Scientists at the Washington State Department of Fish and Wildlife have found that mussels in Seattle’s waters are testing positive for opioids.

The finding suggests “a lot of people” are taking oxycodone in the Puget Sound, researchers say.

Scientists used mussels as a way to test pollution in Seattle’s waters and discovered high enough oxycodone levels for the shellfish to test positive.

Mussels do not metabolise opioids, but some fish can become addicted.

Mussels are filter-feeders, which means they filter water for nutrients to nourish themselves. In the process, they end up storing pollutants in their tissues, which makes them a prime indicator species.

State researchers distributed clean mussels around the Puget Sound and extracted them months later to test the waters.

Of the 18 locations scientists used, three showed traces of oxycodone. The drug traces were not enough to get any humans high from consumption, but enough to indicate a problem, officials said.

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