Opioids aren’t just a crisis for the thousands of people overdosing on them: They’re also a threat to our fish. Researchers have found traces of oxycodone for the first time in bay mussels in an urban area of Puget Sound, according to a report by the Puget Sound Mussel Monitoring Program. The levels were thousands of times lower than what would affect humans, and they weren’t near commercial shellfish beds, but that doesn’t mean that experts aren’t concerned.
In fact, scientists have found traces of drugs in all sorts of fish for years. A 2009 pilot study by Baylor University and the U.S. Environmental Protection Agency (EPA) found low-level residues of several human medications in fish — like antidepressants and sleep aids — in areas near wastewater treatment plants nationwide, from Chicago to Phoenix to Orlando. Another 2017 study found high concentrations of antidepressants in a variety of fish in the Niagara River in the upper Great Lakes region, including white bass, white and yellow perch, bowfin and steelhead.
“The USGS has been studying this topic for 20 years. In fact, my research team was the first to document the presence of pharmaceuticals in U.S. streams at the national scale, published in 2002,” says researcher Dana Kolpin, Ph.D., the project chief of the U.S. Geological Survey (USGS) Toxic Program’s Emerging Contaminants Project.
In the early 2000s, the U.S. Geological Survey sampled 139 streams in 30 states and found that 80 percent contained traces of drugs, natural and synthetic hormones, insecticides, blood thinners and heart medications, among other chemicals — mostly coming from wastewater treatment plants and septic systems. A 2012 report by the World Health Organization (WHO) notes that heart meds, pain relievers and birth control have all been found in U.S. wastewater since the 1970s.
That’s in large part because more of us than ever are living in cities — and high concentrations of people means traces of the chemicals we use inevitably end up back in our local environments, explains Bryan W. Brooks, Ph.D., a professor of environmental science and biomedical studies at Baylor University and the editor-in-chief of Environmental Management. “It’s not surprising to see residues of medicine being released from cities and accumulating in aquatic life because these chemicals are indicators of an urbanizing water cycle,” he says.
How Chemicals Get Into Our Fish
Our bodies don’t use the majority of the meds we pop, which means the unused chemicals come right back out in our excrement (i.e., poop and pee). What’s more, people only take about half of the medications they’re prescribed, so some of the rest is flushed down the toilet, says John Sumpter, Ph.D., who heads a research group at Brunel University in London focused on chemicals in water and their effects on fish.
While wastewater treatment plants remove most chemicals from our water supply, a small amount doesn’t degrade and makes it into what’s known as effluent, or liquid waste discharged into a river or the sea. “If you have a location that receives a lot of effluent, you will find pharmaceuticals in the marine and freshwater environment,” Dr. Sumpter explains. Dr. Kolpin says USGS researchers have, in fact, already found codeine, oxycodone and methadone in trace levels coming out of wastewater treatment plants and in corresponding streams. Fish, in turn, accumulate some of those chemicals as water passes over the gills and skin.
Troublingly, the FDA actually authorizes a “flush list” for leftovers of certain strong medications — specifically, fentanyl patches for pain along with morphine, hydrocodone and oxycodone — to ensure they’re not used by other people. More research is needed, Dr. Kolpin and Dr. Brooks say, to understand the problem and the long-term effects, although the FDA released a report in 2017 that found that all 15 drugs on the group’s flush list “present negligible risk through ingestion of water and fish.”
“The FDA is charged with protecting human health,” says Dr. Brooks. “Risk-tradeoff decisions have been made for human medicines that prioritized human health over environmental concerns.”
What Is Your Risk of Eating Contaminated Fish?
All types of fish and bivalves can become contaminated with pharmaceuticals and other chemicals in the water supply, says Dr. Sumpter. Some medications — like artificial hormones, antidepressants and opiates — accumulate in fat tissue, he says, so fatty fish (like salmon) are more likely to build up these drugs than leaner fish. However, levels pose virtually no health risks to humans. Experts looking at the minimum therapeutic dose, which is the lowest concentration you’d have to take for a drug to have an effect on you, say current levels in fish and water are thousands of times lower. “The levels reported in farmed mussels and bivalves are well below human therapeutic doses,” says Dr. Brooks.
“I don’t know anyone who thinks these drugs are a risk to humans,” agrees Dr. Sumpter. “The risk to humans from environmental exposure is somewhere next to nil. The amount we’d have to consume is much larger than what we’d get from seafood.”
Fish on Pharma
Fish and mussels, however, are at risk from our drug-taking habits: Those living in contaminated water are continuously exposed to chemicals and can absorb significant doses over long periods of time. While some drugs affect fish and others don’t, experts are concerned about the potential harm.
“A small number of pharmaceuticals can probably get up to a concentration in animals that’s relatively similar to a concentration in [humans], and that’s when you get worried,” says Dr. Sumpter. He says the biggest concerns are hormonal medications (like the birth-control pill), which can have the same effects in fish as in humans, even in very low levels in the water.
Psychoactive drugs like antidepressants and oxycodone may also have short- and long-term behavioral effects in fish — although those effects are tricky to study. “Perhaps they swim more slowly, so they’re more susceptible to predators or might find it more difficult to get food,” says Dr. Sumpter, whose team is currently studying the effect of opiates in water on fish. A 2013 study found that even very low levels of anti-anxiety drugs like Valium and Xanax in the water can build up in fish tissues, causing them to behave more aggressively. A 2010 study found that shrimp exposed to antidepressants in the water became “suicidal,” swimming toward (instead of away from) light, where they can be caught by predators.
Cleaning Up Our Act
Very advanced technologies at wastewater treatment plants already exist to reduce chemicals in our water to nearly zero. Switzerland and Germany are already in the process of installing these technologies at all of the countries’ treatment plants nationwide to prevent nearly all chemicals from entering the water, says Dr. Sumpter — although they still can’t eliminate every last trace of drugs.
And even though these technologies are a good idea for the environment, they’re reserved for countries that can afford them. “Oftentimes those technologies are associated with high energy requirements and elevated costs to operate and maintain,” says Dr. Brooks, who adds that 80 percent of the world’s sewage actually isn’t treated in the first place.
Is Your Fish Safe?
Dr. Sumpter says the best — and really only — advice he has to avoid traces of medications and other chemicals in your seafood is to stay away from fish that live in a contaminated environment. These fish often contain chemicals like mercury, PCBs and DDT at much higher levels that can be dangerous for your health.
Mussels and fish from commercial farms are a safer bet because they don’t set up shop next to a wastewater treatment plant. If you plan to eat fish you’ve caught yourself, check out the EPA’s National List of Advisories to search by state to see if there are any local advisories for bodies of water or limits on certain species of fish.
How You Can Keep Drugs Out of Our Systems
While you can’t stop peeing and pooping, you can avoid flushing your meds down the toilet. The FDA recommends first taking advantage of local medication take-back programs or collection sites. Otherwise, mix your meds with used coffee grounds or cat litter and dispose in a tightly sealed bag in the trash. Landfills are a safer bet than your toilet, Sumpter says, since medications that wind up there are much less likely to reach the environment.
Also try not to take medications you don’t need. “Everything we use has the potential to be an environmental contaminant … some are coming at a steep price to the environment,” says Dr. Kolpin.
What Do YOU Think?
Will you think twice the next time you need to dispose of your unused meds? Are you concerned about how pollutants are contaminating our oceans and negatively impacting marine life? Let us know in the comments.