in PCBs and DDT due to longstanding restrictions on the production, use and disposal of these compounds that started in the developed countries in the 1970s (Corsolini et al., 2006). Tanabe et al. (2003) showed decreases in contaminant concentrations in Caspian Sea seals (Phoca caspica) that were sampled in 1993 and 1998, with DDT, HCH, chlordanes, and coplanar PCBs decreasing by factors of 2.7, 1.8, 1.5, and 1.8, respectively, over this period. However, the HCH trends suggest the extensive and recent use of HCH in the Caspian Sea region (Watanabe et al., 1999). HCH bioaccumulation patterns also tend to differ from other OCs since this compound is relatively water soluble. 3.1. Biomonitoring Concentrations of persistent toxic substances in muscle reflect discharges of these substances into receiving waters, bioaccumulation through the food web, and chemical partitioning and breakdown kinetics in the sturgeon fish. Further, concentrations are affected by species, region, nutritive conditions, sex, age, and spawning/sampling season. For these reasons, concentrations of different contaminants can vary greatly within and among species. A study of sturgeon fish and caviar from the Caspian Sea in early 2002 and 2006 ranked OC concentrations as DDT > PCBs > HCH > HCB (Kajiwara et al., 2003; Wang et al., 2007). Similar patterns were found in the muscle of sturgeon. Despite the large concentration differences, biomonitoring using various species and tissues can successfully track contaminant trends in a region, often with good correlation between species. On the other hand, biomonitoring using muscle of fishes may not be effective for some contaminants, including OCs that may accumulate in other organs such as gonads, liver and kidney, and where levels may reflect physiological requirements of the species (Wirth et al., 2000). Acipenseriformes (an order of primitive ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families) typically are long-lived and migrating, thus monitored concentrations portray a mixture of current and historical conditions that may encompass a potentially large water area; possibly one that differs from the collection/harvest area. For example, H. huso migrates can forage along the Western Caspian Sea where high levels of agricultural contaminants are likely a different ecosystem (Wang et al., 2007). In contrast, A. stellatus migrates primarily along the eastern Caspian Sea, where the contaminant levels appear to be low, though data are lacking. Contaminant source areas cannot be identified due to the region’s lack of monitoring programs for contaminants in water, sediment, and biota.
Fig. 3. Composition of organochlorine pesticides in sturgeons (12 samples per each species) collected from the Caspian Sea.
978
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
Additionally, comparisons across different species must account for age, diet, and other effects. Specifically, H. huso is at the top trophic level for Acipenseriformes. They eat primarily herring and anchovies, and have the longest life span (females typically mature at 15–20 years). In contrast, A. stellatus is lower on the trophic ladder, subsists on polychaetes (segmented bristleworms), and has a shorter lifespan (females mature in 8–14 years). A. persicus occupies an intermediate trophic position. The results show the significance of tropic level in the biomagnification of OC in muscle as has been seen in previous analyses as well as in this study (e.g., Kajiwara et al., 2003; Shokrzadeh and Ebadi, 2006). 4. Conclusions The concentrations of OCs for sturgeon are generally amongst the lowest values reported in the literature and reflect a cleaner environment in the Caspian Sea at this time in the Iranian waters. But the quantity of measured OCs in the studied sturgeon was high when it was compared with other fish in the other geographical regions. This shows that there is still some illegal usage of these toxic compounds in recent years, also indicates the serious contamination of OCs in the Caspian region. Particularly, very high concentrations of DDTs and PCBs in some specimens were observed, especially H. huso, which may be enough to cause adverse effects on this species and their population (Barannikova, 1999; Kajiwara et al., 2003; Pourkazemi, 2006). The results obtained in this work allow the conclusion that the concentration levels of the OCPs studied appear to be below the permissible limits for human consumption, established by legislation for other foods in most cases, although exceptions were noted. In summary, the Caspian Sea is a unique ecosystem confronted by a series of environmental stresses. For the most part the problems outlined here are not unique to the Caspian Sea, but have become intensified due to its land-locked nature. Unilateral solutions will not succeed in the long term and the five riparian states must cooperate to mitigate current, and prevent future, pollution. While the Caspian Sea region cannot yet serve as a successful model of international collaboration for environmental management and sustainable development, the establishment of the Caspian Environment Programme and recent openness between countries has allowed a better understanding of the environmental problems and a wide felt appreciation for what is at stake. The next, but not final, step will be the signing and ratification of the Framework Convention for the Protection of the Marine Environment of the Caspian Sea. Acknowledgements We sincerely thank to Prof. Barbara Rasco, from Department of Food Science, Washington State University, USA and Prof. Joe M. Regenstein from Department of Food Science, Cornell University, USA for critically reading the manuscript and making a number of helpful suggestions. We are also grateful to Mrs Haghdost for her assistance in measurements of OCs. References P Aguilar, A., 1984. Relationship of DDE/ DDT in marine mammals to the chronology of DDT input into the ecosystem. Can. J. Fish Aquat. Sci. 41, 840–844. Andersen, G., Kovacs, K.M., Lydersen, C., Skaare, J.U., Gjertz, I., Jenssen, B.M., 2001. Concentrations and patterns of organochlorine contaminants in white whales (Delphinapterus leucas) from Svalbard Norway. Sci. Total Environ. 264, 267–281. Barannikova, I.A., 1999. Sex steroids in the serum of Caspian sturgeon and their specific cytosol binding in brain and gonads during the migratory cycle. J. Appl. Ichthyol. 15, 193–195. Bernes, C., 1998. Persistent Organic Pollutants: A Swedish View of an International Problem. Swedish Environmental Protection Agency, Stockholm.
Billard, R., Lecointre, G., 2001. Biology and conservation of sturgeon and paddlefish. Rev. Fish Biol. Fisher. 10, 355–392. Bocio, A., Domingo, J.L., Falcó, G., Llobet, J.M., 2007. Concentrations of PCDD/PCDFs and PCBs in fish and seafood from the Catalan (Spain) market: estimated human intake. Environ. Int. 33, 170–175. Boon, J.P., Lewis, W.E., Tjoen-A-Choy, M.R., Allchin, C.R., Law, R.J., de Boer, J., ten Hallers-Tjabbes, C.C., Zegers, B.N., 2002. Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food web. Environ. Sci. Technol. 36, 4025–4032. Bordajandi, L.R., Gomez, G., Fernandez, M.A., Abad, E., Rivera, J., Gonzalez, M.J., 2003. Study on PCBs, PCDD/Fs, organochlorine pesticides, heavy metals and arsenic content in freshwater fish species from the river Turia (Spain). Chemosphere 53, 163–171. Borga, K., Gabrielsen, G.W., Skaare, J.U., 2001. Biomagnification of organochlorines along a Barents sea food chain. Environ. Pollut. 113, 187–198. Chen, W.Q., Zhang, L.P., Xu, L., Wang, X.H., Hong, L.Y., Hong, H.S., 2002. Residue levels of HCHs, DDTs and PCBs in shellfish from coastal areas of east Xiamen Island and Minjiang Estuary, China. Mar. Pollut. Bull. 45, 385–390. Çok, I., Karakaya, A.E., Afkham, B.L., Burgaz, S., 1999. Organochlorine pesticide contaminants in human milk samples collected in Tebriz (Iran). Bull. Environ. Contam. Toxicol. 63, 444–450. Coelhan, M., Strohmeier, J., Barlas, H., 2006. Organochlorine levels in edible fish from the Marmara Sea, Turkey. Environ. Int. 32, 775–780. Commission of the European Communities, 1999. EU commission decision 1999/ 788/EC of 3 December 1999 on protective measures with regard to contamination by dioxins of certain products of porcine and poultry origin intended for human or animal consumption. G.U. EU-L 310/62 of 04/12/1999. Corsolini, S., Covaci, A., Ademollo, N., Focardi, S., Schepens, P., 2006. Occurrence of organochlorine pesticides (OCPs) and their enantiomeric signatures, and concentrations of polybrominated diphenyl ethers (PBDEs) in the Ade´ lie penguin food web, Antarctica. Environ. Pollut. 