Fish know all about your grimy excretions. They have to live with what you flush down the toilet every day, after all. And the unluckiest ones have an even closer relationship with you, depending on what medicines you take, where you are, and what part of the year it is.
Our understanding of pharmaceutical pollution begins nearly 20 years ago, when ecologist JP Sumpter discovered something surprising: unusually high numbers of feminized fish—egg-producing males with ovaries—were swimming in English rivers. When Sumpter and colleagues tested the water, they found something even stranger: estrogen from human birth control pills.
It was one of the first signs that pharmaceuticals flushed down the drain could build up in lakes and rivers to levels high enough to affect fish. Public concern has since grown about the environmental impacts of dozens of drugs, from Advil to antidepressants, which have been detected in water and absorbed by wildlife.
"Between 2002 and now, there's been more than a thousand publications on the topic," said Heiko Schoenfuss, an aquatic toxicologist at St. Cloud State University in Minnesota.
Despite all that research, however, the latest batch of studies suggests that we still have a long way to go in understanding the effects of pharma pollution. It turns out that our drugs alter fish behavior in much more subtle and hard-to-measure ways than the more lethal "legacy" pollutants like PCBs and the insecticide DDT, both of which have long been banned for killing wildlife but are still present in the environment at low levels. The evolving picture complicates a drive by some advocates to begin requiring sewage treatment plants to remove pharmaceuticals from wastewater before discharging it into open water.
Currently, there are no such requirements in the United States, said Dana Kolpin, a research hydrologist for the US Geological Survey in Iowa.
"We just don't have a good way to understand how the fish population is reacting to these drugs."
Researchers studying pharma pollution feel mounting pressure because two big trends, urbanization and global warming, will likely lead to ever higher concentrations of pharmaceuticals in water, as well as greater risks to fish and people. "Seventy percent of all people will be concentrated in urban areas by 2050," said Bryan Brooks, a professor of environmental science at Baylor University in Texas. Areas with climate stress or drought will be hit hardest, he added, concentrating pollution as water levels decline.
The problem is a challenge to monitor: Unlike a pesticide like DDT, pharmaceuticals aren't meant to be lethal; they're designed to produce subtle physiological and neurological changes, which complicates testing their effects on wild populations.
"We just don't have a good way to understand how the fish population is reacting to these drugs," said Schoenfuss. "The old paradigm of exposing animals to compounds and seeing what dies at what concentration doesn't work in a risk assessment for pharmaceuticals. The concentration of drugs required to kill is so high that it's not realistic."
A study published in October, for example, showed that out of 23 drugs contaminating the Chesapeake Bay, only one made its way into the osprey feeding on local fish.
"This finding is good news for ospreys," said Rebecca Lazarus, co-author of the study and a graduate student of environmental science at University of Maryland. "For 10 years, there's been a lot of research on pharmaceuticals in water, but this is the first field-monitoring study where we look at exposure of high-trophic wildlife to these drugs."
Most of the drugs in the osprey study did not increase in concentration as they moved up the food chain from fish to osprey. This is in stark contrast to PCBs, which famously collect in greater quantities in predators, said Brooks. Animals at the top of a food chain consume more PCBs over a lifetime as chemicals become further concentrated at each higher link in the food chain.
But although Lazarus's study showed minimal accumulation of drugs in Chesapeake Bay osprey, pharmaceuticals are not totally benign in the aquatic environment either. While they don't directly kill fish, they may still alter fish behaviors in ways that threaten their survival.
"Species that typically stay in a school, or in the dark, [are] becoming braver and wandering off by themselves. They are changing their behaviors in a way that makes them more susceptible to predation," said Kolpin.
For example, a 2009 study showed that when minnow larvae were exposed to concentrations of antidepressants that have been measured in water bodies, the fish developed a slower escape response to electroshock, the experiment's simulation of a perceived predator.
Often the effects on fish behavior are more difficult to measure. "Unlike legacy contaminants, which are considered poison, many of these drugs are designed not to destroy pathways, but instead lightly alter them, stimulating or inhibiting processes to elicit a much more complex and subtle response," said Schoenfuss, of St. Cloud State. A further complication is that the environmental effects of pharmaceuticals depend on their location, whether it's the Gulf of Mexico or the Chesapeake Bay.
"Have you gone on vacation where the water feels a little sticky?" asked Baylor's Brooks. If so, you're swimming in water that has a different amount of minerals, and probably a different pH, than what you're used to, he explained. Weather can drive changes in acidity, too, which is why pH can vary greatly in a single water body, depending on the time of year.
This variability is a major headache for researchers trying to assess the environmental effects of pharma pollution because pH is a key factor in determining whether waterborne drugs reach wildlife. Depending on the acidity of the water, some chemicals from our pills may split up to take a form that is more likely to be absorbed by an animal.
"Water pH determines how much some chemicals can cross biological membranes to get into a fish. If less gets into the fish, the osprey are also getting exposed to less of the chemical," said Brooks.
Scientists are scrambling to understand the phenomenon so that they can contribute to a better regulation of drugs in the environment. The Environmental Protection Agency's major industrial waste law, the Resource Conservation and Recovery Act, doesn't cover household waste or pharmaceutical waste. In fact, the EPA lists just 10 pharmaceutical contaminants that officially merit more research.
"Anything we use has potential to become an environmental contaminant. Each one of us is now part of the equation."
Europe also doesn't regulate the release of drugs into the environment, but Sweden and Germany are now lobbying the European Union to start controlling pharmaceuticals in open waters.
With no formal regulation in the works in the US, local governments are encouraging citizens to change what they do with unwanted drugs. Some states and cities are teaching people to bring their unused pills to special collection programs so they be disposed of as solid waste, instead of being flushed down toilets and ending up in waterways. That won't eliminate the problem, however, because most drugs are excreted into wastewater, not flushed away in pill form.
Research efforts, meanwhile, are continuing to ramp up. The US combined forces from various federal agencies to establish a workgroup on pharmaceuticals in water. Even pharmaceutical companies such as Swiss-based Roche are participating in this wave of collaborative research.
Besides these new interdisciplinary research projects, advances in technology are also contributing to more nuanced studies. New tools to measure pharmaceuticals at very low levels, both in water and in fish tissue, are already helping researchers give better advice to policymakers, Brooks said.
"As more research shows these compounds are having an effect, the public will see the problem with wastewater treatment plants having no regulations on pharmaceuticals," said Kolpin, of the US Geological Survey.
Traditionally, a lot of the blame for chemical wastes in our lakes, rivers and harbors has been borne by factories, huge agricultural operations and other mega-polluters. But our pills have turned the tables on us. No one escapes the blame for pharmaceutical waste.
"Anything we use has potential to become an environmental contaminant," said Kolpin. "Each one of us is now part of the equation."