2004
Technical Report No. 7
Dr Ray Corell and Dr Jochen Müller
Department of the Environment and Heritage, May 2004
ISBN 0 642 54999 0
Executive summary
This study was a component of the National Dioxins Program tasked to quantify and assess the concentrations and relative chemical compositions of dioxin-like chemicals in Australian fauna.
The project involved the collection of several hundred fauna samples (primarily roadkill for terrestrial animals and stranded animals for marine mammals) with emphasis on spatial and biological diversity. The collected specimens were pooled into 66 samples covering all States as well as the Northern Territory.
Chemical analysis of the fauna samples was conducted by the Australian Government Analytical Laboratories, and a series of quality assurance/quality control (QA/QC) procedures were incorporated into the study, including replicate field sampling, replicate analysis and an interlaboratory comparison of analyses using an overseas laboratory highly regarded for its experience in the analysis of dioxin-like chemicals in fauna samples. The QA/QC procedure suggested that chemical analysis reproducibility was high, and that the identification of individual dioxin-like chemicals and quantification of their concentrations in fauna samples was reliable. The analysis of sampling replicates, or samples collected at different sites within the regions, demonstrated that the greatest uncertainty of the results related to variability in chemical concentrations between different individuals from a given species.
The concentrations of dioxin-like chemicals in the fauna samples were assessed both in terms of actual concentrations and their toxic equivalents (TEQs). In addition, the patterns of component chemicals were evaluated, and assessments of concentration patterns were made with respect to species and considering their respective food.
Dioxin-like chemicals were detectable in all samples and the levels expressed as toxicity equivalencies ranged from the limit of detection to 3,900 pg TEQ g-1. Overall the survey found highest concentrations in birds of prey (sparrowhawks, goshawks, falcons, eagles etc.) with a maximum level of 3,900 pg TEQ g-1 lipid (middle bound). Piscivorous marine mammals also had high levels with a dolphin from the Port River in South Australia having a level of 590 pg TEQ g-1 lipid. In contrast, levels were generally low in herbivorous animals such as macropods, a galah and a dugong (marine mammal that feeds exclusively on seagrass).
Concentrations of dioxin-like chemicals in the 22 macropod samples (mostly pooled samples of several animals) that were analysed in the study were relatively low with a median concentration of 0.71 pg g-1 lipid. The highest concentrations of dioxin-like chemicals in macropods were detected in a sample (pool of three kangaroos) that was collected from the Para Wirra National Park located 25 km north north-east of Adelaide; this sample had a TEQ of 25 pg g-1 lipid.
Of the three groups of compounds (PCDDs, PCDFs and PCBs), the main contributors to the TEQ were the PCDDs - in the case of the galah (a primary feeder) this was dominated by OCDD, but in other bird samples (for example, black-shouldered kites) the main components were PeCDD and HxCDDs. PCBs contributed significantly to the TEQ load of birds. An example was a collared sparrowhawk from South Australia that had a TEQ of 3,900 pg g-1 lipid with a contribution of 2,200 pg TEQ g-1 lipid of the total TEQ coming from PCB 126.
Contribution of dioxin-like PCBs to TEQs was most dominant in marine mammals and the congener profiles of the PCDD/PCDFs and dioxin-like PCBs were similar for all marine mammals sampled. There was, however, an indication of elevated concentration of 1,2,3,7,6-PeCDD relative to the PCBs in both the dugong and dolphin samples from Darwin. It was noted that the bottlenosed dolphin from Port River South Australia had much higher PCB levels than those from a previous study in Spencer Gulf.
The TEQ of the other marsupials (possum, koala and bandicoot) were low and comparable to that of the macropods. The relative contributions of PCDD/PCDFs and PCBs were similar to those of the macropds but were very variable from sample to sample. The TEQ of the monotremes were intermediate between those of birds and the macropods, with typically PCDD/PCDFs (especially PeCDD) making the greatest contribution. The highest value was 60 TEQ pg g-1 lipid that was found in an echidna from Port Elliot, South Australia. There was one sample of platypus from Tasmania where PCBs contributed more than PCDD/PCDFs to the TEQ.
Field variability
Estimates of field variability were obtained as part of the study. Coefficients of variation of 80% were typical between observations from similar animals from a similar location. The highly variable levels of analytes indicate that caution should be applied when comparisons are made between individual samples. Furthermore, there is evidence of local anomalies. Together these factors present a challenge to the interpretation of the data.
Comparison with overseas studies
In general the levels of dioxin-like compounds were low by overseas standards.
The predatory birds from Australia generally had lower TEQ than did comparable birds from North America, Europe, India and Japan.
The macropods generally had a low TEQ (median 0.71 pg g-1 lipid) which was at the lower end of the range of values reported from caribou in Yukon (0.7-6.4 pg g-1 lipid) and less than sika deer from Japan 3.2-330 pg g-1 lipid). Six of the 22 macropod samples had a TEQ greater than 3 pg g-1 lipid, which is the EU maximum permissible limit in meat for human consumption. However it is noteworthy that on a fresh weight basis the levels of dioxin-like chemicals are relatively low and the high levels recorded may be the result of the relatively low fat content of macropod meat.
The TEQs in the marine mammals reported in this survey are also low by world standards.