www.elsevier.com/locate/marpolbul

Marine Pollution Bulletin 51 (2005) 677–687

Organochlorines and dioxin-like compounds in green-lipped musselsPerna viridis from Hong Kong mariculture zones

M.K. So a, X. Zhang b, J.P. Giesy a,b, C.N. Fung a, H.W. Fong a, J. Zheng a,M.J. Kramer b, H. Yoo b, P.K.S. Lam a,*

a Centre for Coastal Pollution and Conservation, Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue,

Kowloon, Hong Kong SAR, People�s Republic of Chinab Department of Zoology, National Food Safety and Toxicology Center, Center for Integrative Toxicology, Michigan State University,

East Lansing, MI 48824, USA

Abstract

Concentrations of persistent organic pollutants including polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides anddioxin-like compounds were measured in green-lipped mussels, Perna viridis, collected from seven mariculture zones in Hong Kongbetween September and October in 2002 in order to evaluate the status, spatial distribution and potential sources of pollution inthese areas. Concentrations ranged from 300 to 4400 ng/g lipid weight for total OCs and 170–1000 ng/g lipid weight for total PCBs(based on 28 congeners). Relatively smaller DDT concentrations in mussels compared with previous studies suggest reduced dis-charges of DDTs from nearby regions into Hong Kong waters. Detection of a mixture of HCH isomers in the mussels indicatedthat Hong Kong waters were predominantly contaminated by technical HCHs rather than lindane. Mussel samples from all sam-pling locations elicited significant dioxin-like activity in the H4IIE-luc bioassay. The greatest magnitude of dioxin-like response(39 pg TEQ/g wet wt.) was detected in mussels from Ma Wan in the western waters of Hong Kong, which is strongly influencedby the Pearl River discharge. Human health risk assessment was undertaken to evaluate potential risks associated with the consump-tion of the green-lipped mussels. Risk quotient (RQ) for dioxin-like compounds was greater than unity suggesting that adversehealth effects may be associated with high mussel consumption.� 2005 Elsevier Ltd. All rights reserved.

Keywords: Green-lipped mussel; Mariculture zone; Hong Kong; OC pesticides; PCBs; Dioxin-like compounds; H4IIE-luc cell bioassay; Humanhealth risk assessment

1. Introduction

Persistent organic pollutants (POPs) of particularconcern include organochlorine (OC) pesticides whichhad been extensively used in agricultural practices inthe past; polychlorinated biphenyls (PCBs) which weremainly used for insulation in electrical equipment; poly-cyclic aromatic hydrocarbons (PAHs) which were emit-

0025-326X/$ - see front matter � 2005 Elsevier Ltd. All rights reserved.doi:10.1016/j.marpolbul.2005.06.004

* Corresponding author. Tel.: +852 2788 7681; fax: +852 2788 7406.E-mail address: bhpksl@cityu.edu.hk (P.K.S. Lam).

ted through processes such as incomplete combustion offossil fuel and from petrochemical industrial activities; aswell as dioxin-like compounds (Fu et al., 2003). Dioxin-like compounds, also known as planar halogenatedhydrocarbons (PHHs), include certain co-planar PCBs,polychlorinated dibenzo-p-dioxins (PCDDs), polychlo-rinated dibenzofurans (PCDFs), and are unintentionallyreleased through combustion processes, burning of fuel,production and use of chlorohydrocarbons, and chlo-rine bleaching in the pulp and paper industry (Fiedler,1996). Among the POPs, dioxin-like compounds areconsidered to be the most toxic man-made chemicals

678 M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687

(Lai et al., 2004) and the toxic effects arise as a conse-quence of their abilities to bind to aryl hydrocarbonreceptor (AhR) (Schoeters et al., 2004). Toxicities asso-ciated with PHH exposure include hepatoxicity, bodyweight loss, thymic atrophy, impairment of immuneresponses, dermal lesions and reproductive toxicity(Giesy et al., 1994; Safe, 1994). While a number of stud-ies in Hong Kong have demonstrated the contaminationwith OCs, PCBs, PAHs in bottom sediments (Connellet al., 1998b; Hong et al., 1995), green-lipped mussels(Perna viridis) (Phillips, 1985) and fish purchased fromlocal markets (Chan et al., 1999), information on theconcentrations of dioxin-like compounds in the HongKong coastal environment is limited.

Hong Kong, situated on the southern coast of China,has experienced severe pollution stress through variousanthropogenic sources. Pearl River discharge is consid-ered to be one of the major pollution sources to theHong Kong marine environment, particularly to thewestern regions (Broom and Ng, 1995; Wu, 1988). Thisinfluence is relatively greater in the wet summer seasonwhen the Pearl River runoff constitutes about 80% ofthe annual total discharge (Xue and Chai, 2001). Otherfactors, such as population expansion and rapid urban-ization, have resulted in increasing pollution loads beingintroduced into Victoria and Tolo Harbours (Black-more, 1998). Historically, discharges of largely un-treated domestic and industrial wastewater and thedisposal of contaminated mud into Hong Kong�s coastalwaters have resulted in high levels of POPs in the watercolumn, sediment and biota (Connell et al., 1998a,b;Wu, 1988).

Human breast milk samples from Hong Kong hadbeen found to contain relatively great concentrationsof DDTs, HCHs (Ip, 1983) and dioxin-like compounds(Lai et al., 2004). Consumption of contaminated food-stuff, especially marine fish and shellfish, is consideredto be a major pathway for human exposure to POPs(Lai et al., 2004; Liem et al., 2000). Indeed, over 90%of human exposure to dioxin-like compounds is thoughtto be via ingestion of contaminated food (Winters et al.,1995). People in Hong Kong are estimated to consumemarine fish or shellfish at least three times a week (Chanet al., 1999). Therefore, mariculture is an importantindustry in Hong Kong, despite the increasing supplyof high quality live fish and shellfish from overseas.The 28 designated mariculture zones in Hong Kongare mostly located in the northeast New Territories(Chan et al., 1999; Lam, 1990). Being located in closeproximity to urban areas, these mariculture zones mayconceivably be impacted by various pollution sources,and consequently fish or shellfish from these areas couldpose potential public health problems (Chan et al.,1999).

