A review of heavy metal and organochlorine levels in marine mammals in Australia.

Study of toxic contaminants in marine mammal specimens collected around Australia is currently uncoordinated and piecemeal. Most states collect samples but there is little or no financial support for their analysis. This study combines data, published or unpublished, from 13 sources. Heavy metals have been analysed in about 676 specimens; over 400 were for mercury levels in P. macrocephalus taken at a whaling station. The remaining samples were mostly from toothed whales, a few baleen whales (< 20), pinnipeds (41) and dugongs (49). The most consistently analysed metals were lead, mercury and cadmium. Liver and kidney lead levels ranged from < 1-3 ppm; levels in bone were 0-418 ppm, with most less than 10 ppm. Mercury levels in a large sample of P. macrocephalus muscle were < 12.2 ppm. Mercury levels in the small number of samples from other species were 0.51-143 ppm (kidney), 1.52-479 ppm (liver) and < 0.1-36 ppm (muscle). Cadmium levels in liver (0-52 ppm) and kidney (0-106 ppm) were extremely variable. Levels greater than 10 ppm were recorded in many species and were especially high in Hydrurga leptonyx, Dugong dugon, Mesoplodon layardii and Pseudorca crassidens. Adult Tursiops truncatus inhabiting the inshore gulfs of South Australia had considerably higher levels of cadmium compared with other regions. Information on organochlorine levels is sparse (approximately 39 specimens) and suggest low levels when compared to other parts of the world. Total DDT was highest (28.4 ppm) in a neonatal Orcinus orca. Some high levels of DDT were recorded in Tursiops truncatus, Delphinus delphis and Arctocephalus pusillus doriferus. PCBs ranged from < 0.05 to 3.87 ppm. A comprehensive pathological assessment of marine mammals is needed in order to evaluate the effects of toxic contaminants.