For the first time, wildlife researchers have found traces of opioids in Mussels taken from the Puget Sound off of the northern US city of Seattle.

"We found antibiotics, we found antidepressants, chemotherapy drugs, heart medications and also oxycodone," said biologist Jennifer Lanksbury of the Washington Department of Fish and Wildlife.  "Because we're finding them in mussels, that means these chemicals are present in the water, and that means they're likely affecting fish and other invertebrates in the water," she added.

Mussels are "filter feeders", so scientists test them every two years to determine the level of pollution running off of the urban area into the sound.  Lanksbury said that this time, three of 18 sets of mussels analyzed tested positive for the painkiller oxycodone.  Traces of the drug were in amounts far lower than a normal therapeutic dose for humans.  The mussels, which were several kilometers apart, likely ingested the drugs by feeding on contaminants from human sewage that can't be completely filtered by wastewater treatment plants.

But they're a marker of the larger opioid crisis impacting America.  Out of more than 63,600 drug overdose deaths in the United States in 2016, two-thirds are caused by either prescription or illicit opioids.