Mussels act like filters in water, trapping any contaminants.
Scientists in Washington state use mussels to monitor pollution from stormwater runoff, groundwater, overflows from sewers, and sewage treatment plants, as well as marinas, industrial plants, and other sources.
In the monitoring program, they take uncontaminated mussels and place them in the water in 70 different locations for two to three months, then collect them and test for pollutants.
Environmental scientists recently discovered that mussels in the Seattle and Bremerton area harbors contain trace amounts of oxycodone, the opioid painkiller found in OxyContin, Oxycet, Percocet, Percodan, and other drugs. This is one of the drugs fueling the opioid addiction crisis in the US and around the world.
"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.
The oxycodone is thought to be from sewage treatment plants. In other words, people who take the drugs can excrete them in their urine or feces, which ends up in sewage treatment plants and can be released into the water. Even filtered wastewater can contain what scientists call contaminants of emerging concern.
It's not unusual for drugs taken by people to end up as contaminants in harbors and waterways surrounding cities, including antibiotics and cocaine. However, this is the first time scientists have discovered opioids in this area, the Puget Sound Institute said.
The researchers also found the chemotherapy drug melphalan in the mussels, which is a potential carcinogen because the drug can harm DNA.
"The mussels had ingested amounts of Melphalan relative by weight to a recommended dose for humans," according to the statement, so it might be worth studying for the biological impact, they said.
The "highly urbanized" areas that were tested were not near commercial shellfish beds.
"You wouldn’t want to collect (and eat) mussels from these urban bays,” said Puget Sound Institute research scientist, Andy James, in the statement.
Although the opioids are not thought to harm mussels, the drugs could be harmful for other aquatic wildlife, like salmon, because fish have been shown to respond to opioids.