Environ. Sci. Techno/. 1995, 29, 2673-2683

Accumulation Features of Organochlorine Residues in Fish in Tropical Asia and Oceania K U R U N T H A C H A L A M K A N N A N , * S H I N S U K E T A N A B E , A N D R Y O T A T S U K A W A 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 to 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 (DDT and its derivatives), chlordanes, and PCBs in the Arctic eco- system, despite the ban on many of these compounds in most of the industrialized nations of the Northern Hemi- sphere, 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: kannan@skio.peachnet.edu; fax: (912)-596-2310; tele- phone: (912)-598-2306.

researchers during the last decade have revealed that mid- and 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 organochlorine pesticides 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 environmental compartments. Our earlier studies showed the widespread occurrence of organochlorines in air, water, sediment (13, soil (la, and foodstuffs (1 7-21) in tropical countries ofAsia and Oceania. The determination of organochlorine concentrations in fish may indicate the extent of aquatic contamination and the accumulation characteristics of these compounds in tropi- cal 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 organochlorine concentrations in aquatic biota of developing Asian countries was compiled to understand trends in such levels and to establish baseline information for the ongoing Mussel Watch Program in Asia (13,221. The geographical distribution and the concentra- tions of organochlorines in fish are compared here with those reported in air, water, and sediments to elucidate their partitioning behavior in various environmental ma- trices. 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 contamination in Asia on global terms. In addition, walleye pollock (Theragra chakogramma) 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 sampling locations 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 specimens were 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 (1 7,19-21). 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 organochlo-

0013-936x/95/0929-2673$09.00/0 D 1995 American Chemical Society VOL. 29, NO. 10, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 2673

40' N 1

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.

Chemical Analysis. 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 extracts were then transferred to a glass column packed with 20 g of Florisil (Floridin Co.), followed by elution with a mixture of 150 mL of 80% acetonitrile and 20% hexane-washed water. The eluate from the Florisil column was collected in a separating funnel containing 100 mLof hexane and 600 mLof hexane-washed water. After thorough shaking and partitioning, the con- centrated hexane layer was K-D concentrated and frac- tionated 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, cis- chlordane, trans-nonachlor, cis-nonachlor, and oxychlo- rdane) 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 organochlorines was made on a gas chromatograph (Hewlett-Packard 5890 Series 11) equipped with a 63Ni electron capture detector and moving needle- type injection port. Fused silica capillary columns (30 m x 0.25 mm i.d.1 coated with DB-1 (100% dimethyl polysi- loxane) 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 determi- nation 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 organochlorines by this method with fortified samples

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 Residue concentrations and the contamination patterns of organochlorines in fish varied between as well as within the country of origin (Table 1). In general, DDT concen- trations were the highest in fish from all the 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. Concentrations of 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., trans- formers) 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 artillery and other chemical weapons during the second Indo-Chinese war, which lasted from 1961 to 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 concentra- tions of PCBs in the blubber of Ganges River dolphins (PZutunistu gungeticu) collected in India were in the range of 360-620 nglg wet wt (24, 23 , some 1-2 orders of magnitude lower than those observed in cetaceans inhab- iting the coastal marine regions of developed nations (26). Several species of market fish collected in Bangladesh contained PCB concentrations ( ~ 2 0 nglg wet wt) lower than those reported for fish from other Asian countries (27). These results indicate that the environmental con- tamination 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 considered as 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.

2674 ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 10,1995

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 2.4 3.5 15 28 3.1 2.4 0.07

Thailand 17 5.3 1.6 6.2 0.82 3.7 2.6 0.24

Vietnam 19 1.9 10 26 1.8 0.29 0.1 1 0.05

Indonesia 5 3.0 2.6 28 0.73 1.2 0.45 0.05

PNG 13 0.68 7.5 0.43 0.57 1.3 0.37 0.03

SI 10 0.68 3.6 4.8 0.53 0.32 0.57 0.02

Australia 37 3.4 55 22 0.34 10 51 4.2

(0.11-12) (0.38-110) (0.86-140) (0.48-380) (<0.1-15) (<0.01-30) (<0.01-0.55)

(0.70-17) (0.8-2.7) (0.48-19) (0.22-1.8) (0.97-9.6) (0.1 -15) (0.01-2.1)

(0.61 -8.0) (3.1 -24) (3.9-76) (0.58-4) (<O*I- l . l ) ( <0.01-0.35) (0.01 -0.31)

(1.3-6.6) (2-3.8) 10.66-76) (0.06-1.4) (cO.1-2.3) (0.24-0.69) (0.01 -0.08)

(<0.01-2.1) (<0.01-0.05) (0.2-1.5) (0.8-16) (0.07-1.4) (0.18-1.6) (0.1 -3.0)

(0.16-3.0) (0.66-15) (0.91-24) (0.23-1.9) (0.1-1.6) (0.11-1.6) (0.01-0.06)

(0.14-20) (0.22-720) (0.14-230) (<0.01-2.1) (0.12-55) (0.06-720) (<0.01-60)

DDTs: p,p’-DDT + p,p’-DDE + p,p’-DDD + o,p’-DDT. HCHs: a- + B- + y- + &isomers. Chlordanes = cischlordane + trans-chlordane + cis- nonachlor + tfens-nonachlor + oxychlordane.