Green-lipped mussels, P. viridis, are commerciallyvaluable seafood, and are widely distributed in the

Asian coastal waters. They have been recognized as asuitable bioindicator for monitoring toxic contaminantsin coastal waters (Monirith et al., 2003). Concentrationsof environmental contaminants in mussels could be usedto assess potential risks to seafood consumers (Funget al., 2004).

Most of the previous studies on pollution monitoringin Hong Kong have been concentrated around Victoria(Tanner et al., 2000; Yung et al., 1998) and Tolo Har-bours (Owen and Sandhu, 1999; Wong et al., 2000),and relatively limited information is available on theconcentrations of contaminants, particularly POPs, inmussels from local mariculture farms. In this presentstudy, green-lipped mussels, P. virids, were collectedfrom seven mariculture zones in Hong Kong, and ana-lyzed for OC pesticides and PCBs. The concentrationsof dioxin-like compounds were also determined usingH4IIE-luciferiase (H4IIE-luc) bioassay. Human healthrisk assessment was also undertaken to evaluate therisks associated with the consumption of mussels col-lected from Hong Kong mariculture zones.

2. Materials and methods

2.1. Sampling

Green-lipped mussels, P. virids, were collected fromseven mariculture zones: Kat O (KO), O Pui Tong(OPT), Tap Mun (TM), Yim Tin Tsai (YTT), Kau Sai(KS), Lo Tik Wan (LTW) and Ma Wan (MW), duringSeptember and October 2002 in Hong Kong (Fig. 1).Immediately after collection, samples were stored inpolyethylene bags, kept in ice, and transported to thelaboratory. Upon return to the laboratory, the sampleswere stored at �20 �C until analyzed.

2.2. Sample preparation

The procedures for chemical treatment were similarto those described by Fung et al. (2004), but with somemodifications. The frozen mussel samples were thawed,and the whole soft tissues of about 30 mussels, sizesranging between 80 mm to 120 mm, from each locationwere pooled and homogenized in a blender. Approxi-mately 10 g of homogenized tissue was transferred intoa 50 ml centrifuge tube, freeze–dried for 7 d and thedried tissues were ground into powder. Approximately1 g of the dried tissue powder was accurately weighedinto a new 50 ml centrifuge tube. Duplicate sampleswere prepared for each location. The dried mussel pow-der was extracted in a 50 ml centrifuge tube, containingan internal standard [Decachlorobiphenyl (DCB)], 35 mlmethylene chloride, and 1 g of anhydrous sodium sul-phate (preheated at 450 �C for 5 h). The combined mix-ture was then shaken by a horizontal shaker at a rate of

Fig. 1. Map showing sampling locations of mussels in seven mariculture zones in Hong Kong (KO: Kat O, OPT: O Pui Tong, TM: Tap Mun, YTT:Yim Tin Tsai, KS: Kau Sai, LTW: Lo Tik Wan, MW: Ma Wan).

M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687 679

20 oscillations per min. The tubes were then centrifugedat 2000 rpm for 10 min and the supernatant was dec-anted into a 250 ml round bottom flask. The aboveextraction and centrifugation processes were repeatedtwo more times with all the three supernatants combinedand filtered through a glass fibre filter. The mixture wasthen concentrated to approximately 5 ml using a rotaryevaporator under reduced pressure. The solvent wasexchanged by adding 30 ml hexane and the combinedvolume was further reduced to about 1 ml. The lipidcontent was determined from an aliquot of the extractby reducing to dryness using nitrogen blowdown (Yuet al., 2002). The extract was then redissolved in hexane,and loaded onto a silica gel column for separation.

A fractionation column of internal diameter of 1 cmwas prepared by adding 13 cm in length of activated sil-ica gel with 6 nm average pore size (preheated at 450 �Cfor 5 h), followed by 3 cm in length of anhydrous so-dium sulphate. The column was then washed sequen-tially with 15 ml acetone, 15 ml methylene chlorideand 30 ml hexane. The mussel extract was then loadedonto the silica gel column. The extract was allowed topass through into the sodium sulphate. Until the aliquotreached the surface of sodium sulphate, 15 ml hexanewas added to the column, and the eluate was discarded.Another 15 ml of 20% methylene chloride in hexane wasloaded onto the column and the eluate was collected forOC pesticide and PCB determination. The volume ofeluate was reduced to approximately 0.3 ml by rotaryevaporation under reduced pressure. The aliquot extractwas transferred to a 0.3 ml insert in a 1.5 ml vial andinjected into a gas chromatograph for analysis.

2.3. Organochlorine identification and quantification

PCBs, HCHs, HCB, heptachlor, heptachlor epoxide,aldrin, dieldrin, endrin, kepone, chlordanes, and DDTand its metabolites were measured. Concentrations ofindividual compounds were calculated from the peakarea of the sample to a corresponding external standard.The PCB standard (SRM 2262) used for quantificationwas a mixture with known composition and content,containing 28 congeners (PCB 1, 8, 18, 28, 29, 44, 50,52, 66, 77, 87, 101, 104, 105, 118, 126, 128, 138, 153,154, 170, 180, 187, 188, 194, 195, 200, 206). OCs werequantified by a Hewlett Packard 6890 series gas chro-matograph equipped with a microelectron capturedetector (GC-lECD) employing 30 m HP-5MS capil-lary column (0.2 mm internal diameter and 0.25 lmthickness film of 95% dimethyl-5%polysiloxane) andequipped with an autoinjector (Hewlett Packard 7683series). The column head pressure was kept at 12 psi.The oven temperature was programmed from 90 �C atthe beginning, held for 2 min, then increased to 180 �Cat a rate of 20 �C per min, held for 1 min, and finallyraised to 270 �C at a rate of 3 �C per min and held for20 min. Injector and detector temperatures were set at230 �C and 300 �C, respectively. Detection limits were0.05 ng/g dry weight for individual OC pesticide and0.1 ng/g dry weight for individual PCB. Recoveries ofOC pesticides and PCBs were in the range of 81–108%and 93–100%, respectively. Concentrations of OC pesti-cides and PCBs were not corrected for recoveries andare presented on both ng/g dry weight and lipid weightbasis.

