bifenthrin, currently in widespread urban use in gardens, on golf courses and ... guidelines in some canals, and that bifenthrin may be at the threshold for ...
CONTAMINANTS IN OYSTERS COLLECTED FROM RESIDENTIAL CANALS BETWEEN RUNAWAY BAY AND THE SOVEREIGN ISLANDS IN JANUARY 2000.
Munro R. Mortimer Queensland Environmental Protection Agency
April 2000
EXECUTIVE SUMMARY In January 2000, oysters were sampled from five locations in the Runaway Bay Hollywell - Paradise Point canal system between Lae Drive and the Coombabah River, and nearby at the Sovereign Islands in the Broadwater, by officers of the Queensland Environmental Protection Agency. Oyster tissues were analysed for pesticides, polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), trace metals and metalloids, and indicators of bacterial contamination, by Queensland Government and CSIRO laboratories. Four contaminants detected were of potential public health concern. Tests showed that oysters at two sites within the Paradise Point - Hollywell portions of the canal system contained concentrations of E. coli bacteria unacceptable under the Australian and New Zealand Food Standards Code (ANZFA, 1999). In addition, concentrations of copper in oysters from all canal sites, but not at the Sovereign Islands site, exceeded the food code, although by a narrow margin, and trace concentrations of two pesticides detected in oysters from some canals were not acceptable under the code. Although no PCBs or PAHs were detected, traces of two pesticides, chlorpyrifos and bifenthrin, currently in widespread urban use in gardens, on golf courses and bowling greens, and as termite barriers, were present. Estimates of the ambient concentrations of these chemicals in canal waters, based on their bioconcentration characteristics, indicate that chlorpyrifos concentrations probably exceed current ANZECC water quality guidelines in some canals, and that bifenthrin may be at the threshold for causing harmful effects on sensitive marine organisms. As with the previous study (September 1998), traces of a very persistent metabolite of the organochlorine DDT, banned some years ago, were present. However bioconcentration-based estimations indicate that ambient environmental concentrations of this metabolite (DDE) in the canals are less than thresholds of concern. The study found no pattern of contamination in the oysters which could be associated with the location of the former landfill site at Runaway Bay. Those locations where oysters were contaminated by bacteria were among the most distant from the former landfill site, and although copper marginally exceeded human consumption standards in oysters within the canal system, concentrations were similar across locations. Similarly, there is no evidence of a link between the presence of pesticides and proximity to the former landfill site. Although studies conducted by others over the past few years have found some of the contaminants evaluated in this study at similar, or in some cases greater concentrations, and some people have associated the presence of these contaminants in the canals with the former landfill at Runaway Bay, the levels of contamination appear to be similar throughout the canal system, and not correlated with proximity to the former landfill site. This suggests that the presence of the contaminants is more likely to be from a common source such as urban stormwater, which is a recognised source of such materials. An additional and likely source of copper is copper-based antifouling paint on the hulls of pleasure craft which are moored in the canals in large numbers.
Munro R Mortimer PhD, BSc(Hons), AUA, MACE
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INTRODUCTION This study was commissioned in late 1999 by Gold Coast City Council as a follow up to a previous study in September 1998 (Mortimer and Cox, 1998). The objectives of this second study were to further quantify the concentrations of pesticides, polychlorinated biphenyls (PCBs), metal and metalloid contaminants in oysters resident in the Runaway Bay canal system at various locations relative to the former landfill site north of Lae Drive, and to include additional sites and potential contaminants, including polyaromatic hydrocarbons (PAHs) and indicators of bacteriological contamination not surveyed previously. The field work was conducted by officers from the Monitoring and Modelling Unit of the Environmental and Technical Services Division, Queensland Environmental Protection Agency QEPA), in January 2000. Analysis of pesticides, PCBs and PAHs was conducted by the Queensland Health Scientific Services Laboratory at Coopers Plains, analysis of trace metals and metalloids by the CSIRO Cunningham Laboratory at Indooroopilly, and bacteriological analyses by the Department of Primary Industries Centre for Food Technology Laboratory at Hamilton.