In contrast to those in Asian developing countries, the concentrations of PCBs in Australian fish were high, ranging from 0.22 to 720 ng/g wet wt. The wide range of values indicates the presence of specific sites of contamination. Details regarding the spatialvariation in PCB concentrations are discussed later. The PCB concentrations recorded in Australian fish were comparable to those reported in fish from Japan (30,31), which leads the Asian region as a whole in industrialization. Like Australia, coastal regions of New Zealand have been shown to experience fresh inputs of PCBs (32). It is estimated that over 1000 t of PCBs were imported and consumed in Australia during 1971-1980, and approximately 900000 L was in use in electrical installations in 1974 (23). Considering an average lifetime of 30 years for large transformers and capacitors and that PCBs were used in Australia until 1980, it is presumed that PCB-containing wastes will continue to be generated in Australia in the future. Comparison of the concentrations of PCBs in fish samples with those of earlier reports may indicate a slowly declining trend in PCB pollution in Australian aquatic environments. Details regarding PCB contamination in Australia and New Zealand have been summarized in earlier reports (33-33.

DDTs. Invariably elevated levels of DDTs in fish from tropical Asian countries suggest its continued use in malaria eradication programs. The major considerations in the case for continuing DDT for anti-malaria spraying have been its cheapness, effectiveness, and durability. Debate persists concerning the advantages or phasing out of DDT use in malaria vector control (36, 37). A few developing countries that once banned DDT have recently started using it again because of increased outbreaks of malaria after the ban (38, 39).

In Asia, Japan and Korea prohibited the use of DDT in the 1970s (40). Although DDT was reported to have been banned in Taiwan in the 1970s, mussels and sediments collected in 1980- 1982 contained remarkably higher proportions of p,p’-DDT than its metabolites (41). Restric- tions were imposed on DDT production in China in 1983 (421, but its use in recent years is not clear. DDT concentrations in mussels from Junk Bay, Hong Kong, were up to 2 pglg dry wt with high amounts of unmetabolized DDT, suggesting that its utilization in Hong Kong and/or China persisted until the late 1980s (28). Similarly, in

Indonesia, high concentrations of DDT (700 ng/g wet wt) with an elevated proportion of p,p’-DDT were noted in carp muscle collected near DDT-sprayed sites in the early 1990s (43). In Thailand, about 110 t of DDT was used for malaria vector control in 1990 (44). The prevalence of p,p’- DDT (the technical mixture of DDT contains 80% p,p’- DDT and 20% o,p’-DDT) in meat products collected from Thailand (1 7) and Vietnam (20) suggested the application of DDT near cattle sheds, which are common breeding sites of mosquitoes. In fish, p,p’-DDE comprised ‘40% of CDDT levels, while p,p’-DDT occupied 5-35% of the CDDT in Asia and Oceania (Figure 2). It is also worth noting that the DDT concentrations in fish from tropicalhian countries were 1-2 orders of magnitude lower than those reported in temperate developed nations at the time of maximum usage of this compound.

Concentrations of DDT in fish from Australia were comparable to or higher than those in fish from tropical Asian countries. Although the use of DDT has been banned inAustraliasince 1981 (211, runoff from soils contaminated heavily by the extensive use of DDT in the past continues to be a major source of this contaminant to the aquatic ecosystem (451.

HCHs. Concentrations of HCHs were relatively low in fish from all the countries except India. a-HCH was the predominant isomer in fish from India and Thailand, while P-HCH constituted a major proportion of total HCH in fish from Vietnam, Papua New Guinea, and Australia (Figure 2). The predominance of a-HCH in some samples reflects the use of a technical mixture of HCH containing 55-70% a-, 5-14%/3-, 10-18% y-, and 6-10% b-isomer. Fish from Indonesia and the Solomon Islands contained higher percentages of y-HCH, suggesting the use of lindane (purified y-HCH) in these countries. Recent reports have indicated the use of lindane in Malaysia (4@, Indonesia (47), and Vietnam and the Solomon Islands (11).

The use of technical HCH in India is well-documented (19), while it is reported to be banned in Thailand in 1980 (1 7). The annual consumption of technical HCH in Pakistan in 1982 was 138 t (48). Among Asian countries, HCH was used extensively in Japan with the cumulative consumption of 400 000 t until the early 1970s (311, and annual usage of HCH in China in the late 1970s was 20 000 t (40).

