A review of Melbourne rivers has revealed a cocktail of pharmaceuticals that could put wildlife at risk.

More than 60 pharmaceutical compounds, including antidepressants, were found in at disturbing levels in a review of six streams in Melbourne’s eastern suburb.

Many pharmaceuticals enter streams via wastewater treatment facilities, which are not designed to remove all the compounds we consume, or via septic tanks and leaky pipes. 

A Monash University research team tested for 98 different pharmaceutical compounds, and found that larval invertebrates living in the stream can accumulate pharmaceuticals.

Their predators - platypuses and brown trout - could theoretically be consuming those drug-contaminated larvae at up to half the daily dosage for humans.

“The concentrations of drugs in stream invertebrates that we have found 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,” Monash researcher Dr Erinn Richmond said.

“Our research is significant because we confirm that 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 for example.”

The researchers collected invertebrates and spiders that feed predominantly on aquatic insects, from six streams around Melbourne, some with very little wastewater, two receiving some leachate from septic tanks two just downstream of a wastewater treatment plant.

“The drugs we take have a targeted physiological response in humans – that’s why we take them,” said study co-author, Associate Professor Michael Grace, Director of the Water Studies Centre at the Monash School of Chemistry.

“But what we have shown is that a wide variety of these same drugs are also being taken up by invertebrates in streams and then moving up the food web and out of the waterway when these insects emerge,” he said.

“It is now important to find out what effects the pharmaceuticals we take are having on these non-target organisms.”

The study is accessible here.