The Complicated Question of Drugs in the Water
When you get right down to it, water treatment plants don’t look like much. As we drive up to the plant, John Langley, the deputy director for the utility department, waves his wallet at a sensor outside a security gate. It opens, and we motor in. Beyond the gate, a long row of what look like connected warehouses stand in a line. A gigantic water tank squats beside them, and a chain link fence snakes around a group of pools.
Bloomington, Indiana, where we are currently standing, is a pretty small town. This water utility serves just over 120,000 people. This drinking water treatment plant, built in the late 1950s, sucks in water from the nearby Lake Monroe reservoir. Giant pipes dump the raw water into standing water tanks outside, open to the sky above. Then the plant transfers it into similar but smaller tanks inside, where much of the cleaning up happens. “It’s a 24-hour operation here,” explains Rachel Atz, the water quality coordinator.
Lake Monroe, the source of Bloomington, Indiana's drinking water.
“We first add alum, which attracts the clay particles,” says plant superintendent John Trotter, waving his arm over the murky pool we’re now looking down on. As we stand on a walkway spanning the open tanks, the water churns its way to purity below. A life preserver hangs on the rail opposite us, and I briefly imagine someone falling in.
Trotter is describing the first step of water purification, called coagulation. Like blood forming a scab, the alum helps to chunk up the organic material in the water, so it can fall to the bottom of the tank. It works because alum—also known as aluminum sulfate—has a positive charge, whereas the organic gunk floating in the water tends to be negatively charged. They stick together and form a solid, which falls out of the water in a process called sedimentation. Then the now clear water goes through the filtration step, where it wends its way through several layers of sand, gravel, and charcoal. This removes much of the smaller particles, Trotter says. In the last step, it’s treated with chloramines to kill bacteria and other microorganisms, giving the water its faintly stinky swimming pool smell.
The techniques Bloomington uses to treat its drinking water are used around the world, and those methods have proven successful so far. The drinking water in Bloomington is pretty high in quality, and it’s something that the people who work at the water utility take a great deal of pride in. On the way out to look at the reservoir, Atz and Langley tell me a story about going to a customer’s house and personally testing their water after a complaint. It turns out there wasn’t any contaminant at all in the water, or “my water,” as Atz calls it.
That’s because the Bloomington drinking water treatment facility closely follows the EPA’s treatment guidelines, Langley tells me. This means they test for a wide gamut of potentially harmful contaminants. Some of these include naturally occurring microorganisms, such as cryptosporidium and coliform bacteria; metals such as barium, copper, lead; and herbicides such as atrazine.
Like many drinking water treatment plants in the U.S., Bloomington publishes a water quality report every year, noting contaminates that were present above the detection level. In total, the EPA requires drinking water treatment plants to test for almost 90 different contaminants. But noticeably absent from this list are any type of drug or pharmaceutical.
Drugs in Our Water?
In 1999, Christian Daughton, an environmental chemist from the Environmental Protection Agency, wrote a paper along with Thomas Ternes of ESWE-Institute for Water Research and Water Technology in Germany that called attention to the persistence of pharmaceuticals in the freshwater cycle. It was one of the first journal articles on the topic to get widespread attention, and its publication sparked a flurry of research and media coverage, including an Associated Press series that surveyed water quality in a handful of cities.
“There’s been a fair amount of work done in both the U.S. and Canada as well as Europe that documents [pharmaceuticals] in wastewater and in water,” says Joanna Wilson, a biologist at McMaster University in Ontario, Canada. She studies how drugs in the water affect zebrafish, a tiny freshwater fish in the minnow family. More recent data shows that the same types of compounds are in drinking water. One study found several pharmaceuticals in treated tap water, including atenolol (a beta-blocker), carbamazepine (an anticonvulsant), gemfibrozil (an antilipidemic), meprobamate (an antianxiety medication), and phenytoin (an anticonvulsant). The concentrations of these compounds were very low, usually less than 10 nanograms per liter, which is parts per trillion. For reference, one part per trillion is equivalent to about one second in 64 years.
Numerous studies have found low concentrations of pharmaceutical compounds in drinking water.