VOL. 29, NO. IO, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 2675

DDT p,p'-DDD

DDT

India

Thai I and

Vietnam

SI

Australia

0

HCH s

India

Thailand

Vietnam

Indonesia

PNG

SI

Auclralia

0 2n 40 60 SO 100

Composition (%)

FIGURE 2. Compositions of DDT compounds and HCH isomen in fish from tropical countries in Asia and Oceania.

In spite of the use of HCH in southeast Asian countries until at least the 1980s and in recent years in India, the residue levels in fish were low, illustrating the rapid volatilization of HCH isomers in tropical latitudes. De- scriptions regarding the behavior of HCH and DDT in the tropical environment are providedlaterinthis paper, based on their distribution in various environmental compart- ments.

Generally, the contamination pattern of HCH and DDT infishretlectsthepresenttrendsoftheuusageindeveloping Asian countries. Greater concentrations of HCHs than DDTs in Indian fish, despite the higher bioaccumdation potential of the latter, were due to the increased consump- tion of HCH rather than DDT. The annual use of HCH in India amounted to 45 000 t and that ofDDT totaled 19 000 t during the mid-1980s (49). While the consumption of HCH is predominantly for agricultural purposes, 85% of the total DDT usage is for malaria vector control. Earlier studies showed the predominance of HCHs over DDTs in human breast milk (50). foodstuffs (19). and wildlife (51) collected from southern India. In contrast, DDTs were relativelymoreabundant thanHCHsinfishfromThailand. Vietnam, Indonesia, and other southeast Asian nations, including China (52,531, Hang Kong (54), and Taiwan (41). suggesting DDT usage in recent years.

Cyclodiene Compounds (Aldrin, Dleldrin, and Chlor- danes). Concentrations of aldrin and dieldrin in fish were

low despite their use in recent years for the control of crop pests in India and Pakistan (191, Thailand (17). Malaysia (46),IndonesiaandthePhilippines (59, andasatermiticide inAustralia (21). Similarly, the concentrations of chlordanes were low in fish from all the Asian countries. Information pertaining to the production and usage of chlordanes in developing Asian countries is sparse. Velsicol Chemical Corporationis the majorproducerofchlordane, amounting to 70000 t during 1946-1988 (56). While the use of chlordanes was banned in the United States in 1988, over 280 t of heptachlor and 10 t of chlordanes were exported to Australia between 1987 and 1989. Chlordane has been reported to be the predominant organochlorine insecticide in the aquatic environment ofthe United States (57), Japan (31). and Newzealand (58). Theincreasing concentrations of chlordanes in the Antarctic in recent years suggest that Australia may be an important source of these compounds to the south pole region. HCB. Pollution by HCB in fish is minimal in developing

Asian countries, suggesting limited use of this compound in the region. The existing HCB levels in fish might reflect contamination of pesticide formulations, which contain small amounts of HCB as an impurity. HCB is also a byproduct of various chlorination processes and the combustion ofindustrialproducts, whichmight constitute asourcetotheenvironment. However, HCBhasthehighest Henry'slawconstant (HI andvaporpressureofallthemajor organochlorines andis likelyto volatilize rapidly in tropical regions (59). It is notable that HCB is one of the major organochlorines detected in Arctic air and seawater (6).

Spatial Variation in Organochlorine Concentrations. In India, fish collected in New Delhi and Bombay contained higher levels of ZDDT than ZHCH (Table 2). DDT was the predominantcompoundinhumanbreastmilkfromcotton growing areas in Punjab, India (60). Similarly, dairy milk collected in and around New Delhi contained DDT concentrations that were double those of HCH (61). By contrast, fish from Calcutta and Porto Novo recorded an increased prevalence of HCHs as compared to DDTs. Humanandwildlife samples collected frompaddygrowing areas in southern India (predominantly Porto Novo and its environs) also exhibited an increased abundance of HCH rather than DDT (19,50,51). Generally, paddy areas are considered to be predominated by HCHs, while DDT is more abundant than HCH in cotton growing and urban areas. The concentrations of DDT observed in Indian fish liewithinthe rangemeasuredearlierforeast andwestcoast aquatic organisms in India (62, 63). Fish collected from the Jamuna River in New Delhi in 1976-1978 contained high concentrations of DDT (up to 56 pg/g wet wt in the muscle), as the river received direct discharges of DDT from manufacturing factories (64). Fish collected in the Mahala water reservoir in northern India in 1987 had a maximum DDT concentration of 1.8 pg/g wet wt (65).

The concentrations of DDT in fish from Bangkok were ~ 2 0 ng/g wet wt (Table 2), falling within the lower end of the range of values reponed for Thai coastal organisms in 1987 (66) and 1975 (67).

