Plastic bags, water bottles, and other kinds of trash and debris regularly find their way into our waterways, including Baltimore Harbor and the Chesapeake Bay. But another kind of human-made contaminant—one that is far less visible—also flows into these waters: pharmaceuticals. These substances can negatively affect various biological and ecological processes even at low concentrations. However, despite their potentially detrimental impact, little is known about the amount of pharmaceuticals that end up accumulating in our watersheds.
In a new study published in Environmental Science and Technology, researchers reported that each year, tens of thousands of doses of pharmaceuticals flow through the waterways around Baltimore and into the Chesapeake Bay because of leaky sewage pipes—an infrastructure problem that likely pervades the rest of the country and the world.
“In a perfect world where all of our infrastructure is working as it should, we [would] see no pharmaceuticals at all in the stream because they [would] all be in pipes going to a wastewater treatment plant,” said Megan Fork, an ecosystem ecologist at the Cary Institute of Ecosystem Studies and lead author of the study.
Studies like this one reaffirm “a direct connection between human health and environmental health,” said Paul Bradley, a hydrologist at the U.S. Geological Survey who conducts research on water pollution. “We’re very much connected to the environment, and there are very few contaminants that make that point more clearly than pharmaceuticals.”
Crunching the Numbers
The researchers tested the waters of the Gwynns Falls watershed around Baltimore for pharmaceutical compounds every week for a year. Wading into streams, they collected water samples in plastic vials that were then frozen and shipped via commercial airline to Umeå University in Sweden for chemical screening.
Of 92 compounds screened, the researchers detected 37 unique compounds from 11 pharmaceutical classes across the seven study sites. The antibiotic trimethoprim—commonly used to treat bladder infections—was most frequently detected, and the pain reliever acetaminophen was the compound found at the highest concentration.
As expected, the highest concentrations of pharmaceuticals tended to be found where the population was densest, but the scientists detected variability in the concentrations of pharmaceuticals in the water from week to week, Fork said.
The new research is the first to measure pharmaceutical load, which is the amount of contaminant accumulated over time and critical for estimating how much of a compound may be found downstream and in sediments. Load, not concentration, is used by regulations that protect waterways, such as the Clean Water Act. Such measurements are rare because the tests are time intensive and expensive to run, especially on such a regular basis.
According to Fork, “it’s like being a detective” because by pulling together disparate data sets and making educated conclusions, the researchers could calculate the amount of pharmaceuticals—and how much sewage—was leaking into the Gwynns Falls watershed. They estimated that roughly 30,000 doses of antidepressants, 1,700 doses of antibiotics, and the equivalent of 30,000 tablets of acetaminophen flow into the harbor every year.
Pharmaceuticals’ Unintended Effects
Although it is still not known how long these different compounds persist in the water or in the sediments, even minute concentrations of drugs can have profound effects on the organisms living in the water. “Pharmaceuticals are designed to cause biological responses, so they’re kind of inherently likely to cause a biological effect in whatever system [they’re in],” said Bradley, who was not involved in the study.
Previous research has found that similar levels of drugs alter the biology and behavior of organisms living in the water. For example, exposure to antidepressants changes crayfish behavior, which could affect the broader ecosystem. In addition, antibiotic-resistant bacteria have been found in these same Baltimore waters.
Repairing the Leaky Pipes
Because water from the streams sampled did not pass through any water treatment plants, the drugs in the water likely came from another, often overlooked source: sewage pipes, which leak roughly 1% of raw sewage.
“Our infrastructure is in bad shape,” said Fork. “And it’s not just in Baltimore; it’s everywhere throughout the country.”
But the problem of pharmaceuticals contaminating waterways is likely worse elsewhere in the world. Although Baltimore’s pipes are leaky, “when we look at the vast majority of the world’s population, something like 80% of wastewater goes into the environment and without adequate treatment,” Fork said.
To reduce the amount of drugs making it into the streams and rivers, Fork recommended that individuals properly dispose of unused and unwanted pharmaceuticals instead of flushing them down a toilet or sink. But fixing the leaking pipes requires a solution: upgrading the infrastructure.
“We recognize the problem, and we have this solution. It’s ready to go,” Fork said. “We just need to have the will and the money to do it.”
—Richard J. Sima (@richardsima), Science Writer