140, 371–382. de Mora, S.J., Turner, T., 2004. The Caspian Sea: a microcosm for environmental science and international cooperation. Mar. Pollut. Bull. 48, 26–29. de Mora, S., Villeneuve, J., Sheikholeslami, M.R., Cattini, C., Tolosa, I., 2004. Organochlorinated compounds in Caspian Sea sediments. Mar. Pollut. Bull. 48, 30–43. Decreto Ministeriale 19 maggio, 2000. Maximume limite of pesticide residue in foods (Recepimento delle Direttive n. 97/41/CE, n. 1999/65/CE e n. 1999/71/CE). G.U. 207 del 05/09/2000 (in Italian). EC, 2005. Available at. doc; 2005. Falandysz, J., Wyrzykowska, B., Warzocha, J., Barska, I., Garbacik-Wesolowska, A., Szefer, P., 2004. Organochlorine pesticides and PCBs in perch Perca fluviatilis from the Odra/Oder river estuary, Baltic Sea. Food Chem. 87, 17–23. Fromme, H., Otto, T., Pilz, K., Neugebauer, F., 1999. Levels of synthetic musks: bromocyclene and PCBs in eel (Anguilla anguilla) and PCBs in sediment samples from some waters of Berlin/Germany. Chemosphere 39, 1723–1735. Haynes, D., Johnson, J.E., 2000. Organochlorine, heavy metal and polyaromatic hydrocarbon pollutant concentrations in the great barrier reef (Australia) environment: a review. Mar. Pollut. Bull. 41, 267–278. Hong, C.S., Xiao, J., Bush, B., Shaw, S.D., 1998. Environmental occurrence and potential toxicity of planar, -mono -di and -ortho polychlorinated biphenyls in the biota. Chemosphere 36, 1637–1651. Ivanov, V., Sandell, E., 1992. Characterization of polychlorinated biphenyl isomers in Sovol and trichlorodiphenyl formulations by high-resolution gas chromatography with electron capture detection and high-resolution gas chromatography–mass spectrometry techniques. Environ. Sci. Technol. 26, 2012–2017. Ivanov, V.P., 2000. Biological Resources of the Caspian Sea, Astrakhan, KaspNIRKH Publication, 96 pp. Iwata, H., Tanabe, S., Sakai, N., Tatsukawa, R., 1993. Distribution of persistent organochlorines in the oceanic air and surface seawater and the role of ocean on their global transport and fate. Environ. Sci. Technol. 27, 1080–1098. Kannan, K., Tanabe, S., Tatsukawa, R., 1995. Geographical distribution and accumulation features of organochlorine residues in fish in tropical Asia and Oceania. Environ. Sci. Technol. 29, 2643–2683. Kajiwara, N., Ueno, D., Monirith, I., Tanabe, S., Pourkazemi, M., Aubrey, D.G., 2003. Contamination by organochlorine compounds in sturgeons from Caspian Sea during 2001and 2002. Mar. Pollut. Bull. 46, 741–747. Kiviranta, H., Ovaskainen, M.L., Vartiainen, T., 2004. Market basket study on dietary intake of PCDD/Fs, PCBs, and PBDEs in Finland. Environ. Int. 30, 923–932. Kouras, A., Zouboulis, A., Samara, C., Kouimtzis, Th., 1998. Removal of pesticides from aqueous solutions by combined physicochemical processes – the behavior of lindane. Environ. Pollut. 103, 193–202. Li, X., Gan, Yiping., Yang, X., Zhou, J., Dai, J., Xu, M., 2008a. Human health risk of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in edible fish from Huairou Reservoir and Gaobeidian Lake in Beijing, China. Food Chem. 109, 348–354. Li, X., Zhang, Q., Dai, J., Gan, Y., Zhou, J., Yang, X., Cao, H., Jiang, G., Xu, M., 2008. Pesticide contamination profiles of water, sediment and aquatic organisms in the effluent of Gaobeidian wastewater treatment plant. doi:10.1016/ j.chemosphere.2008.03.049. Manirakiza, P., Covaci, A., Nizigiymana, L., Ntakimazi, G., Schepens, P., 2002. Persistent chlorinated pesticides and polychlorinated biphenyls in selected fish species from Lake Tanganika, Burundi, Africa. Environ. Pollut. 117, 447–455.
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979 Muir, D., Savinova, T., Savinov, V., Alexeeva, L., Potelov, V., Svetochev, V., 2003. Bioaccumulation of PCBs and chlorinated pesticides in seals, fishes and invertebrates from the White Sea, Russia. Sci. Total Environ. 306, 111–131. Nakata, H., Hirakawa, Y., Kawazoe, M., Nakabo, T., Arizono, K., Abe, S., Kitano, T., Shimada, H., Watanabe, I., Li, W., Ding, X., 2005. Concentrations and compositions of organochlorine contaminants in sediments, soils, crustaceans, fishes and birds collected from Lake Tai, Hangzhou Bay and Shanghai city region, China. Environ. Pollut. 133, 415–429. Naso, B., Perrone, D., Ferrante, M.C., Bilancione, M., Lucisano, A., 2005. Persistent organic pollutants in edible marine species from the Gulf of Naples, Southern Italy. Sci. Total Environ. 343, 83–95. OSPAR, 2000. Quality Status Report 2000. OSPAR Commission, London. Pourkazemi, M., 2006. Caspian Sea sturgeon conservation and fisheries: past present and future. J. Appl. Ichthyol. 22, 12–16. Pruel, R.J., Rubenstein, N.I., Taplin, B.K., Livolski, J.A., Bowen, R.D., 1993. Accumulation of polychlorinated organic contaminants from sediments by three benthic marine species. Arch. Environ. Contam. Toxicol. 24, 290–297. Rajendran, R.B., Imagawa, T., Tao, H., Ramesh, R., 2005. Distribution of PCBs, HCHs and DDTs, and their ecotoxicological implications in Bay of Bengal, India. Environ. Int. 31, 503–512. Ruus, A., Ugland, K., Espeland, O., 1999. Organochlorine contaminants in a local marine food chain from Jarfjord, northern Norway. Mar. Environ. Res. 48, 131– 146. Sapozhnikova, Y., Zubcov, N., Hungerford, S., Roy, L.A., Boicenco, N., Zubcov, E., Schlenk, D., 2005. Evaluation of pesticides and metals in fish of the Dniester River, Moldova. Chemosphere 60, 196–205. Senthil-kumar, K., Kannan, K., Subramanian, A.N., Tanabe, S., 2001. Accumulation of persistent organochlorine pesticides and polychlorinated biphenyls in sediments, aquatic organisms, birds, bird eggs and bat collected from South India. Environ. Sci. Pollut. Res. 8, 35–47. SHmV (Schadstoff-Höchstmengenverordnung), 2003. Available at http:// bundesrecht.juris.de/shmv-2003/BJNR275500003.html. Shokrzadeh, M., Ebadi, A.G., 2006. Investigating and measurement of residues of chlorobenzilate (organochlorine pesticides) in four species of the most consumed fishes in Caspian Sea (Iran). Pak. J. Nutr. 5, 68–70.
979
Storelli, M.M., Barone, G., Garofalo, R., Marcotrigiano, G.O., 2007. Metals and organochlorine compounds in eel (Anguilla anguilla) from the Lesina lagoon, Adriatic Sea (Italy). Food Chem. 100, 1337–1341. Sudaryanto, A., Monirith, I., Kajiwara, N., Takahashi, S., Hartono, P., Muawanah, Omori, K., Takeoka, H., Tanabe, S., 2007. Levels and distribution of organochlorines in fish from Indonesia. Environ. Int. 33, 750–758. Szlinder-Richert, J., Barska, I., Mazerski, J., Usydus, Z., 2008. Organochlorine pesticides in fish from the southern Baltic Sea: levels, bioaccumulation features and temporal trends during the 1995–2006 period. Mar. Pollut. Bull. 56, 927–940. Tanabe, S., Niimi, S., Minh, T.B., Miyazaki, N., Petrov, E.A., 2003. Temporal trends of persistent organochlorine contamination in Russia: a case study of Baikal and Caspian Seal. Arch. Environ. Contam. Toxicol. 44, 533–545. Tulonen, J., Vuorinen, P.J., 1996. Concentrations of PCBs and other organochlorine compounds in eels (Anguilla anguilla L) of the Vanajavesi watercourse in southern Finland, 1990–1993. Sci. Total Environ. 187, 11–18. Tüzen, M., 2003. Determination of heavy metals in fish samples of the middle Black Sea (Turkey) by graphite furnace atomic absorption spectrometry. Food Chem. 80, 119–123. Van den Brink, N.W., Bosveld, B.T.C., 2001. PCB concentrations and metabolism patterns in common terns (Sterna hirundo) from different breeding colonies in The Netherlands. Mar. Pollut. Bull. 42, 280–285. Wang, W., Batterman, S., Chernyak, S., Nriagu, J., 2007. Concentrations and risks of organic and metal contaminants in Eurasian caviar. Ecotoxicol. Environ. Saf. doi:10.1016/j.ecoenv.2007.06.07. Watanabe, M., Tanabe, S., Tatsukawa, R., Amano, M., Miyazaki, N., Petrov, E.A., Khuraskin, S.L., 1999. Contamination levels and specific accumulation of persistent organochlorines in Caspian Seal (Phocacaspica) from the Caspian Sea, Russia. Arch. Environ. Contam. Toxicol. 37, 396–407. Willett, K.L., Ulrich, E.M., Hites, R.A., 1998. Differential toxicity and environmental fates of hexachlorocyclohexane isomers. Environ. Sci. Technol. 32, 2197–2207. Wirth, M., Kirschbaum, F., Gessner, J., Krüger, A., Patriche, N., Billard, R., 2000. Chemical and biochemical composition of caviar from different sturgeon species and origins. Nahrung 44, 233–237. Yang, N.Q., Matsuda, M., Kawano, M., Wakimoto, T., 2006. PCBs and organochlorine pesticides (OCPs) in edible fish and shellfish from China. Chemosphere 63, 1342–1352.