Similarly, the concentrations of PCBs and DDT in fish from Indonesia were lower than those reported in 1984 (47). PCB and DDT concentration ranges in fish collected from Malaysian coastal waters in 1977 were 20-40 and 3-50ng/gwetwt, respectively(68), whilemusselssampled in 1979containedlevelsof 100-600and4-17ng/gdrywt, respectively (69). Concentrations of DDT in Malaysian

2676 m ENVIRONMENTAL SCIENCE &TECHNOLOGY i VOL. 29. NO. 10,1995

TABLE 2

Spatial Variation in Oqanochlorine Concentrations (ng/g Wet Wt) in Fish from Various locations in Tropical Asia and Oceanie -

location

New Delhi

Bombay

Calcutta

Patna Port0 Novo

Bangkok

Hanoi

Phu Da

Ho Chi Minh

Bogor

Port Moresby

Honiara

Sydney

Brisbane

Hobart

Perth

Townsvil le

Atherton

no.

7

6

6

1 [41 28

15

7

6

6

5

13

10

10

6

6

6

6

3

PCBs

23 (0.77-110) 3.3

(0.38-6.8) 3.4

(1.6-9.5) 20

2.8 (0.7-7.6) 1.6

(0.8-2.7) 11 (5.2-18) 12 (3.1 -24) 18 (3.7-59) 2.6

(2.0-3.8) 7.5

(0.8-16) 3.6

(0.66-15) 140

(5.8-720) 32 (1.7- 100) 21 (7.9-48) 1.7

(0.27-4.9) 2.4 (0.22-6.7) 7.6

(7.0-8.5)

DDTs

8.2 (1.6-27) 44 (6.1 -140) 18 (4.2-62)

160 7.6

(0.86-75) 6.2

(0.48-19) 36

(13-76) 20 (3.9-52) 21 (1.7-78)

28 (0.66-76) 0.43

(0.07-1.4) 4.8

(0.91 -24) 51 (1.3-230)

23 (0.74-100) 3.5

(1 -6-6.6) 2.3

(0.18-5.5) 0.49

(0.14- 1.3) 0.47

(0.41 -0.56)

HCHs

5.5 (2.8-8.9) 23 (2.2-49) 73 (4.6-380) 77 40 (0.48-150) 0.82

(0.22-1.8) 2.3

(0.89-4.0) 0.92

(0.6-1.4) 2.0

(0.63-3.8) 0.73

(0.06-1.4) 0.57

(0.18-1.6) 0.53

(0.23-1.9) 0.57

(<0.01-2.1) 0.46

(0.07- 1.3) 0.23

(0.09-0.5) 0.12

(0.04-0.18) 0.12

(<0.01-0.25) 0.02

(<0.01-0.04)

aldrin and dieldrin

4.9 (1 .O-15) 1.2

(0.5-2.0) 1.8

(0.37-3.0) 5.4 1.2

3.7 (0.97-9.6) 0.36

(0.12-0.8) 0.29

(<0.01-0.53) 0.31

(0.12-0.51) 1.2

(<0.1-2.3) 1.3

(0.1-3.0) 0.32

(0.1 -1.6) 19 (1.5-46) 15 (1.5-49) 2.9

(1.7-5.8) 2.3

(0.78-3.8) 0.73 (0.12-2.9) 2.9

(2.7-3.3)

(<0.1-2.0)

a Numbers in parentheses ( ) indicate the range. Numbers in brackets [ 1 indicate the number of samples pooled.

CHIS

0.79 (0.14-2.1) 1.2

(0.47-2.2) 0.21

<0.01-0.27) 30

<0.01-0.34) 0.19

2.6

0.15 <0.01-0.33)

0.17 (<0.01-0.23)

0.06 (<0.01-0.35)

0.45 (0.24-0.69) 0.37

0.57

(0.1 -15)

(‘0.01 -2.1)

(0.1 1-1.6)

(4.0-720) 4.8

(0.16- 18) 13 (5.3-25) 0.38

(0.06-0.78) 0.30

(0.06-0.53) 0.21

(0.13-0.27)

150

waters are still higher than the critical limit of 4 nglL as specified by the Malaysian Interim Standards for Aquatic Life (46).

In Vietnam, the spatial variation in organochlorine concentrations in fish was small, exhibiting comparable values in Hanoi (the north), Phu Da (central), and Ho Chi Minh (the south) (Table 2). Information pertaining to organochlorine contamination in China is not clear. Concentrations of DDT in aquatic foods in China were in the range of 10-450 nglg wet wt, comparable to or higher than those observed in fish from India. HCH levels in Chinese aquatic biota were between 4.9 and 14 nglg wet wt, similar to those in other southeast Asian countries, but lower than those in India (53).