680 M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687

2.4. H4IIE-luc cell bioassay

The cells employed in the present study were rat hep-atoma cells that were stably transfected with a luciferasereporter gene (Sanderson et al., 1996). The proceduresfor the in vitro bioassay were similar to those describedelsewhere (Khim et al., 2000, 2001). In brief, the cellswere trypsinized from culture dishes containing morethan 80% confluent monolayers and were then seededinto the 96-well culture plates at 250 ll per well. Cellswere incubated overnight before dosing. Test wells weredosed with 2.5 ll of the mussel extract. The control wellswere dosed with 2.5 ll of solvent, while the blank wellsreceived no dose. A standard curve was constructed byadding different concentrations of 2,3,7,8-tetrachlo-rodibenzo-p-dioxin (2,3,7,8-TCDD) to the standardwells. Three control wells and blank wells were testedon each plate. Luciferase assays were conducted after72 h of exposure. Culture medium was then removedfrom the plate. After adding LucLite reagent, the plateswere read with a microplate-scanning Dynatech ML3000 luminometer (Dynatech Laboratories, Chantilly,VA, USA). Responses to AhR agonists were quantifiedby measuring the relative luminescence units (RLU) andwere converted to percentages of the mean maximumresponse observed for the TCDD standard curve(%-TCDD-max). The dioxin-like potency of eachextract was expressed as relative potency (REP) to2,3,7,8-TCDD based on EC1 values from the TCDDstandard curve and the sample dose response curve(Villeneuve et al., 2000).

2.5. Human health risk assessment

The risk of specific contaminants to human healthassociated with consumption of mussels is performedby calculating the risk quotient (RQ), which is a com-parison of the exposure concentration to the oral refer-ence dose (RfD). The exposure level for a particularcontaminant is calculated by use of

Average daily exposureðng=kg body weight=dÞ¼ Consumptionðg=kg body weight=dayÞ�Maximum measured contaminant

concentrationðng=g dry wt:Þ: ð1Þ

Due to the lack of shellfish consumption data forHong Kong people, fish consumption data for high con-sumption groups in China, 119 g/person/d (Fung et al.,2004), was adopted. This, together with the maximummeasured contaminant concentration, were used to cal-culate a ‘‘worst-case’’ RQ. Assuming the average bodyweight of an adult is 60 kg, the average consumptionrate becomes 1.98 g/kg bw/d. The RfD values employedin the present study were the criteria from the US Envi-ronmental Protection Agency (USEPA), which is an

estimate of a daily exposure to the human populationthat is unlikely to pose significant lifetime health risks.In this study, risk assessment was only conducted onPCBs, DDTs, chlordanes, dieldrin and dioxin-like com-pounds, for which RfDs are available from USEPA.Using a conservative (worst-case) approach, RQ wascalculated

RQ ¼ Average Daily Exposure

RfDð2Þ

RQ less than unity indicates that the chemical involvedis less likely to pose a significant health risk to the con-sumers. However, RQ greater than unity would indicatethat exposure concentration exceeds RfD and a more re-fined risk assessment is needed to ascertain whetherappropriate control or management measures arerequired.

3. Results and discussion

3.1. Spatial distribution of OC pesticides and PCBs

Concentrations of OC pesticides, on dry and lipidweight basis, in the mussel samples collected from indi-vidual mariculture zones are presented (Table 1). Con-centrations of OCs in mussels varied among locationsof mariculture zones. Concentrations of total OCs ran-ged from 300 to 4400 ng/g lipid wt. Concentrations oftotal DDTs, HCHs and chlordanes ranged from 11 to1400, 18 to 1200 and 59 to 1000 ng/g lipid wt., respec-tively (Table 1).

Mussels from MW contained the greatest concentra-tions of total OCs (4100 and 4400 ng/g lipid wt.), fol-lowed by YTT (3200 and 4100 ng/g lipid wt.). MW,with its close proximity to Tsuen Wan and Kwai Chung,may be subjected to local pollutant discharges fromnearby manufacturing and industrial areas. The degreeof contamination in this area may be further intensifiedby the large spate of freshwater discharge from the PearlRiver Estuary, which is known to contain high concen-trations of various contaminants. The relatively greatconcentrations of contaminants in mussels from YTTcould be attributed to its location within Tolo Harbour.Tolo Harbour, situated at the northeastern part of HongKong, is a semi-estuarine embayment which is con-nected to the outer Mirs Bay by a long narrow ToloChannel (Wu, 1988). As a consequence of continualcoastal reclamation, tidal flushing within the embay-ment has been greatly reduced, resulting in long waterresidence time and poor oceanic exchange (Blackmore,1998). The pollution problem in the area is further exac-erbated by increased population and industries withinTolo Harbour (Owen and Sandhu, 1999). The smallestconcentration of total OCs was recorded in musselsfrom KO (310 and 460 ng/g lipid wt.). This sampling site

Table 1Concentrations (ng/g dry wt. and lipid wt.) of organochlorines in mussel samples collected from mariculture zones in Hong Kong