Contents lists available at ScienceDirect
Chemosphere journal homepage: www.elsevier.com/locate/chemosphere
Contamination by organochlorine compounds in the edible tissue of four sturgeon species from the Caspian Sea (Iran) Seyed Vali Hosseini a,b,*, Reza Dahmardeh Behrooz c,d, Abbas Esmaili-Sari c, Nader Bahramifar c, Seyed Mehdi Hosseini e, Reza Tahergorabi f, Seyed Fakhreddin Hosseini g, Xesús Feás h a
Department of Fisheries, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, P.O. Box 46414-356, Noor, Mazandaran, Iran Department of Fisheries and Environmental Sciences, Faculty of Natural Resources, University of Tehran, P.O. Box 31585-4314, Karaj, Tehran, Iran c Department of Environmental Sciences, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, P.O. Box 46414-356, Noor, Mazandaran, Iran d Department of Environmental Sciences, Faculty of Natural Resources, Zabol University, Zabol, Sistan and Baluchestan, Iran e Department of Environmental Sciences, Engineering and Technical Faculty, Allame Mohaddes Noori-Institute of Higher Education, P.O. Box 451-46415, Noor, Mazandaran, Iran f Department of Fisheries, Islamic Azad University, Tehran, North Branch, P.O. Box 19737-33583, Tehran, Iran g Department of Fisheries, Islamic Azad University-Lahijan Branch, P.O. Box 1616, Lahijan, Guilan, Iran h Departamento de Química Analítica, Nutrición y Bromatoloxía. Facultade de Veterinaria. Universidade de Santiago de Compostela, E-27002 Lugo, Galiza, Spain b
a r t i c l e
i n f o
Article history: Received 6 April 2008 Received in revised form 9 June 2008 Accepted 10 June 2008 Available online 25 July 2008 Keywords: Pollution Organochlorine Sturgeon Caspian Sea Iran
a b s t r a c t This study focused on accumulation of organochlorine compounds (OCs), including dichloro-diphenyltrichloroethanes (DDTs), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), and polychlorinated biphenyls (PCBs) accumulation in the muscle of four sturgeon (Persian sturgeon, Acipenser persicus; Stellate sturgeon, Acipenser stellatus; Ship sturgeon, Acipenser nudiventris and Beluga sturgeon, Huso huso) from the southern Caspian Sea. The DDT group was prominent in all of the sturgeon muscle tested constituting almost half or more of the total organochlorine content. Contaminant concentration generally followed this order: DDTs > PCBs > HCHs > HCB. The OCs concentrations in Beluga sturgeon (H. huso) were the highest and over four times higher than in the next highest species (A. nudiventris). From an ecotoxicological point of view, the concentrations of OCs in experimental fishes do not reflect a comparatively clean and pollution-free environment; however, results from this study shown that the inflow of organic pollutants into the Caspian Sea has been reduced when compared with prior studies. Levels of measured OCs in sturgeon were relatively low, but the level of some OCs in some of the specimens tested exceeded the guidelines for food; therefore, the maximum allowable daily consumption rate for sturgeon from this watershed may be limited by DDTs and PCBs content for high risk populations. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Growth in industrial, agricultural and many other human activities caused by increasing population pressure and poor environmental controls have resulted in chemical contamination of important water bodies across the world. Among these anthropogenic pollutants, major concern has been directed to organochlorine compounds (OCs) such as polychlorinated biphenyls (PCBs) and pesticides (Sudaryanto et al., 2007) because of their persistent, bioaccumulative nature and potential toxic effects on wildlife and humans (Haynes and Johnson, 2000).
* Corresponding author. Present address: Area de Tecnología de los Alimentos, Depto de Química Analítica, Nutrición y Bromatología, Facultad de Veterinaria, Universidad de Santiago de Compostela, E-27002 Lugo, Galiza, Spain. Tel.: +98 912 6049868 (mobile); fax: +98 122 6253499. E-mail address: [email protected] (S.V. Hosseini). 0045-6535/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2008.06.036
Chlorinated organic compounds, due to their chemical persistence and lipophilicity, have a tendency to accumulate up the food chain. Therefore, human exposure to these pollutants occurs mainly from eating food (Tüzen, 2003; Kiviranta et al., 2004; Coelhan et al., 2006; Bocio et al., 2007). Seafood usually contains residues of PCBs, as well as other environmentally persistent OCs, and is often considered to be a major source of intake of those contaminants for humans (Falandysz et al., 2004). Therefore, it is important to determine how these compounds are distributed in fish, as this provide important information for assessing possible health risks and may also provide an incentive to improve water quality. Fish are a suitable indicator organism for environmental pollution monitoring because they can absorb and concentrate pollutants in different tissues directly from the water and also through their diet, thus enabling the assessment of the transfer of pollutants through the trophic web. Data on the presence and distribution of organic and metal contaminants in fish and espe-
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
cially edible fish species are important not only from an ecological perspective, but also from a human health perspective (Boon et al., 2002), even if the fish used for biological monitoring are not normally consumed as food. The Caspian Sea is the biggest land-locked body of water bordered by five countries: Azerbaijan, Iran, the Russian Federation, Kazakhstan and Turkmenistan. It has five major inlet rivers but no outlets and acts as a watershed reservoir for the region. The key biological issues in recent years relate to the decline of the fisheries and caviar harvesting, the massive mortality among seal populations and the introduction of invasive species in the Caspian Sea. There are several important fisheries in the Caspian Sea, but the greatest emphasis has always been placed on the sturgeons. The Caspian Sea has six commercially valuable sturgeon species, four of which produce 90% of the world’s caviar. Several anthropogenic factors, including both land-based and offshore pollution, threaten the survival of all fisheries, but especially sturgeon populations in the Caspian Sea (de Mora and Turner, 2004). Among these, chemical contamination seems to be one of the most significant factors influencing the population of sturgeons in the Caspian Sea (Ivanov, 2000; Pourkazemi, 2006). Many potentially toxic contaminants released into the Caspian Sea are lipophilic and insoluble in water. These properties increase their availability for uptake and accumulation by aquatic organisms. Previous investigations have demonstrated the occurrence of OCs in fishes from the Caspian Sea (Kajiwara et al., 2003; de Mora and Turner, 2004; de Mora et al., 2004; Shokrzadeh and Ebadi, 2006). The life history of sturgeons may leave them particularly vulnerable to the effects of bioaccumulative pollutants. As opportunistic bottom feeders, these fish frequently come in contact with sediments that could contain sediment-adsorbed hydrophobic pollutants. Furthermore, sturgeons are particularly long-lived animals (up to 100 years in the wild) that take 5–30 years to reach sexual maturity (Billard and Lecointre, 2001). These characteristics put the sturgeons at a high potential risk for accumulating persistent organic and inorganic contaminants in their tissues. Therefore, sturgeons were chosen as the target fish for this study due to their elevated risk for bioaccumulation of persistent contaminants. The objectives of this study were to understand the present status of contamination and the specific accumulation of OCs in the muscle of four species of sturgeons in the Caspian Sea (persian sturgeon (Acipenser persicus), stellate or sevruga sturgeon (Acipenser stellatus), ship sturgeon (Acipenser nudiventris) and beluga sturgeon (Huso huso) and to compare these values with guidelines for human consumption and to previous studies. These results would be important for a number of reasons: (1) provide more information about organochlorine concentrations in this aquatic ecosystem of the Caspian Sea, (2) predict possible food safety risk to humans from consumption of Caspian Sea sturgeons, and (3) provide baseline data that could predict the risk of persistent contaminants for the health of these fish, several species of which are considered to be threatened with extinction.
