Platypuses may be having a cocktail of prescription drugs up to half the prescribed human dosage in six streams in Melbourne's east, an international study reveals.
The Monash University led-study, published on Wednesday in Nature Communications, reveals the mammal and other aquatic animals may consume more than 60 pharmaceutical compounds including antidepressants in waterways.
Aquatic insects take in the pharmaceuticals and their predators - such as platypuses and brown trout - eat them and are potentially exposed to the drugs, the research finds.
"The concentrations of drugs in stream invertebrates suggest that animals such as platypuses that eat these invertebrates may be exposed to antidepressants, for example, in doses that are up to half those of human therapeutic doses," lead study author Dr Erinn Richmond said.
"Many pharmaceuticals are accumulating in aquatic invertebrates, but are also leaving the stream and moving to the surrounding landscape where they are consumed by spiders and potentially birds and bats."
The research team tested for 98 different pharmaceutical compounds in the streams.
The pharmaceuticals come into the streams through wastewater treatment facilities which don't remove all the drug compounds, or through septic tanks or leaky pipes.
Study co-author Associate Professor Michael Grace said pharmaceuticals cause physiological responses for humans, but the full effect on organisms needed further research.