METHODOLOGY Choice of indicator organisms Organisms which are relevant as indicators of contamination of the aquatic environment should comprise common and easily collected species resident in the area of interest and have a proven capacity to accumulate contaminants of concern through mechanisms such as feeding or respiration. It is of additional relevance if the species used are taken commercially or recreationally for human consumption. For this study, the edible oyster (Saccostrea commercialis) which is found in large numbers attached to walls and other hard surfaces below the highwater mark throughout the canal system was sampled. The oyster meets each of the necessary indicator organism prerequisites listed above. Being an attached animal throughout its adult life, the oyster is exposed to all contaminants present in the water column, whether dissolved in the water or attached to particulate matter or in food items, and is a widely used indicator organism for studies of this kind. The first study in this series, commissioned by Gold Coast City Council in 1998, collected data on contaminants in the tissues of both oysters and crabs from the canals. The pattern of contamination between collection sites in crabs was similar to that in the oysters. Accordingly, it was decided to conduct further work with oysters only. Fish were not used as an indicator species because they are very mobile and and contaminant concentrations in the tissues of fish caught in the canal are not necessarily attributable to exposure within the canal.
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Sampling design The five study sampling locations are shown at Figure 1. With the exception of the Sovereign Islands site, locations were within the residential canal system between Runaway Bay and Paradise Point on the Gold Coast. The Sovereign Islands location is close to the canal system, but within the Broadwater, and thus relevant as a reference site. Two sampling locations within canals adjacent to Lae Drive and Wau Avenue were closest to the former Runaway Bay landfill site. The canal sampling locations adjacent to Columbus Drive and at Paradise Point were some 1.5 and 3 km north of the former landfill site respectively. At each of these locations, 5 replicate samples each comprising 10 oysters were taken for bacteriological analysis, and 3 replicate composite samples each comprising at least 20 oysters for analysis of chemical contaminants. Each replicate comprised pooled oysters from multiple collection points at a location. Sample handling and laboratory analysis All oysters were collected from rock surfaces, canal walls and structures such as jetty and bridge pilings accessed from a small boat and/or by wading at low tide. All were stored unopened and on ice in labelled new plastic bags at the point of collection. Oysters for bacteriological analysis were delivered to the laboratory unopened and on ice within 24 hours of collection. The flesh of oysters for chemical analysis was removed from the shell within 48 hours of collection and stored frozen in sealed contaminant-free glass containers. Chemical analysis for pesticides, PCBs and PAHs was conducted by standard methods using florosil cleanup and GC-MS identification and quantitation at the Queensland Health Scientific Services Laboratory at Coopers Plains. Pesticide analysis covered organochlorines (including similar halogenated organics such as PCBs), organophosphates, and synthetic pyrethroids. This laboratory also measured lipid content of the tissues on a gravimetric basis after solvent extraction. Analysis of trace metals and metalloids by ICP-MS at the CSIRO Cunningham Laboratory at Indooroopilly followed freeze drying and hot concentrated nitric acid digestion. Bacteriological analysis was conducted by the DPI Centre for Food Technology Laboratory at Hamilton using standard test methods AS1766.2.1 - 1991 and AS1766.2.3 1992. Where data sets contained values less that the detection limit, values equal to half the detection limit were substituted for the purposes of calculating concentration statistics.
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Figure 1 - Sampling locations for contaminants in oysters survey January 2000.
Paradise Point
N
Sovereign Islands
Columbus Drive
Wau Avenue
Lae Drive
0
0.5
1 Kilometres
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RESULTS AND DISCUSSION Pesticides Organic chemical pesticides with a significant potential to bioconcentrate are lipophilic, and accumulate in the fatty tissue. The fraction of lipid in individual animals can vary with factors such as size, age, and reproductive status. This can lead to misinterpretation if wet weight concentrations are used to compare biotic contamination by these chemicals. Consequently, to compare animals collected from different locations, it is most relevant to express their internal concentrations of pesticides on a lipid basis rather than a wet weight basis. The results from the pesticide analysis of animals collected in this study are summarised in Table 1 on a lipid weight basis. These values should be used to compare the relative pesticide exposure of animals at different locations. No other pesticides were detected.
Table 1 - Pesticide concentrations in oyster contents (mg/kg lipid weight basis). Sovereign Paradise Point Columbus Drive Islands Pesticide mean Standard mean Standard mean Standard error error error (n=3) (n=3) (n=3) 0.147 Chlorpyrifos