2. Materials and methods 2.1. Sampling, preparation and storage The Fisheries Organization of Iran has divided the whole area of the southern Caspian Sea (within Iranian waters) into five sturgeon fishery zones. Forty eight sturgeon samples (12 specimens from each of four species) were collected from one of the important sturgeon fishery zones (Babolsar station-E 36° 420 2600 N 52° 380 3500 in Mazandaran Province, Iran; Fig. 1) during January, 2007. This fishing station receives fish from all of Mazandaran Province (approximately 320–345 km of shoreline) and is the largest stur-
973
Fig. 1. Map of the Caspian Sea showing the area of sample collection. Babolsar sturgeon fisheries, Mazandaran catch area.
geon fishery zone in Iran. The specimens were caught using Gill nets with the standardized mesh and dimensions set by the Iran Fisheries Research Organization. These fish were selected from among the daily catch during two week sampling period. The biological characteristics of the samples including total length and weight were recorded (Table 1), then individuals were sacrificed and processed (gutted, washed and cut to pieces) on site in high hygienic conditions. Bioaccumulation of OCs species was evaluated in muscle as this constitutes an integrated measure of exposure over long periods of time. From each harvested fish, two pieces of dorsal muscle (15 ± 1 cm) were taken immediately posterior the head and close to insertion of the dorsal fin and were wrapped in aluminum foil. Samples were placed into plastic bags and transported in an insulated box with a suitable quantity of flaked ice (the ice/fish tissue ratio was 3:1, w/w) to the laboratory. Fish tissues were brought to the laboratory within 1.2 h of sacrifice. The same day any skin and backbone material was removed and the pooled sample was divided in two portions. Then samples were packaged in polyamide bags (S-gruppen, Vinterbro, Norway) with an O2 transmission rate of 30 cm3/m2/24 h at 23 °C at 0% relative humidity. Pouches were nitrogen flushed and heat-sealed using a BOSS model N48 vacuum sealer (BOSS, Hamburg, Germany) and kept in a freezer at 18 °C before chemical analysis (within two weeks). All equipment and materials used for sample collection, transportation, and preparation were free from contamination. The chemical analysis was begun the day after completing of the sampling. 2.2. Determination of OCs 2.2.1. Standard materials, reagents and methods High purity acetone, pentane, n-hexane and dichloromethane (quality for residue analysis grade) were used as the solvents for
974
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
Table 1 Biometry and lipid content of sturgeon fishes from the Caspian Seaa Species A. persicus
A. stellatus
A. nudiventris
H. huso
a b c
Mean ± SD Min–max Median Mean ± SD Min–max Median Mean ± SD Min–max Median Mean ± SD Min–max Median
Body length (cm)
Body weight (kg)b
Lipid (%)c
149 ± 16.6 117–171 155 114 ± 12.1 93–132 117 106 ± 15.5 81.3–128 108 188 ± 24.1 138–217 194
17.2 ± 2.95 12.1–22.4 17.2 7.51 ± 1.52 5.35–10.3 7.35 15.8 ± 2.72 10.8–19.1 16.5 52.4 ± 6.94 40.5–61.6 52.6
12.6 ± 2.58 8.03–15.5 12.6 5.19 ± 1.67 2.90–7.64 4.99 4.80 ± 1.28 2.11–6.80 4.85 5.72 ± 1.87 3.07–8.46 6.08
Mean value is expressed as arithmetic mean ± standard deviation. The weight of the eviscerated fish. The lipid contents were based on the fillets (%wet wt.).
cleaning glassware and for extraction (lipid, PCBs and OC). Sulfuric acid (95–98%) was used to hydrolyze the muscle tissue and to enhance lipid extraction. Silica gel 60 (63–230 mesh) was activated at 200 °C for 24 h and deactivated by addition of 3% distilled water and was applied in the cleanup process. Anhydrous sodium sulfate was dried for 4 h at 130 °C and used to remove trace levels of water in the extracts. All standards (PCB 28, 52, 101, 138, 143, 153 and 180; o,p0 - and p,p0 -isomers of DDT, DDE and DDD; a-, b- and c-isomers of HCH and HCB) were purchased from Ehrenstorfer Inc. (Augsburg, Germany) and all chemicals were purchased from Merck Inc. (Darmstadt, Germany). Glass wool and all glassware were rinsed with acetone before use. Determination of six indicator PCB congeners (IUPAC Nos.: 28, 52, 101, 138, 153 and 180), and selected organochlorine pesticides (OCPs, the o,p0 - and p,p0 -isomers of DDT, DDE and DDD, hexachlorobenzene (HCB) and the a-, b- and c-hexachlorocylohexanes (HCHs) in thawed fish samples was performed as described by Coelhan et al. (2006) with slight modification. Samples were thawed in a refrigerator (Yakhsaran, Tehran, Iran) at 5 ± 1 °C for approximately 12 h before analysis and then were ground in a commercial meat grinder (twice) with stainless steel blades using a 4 mm diameter plate (SAYA, Model: Promeat W-1800, Tehran, Iran). Homogenized fish (20 g) was mixed with 100 g of anhydrous sodium sulfate and put in a glass column (50 cm 2.5 cm i.d.) and left for 4 h in dark cabinet. The extraction of lipid was performed with 200 ml of pentane–acetone mixture (2:1, v/v) in 4 h. Then the solvent was evaporated using a rotary evaporator (Heidolph WB 2000, Kelheim, Germany) and was purged with ultra pure nitrogen gas and lipid recovered. The lipid concentration was determined gravimetrically and expressed as a percentage of wet weight. Extracted lipid (1 g) was dissolved in 10 ml of n-hexane and placed into a centrifuge tube with a teflon lined screw cap. The sample was centrifuged (Labfuge 200, Heraaeus, Germany) at 3000 rpm for 5 min. The lipids remaining in solution were removed by reaction with 10 ml of concentrated sulfuric acid several times. Afterwards, the sample was placed into an oven at 60 °C to complete the degradation of lipids (2 h) and, subsequently, centrifuged at 3000 rpm for 5 min. The hexane phase was reduced to 0.5 ml with a gentle stream of ultra pure nitrogen gas using an evaporator set (Zymark, Turbo VapÒ evaporator, Serial No: TV9907N8675, Hopkinton, MA, USA) at 30 °C and passed through a Pasteur pipet packed with 1 g of silica gel. Before applying the sample extract to the silica gel to recovery OCs, the column was washed with 5 ml n-hexane. OCs was fractionated with 8 ml n-hexane (fraction 1) and 7 ml n-hexane/dichloromethane (1:1, fraction 2). Fraction 1 contained PCBs, HCB, p,p0 -DDE. HCHs, o,p0 - and p,p0 -DDD, o,p0 - and p,p0 -DDT, and o,p0 -DDE were found in the fraction 2.
