A platypus living in a stream on Melbourne’s fringe could receive more than half a human dose of antidepressants every day, a study reveals.

The study raises questions about whether those contaminants could be reaching Melbourne’s drinking supply. Two of the contaminated streams form part of the Sugarloaf Reservoir catchment, a major drinking water source for Melbourne.

Melbourne's platypuses are being exposed to high levels of anti-depressants. Credit:CSIRO

The study, by a global team of experts and published on Wednesday in the journal Nature Communications, found traces of 69 different drugs in insects living in six streams around Melbourne – including, to the team's surprise, a stream in the Dandenong Ranges National Park.

The analysis was only capable of testing for 98 different drugs, so it’s possible the true number is even higher.