Mussels off Seattle coast are ingesting your opiate-laced pooh

[SeattleVet]

5. Pretty much all of the area is closed to shellfishing...

Washington Department of Fish and Wildlife has a good map showing where it is OK to harvest shellfish:

https://fortress.wa.gov/doh/eh/maps/biotoxin/biotoxin.html

For many years they have been detecting pretty much anything that people put into their bodies, and that water treatment plants cannot remove. During late October through December there is a huge spike in cinnamon, nutmeg, ginger, cloves, and allspice in the water and the filter feeders, due to all of the pumpkin pie spice flavored coffee drinks and other foods. Caffeine is always present at relatively high levels, as are birth control pills. Metabolites of THC and CBD are being seen in slightly elevated levels.

If you put it into your body, it will become detectable at some level in the water (and filter feeding marine organisms).