Estrogenic and dioxin-like activities and cytotoxicity of sediments and biota from Hong Kong mudflats.

Persistent organic pollutants, such as organochlorine insecticides and polychlorinated biphenyls (PCBs), were measured in several environmental matrices including aerial deposition, seawater, sediment, and biota in two important coastal wetlands of Hong Kong, China. Specifically, samples were collected from within the Mai Po Marshes Nature Reserve (Mai Po), an internationally acclaimed wetland situated in the northwestern part of the New Territories of Hong Kong, and A Chau in Starling Inlet, a relatively remote island on the eastern side of Hong Kong. Hexachlorobenzene, dichlorodiphenyltrichloroethanes, and hexachlorocyclohexanes were detected in all samples collected from Mai Po. Environmental endocrine disruptors (including dioxin-like compounds and estrogenic chemicals), measured by the use of cell-based chemical activated luciferase expression assays, were found to occur at concentrations that might pose a risk to the ecologic systems in Mai Po. Dioxin-like PCBs were detected at small concentrations in some of the samples. Concentrations of 2,3,7,8 tetrachlorodibenzo-p-dioxin equivalents (TEQs) were primarily related to the relatively great concentrations (>100 ng/g dry weight) of high molecular-weight polycyclic aromatic hydrocarbons in sediments, whereas the relative proportion of TEQs contributed by nonortho-substituted PCBs was small. Polar compounds primarily contributed estrogen equivalents, which were measured in sediments. Significant concentrations of cytotoxic compounds were detected in fish samples collected from the Mai Po but not in fish collected from A Chau.

Application of the comet and micronucleus assays to the detection of B[a]P genotoxicity in haemocytes of the green-lipped mussel (Perna viridis).

Green-lipped mussels (Perna viridis) were exposed to water-borne benzo[a]pyrene (B[a]P) at nominal concentrations of 0, 0.3, 3 and 30 microg l(-1) for up to 12 days, and both the relative levels of DNA strand breaks (assessed using an alkaline comet assay) and the proportion of micronucleus (MN) formation were monitored in mussel haemocytes at days 0, 1, 3, 6 and 12. The results of the comet assay indicated that an increase in the proportion of strand breaks occurred generally with increasing B[a]P concentration, but a significant decrease in the levels of DNA damage was observed after exposure for 12 days at all concentrations tested, suggesting that the patterns of changes in the levels of DNA strand breakage can be explained by the threshold dependent DNA repair theory. Moreover, the relatively slow development and recovery of the DNA damage response in mussel haemocytes in comparison with previous findings utilizing P. viridis hepatopancreas suggests that the response of DNA alteration upon exposure to B[a]P may be tissue-specific in this species. Monitoring the frequency of micronucleus development in mussel haemocytes indicated both dose- and time-response relationships within the exposure period. Furthermore, the levels of DNA strand breakage correlated well with the levels of micronucleus induction, suggesting a possible cause and effect relationship between the two damage types. We suggest that DNA strand breakage and micronucleus formation in mussel haemocytes can potentially be used as convenient biomarkers of exposure to genotoxicants in the marine environment.

Antioxidant responses to benzo[a]pyrene and Aroclor 1254 exposure in the green-lipped mussel, Perna viridis.

In this study, the green-lipped mussel, Perna viridis (L.), was exposed to two concentrations of benzo[a]pyrene (B[a]P) (0.3 microg l(-1); 3 microg l(-1)) and two concentrations of Aroclor 1254 (0.5 microg l(-1); 5 microg l(-1)). In addition, a mixture of the contaminants was used (0.3 microg l(-1) B[a]P+0.5 microg l(-1) Aroclor 1254; 3 microg l(-1) B[a]P+5 microg l(-1) Aroclor 1254). All concentrations were nominal. A suite of enzymes [glutathione S transferase (GST), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR)], glutathione (GSH) level and lipid peroxidation (LPO) in the mussel gill and hepatopancreas were monitored over 18 days. CAT and GSH in gill tissue were positively correlated with concentration of Aroclor 1254. Activity of hepatic GST and SOD was significantly related to body burden of Aroclor 1254. LPO, GR and GPx in gill and hepatopancreas and hepatic GST were positively correlated with B[a]P concentration. The results indicate the importance of using biomarkers specific to the type of contaminant(s) that are likely to be present. Controlled laboratory experiments, such as this study, are useful in ascertaining biomarkers suitable for use with complex contaminant mixtures in the marine environment.

Exposure and time dependent DNA strand breakage in hepatopancreas of green-lipped mussels (Perna viridis) exposed to Aroclor 1254, and mixtures of B[a]P and Aroclor 1254.

Green-lipped mussels (Perna viridis) were exposed to Aroclor 1254 (0.5, 5 and 50 microgl(-1)) and a mixture of benzo[a]pyrene (B[a]P) and Aroclor 1254 (0.3+0.5 and 3+5 microgl(-1)) for 12 days. On day 0, 1, 3, 6 and 12, the levels of DNA strand breaks in the mussel hepatopancreas were monitored using an alkaline unwinding assay. The results were compared to the findings of a previous study in which the levels of DNA strand breakage in the same species were measured following exposure to various concentrations of B[a]P (0.3, 3 and 30 microgl(-1)). The results indicated that Aroclor 1254 at a concentration