To correct for variability due to injection conditions and correct for extraction recovery, 15 ll of an internal standard of PCB 143 and e-HCH was added to each 20 g sample of fish prior to the first extraction. In addition, procedural blanks were analyzed simultaneously with the fish samples to check for interferences or contamination from solvents and glassware. The concentrations of OC were expressed on a lipid weight basis unless otherwise specified. The electron-capture detector (ECD) response was calibrated using a standard mixture containing 18 compounds including 10 OCPs and 6 polychlorinated biphenyls and 2 internal standards. 2.2.2. Quantification The cleaned-up extraction was analyzed by gas chromatography (GC) using a Dani 1000 gas chromatograph (Monza, Italy) equipped with a 63Ni ECD. The GC system was equipped with a slightly polar – DB-5 capillary column (60 m 0.25 mm i.d., 0.25 lm film thickness) from J&W Scientific (Folsom, CA, USA). Helium was used as the carrier gas at a flow rate of 2 ml/min and nitrogen up gas at a flow rate of 42 l/min. The operating conditions were: split open after 30 s, temperature program: 100 °C (hold 1 min), 10 °C/min to 240 °C (hold 1 min), 3 °C/min to 260 °C (hold 1 min), 20 °C/min to 300 °C (hold 10 min). Injection port temperature: 250 °C, detector temperature: 300 °C and injection volume was 1 ll. The GC analysis of the cleaned-up extractions was performed in triplicate. The chromatographic data were digitally recorded and processed by the Clarity Chromatography Software (DataApex, Prague, Czech Republic). 2.2.3. Quality assurance and recovery Multi-level calibration curves were created for the quantification. Good linearity (r2 > 0.998) was achieved for tested intervals that included the whole concentration range found in the samples. Recovery tests were performed to check the efficiency of the residue analysis method for the estimation of pesticide residues in the substrate analyzed during the study. Spiking was done at two levels, 0.4 and 0.8 mg/kg. A method blank sample was included in each batch of 12 samples to monitor the contamination. The results showed all OCs blanks were below the detection limits. The method’s limits of quantification (LOQ) for individual PCBs were between 0.03 and 0.09 ng g1 lipid wt. and for OCPs between 0.01 and 0.2 ng g1 lipid wt. for all compounds tested. The recovery rate of OCPs was between 94% and 110% and for the PCBs, it was between 99% and 110%. Each analyte was identified by a comparison of its relative retention time to the peaks from the calibration standards. Quantification was based on a comparison with calibration curves in the concentration range of 0.03, 0.1, 0.3 and 0.6 ppm. The calibration lines of the standards were slightly quadratic for almost all compounds and quantification was made by a peak-by-peak height comparison and a calibration curve (point-to-point) for each analyte. Peak heights of all analytes were in the range of the calibration line. Samples with higher peaks were diluted. The analyses of OCs were performed at the Department of Environment of Tarbiat Modares University, Noor, Iran. 2.3. Statistical analysis The results are expressed as the geometric mean ± standard deviation. The data were tested for homogeneity of variances at a significance level of P < 0.05 and probability values less than 0.05 were considered as statistically significant (one-way ANOVA). Correlation coefficients were used for determination of the correlation between lipid content of each species and contaminant levels. Excel and SPSS version 13.5 (SPSS Inc., Chicago, IL, USA) were used for data manipulations and statistical analysis.
975
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
3. Results and discussion The levels of organic contaminants in sturgeon are shown in Table 2. Organochlorine contaminants were detected in all samples. Considerable variation was observed in OC levels among species (P < 0.05). Contaminant levels generally followed this pattern: DDTs > PCBs > HCHs > HCB with a mean value of 1780 ng g1 lipid wt. for total organochlorines. Furthermore, the highest concentration of OCs which was found in H. huso (P < 0.05), suggested their higher potential to accumulate persistent organic pollutants, following by A. nudiventris, A. persicus and A. stellatus (Fig. 2). DDT and related compounds were found at moderate to high levels with large variations in concentration across species for P the samples tested. DDT concentrations averaged 1 1260 ± 2480 ng g lipid wt. and in H. huso, was five times higher than the next highest specie (A. nudiventris). For the DDT components measured, p,p0 -DDE was found in the highest level in all fish muscle with values ranging from 254 in A. stellatus to 2840 ng g1 lipid wt. in H. huso (mean: 606 ng g1 lipid wt.). In all tested fish species, the residues were found in the order of DDE, DDD and DDT. This is in agreement with the results of other authors (Ruus et al., 1999; OSPAR, 2000; Szlinder-Richert et al., 2008). p,p0 -DDE was dominant because p,p0 -DDE is the metabolite of p,p0 -DDT (Li et al., 2008a, b; Muir et al., 2003) and generally is the most bioaccumulative and persistent among the isomers in abiotic and biotic components of the aquatic ecosystems (Aguilar,
1984; Andersen et al., 2001). A number previous studies have proved that p,p0 -DDE was the major DDT residue in aquatic species (Naso et al., 2005; Sapozhnikova et al., 2005). The high proportion of DDE in the analyzed samples suggested that this compound may either still be in use in countries around the Caspian Sea or is highly persistent in the soils or sediments in the Caspian Sea and surrounding area. Also, the ratio of DDE/DDT ranged between 2.50 and 3.28 in the studied sturgeons (Table 2). It was remarkably higher than to the ratio found in Herring (Clupea harengus), Spart (Sprattus sprattus), Cod (Gadus morhua), Flunder (Platichtys flesus) and Salmon (Salmo salar) by Szlinder-Richert et al., (2008) and in Common carp (Cyprinus carpio), Goldfish (Carassius auratus), Nile tilapia (Oreochromis niloticus), Catfish (Clarias lazera) and Chinese softshell turtle (Pelodiscus sinensis) by Li et al. (2008a, b) in the southern Baltic Sea and Gaobeidian Lake in China (ranged 0.18– 0.74 and 0.50–0.88, respectively). In addition to some cases mentioned in above, these results suggesting new input of DDE and reflecting the fact that may be some illegal agricultural practices implying fresh input of DDE still occur in Iran or other countries around the Caspian Sea. But one must not forget that somewhat of these differences can be related to the higher size and age of our studied fish with mentioned species. P P In marine mammals, a ratio of p,p0 -DDE/ p,p0 -DDTs ( p,p0 0 0 0 DDTs = p,p -DDT + p,p -DDE + p,p -DDD) below 0.6 has been considered to reflect a fresh DDT exposure (Aguilar, 1984). In the present study this value was above 0.6 only for A. stellatus (Table 2).
Table 2 Concentrations of organochlorines in muscle tissue of sturgeons from the Caspian Sea (ng g1 lipid wt.) Compound
Acipenser persicus
Acipenser stellatus
Acipenser nudiventris
Huso huso
Grand average
pp0 -DDE
375a (141–2120) 136 (81–242) 121 (63–237) 60.3 (34–91) 38.1 (28–53) 56.3 (41–75) 6.41 (4.9–14) 21.1 (17–48) 5.72 (4.6–14) 8.71 (4.1–29.3) 17.5 (11–97) 22.7 (16–115) 68.6 (36–432) 105 (63–738) 58.6 (39–160) 71.5 (43–395) 33.2 634 789 344 2.50 0.59 0.67 1170
254 (96–781) 80.5 (23–231) 78.7 (36–213) 39.7 (21–76) 27.1 (17–43) 44.2 (24–81) 4.52 (3.4–11) 19.8 (15–39) 4.33 (3.2–9.1) 7.39 (3.7–24) 13.09 (6.1–81) 16.1 (8.6–81) 43.1 (13.8–186) 70.9 (24–324) 51.9 (21–217) 39.5 (17–146) 28.6 413 524 234 2.72 0.61 0.66 794
501 (186–2080) 123 (71–1230) 264 (47–1810) 65.6 (34–180) 49.5 (25–98) 74.2 (29–154) 4.22 (3.1–7.3) 14.9 (9.1–31) 3.69 (2.2–9.1) 7.98 (4.1–19) 34.7 (23–140) 32 (19–160) 83.8 (31–910) 118 (81–759) 69.4 (34–475) 107 (69–815) 22.8 888 1080 445 3.28 0.56 0.69 1550
2840 (361–2050) 913 (285–2330) 979 (318–3162) 416 (198–663) 120 (76–193) 471 (275–864) 6.73 (5.6–16) 22.6 (19–46) 8.77 (6.3–17) 12.7 (5.4–38) 72.5 (33–197) 68.5 (41–185) 151 (94–812) 261 (191–1850) 188 (137–1110) 208 (120–1640) 38.1 4740 5740 950 3.17 0.60 0.85 6740
606 ± 1240
pp0 -DDT pp0 -DDD 0
op -DDE op0 -DDT op0 -DDD
a-HCH b-HCH
c-HCH HCB PCB 28 PCB 52 PCB 101 PCB 138 PCB 153 PCB 180 P HCH P 0 pp -DDTs P DDTs P PCBs P P DDEs/ DDTs P pp0 -DDE/ pp0 -DDTs P P DDTs/ OCs P OCs a
Geometric mean (Min–max).
