Mussels showing up positive for opioids

Jun 26, 2018

After transplanting clean mussels from Whidbey Island to eighteen urban shores around Seattle’s Puget Sound, Washington’s Department of Fish and Wildlife has found evidence that opioids have reached the open seas.

Traditionally used as a barometer to measure ocean pollution, filter feeders like mussels absorb contaminants from the water in which they live and store them in their tissues at high levels of concentration.

Mussels are classified as bivalves, alongside clams and oysters, and work as tiny filtration systems as they suck in water laden with their food—a microscopic algae called phytoplankton—and as they filter the water, their tissues absorb some of the chemicals present in their marine environment, like herbicides, pharmaceuticals, and flame retardants. In a study conducted by Stanford University in California, it was shown that in just seventy two hours, bivalves were able to clean up to 80% of contaminants when placed in wastewater.

“Each native mussel filters about two liters of water a day, so it doesn’t take a whole lot to improve water quality,” study co-author Richard Luthy, senior fellow at the Stanford Woods Institute for the Environment and the Silas H. Palmer Professor of Civil and Environmental Engineering, has said.

When the Washington Department of Fish and Wildlife pulled the test mussels from Puget Sound in their study, they found that in three of the eighteen locations, the mussels tested positive for trace levels of oxycodone. None of the contaminated mussels were tested near commercial fishing beds, and the Department clarified that the amount of opioids found in the mussels was thousands of times smaller than the typical human dose, but the findings still raised concern—from both an environmental and human health perspective—regarding the amount of drug tainted sewage being swept into North America’s coastlines.

When humans use opioids, like oxycodone, their bodies act like filters, too—though not terribly efficient ones—and when the drugs are passed through their systems, they usually end up in the toilet and are passed through to waste water management facilities, and from there, everything that can’t be filtered from the water is then released into the oceans. Studies are showing that this isn’t just a result of the opioid epidemic sweeping across North America; in fact, the mussels tested by the Department of Fish and Wildlife, in association with the Puget Sound Institute, found traces of not only opioids but antidepressants and Melphalan, a common drug used in chemotherapy.

Jennifer Lanksbury, a biologist at the Washington Department of Fish and Wildlife, is concerned about the drugs flowing into the Sound. “What we eat and what we excrete goes into the Puget Sound,” she says, “It’s telling me there’s a lot of people taking oxycodone in the Puget Sound area.”

Mussels don’t seem to metabolize opioids, so there is no evidence that they are physically harmed by the drugs that are swept into their marine environment; however, studies by the University of Utah have shown that zebrafish will willingly dose themselves with opioids in their environment, and further hypothesis posits that if given the chance, salmon and other fish may do the same.