Contamination of wildlife by polychlorinated biphenyls (PCBs) and other organochlorine compounds such as BHC, DDT and Heptachlor is a worldwide phenomenon. These are widespread and persistent chemicals in the environment and have been progressively banned since the 1980s and '90s. PCBs were formally used in substances such as transformer oils and hydraulic fluids, plastics, adhesive products, printers ink and many other industrial products. BHC, DDT and Heptachlor were once widely used as pesticides and are now banned.
A survey was conducted during 1999 - 2000 by the Environment Division and Inland Fisheries Service to determine the extent of any contamination of these pollutants. Heavy metal levels were also determined. Sampling occurred in the following catchments - Tamar, Derwent, Forth, Emu, Pipers, South Esk River, North Esk River, together with lakes Pieman, Pedder, Great Lake and Western Lakes.
Approximately 300 samples of trout flesh and livers, eel flesh and livers and 36 sediment samples were taken from these catchments and were analysed for PCBs, BHC, DDT and Heptachlor and heavy metals, arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, lead, zinc and mercury.
In all flesh samples no PCBs were detected at a detection limit of 0.1 ppm. The allowable concentration of PCBs in fish and fish products is 0.5 ppm as defined by the Australian Food Standards Code. All flesh sample concentrations were therefore at least five times less than those allowable.
A number of liver samples from widespread locations had detectable levels of PCBs, most were in the range 0.1 to 0.3 ppm with the maximum level being two samples with 0.6 ppm. This is not unexpected as livers and some other organs typically concentrate such chemicals to a greater degree than flesh. These parts of fish are not generally consumed.
The results show lower levels of PCBs than have been found in most other comparable studies that have been undertaken around the world. Brown trout, for example, taken from remote Scottish lakes have been found to contain PCB levels in the flesh of up to 2.2 ppm and up to 2.5 ppm in the liver.
Flesh from American Great Lake salmon have also been found to contain 0.6 - 1.3 ppm PCBs.
For this study all the flesh and liver samples were found to be below the detection limit for all of the pesticides tested, ie BHC, Heptachlor and DDT.
The study indicates that there is no cause for concern with PCB, BHC, Heptachlor and DDT contamination of trout and eels in the areas sampled and that these species from Tasmanian waters are as clean as those found anywhere in the world in relation to these pollutants.
With regard to sediments, PCBs were only detected in one sample at a level of 0.31 ppm. This is not unexpected as the sample was taken downstream of a populated area and the level is well below the acceptable ANZECC sediment quality guidelines of 23 ppm.
DDT was detected in two sediment samples at levels of 0.58 ppm and 0.31 ppm, which is well below the acceptable ANZECC sediment quality guidelines of 1.6 ppm. This level was not unexpected as the samples were taken adjacent to an area historically used for intensive agriculture.
With regard to heavy metals and sediments, no levels of concern were found.
This study also confirmed previous extensive studies by CSIRO, Inland Fisheries, HEC and DPIWE, that elevated levels of mercury in fish and eel flesh, taken from Lake Gordon, occur as a consequence of natural processes associated with mineralisation.
All analysis was undertaken by Analytical Services Tasmania laboratory. A total of over 6400 analytical determinations were undertaken during this project.
It is intended to publish the results of the study in a scientific journal.