187 ± 400 222 ± 419 89.9 ± 180 49.7 ± 41.9 96.5 ± 206 5.35 ± 1.28 19.3 ± 3.33 5.32 ± 2.25 8.98 ± 2.39 27.5 ± 27.2 29.9 ± 23.1 78.2 ± 46.1 123 ± 83.9 79.3 ± 64.4 89.0 ± 73.1 29.9 ± 6.41 1030 ± 2060 1260 ± 2480 429 ± 316 2.92 ± 0.367 0.58 ± 0.21 0.71 ± 0.08 2560 ± 2800
976
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
Fig. 2. Relative amounts of organochlorine compounds in sturgeons (12 samples per each species) collected from the Caspian Sea.
Kajiwara et al. (2003) showed a ratio above 0.6 for different species of sturgeon (A. persicus, A. gueldenstaedtii, A. stellatus, A. nudiventris and H. huso) from the Caspian Sea in 2003. In addition, Coelhan et al. (2006) reported values of 0.24–0.70 for this ratio for 13 species of fish from the Marmara Sea in Turkey. With regard to DDT and its metabolites, a maximum residue limit (MRL) for fish has not yet been established, while in some food products of animal origin (meat, milk and eggs), the European Union (UE) has recommended a tolerance limit of 1000 ng g1 of lipid, for the sum of p,p0 -DDT, p,p0 -DDE, p,p0 -DDD and o,p0 -DDD (Decreto Ministeriale 19 maggio, 2000). On the basis of this standard, with the exception of H. huso, the other species were below the proposed value. This finding is in agreement with results reported for different fish species from the Caspian Sea, including Rutilus frisii kutum, Clupeonella delicatula, Mugil auratus and Vimba vimba (Shokrzadeh and Ebadi, 2006). There has been no definitive source established for the source of DDTs into the Caspian Sea. However, considering these observations it is probable that some DDT is still being used in the Caspian Sea watershed. Fish lipid content can substantially influence the bioaccumulation of organochlorine compounds. However, the correlation between lipid content and DDT contaminant levels was inconsistent. The highest and lowest correlation coefficients were observed in A. stellatus (r = 0.894) and A. nudiventris (r = 0.410), respectively. The expected relationship between lipid content and lipophilic contaminants was probably not seen due to the limited number of fish tissues examined. Despite this limitation, the differences observed here may reflect other confounding factors including individual migration pattern and/or food habit, body size, sex, age and regional differences besides the lipid concentration. Total HCH levels were between 22.8 and 38.1 ng g1 lipid wt. for all species. In all of the fish muscle tested, b-HCH, a persistent isomer of technical HCHs, was the dominant isomer (Table 2). The reason for higher levels b-HCH might be that a-HCH can be isomerized into b-HCH, which is more persistent with respect to microbial degradation and also has a lower volatility and may show high concentrations in fish (Andersen et al., 2001; Kouras et al., 1998; Li et al., 2008a, b; Manirakiza et al., 2002; Rajendran et al., 2005). Previous researchers have noted that b-HCH is the main congener in fish from the Caspian Sea, making up more than 60% of the HCH burden (Kajiwara et al., 2003; Wang et al., 2007). Similar to the DDT residues, the highest concentrations of HCHs were found in H. huso (38.1 ng g1 lipid wt.; Table 2). This level was comparable to or lowers than those in H. huso reported by Kajiwara et al. (2003) (20–65 ng g1 lipid wt.). Overall, the proportion of a-, bP and c-HCH to HCH concentrations in sturgeon muscle were approximately 17.8, 64.1 and 17.7%, respectively. The high proportion of a-HCH suggests recent input and/or atmospheric transport from other areas because a-HCH can be excreted easily from the
animal’s body (Willett et al., 1998). Due to its high volatility, HCHs can be detected in many matrices all over the world. Iwata et al. (1993), who investigated HCHs concentrations in the surface water from various regions worldwide, found considerable HCHs contamination in latitudes above 40°N. Considering this fact, the high a-HCH level may be related to atmospheric transport from lower latitudes. Relatively high concentrations of HCHs in the fish of the Caspian Sea may indicate extensive local use in the past of this pesticide. However, in general, the HCH concentrations in sturgeon fish in this study were not high. These observations may suggest that lack of new input of HCHs into soil and water (river) around this region. Mean concentrations of hexachlorobenzene (HCB) were relatively consistent, ranging from 7.39 ng g1 lipid wt. in A. stellatus to 12.7 ng g1 lipid wt. in H. huso. Mean concentrations of HCB in this study were lower than in the previous study by Kajiwara et al. (2003) where they reported 9.3–41 for H. huso, 7.4–9.5 for A. nudiventris, 5.2–9.9 for A. persicus and 5–9.3 for A. stellatus ng g1 lipid wt. In general, mean HCB levels of fishes in this study were higher than of fishes from other Asian countries, such as India, Thailand, Vietnam and Indonesia (<5.0 ng g1 lipid wt.; Kannan et al., 1995), but lower than in fishes from Australia (123 ng g1 lipid wt.) and China (61 ng g1 lipid wt.; Nakata et al., 2005). Although little information is available on the contamination of HCB in the Caspian Sea, it is probable from these results that HCB is still in use around the coastal waters of the Caspian Sea. Total PCB concentrations (the sum of six congeners 28, 52, 101, 138, 153 and 180) varied in the range of 234 and 950 ng g1 lipid wt., with an average value of 429 ng g 1 lipid wt. The highest concentration of PCBs was observed in H. huso, followed in order by A. nudiventris, A. persicus and A. stellatus (Table 2). In general, our results indicate that PCB contamination in sturgeons of this study is lower or of the same order as those of Kajiwara et al. (2003). Kajiwara et al. (2003) have reported mean of 700–4900, 300–850, 390–400 and 170–310 ng g1 lipid wt. for H. huso, A. persicus, A. nudiventris and A. stellatus, respectively. Considering the large number of oil wells in Kazakhstan and Azerbaijan, and the resulting industrial effluents containing PCBs and wastewater from human activities (de Mora and Turner, 2004), these impacts might have been reflected in the OC levels in this study. On the other hand, Iran is located at the southern end of the Caspian Sea where there are few oil wells. Therefore, the PCBs concentrations were lower than those from the more industrialized regions as reported by Kajiwara et al. (2003). In the former USSR, technical PCB mixtures have been produced and used in both closed and open systems, such as capacitors, sealing paste additives and plasticizers, since the 1930s (Ivanov and Sandell, 1992). The PCB levels reported here were lower than those reported for other species living in areas with a wide industrial presence, such as the Berlin rivers (1050 ng g1 wet wt.) (Fromme et al., 1999), and in moderately polluted areas, such as the Vanajavesi River in Finland (852– 1740 ng g1 wet wt.) (Tulonen and Vuorinen, 1996). The bioconcentration of PCBs in aquatic organisms correlates with the degree of chlorination, the stereochemistry and lipophilicity (Bordajandi et al., 2003). Also, the chlorination pattern of the PCBs is important for the toxicity of the substance. Generally, congeners with high chlorination numbers are more difficult to metabolize and eliminate than the less chlorinated congeners (Yang et al., 2006). Of the congeners measured, PCB 138, 153 and 180 were the major contaminant congener in all samples (accounting for 26.5–30.5, 16.8–24.1 and 15.5–22.1 of the total PCB concentrations, respectively). This is not surprising since congeners 153 and 138 have a long half-life. These congeners have a particular biological interest, since they exhibit a considerable bioaccumulation starting at low trophic levels (Pruel et al., 1993) and they are toxic (Hong et al., 1998). This finding is in agreement with results reported for differ-
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
