Humans rely on pharmaceuticals—antidepressants, antibiotics, painkillers and antifungal drugs amongst others—to treat various ailments and improve quality of life. But a new study published in Nature Communications suggests these medications come with an unwelcome side effect: After leaving the body via urine, some pharmaceuticals end up in waterways, where they combine to form a cocktail of potentially dangerous contaminants.
Researchers led by Erinn Richmond, a chemist at Australia’s Monash University, identified traces of 69 different medications in insects collected from six streams across Melbourne. The team only tested for the presence of 98 compounds, Liam Mannix writes for The Age, so it’s possible an even greater number of drugs were lurking in the water. Invertebrates living downstream from wastewater treatment facilities or near populous areas with leaking septic tanks had concentrations measuring between 10 to 100 times higher than invertebrates at other sites.
Invertebrates were far from the only animals to reveal evidence of pharmaceuticals. The spiders that prey on these marine insects, as well as the platypuses and brown trout that, in turn, prey on the spiders, all exhibited similar traces of man-made medicine. In fact, Belinda Smith reports for the Australian Broadcasting Corporation, a platypus living in the most contaminated stream could be routinely exposed to up to half of an adult human’s daily dose of antidepressants. Trout didn’t fare much better: As Earther’s Jake Buehler notes, the fish were estimated to ingest nearly 30 percent of a human’s daily dose on a regular basis.
Spiders living on river banks showed traces of 66 drug compounds and other aquatic insects were affected by up to 69 compounds. It’s likely this occurred due to a process known as biomagnification, which Science Trends’ Mohendra Shiwnarain describes as “the accumulation of a certain substance, like a toxic chemical, … as we move up the food chain.” In other words, the higher up an animal is on the food chain, the more susceptible it is to high concentrations of toxins built up by feasting on smaller predators-turned-prey.
Stuart Khan, a water quality chemist and engineer at the University of New South Wales who was not involved in the study, tells Australian Broadcasting Corporation’s Smith that human waste tends to end up at either a treatment plant or a septic tank. Most plants are capable of removing traces of substances such as caffeine, paracetamol, salicylic acid and aspirin, but they’re less equipped to handle the complex compounds used in many pharmaceuticals.
According to Cosmos’ Nick Carne, the six sites featured in the study represent a variety of marine environments. Two receive some septic leachate, while two others are located downstream of a treatment plant. The final two receive limited amounts of wastewater. Writing for The Conversation, Richmond and co-authors Mike Grace, a chemist at Monash University, and Emma Rosi, an aquatic ecologist at New York’s Cary Institute of Ecosystem Studies, note that one of the sites, a stream in a national park, was chosen because it was expected to be free of pharmaceuticals. But the team found evidence of pharmaceuticals—the Alzheimer’s medication memantine, the opiate codeine, antifungals fluconazole and clotrimazol, and antidepressant mianserin were the five most frequently detected drugs—in every insect tested, including the ones from the national park.
“The fact we detected drugs, admittedly in very low concentrations, in this seemingly pristine site suggests finding places ‘free’ from pharmaceutical contamination may be difficult,” the researchers note.
Although the ubiquitous presence of pharmaceuticals in nature is becoming increasingly evident, scientists are still working to gauge the effects such medicines have on wildlife. As the team explains in the study, previous research has shown amphetamines and antidepressants can disrupt the timing of aquatic insects’ transformation to their adult form, while Valium, amphetamine and LSD can undermine spiders’ web-weaving abilities. Earther’s Buehler adds that antidepressant waste leaves shore crabs less suspicious of predators and perch increasingly restless.
In an interview with Australian Broadcasting Corporation’s Smith, Richmond aptly summarizes the potential risks posed by animals’ unintentional exposure to human medications, saying, “If you or I went to the doctor and said we're taking 69 different drugs, they'd probably have a heart attack.”
Echoing this sentiment in The Conversation, Richmond and her colleagues conclude, “We know in humans, there are health risks associated with taking multiple drugs because of drug interactions. Is the same true for animals? Like so many studies, our research leaves us with many unanswered questions.”