We know that if these compounds are in surface water, and the surface water is used for drinking water, then the compounds will be in drinking water as well, Wilson says. But how do they get there in the first place? Obviously, the answer is through humans, and we put pharmaceuticals into the water in two basic ways.
The first is through excretion. “When a drug is ingested, it’s metabolized and what eventually is excreted is the portion of the original parent drug that doesn’t get metabolized, along with metabolites, which may have biological activity of their own,” says Christian Daughton, an environmental chemist from the Environmental Protection Agency.
The amount that our bodies break down drugs varies widely, from drug to drug and even from person to person. For many drugs, Daughton says, about 90% of the drug is metabolized. Others aren’t metabolized as much, and a lot of the parent compound is excreted. The undigested drugs and metabolites, the digested drugs, are either removed from the body as waste or sweat. These are either flushed down toilets are go down the drain in our showers.
However, scientists think that the main way that the vast majority of pharmaceuticals get into the wastewater is through disposal. The vernacular for many years was to flush unwanted medications down the toilet, and many people still do that despite updated federal guidelines that now advise people to either take unused drugs to a collection site or mix them with kitty litter or coffee grounds and put them in the trash. (The only exception to this are narcotic pain relievers and other hazardous substances.) But even with these guidelines, plenty of medications still end up in sewers, wastewater treatment plants, and, to some degree, back our water supplies.
It’s completely unknown how much of their medications people are still dumping down the drain. And what’s more says Daughton, this disposal can be irregular. You can have very large spike in the concentration of one drug going through wastewater treatment plant followed by a spike in another. As a result, the aquatic community has to deal with an ever-changing pharmaceutical profile.
The good news is that pharmaceuticals are actually really well removed by water treatment plants, Wilson says. For her group’s research on how medications in the water affect zebrafish, they took samples from water both going into and coming out of wastewater treatment plants. Both their research and others’ show that they remove about 95 to 98% of pharmaceuticals.
Unknown Risks of Pharmaceuticals
Despite the efficacy of treatment plants, we also need to account for the fact that people drink water all the time, Wilson says, and that there might be sensitive stages of life when it’s best to minimize exposure, such as the elderly, the very young, and pregnant women.
The real problem is trying to find out what the risk really is, Wilson says. “We are exposed to so many different chemicals and chemical compounds, through air and water and what we eat, so that trying to sort out whether this is going to contribute to human health concerns will be difficult.” We can be exposed through drinking water, in the bodies of fish that we eat, or in plants that have soaked up drug residues from water used for irrigation.
“There really have been no studies that have associated the [pharmaceutical] residues in our water with human health problems,” says Ilene Ruhoy, a pediatric neurologist and environmental toxicologist who has studied the issue. That could be a sign that they pose no threat, but like Wilson, Ruhoy stresses how difficult it is to do these types of studies. “You’re talking about exposure to parts per million, parts per billion. And it’s a combination of drugs. It’s not just one drug in the water, it’s multitudes of. It’s exposure to these very, very minute amounts of these drugs, but many drugs over decades—ten, 20, 30, 40, 50, 60 years.”
Right now, the EPA does not have any guidelines about pharmaceuticals in drinking water. So water treatment plants, despite removing most compounds, don’t tend to specifically treat for them.
Whether or not pharmaceuticals in water pose a threat to our health is a question that scientists have been trying to address for 15 to 20 years, Daughton says. “You can speak in terms of the potential risk, but it’s very difficult to talk in terms of known risk, especially in terms of ecological exposure,” which is difficult to pursue and nail down.
These Are Your Fish on Drugs
According to Wilson’s research, chronic, low concentrations of pharmaceuticals in the water have a variety of effects on zebrafish. When exposed to a mixture of drugs from 0.5 to 10 micrograms per liter, or parts per billion, in their tank water in the lab, adult zebrafish tend not to reproduce as much, and developing embryos have developmental problems and anatomical deformations.
“In the wild, fish would only ever see this very complex mixture. And that’s because a wastewater treatment plant releases complex mixtures of pharmaceuticals, as well as other types of compounds,” she says, such as nitrogen and phosphorous compounds, and other types of nutrients. In a mixture of compounds like this, it becomes very complicated to try to determine which medication is causing the harm. In addition, “that composition really changes over time, even from an individual wastewater treatment plant. The concentration of each individual component will go up and down depending on what the population in the area is taking,” Wilson says.
