What happens when opioids are released into the environment?

This week's question comes from Sol Kinnis in Victoria, British Columbia.  She asks:    

I'm curious about whether or not there are any effects from opioids, after they have been consumed, on sea life or fresh water ecosystems, depending on where and how sewage is disposed of?

Dr. Viviane Yargeau, a Professor of Chemical Engineering at McGill University in Montreal, says that opioids have been detected in river water at concentrations only slightly lower than those of other pharmaceuticals such as antibiotics and estrogen.

Opioids, just like those other drugs, make their way through the human body, into sewer systems and ultimately into ecosystems. For that reason, the potential for opioids to do harm to the environment is also similar.

For example, pharmaceuticals are known to change the feeding behaviour of some fish, as well as their predator avoidance response. Specifically, opioids have been detected in fresh water mussels, but it is not clear yet if they are harmed by the drug. But the presence of opioids in mussels suggests a possible impact on the ecosystem.