When scientists from the Puget Sound Institute of the University of Washington-Tacoma tested mussels from three sites near the harbors of greater Seattle, they found traces of oxycodone, a highly-addictive narcotic and one of the most-frequently abused opioids in the US.
But the potential presence of oxycodone in fish would be concerning, however, as they do metabolize opioids.
Lanksbury said the opioids likely entered the water through human waste, either through urine after ingesting the drugs, or in higher concentrations when people flush pills down the toilet.
Scientists determined that the slew of medications are passed into the Puget Sound through discharge from wastewater treatment plants.More news: Fiat Chrysler warns 5.3M owners: Don't use the cruise
In three of the 18 locations, the mussels then tested positive for trace amounts of oxycodone.
The analysis is part of the state's biennial Puget Sound Mussel Monitoring Program, in which uncontaminated mussels are transplanted into various locations to study pollution levels.
Mussels in Puget Sound are testing positive for a slew of contaminants and personal care products, including opioids. But as they filter food from the water, mussels may also absorb any chemicals and pollutants floating around them, Live Science reported in 2014.
Andy James, a research scientist at the PSI, noted in the statement that the levels of opioids detected in the mussels were thousands of times lower than a therapeutic dose in humans and would not be expected to affect the mussels, which don't break down the drug. "It's telling me there's a lot of people taking oxycodone in the Puget Sound area".More news: Syria state-run media reports US-led airstrike on army posts
"Hopefully our data shows what's out there and can get the process started for cleaning up our waters", Lanksbury said.
Mussels are filter feeders; to eat, the shellfish constantly sift the water around them in their hunt for bacteria or microscopic algae.
The mussels came from very urban areas and are reportedly not near any commercial shellfish beds where mussels are harvested for food.
Lanksbury said the containments can have negative impacts on fish and shellfish in the surrounding areas. A previous study showed that zebrafish self-administer the commonly prescribed painkiller hydrocodone, and seek out the drug in unsafe situations, once they are hooked.More news: 10-year study shows obesity increases risk for 12 cancers