Based on these data, DDT levels appear to have declined with time in tropical Asian fish, while the temporalvariability of other organochlorines is small. The limited monitoring data in the past and the low accumulation in tropical organisms might explain the reason for minor temporal variability.

The regional difference in PCB concentrations in Aus- tralia suggested that fish samples collected from Sydney, Brisbane, and Hobart contained relatively higher concen- trations than those from rural areas (such as Townsville and Atherton; see Table 21, implying that most PCB contamination in Australia is associated with large urban areas. Fish samples in particular collected from Sydney [including snapper (22-34 nglg wet wt), rubberlip morwong

(99-100 nglg), blue groper (720 nglg), and shovelnose ray (5.8-160 nglg)] recorded high concentrations of PCBs. In contrast, the concentrations of chlordanes in fish collected across the various Australian locations were generally comparable (except for fish samples from Sydney, where the levels were high), indicating the widespread use of chlordanes. DDT and dieldrin concentrations were higher in fish from Sydney and Brisbane than in those of other locations.

Distribution and Partitioning of Organochlorines. The spatial differences for organochlorine levels in fish suggested the presence of elevated levels of HCHs in India and chlordanes in Australia (Figure 3). The concentrations of PCBs, DDTs, and dieldrin in fish showed relatively smaller geographical Variability (Figure 3). Higher concentrations of these chemicals tend to be found only in areas of current intensive use (Le., HCHs in certain locations in India and chlordanes in parts of India and Australia). In general, the spatial variations in organochlorine concentrations in fish were relatively smaller than those observed for air and water (15). The pattern of geographical variation in organochlo- rines in fish is similar to that observed for sediments collected in this region (sediments were taken from almost the same locations where fish were collected) (15). In contrast, air and water samples contained elevated con- centrations of DDTs and HCHs in tropical latitudes than in subtropical and temperate latitudes. This distribution pattern results from the short detention time of orga-

VOL. 29, NO. 10, 1995 / ENVIRONMENTAL SCIENCE &TECHNOLOGY 2677

(0.N

20'

0'

FIGURE 3. Mean concentrations of organochlorine compounds in fish collected from several locations in eastern and southern Asia and Oceania.

nochlorines in tropical water bodies, leaving less residues temperature is one of the causes for the low levels of in sediment and aquatic biota. Although an elevated I semivolatile organochlorines in tropical sediments and fish,

2678 ENVIRONMENTAL SCIENCE TECHNOLOGY i VOL. 29, NO. i o , 1995

TABLE 3

Comparison of Concentrations of Organochlorines in Various Environmental Compartments in India (TrepicaP), Australia (Subtropical), and the Bering Sea (Temperate) during 1988-1932*

media units HCHs CHLs DDTs PCBs

air [71

water [81

agriculture soil [321

sediment [61

f ish 1481

air [4]

water [201

agriculture soil [211

sediment [I91

f ish [371

air [51

water [41

sediment (11 fish [31

India (1908-1S9) 1 580 000 4100 (13-11 x IO') (5.7-20 000) 226 000 760 (6200-660 000) (c8.0-2800) 2800 NAC (5.6-86 000) 12 31 (0.58-38) (0.47-130) 28 2.4 (0.48-380) (<0.01-30)

520 300 (350-900) (30-650) 360 280 (79-820) (<6.0-1200) 5.0 21 (0.05-38) (<0.01-240) 1.6 20 (0.02-17) (0.17-230) 0.34 51 (<0.01-2.1) (0.06-720)

340 14 (250-420) (9.1 -26) 1700 3.9 (1400-2100) (2.9-4.6) 0.04 0.01 1.1 1.9 (0.77-1.7) (1.5-2.7)

Australia (1W-1992)

Bering Sea (1989-1992)

3500 (22-12 000) 17 500 (870-120 000) 480 (0.85-4400) 180 (8.0-450) 15 (0.86-140)

17 (8.8-22) 170 (1.3-1 100) 490 (0.48-8000) 140 (0.22- 1700) 22 (0.14-230)

3.6 (1.1 -5.6) 1 .o (0.2-2.9) 0.006 2.5 (1.4-3.9)

1600 (74-4600) 16 700 (340-48 000) NA

270 (4.8- 1000) 3.5 (0.38-110)

8400 (3900-17 000) 500 (<50-2200) 36 (0.50-350) 110 (0.49-790) 55 (0.22-720)

93 (18-260) 12 (11-12) 0.13 7.2 (6.6-7.5)

Most air, water, sediment, soil, and fish were collected from southern India. Values for air, water, sediment, and soil were cited from refs 15, 16, and 70. Figures in brackets [ 1 indicate the number of samples,and those in parentheses ( 1 indicate the range of concentrations. Soil and sediment concentrations are expressed on a dry wt basis and those of fish are e ressed on a wet wt basis. NA, data not available.