Replicate Site

KO OPT TM YTT KS LTW MW

1 2 1 2 1 2 1 2 1 2 1 2 1 2

Dry weight basis

HCHs 5.5 7.2 7.6 19 19 21 62 49 2.6 1.1 1.6 3.8 38 62HCB 1.6 3.7 4.2 11 8.2 12 35 21 4.0 1.6 2.9 5.3 16 16Heptachlor 1.3 1.5 2.5 1.2 4.4 6.5 53 53 2.3 0.87 2.9 5.3 24 31Heptachlor epoxide <0.05 <0.05 4.2 <0.05 2.2 <0.05 <0.05 <0.05 0.60 0.32 1.2 1.0 <0.05 <0.05Aldrin <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 3.3 1.5 3.8 5.4 <0.05 <0.05Dieldrin <0.05 <0.05 2.2 0.15 <0.05 <0.05 <0.05 <0.05 0.53 0.35 1.1 0.75 <0.05 <0.05Endrin 12 0.53 3.5 <0.05 12 20 65 44 0.33 0.13 <0.05 <0.05 32 28Kepone <0.05 <0.05 1.9 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05a-chlordane 2.0 4.0 0.82 0.91 4.1 5.4 24 9.9 2.1 9.5 16 13 21 32c-chlordane 1.9 2.9 6.1 3.2 3.4 5.1 11 20 5.2 1.2 1.1 1.6 18 22Chlordanes 3.9 6.9 6.9 4.1 7.5 10 35 30 7.3 11 17 14 40 55p,p 0-DDE 1.0 1.7 0.76 0.72 5.0 6.6 51 56 1.3 0.35 2.9 3.1 68 23p,p 0-DDD&o,p 0-DDT <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 19 20 1.3 1.1 0.71 4.9 <0.05 <0.05p,p 0-DDT <0.05 <0.05 <0.05 0.52 <0.05 <0.05 17 14 0.53 0.21 <0.05 <0.05 <0.05 <0.05DDTs 1.1 1.7 0.81 1.3 5.0 6.6 87 89 3.2 1.6 3.6 8.0 68 23

Total OCsa 26 22 34 36 58 78 340 290 24 18 34 44 220 210

Lipid weight basis

HCHs 97 100 100 270 480 540 750 550 51 18 20 46 780 1200HCB 29 52 57 160 200 320 430 240 79 26 36 64 320 300Heptachlor 23 22 34 17 110 170 640 590 45 14 37 64 480 590Heptachlor epoxide <0.90 <0.70 56 <0.70 55 <1.30 <0.60 <0.60 12 5.3 15 12 <1.00 <1.00Aldrin <0.90 <0.70 <0.70 <0.70 <1.20 <1.30 <0.60 <0.60 66 25 48 66 <1.00 <1.00Dieldrin <0.90 <0.70 29 2.1 <1.20 <1.30 <0.60 <0.60 11 5.8 14 9.1 <1.00 <1.00Endrin 220 7.6 47 <0.70 290 520 790 490 6.6 2.1 <0.60 <0.60 650 530Kepone <0.90 <0.70 25 <0.70 <1.20 <1.30 <0.60 <0.60 <1.00 <0.80 <0.60 <0.60 <1.00 <1.00a-chlordane 36 57 11 13 100 140 290 110 41 160 200 150 440 610c-chlordane 33 42 81 46 83 130 140 220 100 20 14 19 370 430Chlordanes 69 98 92 59 180 270 430 330 150 180 220 170 810 1000p,p 0-DDE 18 24 10 10 120 170 620 620 26 5.8 36 37 1400 430p,p 0-DDD&o,p 0-DDT <0.90 <0.70 <0.70 <0.70 <1.20 <1.30 230 220 26 18 9.0 60 <1.00 <1.00p,p 0-DDT <0.90 <0.70 <0.70 7.4 <1.20 <1.30 210 150 11 3.5 <0.60 <0.60 <1.00 <1.00DDTs 19 24 11 18 120 170 1100 990 63 27 45 98 1400 430

Total OCsa 460 310 450 520 1400 2000 4100 3200 480 300 430 530 4400 4100

a Concentration of total OCs is calculated assuming that concentrations of non-detected contaminants are equal to one half of the detection limit.

M.K.Soetal./MarinePollutionBulletin

51(2005)677–687

681

682 M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687

is located near a remote island with well-circulated oce-anic waters. Notwithstanding, this area could still be af-fected by transboundary transfer of pollutants viaindustrial effluents from mainland China where thereare signs of increased industrial activities (Chiu et al.,2000).

Previous studies reported that DDTs were the mostabundant OC contaminants in sediment (Hong et al.,1995), mussel (Phillips, 1985; Monirith et al., 2003)and fish (Chan et al., 1999) samples from Hong Kongmarine waters. However, in the present study, greaterconcentrations of PCBs than DDTs were found in mus-sel samples from most of the mariculture zones. Thegreatest residue level of DDTs (1400 ng/g lipid wt.)was found in MW. DDT concentrations found in thepresent study were much smaller than those reportedin previous studies. For example, Monirith et al.(2003) measured up to 61,000 ng/g lipid wt. of DDTsin mussels from Cheung Chau. Even greater concentra-tion (130,000 ng/g lipid wt.) was detected in musselsfrom Wu Kwai Sha (Phillips, 1985). Greater DDT con-centrations were also found in mussels from urbanizedareas in India and Thailand where DDT was still beingused for malaria vector control (Kan-atireklap et al.,1997; Tanabe et al., 2000). Mussels from YTT, havinga DDE/DDTs ratio of 0.6, had more than 50% of theDDTs existed in the form DDE. In other locations, suchas KO, TM and MW, the concentrations of p,p 0-DDTwere below detection. These findings may indicate theabsence of fresh sources of DDTs in Hong Kong waters.The high level of p,p 0-DDE in mussels from MW reflectsa history of significant pollution by DDT, probablyattributable to the Pearl River discharge. Indeed, theuse of DDT has continued in China even after the offi-cial ban in the production and usage of OC pesticides

Fig. 2. Profile of HCHs in mussels collected from

in 1983. This is evident from a number of studiesshowing high p,p 0-DDT/total DDTs ratios in sedi-ments from the Zhujiang, Shiziyang, Xijiang Rivers(Mai et al., 2002) and Daya Bay (Zhou et al., 2001).Concentrations of DDTs in KO, OPT, TM, KS andLTW were comparatively low (Table 1), and their occur-rence could be attributed to oceanic or atmosphericinputs from other sources outside Hong Kong (Wonget al., 2004, 2005).

