Environ. Sci. Techno/. 1995, 29, 2673-2683
Accumulation Features of Organochlorine Residues in Fish in Tropical Asia and Oceania KURUNTHACHALAM KANNAN,* SHINSUKE TANABE, AND RYO TATSUKAWA Department of Environment Conservation,Ehime University,
Tarumi 3-5-7, Matsuyama 790, Japan
Concentrations of persistent organochlorine residues were determined in fish collected from several locations in eastern and southern Asia and Oceania to identifythe accumulation features of such residues in tropical aquatic organisms and to elucidate their distribution in tropical developing countries. DDT and its derivatives (DDTs) were the predominantly identified compounds in most locations. In general, the concentrations of organochlorines in tropical fish were lower than those in fish of the temperate regions. Residue levels in fish showed little spatial variability, as reported for tropical sediments. This is different from the patterns observed for air and water in which higher concentrations occur in tropical latitudes compared t o mid-latitudes. Compilation of limited available data on the organochlorine residue levels in fish in tropical Asian countries seemed to indicate little temporal variability due to the low levels of accumulation in aquatic organisms, despite the continuous use of these compounds. A short residence time of semivolatile organochlorines in the tropical aquatic environment results in lower levels of accumulation of residues in fish. Examination of walleye pollock (Theragra chalcogramma) collected from the Bering Sea indicated that organochlorine residue levels are declining in temperate water bodies near the Arctic Ocean in recent years.
Introduction The occurrence of high concentrations of organochlorine compounds such as HCHs (HCH isomers),DDTs (DDTand its derivatives), chlordanes, and PCBs in the Arctic ecosystem, despite the ban on many of these compounds in most of the industrialized nations of the Northern Hemisphere, has prompted the need to identify possible emission sources (1-5). Investigations conducted by numerous * Corresponding author present address: Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah,GA31411; e-mail address:
[email protected]; fax: (912)-596-2310; telephone: (912)-598-2306.
0013-936x/95/0929-2673$09.00/0
D 1995 American Chemical Society
researchers during the last decade have revealed that midand low-latitude countries,particularly those in the tropical region, are possible sources of contamination in the Arctic in recent years (6-10). This concept is supported by the high current consumption of organochlorinepesticides in tropical developing countries, enhancing food production, and eradicating vector-borne diseases (11-14). In order to analyze the role of tropical developing countries as possible emission sources of organochlorines,it is necessary to elucidate the distribution, behavior, and fate of these compounds in various environmentalcompartments. Our earlier studies showed the widespread occurrence of organochlorinesin air,water, sediment (13,soil ( l a ,and foodstuffs (17-21)in tropical countries ofAsia and Oceania. The determinationof organochlorine concentrations in fish may indicate the extent of aquatic contamination and the accumulation characteristics of these compounds in tropical aquatic biota. In this study, we attempted to elucidate the geographical distribution of organochlorine residues in fish collected from certain countries in Asia and Oceania. Existing information on organochlorineconcentrations in aquatic biota of developing Asian countries was compiled to understand trends in such levels and to establish baseline informationfor the ongoing Mussel Watch Program in Asia (13,221. The geographical distribution and the concentrations of organochlorinesin fish are compared here with those reported in air, water, and sediments to elucidate their partitioning behavior in various environmental matrices. Further, the residue levels of organochlorines in fish are compared with those reported in several tropical and temperate regions to elucidate the present status of contaminationin Asia on global terms. In addition, walleye pollock (Theragrachakogramma)collected from the Bering Sea in 1992 were analyzed to identify the current status of organochlorine contamination in the remote subarctic region.
Materials and Methods Collection of Samples. One hundred and fifty samples of fish were collected from various urban and suburban areas in eastern and southern Asia (India, Thailand, Vietnam, Indonesia, Papua New Guinea, and the Solomon Islands) and in Australia. Fish were obtained from research institutions and seafood shops or were caught specifically for this survey during 1989- 1993. The samplinglocations are shown in Figure 1. Similarly, fish were collected in the Bering Sea during a cruise in June-July 1992. Only the muscle tissue was used for analysis. In most cases, three specimenswere collected from each species and analyzed. Wherever possible, several specimens were pooled to obtain a single sample. Most fish collected were coastal marine species, while a few were freshwater species. Details of fish species collected are summarized in Table 4, in the supporting information. More information on the fish species is described elsewhere (17,19-21).Fish collected from the Bering Sea during June-July 1992 were three specimens of walleye pollock (Theragra chalcogramma). Whole fish were dissected, and the muscle was preserved in 10%formalin, transported to Japan, and stored at 4 "C prior to analysis. The preservation of tissues in 10% formalin did not alter the concentrations of organochloVOL. 29, NO. 10, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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ranged from 95 to 105%. Reported concentrations were not corrected for the recovery percentage. The detection limit was 0.01 nglg for all organochlorines,except 0.1 ng/g for aldrin and dieldrin. A procedural blank was run with every set of five samples to check for contamination from solvents and glassware.