These fluctuations are due to the fact that once these drugs get into the water, they break down fairly quickly. So if we stopped putting these compounds in the water, they would go away, Wilson says. They’re consistent in the environment because we continually release them.
The dilemma is that wastewater treatment plants were never built to deal with this kind of compound, she says. Though Wilson has found that they remove 95 to 98% of pharmaceuticals from the sewage, many are still biologically active at low concentrations, which means you have to remove a lot of it to see the benefit. “Yet that’s very difficult to do when you’re trying to treat such extraordinarily large volumes as we do with wastewater treatment,” Wilson says.
New Types of Medicine
Today, one possible solution is to more carefully control the pharmaceutical supply at its source: doctors. Ruhoy believes that if doctors prescribed lower doses of pharmaceuticals, fewer of the metabolites and leftovers would make it into the sewers. This might involve a doctor starting a patient out on a lower dose, then upping that if it’s ineffective. Ruhoy admits that this approach has some downsides. Doctors want their patients to get better as soon as possible, so may be reluctant to start at a lower dose. Plus, implementing it would be complicated as well, since our health care system is already complex. But as we move into a future, personalized medicine may take care of some of this, as doctors will be able to more easily prescribe a tailored dose to a patient.
Even with personalized medicine, there is one class of medications that remain stable in the water—nanomedicines. These new drugs are used primarily to treat diseases such as cancer, because they limit the harmful side effects of chemotherapy. With nanomedicines, scientists basically create a tiny ball that’s filled with medication. “Think of a balloon. But instead of filling it with air, you are filling it with drug,” says Mustafa Akbulut, a professor of chemical engineering at Texas A&M who studies how nanomedicines interact with the environment. The ball then goes to the right part of the body before releasing its drug payload, so only the cancer cells get the tumor killing medicine, not every cell in the body.
And while this might be great news for cancer patients, it has the potential to be harmful for aquatic organisms. Traditional pharmaceuticals tend to be slightly hydrophobic, meaning that they don’t move through water very well. But nanomedicines are designed to get the drug where it needs to be in the body, so they “enable the transport of the material that is not otherwise possible, or possible at a very limited extent,” Akbulut says.
At this point, scientists don’t really know the fate of nanomedicines in the environment. “We have to be careful with nanomedicines, because there aren’t many studies about their toxic effects,” he says. His research group is looking at what happens when nanomedicines come into contact with plants, as they would if they were excreted or dumped into the sewer system, then went through a water treatment plant.
“Our studies show that if the nanomedicine comes into the vicinity of a plant, it can be absorbed, and go inside.” If the plant taking up the nanomedicine were grass in a field for example, an herbivore might eat it, and potentially move up the food chain this way. Other scientists have found that metal nanoparticles, such as gold, can move from plants to caterpillars.
“It is important to realize that nanomedicines are relatively new, and the amount that is used is much, much smaller than traditional medicine,” Akbulut says. Still, in the long run, if the use of these types of drugs becomes more widespread, nanomedicine pollution may become more of a problem. “It’s just a matter of how many people are using and excreting them.”
More Drugs to Come
Drug use is going to continue to climb, Wilson says. “We have an aging demographic, and we have an increased reliance, in North America and Europe in particular, with the treatment of health concerns with pharmaceuticals.” This translates to more medicines making their way into the water system, and we need to determine how to deal with it, she says. “Long-term exposures [to pharmaceuticals] are quite a bit different than short term exposures, and we need to really start testing and figuring out if chronic exposures of low doses are relevant for the health of an individual or population of animals.”
But as for now, there are no easy answers to stemming the flow of pharmaceuticals into our water system, or even if it will pose health problems for humans. “I think right now there are more questions than we necessarily have answers for,” Wilson says.
The hope is that research will eventually allow us to develop environmental limits, or there will be sufficient data to upgrade wastewater treatment plants so they can filter out more of the pharmaceuticals. “We need good strategies for how to treat the water better,” she says.