physicochemical characteristics of organochlorines re- flected by their octanol-water partition coefficients (&,) and air-water partitioning (measured by Henry's law constants, H) also influence their partitioning among the various environmental compartments. For example, HCH isomers with low &, values tend to remain in the aqueous phase rather than in sediments or biota. Furthermore, because of their greater H values than other organochlo- rines, they partition more toward the gaseous phase than to water. Tropical high temperatures enhance the process of partitioning from water to air as the Hvalues are positively correlated with temperature. On the other hand, DDTs possess high &, and relatively low H values and thus accumulate preferentially in organismslsediment close to the emission sources. Due to its relatively low volatility, DDT tends to remain in the particulate liquid phase longer than HCH.

The partitioning behavior of organochlorine compounds in environmental compartments of tropical (India), sub- tropical (Australia), and temperate (Bering Sea) regions can be analyzed by their relative concentrations in various environmental media (Table 3). The relative abundance of HCHs was higher in air and water than in soil, sediment, or fish for both tropical and temperate regions, although their absolute concentrations were greater in the tropics than in temperate regions. DDTs seemed to fractionate mainly toward the particulate aqueous phase in the tropics and the solid phase (soil/sediment/biota) in subtropical and temperate regions. Chlordanes tend to remain in the gaseous phase of tropical and temperate regions, while in

subtropical regions their abundance in both the atmosphere and hydrosphere was comparable. This trend may suggest that subtropical regions have acted as major sources of chlordanes in recent years. The distribution pattern of PCBs was comparable to that of DDTs, with higher levels in the tropical particulate aqueous phase but a comparable distribution among various media in the temperate region. The abundance of HCHs and chlordanes in the atmosphere suggests their more volatile and transportable nature, whereas the prevalence of PCBs and DDTs in the particulate aqueous phase and in biota indicates their more bioac- cumulative but less transportable nature.

The distribution of chemical species in a multiphase system is governed by physical and chemical properties such as vapor pressure, water solubility, octanol-water partition coefficients (&,I, bioconcentration factors (BCF), adsorption coefficient in sediments (&J, Henry's law constant (H), and HIK,, ratio (71). Accordingly, HCH isomers with high vapor pressure and low octanol-water partition coefficients (72) fractionate mainly between air and water. Relatively higher air to water concentration ratios of HCHs in the tropics than in the temperate areas might be due to their high Hvalues at high temperatures. Wania and Mackay (5) explained the latitudinal changes in organochlorine concentrations in light of volatility and temperature. DDT and higher chlorinated PCB congeners were shown to condense close to sources, whereas HCHs migrated further north and were then scavenged by wet and dry deposition at lower ambient temperatures.

VOL. 29. NO. 10, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 2679

FIGURE 4. Comparison of organochlorine concemrmions inwalleye pollock (Theragra chalcognrmma) collected in the Bering Sea in 1982 and 1992. Values for 1982 are from ref 13.

Organochlorine levels and Trends In Bering Sea Pish. The concentrations of HCHs, DDTs, chlordanes, and PCBs in walleye pollock (n = 3; mean fat = 3.4%) collected from the Bering Sea (58O N, 177" E) were 32 (range 27-40 ng/g fat wtl, 81 (33-140 ng/g), 62 (40-95 ng/g), and 230 ng/g fat wt (160-260 ng/g), respectively. These residue con- centrations were compared with those reported in 1982 (collected in Bering Sea, 57" N, 179" E) to studythe temporal variation in contaminationlevels (73). The concentrations of organochlorines in fish in the Bering Sea (Figure 4) declined between sampling events (a2-fold decline for PCBs and chlordanes, 4-fold for DDTs, and 7-fold for HCHs). The reduction is also evident from the isomerlmetabolite composition of HCH and DDT. The mean percentage of a-HCH and p,p'-DDT in pollock compared to ZHCH or ZDDT in the recent samples was 70 and 1596, respectively. Pollock collected in 1982 contained a much higher propor- tion of both a-HCH (90%) and p,p'-DDT (30%). The lower proportionsofa-HCHandp,p'-DDTaswellasthedecreased ZHCH and ZDDT concentrations imply a reduction in the input of these insecticides during the last decade in temperate regions. However, thelowervaluesinthe pollock collected in 1992 (weight, 1.1-1.6 kg) might also be due to dilution of organochlorines by growth, as these fish were heavierthan thoseanalyzedin 1982 (weight, 0.57-0.61 kg).

