Washington state scientists are using mussels to monitor pollution from industrial plants, marinas, sewage treatment plants, overflows from sewers, groundwater, stormwater runoff, and other sources.

The monitoring program uses uncontaminated mussels, and they will be placed in 70 different water locations for about two to three months. After that period, the mussels will be collected again to test for pollutants.

Scientists recently found that the mussels in the Seattle and Bremerton area harbors have amounts of oxycodone – the opioid painkiller in Percodan, Percocet, Oxycet, OxyContin, as well as in other drugs. This is also one of the drugs that fuel opioid addiction crisis in the United States and around the world.

It is not unusual that drugs ended up in harbors and waterways, but this is the first time scientists have discovered opioids in the area. Mussels act like water filters, trapping any contaminants.

The sewage treatment plants likely carry the oxycodone. Hence, those who are taking the drugs can excrete it in their feces or urine, ending up in sewage treatment plants and eventually released into the water.

Scientists also believe that even the filtered freshwater may contain “contaminants of emerging concern.”

“The oxycodone was found in amounts thousands of times lower than a therapeutic dose for humans and would not be expected to affect the mussels, which likely don’t metabolize the drug,” according to a statement released by the Puget Sound Institute at the University of Washington, Tacoma.

Opioids are said to be not harmful to mussels. However, the drugs could be harm other aquatic wildlife, such as salmon, since fish have been shown to respond to opioids.

Aside from opioid, scientists also found that the mussels were contaminated with a chemotherapy drug called melphalan – a potential carcinogen that can harm the DNA.

“The mussels had ingested amounts of Melphalan relative by weight to a recommended dose for humans,” the statement further noted.