Concentrations of total HCHs in mussels are shownin Table 1. Mussels from MW contained the greatestconcentrations (780 and 1200 ng/g lipid wt.), followedby mussels from YTT (550 and 750 ng/g lipid wt.) andTM (480 and 540 ng/g lipid wt.). HCHs are known tobe widely used as insecticides against grasshopper andrice insects, and have also been used for seed protection,livestock treatment as well as household vector controlin places such as China, India and Japan (Li, 1999).Information on HCH usage in Hong Kong is limited,but HCHs have been employed as pesticides and utilizedby some industries in small amounts (Phillips, 1985).The perceived pollution source of HCHs in MW wasmainly from China. It is noted, however, that dischargeof HCHs has been reduced in China; concentrations ofHCHs in water had decreased from 1700 ng/l in 1979to 24 ng/l in 1992 (Li, 1999). Again, discharges fromnearby agricultural areas, together with poor oceanic ex-change, may account for the relatively great concentra-tions of HCHs in YTT. Concentrations of total HCHsmeasured in the present study were less than those pre-viously reported in mussels from Hong Kong. Musselsfrom Reef Island, Mei Foo and Causeway Bay were re-ported to contain up to 29,000, 7100 and 6800 ng HCH/glipid wt., respectively (Phillips, 1985). However, thepresent contamination level appears to be significantly

individual mariculture zones in Hong Kong.

Table 2Concentrations (ng/g dry wt. and lipid wt.) of 28 PCB congeners in mussel samples collected from mariculture zones in Hong Kong

Replicate Site

KO OPT TM YTT KS LTW MW

1 2 1 2 1 2 1 2 1 2 1 2 1 2

Dry weight basis

PCB1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 4.2 4.6 2.4 1.8 4.0 <0.1 <0.1PCB8 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1PCB18 0.6 0.4 0.8 0.6 1.3 4.3 3.5 4.3 1.0 0.4 0.7 2.8 7.1 8.6PCB28 0.4 0.5 1.5 0.5 1.0 1.9 2.8 6.9 <0.1 <0.1 0.1 <0.1 11.2 3.4PCB29 <0.1 <0.1 <0.1 0.7 0.7 1.5 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1PCB44 <0.1 <0.1 4.0 2.4 <0.1 <0.1 <0.1 <0.1 2.0 0.6 3.1 2.6 <0.1 <0.1PCB50 <0.1 <0.1 <0.1 0.5 <0.1 <0.1 <0.1 <0.1 2.0 0.9 2.4 4.3 <0.1 <0.1PCB52 0.5 0.7 1.3 0.2 2.1 3.0 15.7 8.3 0.5 0.4 1.5 1.8 8.2 7.0PCB66 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.1 0.4 4.9 <0.1 <0.1PCB77 <0.1 <0.1 2.3 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 2.0 3.9 4.3 <0.1 <0.1PCB87 <0.1 <0.1 0.9 0.1 <0.1 <0.1 <0.1 <0.1 0.8 0.5 0.3 0.5 <0.1 <0.1PCB101 1.9 3.6 5.9 4.6 3.9 3.5 7.2 6.8 5.3 1.7 3.6 6.2 11.4 8.2PCB104 7.6 7.3 8.4 6.6 5.9 7.4 3.6 5.3 <0.1 <0.1 0.2 0.2 9.0 9.1PCB105 0.6 <0.1 <0.1 <0.1 <0.1 <0.1 5.0 5.6 1.3 0.9 4.7 <0.1 <0.1 9.6PCB118 1.3 1.8 3.2 0.9 1.7 5.1 8.3 7.1 1.7 2.3 7.5 12.9 9.7 9.3PCB126 0.7 0.7 7.3 4.9 1.4 2.1 11.0 9.7 <0.1 <0.1 <0.1 <0.1 12.0 9.3PCB128 0.2 0.3 1.7 <0.1 <0.1 <0.1 <0.1 6.9 3.8 1.9 0.9 0.9 <0.1 <0.1PCB138 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.5 0.1 <0.1 <0.1 <0.1 <0.1PCB153 0.5 0.9 0.7 4.7 1.6 3.6 6.7 8.5 <0.1 <0.1 9.9 13.1 6.9 4.8PCB154 <0.1 <0.1 3.0 2.0 <0.1 <0.1 <0.1 <0.1 <0.1 0.2 0.2 3.4 <0.1 <0.1PCB170 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 2.7 2.2 2.7 3.5 <0.1 <0.1PCB180 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 9.3 8.9 0.7 <0.1 <0.1 <0.1 3.9 5.7PCB187 <0.1 0.2 <0.1 <0.1 <0.1 <0.1 8.2 6.8 <0.1 <0.1 <0.1 <0.1 2.1 6.3PCB188 <0.1 <0.1 3.0 0.2 <0.1 <0.1 <0.1 <0.1 1.0 0.7 1.3 0.9 <0.1 <0.1PCB194 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 9.1 8.7 1.4 1.1 1.4 1.2 1.3 3.0PCB195 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 4.5 6.8 1.5 <0.1 <0.1 <0.1 10.1 9.0PCB200 0.9 1.6 2.0 1.1 <0.1 <0.1 2.3 5.2 0.7 0.6 3.1 2.5 7.8 9.0PCB206 4.0 8.3 4.2 1.1 4.0 1.1 3.5 4.3 55.1 40.1 7.9 11.0 6.9 9.8

Total PCBsa 20 27 51 32 25 35 101 111 88 59 57 81 111 111

Lipid weight basis

PCB1 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 38 42 22 16 36 <0.9 <0.9PCB8 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 0 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9PCB18 5 3 7 5 12 39 31 39 9 4 6 25 63 78PCB28 4 5 13 5 9 17 25 62 <0.9 <0.9 1 <0.9 101 30PCB29 <0.9 <0.9 <0.9 7 6 13 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9PCB44 <0.9 <0.9 36 21 <0.9 <0.9 <0.9 <0.9 18 5 28 23 <0.9 <0.9PCB50 <0.9 <0.9 <0.9 5 <0.9 <0.9 <0.9 <0.9 18 8 21 39 <0.9 <0.9PCB52 5 6 12 2 18 27 141 74 5 3 14 16 74 63PCB66 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 1 3 44 <0.9 <0.9PCB77 <0.9 <0.9 21 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 18 35 39 <0.9 <0.9PCB87 <0.9 <0.9 8 1 <0.9 <0.9 <0.9 <0.9 7 4 3 4 <0.9 <0.9

(continued on next page)

M.K.Soetal./MarinePollutionBulletin

51(2005)677–687

683

Table 2 (continued)