The ratio of a- to y-HCH in the recent pollock samples ranged between 4.5 and 5.0 @fold lower than in 19821, which is similar to that observed for Bering seawater of 4.1 in 1988 (74). The ratio observed for fish collected in India waslower (mean3.8range2.4-5.1) thanthatoftheBering Sea. From the composition of technical HCH, a/y ratios of 4-7 might be expected in fish, if no isomer-selective uptake or metabolism occurs. Relatively lower a-/ y-HCH ratios in tropical fish may be suggestive of less exposure to the a-isomer in the tropics. The H value and the vapor pressure of a-HCH are higher than those of other HCH isomers, suggesting its increased volatilization and atmo- spheric transport. The rapid dissipation of a-HCH in tropical latitudes would imply its increased deposition in temperate or polar regions. The annual input of a-HCH in the Arctic Ocean was reported to be about five times higher than that for y -HCH (6). Although the purified form of y-HCH (lindane) is still being used in most of the

Northern Hemisphere, it is either microbially degraded or photochemically isomerized into the a-isomer (75, 76).

A n examination of temporal trend data from temperate waters suggested areduction in theinput of organochlorine insecticides in recent years. Atmospheric concentrations of HCHs in the Bering Sea and the Arctic Ocean in 1993 were3-foldlower thanin 1988 (77, 78). Similarly, thelevels of HCHs and chlordanes in air from stations in the Norwegian Arctic were lower in 1992 than in 1984 (79). A decreasing trend in the net quantity of pesticide residues was observed in the Arctic glacier for the period from 1971 to 1985 (80). Kannanetal. (8l)foundasigniIicantreduction in DDT concentrations in cod liver oil collected from fish from the southern Baltic Sea since 1975, although HCHs exhibited a slower downward trend, due to inputs from EasternEuropeancountries. AsigniIicant decrease inPCBs, DDTs, and chlordanes was noticed along a south-north gradient, while the distribution of HCHs was statistically similar at such locations in cod liver oil from fish of the southern Baltic Sea and the northern Norwegian Sea (82). Despite the reduction in HCH concentrations in pollock during the last decade, fur seals (Callorhinus ursinus) feeding preferentially on pollock (83) showed only a small decline in HCH concentrations between 1982 (0.8 pg/g fat wt) and 1988 (0.6pg/g fat wt) (84). This may be due to the fact that in higher trophic organisms such as dolphins and seals, the impact of any reduction in the environmental input of persistent contaminants is realized only slowly (85.86). In any event, these data suggest a reduction in the recent atmospheric input of organochlorines to remote temperate regions when compared to those of the 1970s. Bidleman and McConnell (77) showed the reversal of the a-HCH flux direction since 1988 (from atmospheric depo- sition to volatilization). These results also suggest that the decrease in atmospheric concentrations resulting from global reductions in the use of HCHs will be buffered by reemission of HCHs present in the surface of the oceans.

Global Comparison of Concentrations. The concen- trations of HCHs, DDTs, and PCBs in fish from tropical Asia and Oceania were compared with those in the 1970s and 1980s in the United States (87) and Japan (30) and in themid 1980s in certainAfrican (Nigeria, Zimbabwe, Egypt; 88-90) and MiddleEasterncountries (Iraq, Kuwait; 91,92) (FigureS). HCHlevelsinfishfromIndia,Af~ica, andMiddle Eastern countries were comparable to those reported in the United States and Japan. However, HCH levels in fish from southeast Asia and Oceania were relatively low. The concentrations of DDTs and PCBs were higher in the US. fish than in tropical countries. Apart from environmental and physicochemical parameters, the quantity and rate of use of organochlorines may also influence the magnitude of contamination in the environment. On a global scale, India and the United States were the major users of HCHs and DDTs, respectively, although the utilization of these compounds was discontinued in the United States in the early 1970s (93). It was estimated that about 600 000 t of PCBs, 1 million t of DDTs, and 400 000 t of HCHs were used in the United States up to the 1970s (6). The cumulative consumption of HCHs and DDTs in India to 1985 was 575 000 and 250 000 t, respectively (94, 9.3, while their corresponding usage in recent years was 45 000 and 19 000 t annually. Considering these estimates, about 500 000 t of DDTs and 1 million t of HCHs have been used in India before 1995. Despite the higher quantity of consumption, HCH levels in fish in India were lower than those in the

2080 m ENVIRONMENTAL SCIENCE 5 TECHNOLOGY I VOL. 29. NO. 10,1995

10'

10' :I 10" 10''

FIGURE 5. Comparison of the concentrations of HCHs, DDTs, and PCBs in fish from tropical Asian countries with those in Japan (M, USA (83, certain African nations (SS-SO), and Middle Eastern countries (91.92). HCH values for the American fish are the sum of a- and y-HCH. whereas those for other countries include a-,#l-, y-, and 6-HCH isomers. Values below the detection limit are illustrated by the vertical slotted lines.