Results a d Discussion
FIGURE 1. Map showing the sampling locations of fish fmmtropical Asia and Oceania.
rines. Muscle was removed prior to analysis, and the formalin was air-dried. ChemicalAnalysis. Organochlorine pesticides and PCBs were analyzed according to the method described elsewhere (19). The method consists of extraction with mixed solvents of diethyl ether (300 mL) and hexane (100 mL) using a Soxhlet apparatus for 7 h. Fat content was determined from the K-D (Kuderna-Danish) concentrated aliquots of these extracts. The remaining extractswere then transferred to a glass column packed with 20 g of Florisil (FloridinCo.), followed by elution with a mixture of 150 mL of 80% acetonitrileand 20%hexane-washedwater. The eluate from the Florisil column was collected in a separating funnel containing 100mLof hexane and 600 mLof hexane-washed water. After thorough shaking and partitioning, the concentrated hexane layer was K-D concentrated and fractionated by passing through 2 g of silica gel Wako gel $1) packed in a glass column (12 mm i.d.1. The first fraction eluted with 160 mL of hexane contained HCB, PCBs, p,p'DDE, and aldrin. The second fraction eluted with 20% dichloromethane in hexane (100 mL vlv) comprised the HCHisomers (a-,B-,y-,andd-),p,p'-DDD, p,p'-DDT,o,p'DDT, and dieldrin. Chlordanes (trans-chlordane, cischlordane, trans-nonachlor, cis-nonachlor, and oxychlordane) were distributed in both fractions and were calculated by summing the peaks identified in the first and second fractions. Eachfraction was concentrated, and after retaining 1 mL for the quantification of aldrin and dieldrin, the extracts were subjected to a further clean up with 5% fuming sulfuric acid in concentrated H2S04. Quantification of organochlorineswas made on a gas chromatograph (Hewlett-Packard5890 Series 11) equipped with a 63Nielectron capture detector and moving needletype injection port. Fused silica capillary columns (30 m x 0.25 mm i.d.1 coated with DB-1 (100%dimethyl polysiloxane) and DB-1701 (14% cyanopropylphenyl and 86% dimethyl polysiloxane) having a film thickness of 0.25 pm U&W Scientific, Folsom, CA) were used for the determination of PCBs and organochlorine pesticides, respectively. The column oven temperature was programmed from 160 to 240 "C at a rate of 2 "Clmin, with a final hold of 20 min. The injector temperature was kept at 280 "C while the detector temperature was 300 "C. Helium was used as a carrier gas, and nitrogen was the makeup gas. Recoveries of organochlorinesby this method with fortified samples 2674
ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 10,1995
Residue concentrationsand the contamination patterns of organochlorines in fish varied between as well as within the country of origin (Table 1). In general, DDT concentrations were the highest in fish from allthe southeast Asian countries (Thailand, Vietnam, and Indonesia), while both HCH and DDT constituted the dominant organochlorines in Indian fish. The contamination pattern in Australian fish was different from those observed in Asian countries, with the highest concentrations of PCBs followed by chlordanes. The concentrations of HCB were uniformly low in fish from all the countries studied. PCBs. Concentrationsof PCBs in fish from tropical Asian countries were low, ranging from 0.38 to 110 ng/g wet wt. Vietnamese fish contained relatively higher concentrations of PCBs than those of other Asian countries. The reason for the elevated concentrations of PCBs in Vietnam is not clear. Electrical equipment containing PCBs (e.g., transformers) were imported in Vietnam from Australia until the mid-1980s (23). High concentrations of PCBs in soils from U.S.army bases and in street dust collected inVietnam also suggested the use of PCBs in artilleryand other chemical weapons duringthe second Indo-Chinese war, which lasted from 1961to 1971 (16). PCB concentrations in Indian fish were relatively low, except for a scombrid fish collected in New Delhi containing 110 ng of PCBslg wet wt. A pooled sample of mud-frequenting fish (Chela Zuubucu, Colisu fusciutus, Mustucembelus panculus, and Puntius sophore) collected from the Ganges River, Patna, contained 20 ng of PCBslg wet wt. Earlier studies showed that the concentrations of PCBs in the blubber of Ganges River dolphins (PZutunistugungeticu) collected in India were in the range of 360-620 nglg wet wt (24, 2 3 , some 1-2 orders of magnitude lower than those observed in cetaceans inhabiting the coastal marine regions of developed nations (26). Several species of market fish collected in Bangladesh contained PCB concentrations ( ~ 2 nglg 0 wet wt) lower than those reported for fish from other Asian countries (27). These results indicate that the environmental contamination by PCBs in developing Asian countries is minimal. An interesting divergence with respect to PCB contamination is seen in Hong Kong and Taiwan, two of the relatively more developed and newly industrialized countries in Asia. Green mussels (Perna viridis) collected in Junk Bay, Hong Kong, contained PCB concentrations in the range of245-1670nglgdrywtwithahigherproportion of lower chlorinated members, suggesting the presence of recent inputs (28). Roadside soils collected from Taipei, Taiwan, contained much higher concentrations of PCBs (up to 960 nglg dry wt) than those in similar samples from other Asian countries (16). Transformers and capacitors are consideredas the major sources of PCBs in developing Asian countries. It has been reported that developing countries hold 15%of the total PCB stock in the world (29). Rapid industrialization might elevate the contamination levels for PCBs in the Asian countries unless safe disposal measures are taken.
TABLE 1
Range (in Parentheses) and Mean Concentrations of Organochlorines (ndg Wet Wt) in Fish from Tropical Asia and Oceanie country
no.
fat (Yo)
PCBs
DDTs
HCHs
aldrin and dieldrin
CHLs
HCB
India
48
Thailand
17 19
3.5 (0.38-110) 1.6 (0.8-2.7) 10 (3.1-24) 2.6 (2-3.8) 7.5 (0.8-16) 3.6 (0.66-15) 55 (0.22-720)
15 (0.86-140) 6.2 (0.48-19) 26 (3.9-76) 28 10.66-76) 0.43 (0.07-1.4) 4.8 (0.91-24) 22 (0.14-230)
28 (0.48-380) 0.82 (0.22-1.8)
Vietnam
2.4 (0.11-12) 5.3 (0.70-17) 1.9 (0.61-8.0) 3.0 (1.3-6.6) 0.68 (0.2-1.5) 0.68 (0.16-3.0) 3.4 (0.14-20)
3.1 (