Replicate Site

KO OPT TM YTT KS LTW MW

1 2 1 2 1 2 1 2 1 2 1 2 1 2

PCB101 17 33 53 42 35 32 65 61 48 16 32 55 103 73PCB104 68 65 76 59 53 66 32 48 <0.9 <0.9 2 2 81 81PCB105 5 <0.9 <0.9 <0.9 <0.9 <0.9 45 51 12 8 42 <0.9 <0.9 86PCB118 12 16 28 8 15 46 75 64 15 21 67 116 87 84PCB126 6 6 65 44 13 19 99 87 <0.9 <0.9 <0.9 <0.9 108 84PCB128 2 2 15 <0.9 <0.9 <0.9 <0.9 62 34 17 8 8 <0.9 <0.9PCB138 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 5 1 <0.9 <0.9 <0.9 <0.9PCB153 5 8 6 42 14 33 61 77 <0.9 <0.9 89 118 62 43PCB154 <0.9 <0.9 27 18 <0.9 <0.9 <0.9 <0.9 <0.9 1 2 31 <0.9 <0.9PCB170 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 24 20 24 32 <0.9 <0.9PCB180 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 84 80 6 <0.9 <0.9 <0.9 35 51PCB187 <0.9 2 <0.9 <0.9 <0.9 <0.9 74 61 <0.9 <0.9 <0.9 <0.9 19 57PCB188 <0.9 <0.9 27 2 <0.9 <0.9 <0.9 <0.9 9 6 12 <0.9 <0.9 <0.9PCB194 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 82 78 13 10 12 11 12 27PCB195 <0.9 <0.9 <0.9 <0.9 <0.9 <0.9 41 62 14 <0.9 <0.9 <0.9 91 81PCB200 8 14 18 10 <0.9 <0.9 21 47 6 5 28 22 70 81PCB206 36 74 38 10 36 9 31 39 496 361 71 99 62 88

Total PCBsa 180 241 455 286 218 308 916 1005 785 534 523 725 976 1006

a Concentration of total 28 PCB congeners is calculated assuming that concentrations of non-detected contaminants are equal to one half of the detection limit.

684M.K.Soetal./MarinePollutionBulletin

51(2005)677–687

Table 3Concentrations of dioxin-like compounds expressed as pg TEQ/g wetweight (mean ± S.D.) in mussels from individual sampling location

Sampling locations Concentration (pg TEQ/g wet wt.)

KO 15 ± 5.8OPT 10 ± 0.8TM 19 ± 10YTT 37 ± 11KS 8.6 ± 7.2LTW 20 ± 2.2MW 39 ± 21

Table 4The RfD and maximum measured environmental concentrations forindividual contaminant

Chemical of concern RfD fromUSEPA(ng/kg/day)

Maximummeasuredconcentration(ng/g wet wt.)

RQ

Chlordane 60 8.3a 0.27HCB 800 5.3a 0.01Dieldrin 50 0.33a 0.01DDTs 500 13a 0.05PCBs 20 17a 0.85Dioxin-like compounds 0.001–0.004 0.04 20–79

a Concentrations on wet weight basis were converted from the cor-responding concentrations expressed on dry weight basis in Tables 1and 2.

M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687 685

greater than those reported in more recent studies inHong Kong and China (Hong et al., 1995; Monirithet al., 2003). The maximum concentration recorded inthe present study was even greater than the greatest con-centration, 430 ng/g lipid wt., measured in mussels fromIndia, one of the largest consumers of HCH in the world(Monirith et al., 2003). The reason for the temporal vari-ations in HCH concentrations is not known. However,our results indicate the necessity for continuous moni-toring and identifying the relevant sources. The HCHprofiles in Hong Kong mussel samples are shown inFig. 2. Compositions of HCH isomers varied amongthe seven sampling locations. c-HCH was the dominantisomer found in mussels from KO, OPT and TM;whereas b-HCH was predominantly found in musselsfrom YTT and MW. Detection of a mixture of HCHisomers indicated that the mussels were mainly contam-inated by technical HCH, rather than lindane whichcontained more than 90% of c-HCH (Li, 1999).

Similar to the distribution pattern of HCHs, greatestconcentrations of total PCBs were found in musselsfrom MW (980 and 1010 ng/g lipid wt.), followed byYTT (920 and 1010 ng/g lipid wt.) and KS (530 and790 ng/g lipid wt.) (Table 2). These contamination levelswere significantly smaller than those reported in 1983from Causeway Bay (130,000 ng/g lipid wt.) and Ren-nies Mill (110,000 ng/g lipid wt.) (Phillips, 1985). Themaximum PCB concentration detected in the presentstudy was also smaller than those found in sites heavilycontaminated by PCBs in Japan and Russia (Monirithet al., 2003). Concentration of PCBs found in musselsfrom Tokyo Bay in Japan and Amursky Bay in Russiawere 5500 and 3700 ng/g lipid wt., respectively.

3.2. Dioxin-like compounds

H4IIE-luc cell bioassay was used to screen for thepresence of dioxin-like activities in the mussel samples(Giesy and Kannan, 1998). Results of the H4IIE-luc cellbioassay performed on mussels from different samplinglocations are shown in Table 3. The greatest concentra-tion of dioxin-like compounds (39 pg TEQ/g wet wt.)was detected in mussels from MW, followed by YTT(37 pg TEQ/g wet wt.). The lowest concentration wasmeasured in mussels from KS (8.6 pg TEQ/g wet wt.).The maximum dioxin-like activity detected in thepresent study was less than the maximum activity(44%-TCDD-max) obtained from blue mussels, Mytilus

edulis, from Korean coastal waters (Khim et al., 2000)and from the sediment samples from Ulsan Bay, Korea(Khim et al., 2001). Negative responses that occurred inother studies (Khim et al., 2001) were not observed inthe present study. There are only a limited number ofstudies on dioxin-like compounds in Hong Kong. Signif-icant dioxin-like responses exhibited by mussels indi-cated the presence of dioxin-like substances, which

may include dioxin-like PCBs, PCDDs, PCDFs, PAHsand others. Future studies involving instrumental analy-ses will be required to determine the contaminantsresponsible for the dioxin-like activities.

