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Title: A study of synthetic polycyclic musks in the aquatic environment of Hong Kong
Other Titles: Xianggang shui huan jing zhong he cheng duo huan she xiang wu zhi de yan jiu
Authors: Shek, Wai Man (石慧敏)
Department: Dept. of Biology and Chemistry
Degree: Master of Philosophy
Issue Date: 2007
Publisher: City University of Hong Kong
Subjects: Sewage disposal -- China -- Hong Kong
Water -- Pollution -- China -- Hong Kong
Notes: CityU Call Number: TD613.H85 S54 2007
Includes bibliographical references (leaves 95-101)
Thesis (M.Phil.)--City University of Hong Kong, 2007
xv, 101 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: Synthetic musks are artificial chemicals produced in large quantities and widely used as fragrance ingredients in numerous consumer products, including detergents, cleansing products, air fresheners, perfumes, aftershaves, cosmetics and personal care products. Because of their typical musky scent and fixative properties, enormous quantities of these compounds are manufactured to replace the rare and expensive natural musks obtained from musk deer. One prevalent group of synthetic musks is polycyclic musks, which include Cashmeran (DPMI), Celestolide (ADBI), Phantolide (AHMI), Traseolide (ATII), Galaxolide (HHCB) and Tonalide (AHTN). In the late 20th century, polycyclic musks (especially HHCB and AHTN) gained much attention as environmental contaminants due to their elevated levels in both environmental and human samples. The results of various risk assessments have shown that the risks of polycyclic musks were generally low; however, HHCB and AHTN were included on the Oslo and Paris Commissions for the Prevention of Marine Pollution (OSPAR) list of Chemicals for Priority Action in 1998 in the category of diffuse sources and groups of substances to be considered for action (OSPAR, 2000). Hong Kong's population was approximately 6.88 million in mid-2004, with a population density of 6,380 people per square kilometre. There is no doubt that personal care products and perfumes are extensively used within this dense population and that the musks in these consumer products follow the domestic down-the-drain pathway to sewage treatment facilities, thus ending up in the environment. There are a total of 43 submarine outfalls and two sewage effluent disposal tunnels built around Hong Kong for discharging effluent from treatment of the 2.6 million cubic metres of sewage that are produced daily in the city. Therefore, there exists a possibility that Hong Kong waters may be polluted by synthetic musk compounds from treated sewage, if the current sewage treatment processes are not sufficient to remove these compounds. Studies have reported the widespread occurrence of polycyclic musks in surface waters, sediments and biota from European countries. However, information on contamination of polycyclic musks in Asian regions is very limited and there is currently no study researching the status of polycyclic musks in Hong Kong’s environment. Due to the increasing concern about chemical contaminants in the environment, this project was undertaken to determine the concentrations of six synthetic polycyclic musks (HHCB, AHTN, DPMI, AHMI, ATII and ADBI) in sewage sludges and mussels collected in Hong Kong in order to quantify musk release as well as potential uptake of these compounds by local biota. In 2005, dewatered sewage sludge was obtained from ten major sewage treatment plants using Primary Treatment (PT), Secondary Treatment (SecT) or Chemical-Enhanced Primary Treatment (CEPT). HHCB, AHTN, AHMI and ADBI concentrations ranged from below detection limit (BDL) to 78.58 mg/kg dry weight in Hong Kong sludge samples. HHCB and AHTN were the two most predominant polycyclic musks in sludge samples, suggesting the extensive use of these two polycyclic musks in Hong Kong. Polycyclic musk levels in CEPT sludge were significantly higher than those in SecT and PT sludge, suggesting that CEPT sludge has a higher ability to retain polycyclic musks. Compared with worldwide samples, HHCB and AHTN concentrations detected in Hong Kong sludge ranked first and second respectively, indicating that there is probably a relatively high usage of HHCB and AHTN in the Hong Kong community. However, the estimated levels of HHCB and AHTN in the discharged effluent from sewage treatment plants may pose low potential risk to aquatic organisms according to the threshold effect levels derived from fish. Nevertheless, the high concentrations measured in sewage sludges indicated that musk compounds might be bioconcentrated and bioaccumulated in the marine environment in Hong Kong. Therefore, it was deemed necessary to carry out a monitoring study on a marine organism, particularly for the two prevailing polycyclic musks. In this investigation, green lipped mussels (Perna viridis) were collected from nine coastal locations of Hong Kong. Sampling locations were situated in central waters (Victoria Harbour), which are strongly influenced by human activities, as well as in southern and eastern waters where there are relatively less anthropogenic impacts. HHCB, AHTN and ADBI concentrations ranged from BDL to 6.08 mg/kg lipid weight in mussel samples. The highest levels of polycyclic musks were found in Victoria Harbour, implying that the harbour is heavily affected by the effluent discharged from the nearby main sewage outfalls. Similar to the concentrations measured in sewage sludge, levels of HHCB and AHTN detected in Hong Kong mussel samples are the highest and the second-highest, respectively, compared to previous studies. This is an initial indication of relatively extensive use of these two musk compounds by the Hong Kong population and their possible release from sewage treatment works into the aquatic environment. A preliminary human health risk assessment was conducted to elucidate the potential risks associated with the consumption of shellfish from local waters. Results indicated that levels of HHCB and AHTN in biota pose little or no threat to the health of shellfish consumers. Nevertheless, the massive amount of polycyclic musks being used by the dense population in Hong Kong may increase the overall level of pollution over time, and limited toxicological data is currently available for these compounds. Therefore, more comprehensive studies are required to further assess the ecological and human health risks that are associated with polycyclic musks. Overall, the present study has provided baseline information on a range of polycyclic musks, and has assessed the potential hazards of these contaminants to the Hong Kong aquatic environment. These results will contribute to the continued evaluation of the levels of polycyclic musks, as well as tracking the overall quality of Hong Kong waters.
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