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Antidepressant drugs in water affect fish behaviour

Elevated levels of antidepressant drugs found downstream of one Canadian wastewater treatment plant have been impacting the behaviour of fish, with research showing aquatic animals are bolder when affected by the drugs.

Environment Canada, Climate Change Canada and McMaster University collaborated on the study, with results highlighting the ongoing problem of prescription medications and other drugs that end up in the watershed.

McMaster University Professor Sigal Balshine told Science Daily that the fish have been shown to react to antidepressants in similar ways to humans.

"Fish can be seen as the canaries in the coal mine," Balshine said.

"The fish that make their homes in the receiving waters downstream from wastewater treatment plants absorb these chemicals and therefore can be our water sentinels."

The researchers caged gold fish in the Cootes Paradise watershed and at a control site on Lake Ontario. Results showed several commonly prescribed antidepressants in the blood plasma of fish in the watershed.

The drugs were found to have increased serotonin levels in the fish, affecting their swimming behaviour ‒ affected fish were found to be bolder, less anxious, more willing to explore and more active.

"Taken together, our results suggest the fish downstream of wastewater treatment plants are accumulating pharmaceuticals and personal care products at levels sufficient to alter neurotransmitter concentrations and to also impair ecologically relevant behaviours," Environment Canada research scientist and lead author of the study Jim Sherry said.

Balshine added that the results highlight a need to make water treatment and safe disposal a priority.

"Over one billion people on our planet lack access to clean drinking water and a number of serious water borne diseases are caused by improper water treatment," Balshine said.

"Water treatment and reuse must be a top priority for municipalities, regions and countries and so understanding the impacts of water treatment on ecosystem function is necessary first step to ensure that we have a sufficient water supply, maintain our biodiversity and protect the health of our ecosystems."

An Australian study in late 2016 also found that traces of over-the-counter drugs in sewage could present a danger to local agriculture as the use of recycled wastewater for irrigation grows.