ent fish species from Marmara Sea (Coelhan et al., 2006) and the Adriatic Sea (Storelli et al., 2007). PCB 28, 52 and 101 were detected at lower concentrations following the order PCB 28 > PCB 52 > PCB 101. It is easier for lower chlorinated PCBs to pass through the body’s cell membranes than for higher chlorinated PCBs, which means that higher chlorinated PCBs have much stronger abilities of accumulation in fish samples (Bernes, 1998). As mentioned in above, because of the lipophilic nature, stability and persistence of the high chlorinated biphenyls, a higher rate of bioaccumulation is favored in studied fish than the low chlorinated ones (Borga et al., 2001). As it is known the biotransformation rate of PCBs is strongly affected by their degree of chlorination and by the position of the chlorine atoms on the biphenyl rings. The lack of unsubstituted adjacent-meta and -para positions on the biphenyl rings of the congeners 180, 153 and 138 enhance the resistance to metabolic attack by the cytochrome P450 iso-enzymes, which can metabolize the less chlorinated congeners (PCBs 28, 52 and 101) (Van den Brink and Bosveld, 2001). When considering the OCs in marine organisms suitable for human consumption, the most important aspect is their toxicity to humans. In this way, the European Union has set PCB standards with directive 1999/788/CE which permits a maximum content of 200 ng g1 lipid basis, calculated as the sum of the concentrations of the seven ‘‘target” congeners (PCBs 28, 52, 101, 118, 138, 153 and 180) in meat, poultry and derived products (Commission of the European Communities, 1999), but not in fish. In our study, as shown in Table 2, the mean PCB concentrations exceeded the above-mentioned limit. Furthermore, in Germany, a maximum residue limit exists for 6 individual PCB indicators (SHmV, 2003). For each PCB 138 and 153 congener, the maximum allowed concentration for marine fish is 100 ng g1 fresh weight, while the limit for PCBs 28, 52, 101 and 180 is 80 ng g1 fresh weight. On the basis of this, with the exception of the 138 congener, the other measured concentrations are clearly below these limits for all fish samples analyzed. There has been a European proposal to impose a limit of 8 pg TEQ/g fresh weight in fish, i.e., for the sum of the dioxins and dioxin-like PCBs (EC, 2005). For DDTs and HCHs, the residual concentrations are proposed as 2000 and 5000 ng g1 wet wt, respectively in China (Chen et al., 2002). The detected levels of DDTs and HCHs were below these guidelines in the present study. Over 60% of the total organochlorine contamination is due to the DDT components (Fig. 3). While the usage of DDTs in agriculture has been banned in Iran since 1983 (Çok et al., 1999), nothing is known about its illegal use. Another explanation may be inputs from the other countries around the Caspian Sea (Senthil-kumar et al., 2001). Confirmation of this assumption could be done by measuring the DDTs in local species at several points in the Caspian Sea. Taken as a whole, the organochlorine contamination in the sample analyzed was high, but it is significantly lower than in previous
977
samples (Kajiwara et al., 2003). Also, Wang et al. (2007) demonstrated a decline in PCB and DDT levels and a more recent decline in HCH levels in sturgeon caviar from the Caspian Sea. Still, it is not surprising to find declining trends in PCBs and DDT due to longstanding restrictions on the production, use and disposal of these compounds that started in the developed countries in the 1970s (Corsolini et al., 2006). Tanabe et al. (2003) showed decreases in contaminant concentrations in Caspian Sea seals (Phoca caspica) that were sampled in 1993 and 1998, with DDT, HCH, chlordanes, and coplanar PCBs decreasing by factors of 2.7, 1.8, 1.5, and 1.8, respectively, over this period. However, the HCH trends suggest the extensive and recent use of HCH in the Caspian Sea region (Watanabe et al., 1999). HCH bioaccumulation patterns also tend to differ from other OCs since this compound is relatively water soluble. 3.1. Biomonitoring Concentrations of persistent toxic substances in muscle reflect discharges of these substances into receiving waters, bioaccumulation through the food web, and chemical partitioning and breakdown kinetics in the sturgeon fish. Further, concentrations are affected by species, region, nutritive conditions, sex, age, and spawning/sampling season. For these reasons, concentrations of different contaminants can vary greatly within and among species. A study of sturgeon fish and caviar from the Caspian Sea in early 2002 and 2006 ranked OC concentrations as DDT > PCBs > HCH > HCB (Kajiwara et al., 2003; Wang et al., 2007). Similar patterns were found in the muscle of sturgeon. Despite the large concentration differences, biomonitoring using various species and tissues can successfully track contaminant trends in a region, often with good correlation between species. On the other hand, biomonitoring using muscle of fishes may not be effective for some contaminants, including OCs that may accumulate in other organs such as gonads, liver and kidney, and where levels may reflect physiological requirements of the species (Wirth et al., 2000). Acipenseriformes (an order of primitive ray-finned fishes that includes the sturgeons and paddlefishes, as well as some extinct families) typically are long-lived and migrating, thus monitored concentrations portray a mixture of current and historical conditions that may encompass a potentially large water area; possibly one that differs from the collection/harvest area. For example, H. huso migrates can forage along the Western Caspian Sea where high levels of agricultural contaminants are likely a different ecosystem (Wang et al., 2007). In contrast, A. stellatus migrates primarily along the eastern Caspian Sea, where the contaminant levels appear to be low, though data are lacking. Contaminant source areas cannot be identified due to the region’s lack of monitoring programs for contaminants in water, sediment, and biota.
Fig. 3. Composition of organochlorine pesticides in sturgeons (12 samples per each species) collected from the Caspian Sea.
978
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979
Additionally, comparisons across different species must account for age, diet, and other effects. Specifically, H. huso is at the top trophic level for Acipenseriformes. They eat primarily herring and anchovies, and have the longest life span (females typically mature at 15–20 years). In contrast, A. stellatus is lower on the trophic ladder, subsists on polychaetes (segmented bristleworms), and has a shorter lifespan (females mature in 8–14 years). A. persicus occupies an intermediate trophic position. The results show the significance of tropic level in the biomagnification of OC in muscle as has been seen in previous analyses as well as in this study (e.g., Kajiwara et al., 2003; Shokrzadeh and Ebadi, 2006). 4. Conclusions The concentrations of OCs for sturgeon are generally amongst the lowest values reported in the literature and reflect a cleaner environment in the Caspian Sea at this time in the Iranian waters. But the quantity of measured OCs in the studied sturgeon was high when it was compared with other fish in the other geographical regions. This shows that there is still some illegal usage of these toxic compounds in recent years, also indicates the serious contamination of OCs in the Caspian region. Particularly, very high concentrations of DDTs and PCBs in some specimens were observed, especially H. huso, which may be enough to cause adverse effects on this species and their population (Barannikova, 1999; Kajiwara et al., 2003; Pourkazemi, 2006). The results obtained in this work allow the conclusion that the concentration levels of the OCPs studied appear to be below the permissible limits for human consumption, established by legislation for other foods in most cases, although exceptions were noted. In summary, the Caspian Sea is a unique ecosystem confronted by a series of environmental stresses. For the most part the problems outlined here are not unique to the Caspian Sea, but have become intensified due to its land-locked nature. Unilateral solutions will not succeed in the long term and the five riparian states must cooperate to mitigate current, and prevent future, pollution. While the Caspian Sea region cannot yet serve as a successful model of international collaboration for environmental management and sustainable development, the establishment of the Caspian Environment Programme and recent openness between countries has allowed a better understanding of the environmental problems and a wide felt appreciation for what is at stake. The next, but not final, step will be the signing and ratification of the Framework Convention for the Protection of the Marine Environment of the Caspian Sea. Acknowledgements We sincerely thank to Prof. Barbara Rasco, from Department of Food Science, Washington State University, USA and Prof. Joe M. Regenstein from Department of Food Science, Cornell University, USA for critically reading the manuscript and making a number of helpful suggestions. We are also grateful to Mrs Haghdost for her assistance in measurements of OCs. References P Aguilar, A., 1984. Relationship of DDE/ DDT in marine mammals to the chronology of DDT input into the ecosystem. Can. J. Fish Aquat. Sci. 41, 840–844. Andersen, G., Kovacs, K.M., Lydersen, C., Skaare, J.U., Gjertz, I., Jenssen, B.M., 2001. Concentrations and patterns of organochlorine contaminants in white whales (Delphinapterus leucas) from Svalbard Norway. Sci. Total Environ. 264, 267–281. Barannikova, I.A., 1999. Sex steroids in the serum of Caspian sturgeon and their specific cytosol binding in brain and gonads during the migratory cycle. J. Appl. Ichthyol. 15, 193–195. Bernes, C., 1998. Persistent Organic Pollutants: A Swedish View of an International Problem. Swedish Environmental Protection Agency, Stockholm.
