Every two years, Washington Department of Fish and Wildlife scientists take mussels out of a pristine aquaculture source on Whidbey Island and place them in the more urbanized regions of the Puget Sound. Because mussels are filter feeders, their tissues are a good way to measure pollution of all kinds, including contaminants like cocaine or pharmaceutical drugs. On Thursday, local news reported that a new substance has been found in the mussels: opioids.

In the tissues of mussels from three of the 18 sites, scientists encountered trace amounts of oxycodone, the active ingredient of OxyContin. A report released May 9 by the University of Washington’s Puget Sound Institute explains that, while humans aren’t in danger of consuming these mussels, the shellfish do serve as an alarming barometer for ocean pollution as well as human health. Even marine life is affected: Previous research indicates that mussels can’t metabolize drugs like oxycodone but fish can, and given high enough amounts they’ll begin to crave the drug.

“What we eat and what we excrete goes into the Puget Sound,” Washington Department of Fish and Wildlife biologist Jennifer Lanksburgy, Ph.D. told the CBS Seattle affiliate KIRO on Wednesday. “It’s telling to me there’s a lot of people taking oxycodone in the Puget Sound area.”

The contaminated mussels were retrieved from urbanized harbors alongside Seattle and Bremerton. In the past eight years, overdose deaths caused by prescribed opioids have steadily risen in Washington — an epidemic that is estimated to have cost the state $34 billion over the past four years.

Elliot Bay, Seattle
Aerial view of Seattle's Elliot Bay, where contaminated mussels were found. 

The contaminants got into the Puget Sound through discharge from wastewater treatment plants, which filter water from local toilets. When humans ingest opioids, they excrete traces of the drugs in their urine, and even wastewater treatment isn’t enough to get rid of all of it. The trace chemicals are being categorized as “contaminants of emerging concern.”

In this year’s batch of mussels, the researchers found oxycodone “in amounts thousands of times lower than a therapeutic dose for humans.” They also found high levels of the chemotherapy drug Melphalan, suggesting that the mussels had ingested a dose of the drug that is proportional to a recommended dose for humans. These are “levels where we might want to look at biological impacts,” said Puget Sound Institute research scientist Andy James, Ph.D., in the statement.

No one is sure what biological effect oxycodone might have on water ecosystems, but they do know that its presence in the ocean means humans are consuming the chemical in dangerous amounts. It does not mean, however, that you shouldn’t be eating mussels from the Pacific: Commercial shellfish beds are far away from these urbanized regions, meaning that for now, your mussel slurping habit is a relatively safe one.

Next up, the same team of scientists are planning on using high-resolution mass spectrometry to look for additional chemical exposure in mussel tissues and plan to further evaluate the biological impact of humans on Puget Sound species. Ironically, University of Utah scientists think that a viable way to stop the opioid crisis might be in the ocean itself: In 2017, they received a grant from the Department of Defense to pursue marine snail venom as a pain management alternative.