Estrogenic and Dioxin-like Activities and Cytotoxicity of Sediments and Biota from Hong Kong Mudflats H. L. Wong, 1 J. P. Giesy, 1,2 W. H. L. Siu, 1 P. K. S. Lam 1 1 Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 2 Zoology Department, National Food Safety and Toxicology Center and Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824-1311, USA Received: 20 July 2004 /Accepted: 19 October 2004 Abstract. 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 Re- serve (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, dichlorodi- phenyltrichloroethanes, 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 aro- matic hydrocarbons in sediments, whereas the relative pro- portion 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. A study was conducted to characterize the current magnitude and extent of contamination in two important coastal marine habitats, Mai Po Marshes Nature Reserve (Mai Po) and A Chau, in Hong Kong. Mai Po is located at the northwest edge of Hong Kong where mudflats and mangroves are important habitats for a wide variety of birds, particularly migratory shore birds. Mai Po is an important midpoint of the Eastern Asian–Australian Flyway. For this reason, the area has been designated a wetland of international importance under the Ramsar Convention. Persistent organic pollutants (POPs)— such as polycyclic aromatic hydrocarbons (PAHs), organo- chlorine (OC) insecticides, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlori- nated dibenzofurans (PCDFs)—have been considered to be the major contaminants of concern that might pose a threat to this valuable and protected system. A Chau is a remote island in the northeastern part of Hong Kong where several species of waterbird breed. A Chau is expected to be less contaminated than Mai Po (Connell et al. 2003), and was selected as a ref- erence area. In this study, a survey of the primary contami- nants of concern was conducted at Mai Po and A Chau. Because POPs are not the only toxicants that could possibly cause effects on wildlife, several bioanalytical techniques were used to screen for larger classes of compounds that might af- fect wildlife. Previous studies demonstrated that several OC pesticides and PCBs in the sediment and biota at Mai Po ex- ceed the guideline values of regulatory authorities, e.g., the United States Environmental Protection Agency (Zheng et al. 1999; Liang et al. 1999; Müller et al. 2002). Notwithstanding, there has been no attempt to correlate body concentrations with hormonal and other signal transduction interference ef- fects. Therefore, baseline studies aimed at characterizing the key environmental contaminants, especially those exerting endocrine-disrupting effects, are needed to establish protective schemes for these valuable ecosystems. Specifically, these bioassays, based on in vitro cell systems, were used to screen for estrogenic potency, total dioxin-like activity, and nonspe- cific cytotoxicity. These screening assays were used in con- junction with toxicity identification and evaluation techniques to determine potential classes of compounds contributing to each of the observed effects. In vitro bioassays are useful for screening biorelevant toxicological end points and providing information that can complement instrumental analysis and allow a more complete and cost-effective characterization of environmental samples (Murk et al. 1996; Hilscherova et al. 2000). Bioassays can Correspondence to: P. K. S. Lam; email: bhpksl@cityu.edu.hk Arch. Environ. Contam. Toxicol. 48, 575–586 (2005) DOI: 10.1007/s00244-004-0166-1