Billard, R., Lecointre, G., 2001. Biology and conservation of sturgeon and paddlefish. Rev. Fish Biol. Fisher. 10, 355–392. Bocio, A., Domingo, J.L., Falcó, G., Llobet, J.M., 2007. Concentrations of PCDD/PCDFs and PCBs in fish and seafood from the Catalan (Spain) market: estimated human intake. Environ. Int. 33, 170–175. Boon, J.P., Lewis, W.E., Tjoen-A-Choy, M.R., Allchin, C.R., Law, R.J., de Boer, J., ten Hallers-Tjabbes, C.C., Zegers, B.N., 2002. Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food web. Environ. Sci. Technol. 36, 4025–4032. Bordajandi, L.R., Gomez, G., Fernandez, M.A., Abad, E., Rivera, J., Gonzalez, M.J., 2003. Study on PCBs, PCDD/Fs, organochlorine pesticides, heavy metals and arsenic content in freshwater fish species from the river Turia (Spain). Chemosphere 53, 163–171. Borga, K., Gabrielsen, G.W., Skaare, J.U., 2001. Biomagnification of organochlorines along a Barents sea food chain. Environ. Pollut. 113, 187–198. Chen, W.Q., Zhang, L.P., Xu, L., Wang, X.H., Hong, L.Y., Hong, H.S., 2002. Residue levels of HCHs, DDTs and PCBs in shellfish from coastal areas of east Xiamen Island and Minjiang Estuary, China. Mar. Pollut. Bull. 45, 385–390. Çok, I., Karakaya, A.E., Afkham, B.L., Burgaz, S., 1999. Organochlorine pesticide contaminants in human milk samples collected in Tebriz (Iran). Bull. Environ. Contam. Toxicol. 63, 444–450. Coelhan, M., Strohmeier, J., Barlas, H., 2006. Organochlorine levels in edible fish from the Marmara Sea, Turkey. Environ. Int. 32, 775–780. Commission of the European Communities, 1999. EU commission decision 1999/ 788/EC of 3 December 1999 on protective measures with regard to contamination by dioxins of certain products of porcine and poultry origin intended for human or animal consumption. G.U. EU-L 310/62 of 04/12/1999. Corsolini, S., Covaci, A., Ademollo, N., Focardi, S., Schepens, P., 2006. Occurrence of organochlorine pesticides (OCPs) and their enantiomeric signatures, and concentrations of polybrominated diphenyl ethers (PBDEs) in the Ade´ lie penguin food web, Antarctica. Environ. Pollut. 140, 371–382. de Mora, S.J., Turner, T., 2004. The Caspian Sea: a microcosm for environmental science and international cooperation. Mar. Pollut. Bull. 48, 26–29. de Mora, S., Villeneuve, J., Sheikholeslami, M.R., Cattini, C., Tolosa, I., 2004. Organochlorinated compounds in Caspian Sea sediments. Mar. Pollut. Bull. 48, 30–43. Decreto Ministeriale 19 maggio, 2000. Maximume limite of pesticide residue in foods (Recepimento delle Direttive n. 97/41/CE, n. 1999/65/CE e n. 1999/71/CE). G.U. 207 del 05/09/2000 (in Italian). EC, 2005. Available at
S.V. Hosseini et al. / Chemosphere 73 (2008) 972–979 Muir, D., Savinova, T., Savinov, V., Alexeeva, L., Potelov, V., Svetochev, V., 2003. Bioaccumulation of PCBs and chlorinated pesticides in seals, fishes and invertebrates from the White Sea, Russia. Sci. Total Environ. 306, 111–131. Nakata, H., Hirakawa, Y., Kawazoe, M., Nakabo, T., Arizono, K., Abe, S., Kitano, T., Shimada, H., Watanabe, I., Li, W., Ding, X., 2005. Concentrations and compositions of organochlorine contaminants in sediments, soils, crustaceans, fishes and birds collected from Lake Tai, Hangzhou Bay and Shanghai city region, China. Environ. Pollut. 133, 415–429. Naso, B., Perrone, D., Ferrante, M.C., Bilancione, M., Lucisano, A., 2005. Persistent organic pollutants in edible marine species from the Gulf of Naples, Southern Italy. Sci. Total Environ. 343, 83–95. OSPAR, 2000. Quality Status Report 2000. OSPAR Commission, London. Pourkazemi, M., 2006. Caspian Sea sturgeon conservation and fisheries: past present and future. J. Appl. Ichthyol. 22, 12–16. Pruel, R.J., Rubenstein, N.I., Taplin, B.K., Livolski, J.A., Bowen, R.D., 1993. Accumulation of polychlorinated organic contaminants from sediments by three benthic marine species. Arch. Environ. Contam. Toxicol. 24, 290–297. Rajendran, R.B., Imagawa, T., Tao, H., Ramesh, R., 2005. Distribution of PCBs, HCHs and DDTs, and their ecotoxicological implications in Bay of Bengal, India. Environ. Int. 31, 503–512. Ruus, A., Ugland, K., Espeland, O., 1999. Organochlorine contaminants in a local marine food chain from Jarfjord, northern Norway. Mar. Environ. Res. 48, 131– 146. Sapozhnikova, Y., Zubcov, N., Hungerford, S., Roy, L.A., Boicenco, N., Zubcov, E., Schlenk, D., 2005. Evaluation of pesticides and metals in fish of the Dniester River, Moldova. Chemosphere 60, 196–205. Senthil-kumar, K., Kannan, K., Subramanian, A.N., Tanabe, S., 2001. Accumulation of persistent organochlorine pesticides and polychlorinated biphenyls in sediments, aquatic organisms, birds, bird eggs and bat collected from South India. Environ. Sci. Pollut. Res. 8, 35–47. SHmV (Schadstoff-Höchstmengenverordnung), 2003. Available at http:// bundesrecht.juris.de/shmv-2003/BJNR275500003.html. Shokrzadeh, M., Ebadi, A.G., 2006. Investigating and measurement of residues of chlorobenzilate (organochlorine pesticides) in four species of the most consumed fishes in Caspian Sea (Iran). Pak. J. Nutr. 5, 68–70.
979
Storelli, M.M., Barone, G., Garofalo, R., Marcotrigiano, G.O., 2007. Metals and organochlorine compounds in eel (Anguilla anguilla) from the Lesina lagoon, Adriatic Sea (Italy). Food Chem. 100, 1337–1341. Sudaryanto, A., Monirith, I., Kajiwara, N., Takahashi, S., Hartono, P., Muawanah, Omori, K., Takeoka, H., Tanabe, S., 2007. Levels and distribution of organochlorines in fish from Indonesia. Environ. Int. 33, 750–758. Szlinder-Richert, J., Barska, I., Mazerski, J., Usydus, Z., 2008. Organochlorine pesticides in fish from the southern Baltic Sea: levels, bioaccumulation features and temporal trends during the 1995–2006 period. Mar. Pollut. Bull. 56, 927–940. Tanabe, S., Niimi, S., Minh, T.B., Miyazaki, N., Petrov, E.A., 2003. Temporal trends of persistent organochlorine contamination in Russia: a case study of Baikal and Caspian Seal. Arch. Environ. Contam. Toxicol. 44, 533–545. Tulonen, J., Vuorinen, P.J., 1996. Concentrations of PCBs and other organochlorine compounds in eels (Anguilla anguilla L) of the Vanajavesi watercourse in southern Finland, 1990–1993. Sci. Total Environ. 187, 11–18. Tüzen, M., 2003. Determination of heavy metals in fish samples of the middle Black Sea (Turkey) by graphite furnace atomic absorption spectrometry. Food Chem. 80, 119–123. Van den Brink, N.W., Bosveld, B.T.C., 2001. PCB concentrations and metabolism patterns in common terns (Sterna hirundo) from different breeding colonies in The Netherlands. Mar. Pollut. Bull. 42, 280–285. Wang, W., Batterman, S., Chernyak, S., Nriagu, J., 2007. Concentrations and risks of organic and metal contaminants in Eurasian caviar. Ecotoxicol. Environ. Saf. doi:10.1016/j.ecoenv.2007.06.07. Watanabe, M., Tanabe, S., Tatsukawa, R., Amano, M., Miyazaki, N., Petrov, E.A., Khuraskin, S.L., 1999. Contamination levels and specific accumulation of persistent organochlorines in Caspian Seal (Phocacaspica) from the Caspian Sea, Russia. Arch. Environ. Contam. Toxicol. 37, 396–407. Willett, K.L., Ulrich, E.M., Hites, R.A., 1998. Differential toxicity and environmental fates of hexachlorocyclohexane isomers. Environ. Sci. Technol. 32, 2197–2207. Wirth, M., Kirschbaum, F., Gessner, J., Krüger, A., Patriche, N., Billard, R., 2000. Chemical and biochemical composition of caviar from different sturgeon species and origins. Nahrung 44, 233–237. Yang, N.Q., Matsuda, M., Kawano, M., Wakimoto, T., 2006. PCBs and organochlorine pesticides (OCPs) in edible fish and shellfish from China. Chemosphere 63, 1342–1352.