Mussels from three of 18 locations near Seattle and Bremerton in Washington’s Puget Sound tested positive for the opioid oxycodone, according to the Puget Sound Institute at the University of Washington Tacoma. The mussels were contaminated because sewage from opioid consumers ended up in the sound after being treated at wastewater plants, scientists explained.
“What we eat and what we excrete goes into the Puget Sound,” Jennifer Lanksbury, a biologist at the Washington Department of Fish and Wildlife, told CBS affiliate KIRO-7 in Seattle. “It’s telling me there’s a lot of people taking oxycodone in the Puget Sound area.”
Mussels are filter feeders that strain water to find nutrients. They also absorb concentrated doses of ocean pollutants in their tissues ― and therefore serve as a valuable gauge of the contents and health of coastal waters.
The researchers said the mussels they study typically test positive for other pharmaceutical drugs, as well as illegal drugs such as cocaine, but they hadn’t tested positive for opioids until now.
The level of oxycodone found in a single mussel was 100 to 500 times smaller than a therapeutic human dose, Lanksbury said. “So you’d have to eat 150 pounds of mussels in that contaminated area to get a minimal dose,” she told NBC affiliate KING-5.
The trace amounts of oxycodone likely haven’t affected the mussels, which don’t appear to metabolize the opioid ― but they could affect fish. Zebrafish, commonly used for research, have apparently learned to dose themselves with opioids. Scientists worry that the oxycodone could affect juvenile chinook salmon and other species in Puget Sound.
Besides oxycodone, mussels tested this year showed levels of antidepressants, heart drugs, antibiotics and the common chemotherapy drug melphalan, which is a potential carcinogen. The drug was found at “levels where we might want to look at biological impacts,” warned Andy James of the Puget Sound Institute, who assisted in the study.
The mussels came from very urban areas and are reportedly not near any commercial shellfish beds where mussels are harvested for food. “You wouldn’t want to collect [or eat] mussels from these urban bays,” James said.
Every two years, scientists from the Washington Department of Fish and Wildlife place uncontaminated mussels in various Puget Sound locations. They then test them for contaminants about three months later as part of the Puget Sound Ecosystem Monitoring Program.