Marine organisms were collected for tissue sample analysis from four stations in Hong Kong waters that cover Deep Bay (DB), Southern Waters (SW), Mirs Bay (MB) and Port Shelter (PS) (see Figure 2.1a). For the tissue sampling stations, it was important to select areas of seabed which represent trawlable ground. Given the small size of most fish and fisheries species in Hong Kong, it is often difficult to collect the amount of tissue required for chemical analysis and thus it is important to maximise sampling success by choosing areas which have been successfully sampled previously. For these reasons, two of the four trawl transects (Port Shelter, Mirs Bay) correspond to areas sampled monthly during 1995-1996 for the Study of Fisheries Resources and Fishing Operations in Hong Kong Waters. The two other transects (Deep Bay, Southern Waters) were initially located on a provisional basis.

Certain organic compounds are especially toxic and may directly affect the aquatic organisms exposed. Aquatic organisms such as fish and crustaceans are often harvested as food (especially in Hong Kong) and contaminant trophic transfer renders human consumers potentially at risk. Monitoring of toxic organic contaminants of concern in the Hong Kong marine environment is thus important owing to their inherent environmental implications. The choice of toxic organic contaminant compounds analysed in the current study is briefly discussed in Section 1 and a more detailed discussion of the toxic nature of these compounds is provided in Section 4. The following toxic organic contaminants were analysed in the tissue samples obtained from the biota (ie fish, crab, shrimp, mollusc):

1. Total Polycyclic Aromatic Hydrocarbons (PAHs) - a class of organic compound some of which are persistent and carcinogenic. These compounds may be bioaccumulated and stored in the fatty body tissues of mammals. PAHs are a diverse group of compounds and their toxicity differs between the various congeners. Available recent toxicity and carcinogenic class data were taken from the USEPA Integrated Risk Information System (IRIS)(16)) and the World Health Organization(17)) for the individual PAHs measured in the biota. The USEPA's carcinogen class system comprises the following categories:

   • Group A - Human carcinogens;

   • Group B - Probable human carcinogens;

   • Group C - Possible human carcinogens;

   • Group D - Not classifiable as to human carcinogenicity; and,

   • Group E - Evidence of noncarcinogenicity for humans.

   • The individual PAHs analysed in the biota during the course of this Study and their carcinogenicity potential to humans and/or toxicity to aquatic biota (predominantly crustaceans) are outlined in

Table 3.1a Reported Values from the Literature on the Toxicity of Individual PAHs
PAH	USEPA Class1	Toxicity2
Acenaphthene	Unknown	48h LC50 to Daphnia magna 41,000 ug L-1
Acenaphthylene	Unknown	No data for crustacean toxicity are available. Fish, 48h LC50 to Oryzias latipes 11,000 ug L-1
Anthracene	D	24h LC50 (dark) 3h LC50 (UV light) to Artemia salina >50 ug L-1 and 20 ug L-1 , respectively
Fluorene	D	48h NOEC to Daphnia magna 17 ug L-1
Naphthalene	C	8d LC50 to Hemigrapsus nudus 2800 ug L-1
Phenanthrene	D	24h LC50 (dark) to Artemia salina 677 ug L-1
Benzo (a) anthracene	B2	96h LC50 (12h light: dark) to Daphnia pulex 10 ug L-1
Benzo (a) pyrene	B2	1.64d LC50 (no UV for 24h) to Daphnia magna 0.7 ug L-1
Chrysene	B2	48h LC50 (UV for 24h) to Daphnia magna 0.7 ug L-1
Dibenzo (a,h) anthracene	B2	1.13d LC50 (no UV for 1d: UV for 0.13d) to Daphnia magna 0.4 ug L-1
Fluoranthene	D	3h LC50 (natural light) to Artemia salina 40 ug L-1
Pyrene	D	3h LC50 (1h UV light) to Artemia salina 8 ug L-1

Table 3.1a.

Note 1: USEPA (1989)
Note 2: WHO (1998)

2. Total Polychlorinated Biphenyls (PCBs) - a class of persistent man-made chemicals which tend to bioaccumulate through the food chain and can cause reproductive failure and cancer;

3. Organochlorine Pesticides (Total DDT) - contaminants which are persistent, highly lipophilic (can be accumulated and stored in fat), have high bioaccumulation and biomagnification potential, and high toxicity to aquatic organisms; and,

4. Tributyltin (TBT) - a moderately persistent toxic compound found predominantly in marine sediments and the surface microlayer which may be bioaccumulated and cause growth abnormalities and reproductive failure.