3.3. Human health risk assessment

The maximum measured environmental concentra-tions of various contaminants, their correspondingRfDs and estimated RQs are summarized in Table 4.The risk assessment was only confined to PCBs, DDTs,chlordane, dieldrin, HCB and dioxin-like compoundsfor which RfDs are available from the US EPA. Sincethe dioxin-like potency of mussel samples were ex-pressed relative to 2,3,7,8-TCDD, guideline value for2,3,7,8-TCDD was used for evaluating the risk of diox-in-like compounds to human health. In the presentstudy, the greatest measured contaminant concentra-tions present in the mussel samples from all samplinglocations were used for estimating exposure levels. Onthis basis, RQ for dioxin-like compounds (20–79) wasgreater than unity, suggesting that adverse health effectsmay be associated with high shellfish consumption. Pos-sible uncertainties in the present study include: (1) safetystandards employed in the present study were fromUSEPA which might not be applicable to the HongKong population; (2) fish, instead of shellfish, consump-tion rate was used to derive RQ; (3) RQ in the present

686 M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687

study was derived based on consumption rates of heavyseafood consumers; (4) the highest measured environ-mental concentration for a particular contaminant wasused to estimate exposure level; (5) different contami-nants may interact additively, synergistically or antago-nistically to modify effects (Connell et al., 1998a; Funget al., 2004); and (6) different age groups will consumedifferent amounts of food, leading to different exposurelevels (Dougherty et al., 2000). In summary, this preli-minary assessment has considered the ‘‘worse-case’’ sce-nario, and a more refined risk assessment should beundertaken in subsequent investigations.

Acknowledgement

The work described in this paper was supported bythe Area of Excellence Scheme under the Univer-sity Grants Committee of the Hong Kong SpecialAdministration Region, China (Project no. AoE/P-04/2004).

References

Blackmore, G., 1998. An overview of trace metal pollution in thecoastal waters of Hong Kong. The Science of the Total Environ-ment 214, 21–48.

Broom, M.J., Ng, A.K.M., 1995. Water quality in Hong Kong and theinfluence of the Pearl River. In: Coastal Infrastructure Develop-ment in Hong Kong—a review. In: Proceedings of the Symposiumon Hydraulics of Hong Kong Waters. Civil Engineering Depart-ment, Hong Kong Government, pp. 193–213.

Chan, H.M., Chan, K.M., Dickman, M., 1999. Organochlorines inHong Kong fish. Marine Pollution Bulletin 39, 346–351.

Chiu, S.T., Lam, F.S., Tze, W.L., Chau, C.W., Ye, D.Y., 2000. Tracemetals in mussels from mariculture zones, Hong Kong. Chemo-sphere 41, 101–108.

Connell, D.W., Wu, R.S.S., Richardson, B.J., Leung, K., Lam, P.K.S.,Connell, P.A., 1998a. Fate and risk evaluation of persistent organiccontaminants and related compounds in Victoria Harbour, HongKong. Chemosphere 36, 2019–2030.

Connell, D.W., Wu, R.S.S., Richardson, B.J., Leung, K., Lam, P.K.S.,Connell, P.A., 1998b. Occurrence of persistent organic contami-nants and related substances in Hong Kong marine areas: anoverview. Marine Pollution Bulletin 36, 376–384.

Dougherty, C.P., Holtz, S.H., Reinert, J.C., Panyacosit, L., Axelrad,D.A., Woodruff, T.J., 2000. Dietary exposures to food contami-nants across the United States. Environmental Research Section A84, 170–185.

Fiedler, H., 1996. Sources of PCDD/PCDF and impact on theenvironment. Chemosphere 32, 55–64.

Fu, J., Mai, B., Sheng, G., Zhang, G., Wang, X., Peng, P., Xiao, X.,Ran, R., Cheng, F., Peng, X., Wang, Z., Tang, U.W., 2003.Persistent organic pollutants in environment of the Pearl RiverDelta, China: an overview. Chemosphere 52, 1411–1422.

Fung, C.N., Lam, J.C.W., Zheng, G.J., Connell, D.W., Monirith, I.,Tanabe, S., Richardson, B.J., Lam, P.K.S., 2004. Mussel-basedmonitoring of trace metal and organic contaminants along the eastcoast of China using Perna viridis and Mytilus edulis. Environ-mental Pollution 127, 203–216.

Giesy, J.P., Kannan, K., 1998. Dioxin-like and non-dioxin-like toxiceffects of polychlorinated biphenyls (PCBs): Implications for riskassessment. Critical Reviews in Toxicology 28, 511–569.

Giesy, J.P., Ludwig, J.P., Tillitt, D.E., 1994. Embryolethality anddeformities in colonial, fish-eating, water birds of the Great Lakesregion: Assessing Causality. Environmental Science & Technology28, 128A–135A.

Hong, H., Xu, L., Zhang, L., Chen, J.C., Wong, Y.S., Wan, T.S.M.,1995. Environmental fate and chemistry of organic pollutants inthe sediment of Xiamen and Victoria Harbours. Marine PollutionBulletin 31, 229–236.

Ip, H.M.H., 1983. Breast milk contaminants in Hong Kong. Bulletinof the Hong Kong Medical Association 35, 16.

Kan-atireklap, S., Tanabe, S., Sanguansin, J., Tabucanon, M.S., 1997.Contamination by butyltin compounds and organochlorines resi-dues in green mussel (Perna viridis L.) from Thailand coastalwaters. Environmental Pollution 97, 79–89.

Khim, J.S., Lee, K.T., Villeneuve, D.L., Kannan, K., Giesy, J.P., Koh,C.H., 2001. In vitro bioassay determination of dioxin-like andestrogenic activity in sediment and water from Ulsan Bay and itsvicinity, Korea. Archives of Environmental Contamination andToxicology 40, 151–160.

Khim, J.S., Villeneuve, D.L., Kannan, K., Hu, W.Y., Giesy, J.P.,Kang, S.G., Song, K.J., Koh, C.H., 2000. Instrumental andbioanalytical measures of persistent organochlorines in blue mussel(Mytilus edulis) from Korean coastal waters. Archives of Environ-mental Contamination and Toxicology 39, 360–368.