United States and Japan, suggesting a lower accumulation in tropical fish, which could be due to the rapidvolatilization of this insecticide in the tropical environment (9s). Simi- larly, DDT levels in tropical fish were about 1-2 orders of magnitude lower than those of the United States, indicating the rapid volatilization of DDT in tropical aquatic environ- ments (97). The high temperatures prevailing in the tropics could also enhance the elimination rate of chemicals in fish (due to the influence of temperature on respiratory requirements of fish), as the biological half-lives of semi- volatile compounds such as DDT are short at high tem- peratures (98). In any event, it is evident that tropical aquatic biota accumulate relatively low levels of orga- nochlorine compounds. Although this is a favorable aspect, the role of tropical regions as possible emission sources of contamination in the Arctic and elsewhere deserves con- sideration of the replacement of these chemicals with substitutes that are effective, economical, and degradable.

Conclusions Fish from tropical latitudes accumulate lower concentra- tions of semivolatile organochlorine compounds than those

from temperate regions due to the short residence time of these compounds in the tropical aquatic environment. DDTs were the predominantly identified compounds in fish in tropical Asian countries, while the concentrations of other organochlorines were low. The distribution of organochlorines in tropical and temperate regions showed that more volatile compounds such as HCHs and chlordanes tend to be prevalent in air, whereas PCBs and DDTs partition preferentially toward water and biota, both in tropical and temperate regions. In this context, it is suggested that PCBs and DDTs persist longer in the environment close to emission sources and may therefore exert toxic effects on aquatic organisms. HCHs and chlordanes accumulate to only minor extents in tropical aquatic biota due to their more volatile and transportable nature; they may therefore contaminate pristine areas such as the Arctic and the Antarctic via long-range atmospheric transport.

It is considered that fish from tropical Asian countries may experience toxic effects from less volatile contaminants. Our recent studies have shown that the concentrations of butyltin compounds (which are relatively less volatile) are higher than those of several organochlorine compounds in tropical fish (99). Therefore, from the global contamination point of view, volatile compounds such as HCHs and chlordanes (which have the tendency to fractionate into polar ecosystems) should be banned in the tropics. On the other hand, based on the human health point of view, an increased exposure of humans to DDT and other orga- nochlorines via foodstuffs in developing countries and the increased risks of cancer (in the order of 10-2-10-4) associated with such exposure (18) suggest the need to replace this insecticide in malaria eradication programs.

Acknowledgments The authors would like to thank Mr. Robert J. Williams (Fisheries Research Institute, Cronulla), Mr. Irynej Skira (Department of Parks, Wildlife and Heritage, Hobart), Mr. John Dobson (Department of Environment and Planning, Hobart), Dr. Kevin A. Francesconi and Dr. John Edmonds (Western Australian Marine Research Laboratories, North Beach), Dr. Michael F. Capra and Dr. Peter Mather (Centre for Biological Population Management, Queensland Uni- versity of Technology, Brisbane), Prof. Helene Marsh and Mr. Paul Besant (Environmental Studies Unit and Centre for Tropical Marine Studies, James CookUniversity of North Queensland, Townsville), Dr. Graham Harrington and Dr. John Maggs (Commonwealth of Scientific and Industrial Research Organization, Division of Wildlife and Ecology, Tropical Forest Research Centre, Atherton), Dr. A. N. Subramanian (Centre ofAdvanced Study in Marine Biology, Porto Novo), Dr. Monthip S. Tabucanon (Environmental Research andTraining Centre, Bangkok), Prof. H. T. Qunyh (Medical College, Hanoi), and Prof. N. D. Hue (Hanoi Univeristy) for their help during sampling of fish. This research was supported by grants-in-aid from the Inter- national Scientific Research Programme of the Ministry of Education, Science and Culture of Japan (Grants 02041061 and 05278240), the Global Environment Research Pro- gramme of the Environment Agency, Japan, and the Sumitomo Foundation (93- 104- 141).

Supporting lnfonnation Available One table (Table 4) containing the sample list of fish collected in Asia and Oceania (2 pp) will appear following these pages in the microfilm edition of this volume of the journal.

VOL. 29, NO. 10, 1995 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 2681

Photocopies of the supporting information from this paper or microfiche (105 x 148 mm, 24x reduction, negatives) may be obtained from Microforms Office, American Chemical Society, 1155 16th St. NW, Washington, DC 20036. Full bibliographic citation (journal, title of article, names of authors, inclusive pagination, volume number, and issue number) and prepayment, check or money order for $12.00 for photocopy ($14.00foreign) or $12.00for microfiche ($13.00 foreign), are required. Canadian residents should add 7% GST. Supporting information is available to subscribers electronically via the Internet at http:/ /pubs.acs.org 0 and pubs.acs.org (Gopher).

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