Lai, K.P., Li, W., Xu, Y., Wong, M.H., Wong, C.K.C., 2004. Dioxin-like components in human breast milk collected from Hong Kongand Guangzhou. Environmental Research 96, 88–94.

Lam, C.W.Y., 1990. Pollution effects of marine fish culture in HongKong. Asian Marine Biology 7, 1–7.

Li, Y.F., 1999. Global technical hexachlorocyclohexane usage and itscontamination consequences in the environment: from 1948 to1997. The Science of the Total Environment 232, 121–158.

Liem, A.K.D., Furst, P., Rappe, C., 2000. Exposure of populations todioxins and related compounds. Food Additives and Contaminants17, 241–259.

Mai, B.X., Fu, J.M., Sheng, G.Y., Kang, Y.H., Lin, Z., Zhang, G.,Min, Y.S., Zeng, E.Y., 2002. Chlorinated and polycyclic aromatichydrocarbons in riverine and estuarine sediments from Pearl RiverDelta, China. Environmental Pollution 117, 457–474.

Monirith, I., Ueno, D., Takahashi, S., Nakata, H., Sudaryanto, A.,Subramanian, A., Karuppiah, S., Ismail, A., Muchtar, M., Zheng,J., Richardson, B.J., Prudente, M., Hue, N.D., Tana, T.S., Tkalin,A.V., Tanabe, S., 2003. Asia-Pacific mussel watch: monitoringcontamination of persistent organochlorine compounds in coastalwaters of Asian countries. Marine Pollution Bulletin 46, 281–300.

Owen, R.B., Sandhu, N., 1999. Heavy metal accumulation andanthropogenic impacts on Tolo Harbour, Hong Kong. MarinePollution Bulletin 40, 174–180.

Phillips, D.J.H., 1985. Organochlorines and trace metals in green-lipped mussels Perna viridis from Hong Kong waters: a test ofindicator ability. Marine Ecology Progress Series 21, 251–258.

Safe, S.H., 1994. Polychlorinated biphenyls (PCBs): environmentalimpact, biochemical and toxic responses, and implications for riskassessment. Critical Reviews in Toxicology 24, 87–149.

Sanderson, J.T., Aarts, J.M.M.J.G., Brouwer, A., Froese, K.L.,Denison, M.S., Giesy, J.P., 1996. Comparison of Ah receptor-mediated luciferase and ethoxyresorufin-O-deethylase induction inH4IIE cells: implications for their use as bioanalytical tools for thedetection of polyhalogenated aromatic hydrocarbons. Toxicologyand Applied Pharmacology 137, 316–325.

Schoeters, G., Goyvaerts, M.P., Ooms, D., Cleuvenbergen, R.V., 2004.The evaluation of dioxin and dioxin-like contaminants in selectedfood samples obtained from the Belgian market: comparison of

M.K. So et al. / Marine Pollution Bulletin 51 (2005) 677–687 687

TEQ measurements obtained through the CALUX bioassay withcongener specific chemical analyses. Chemosphere 54, 1289–1297.

Tanabe, S., Prudente, M.S., Kan-atireklap, S., Subramanian, A., 2000.Mussel watch: marine pollution monitoring of butyltins andorganochlorines in coastal waters of Thailand, Philippines andIndia. Ocean & Coastal Management 43, 819–839.

Tanner, P.A., Leong, L.S., Pan, S.M., 2000. Contamination of heavymetals in marine sediment cores from Victoria Harbour, HongKong. Marine Pollution Bulletin 40, 769–779.

Villeneuve, D.L., Blankenship, A.L., Giesy, J.P., 2000. Derivationand application of relative potency estimates based on in vitrobioassay results. Environmental Toxicology and Chemistry 19,2835–2843.

Winters, D., Cleverly, D., Meier, K., Dupuy, A., Byrne, C., Deyrup,C., Ellis, R., Ferrario, J., Harless, R., Leese, W., Lorber, M.,McDaniel, D., Schaum, J., Walcott, J., 1995. A statistical survey ofdioxin-like compounds in United States beef: a progress report.Chemosphere 32, 469–478.

Wong, C.K.C., Cheung, R.Y.H., Wong, M.H., 2000. Heavy metalconcentrations in green-lipped mussels collected from Tolo Har-bour and markets in Hong Kong and Shenzhen. EnvironmentalPollution 109, 165–171.

Wong, H.L., Giesy, J.P., Lam, P.K.S., 2004. Atmospheric deposition,and fluxes of organochlorine pesticides and coplanar polychlori-

nated biphenyls in aquatic environments of Hong Kong, China.Environmental Science and Technology 38, 6513–6521.

Wong, H.L., Giesy, J.P., Siu, W.H.L., Lam, P.K.S., 2005. Estrogenicand dioxin-like activities and cytotoxicity of sediments and biotafrom Hong Kong mudflats. Archives of Environmental Contam-ination and Toxicology 48, 575–586.

Wu, R.S.S., 1988. Marine pollution in Hong Kong: a review. AsianMarine Biology 5, 1–23.

Xue, H., Chai, F., 2001. Coupled physical–biological model for thePearl River Estuary: a phosphate limited subtropical ecosystem. In:Proceedings of the 7th International Conference on Estuarine andCoastal Modeling, St. Petersburg, FL, November, 2001.

Yu, K.N., Lam, P.K.S., Cheung, C.C.C., Yip, C.W.Y., 2002.Mathematical modeling of PCB bioaccumulation in Perna viridis.Marine Pollution Bulletin 45, 332–338.

Yung, Y.K., Yau, K., Wong, C.K., Chan, K.K., Yeung, I., Kueh,C.S.W., Broom, M.J., 1998. Some observations on the changesof physico-chemical and biological factors in Victoria Harbour andvicinity, HongKong, 1988–1996.Marine Pollution Bulletin 39, 315–325.

Zhou, J.L., Maskaoui, K., Qiu, Y.W., Hong, H.S., Wang, Z.D., 2001.Polychlorinated biphenyl congeners and organochlorine insecti-cides in the water column and sediments of Daya Bay, China.Environmental Pollution 113, 373–384.