Antidepressant-affected fish may swim upstream slowly
Concentrations of drugs in water, sediment and fish brains vary widely, team finds
By Noah Larsen
While a steady stream of antidepressants flows into U.S. waterways, the drugs are deposited in widely different concentrations in stream beds, stream waters and fish brains, a new study has found.
That study, which involved a broad team of experts, includes two faculty members from the University of Colorado and focuses partly on the drug concentrations in Boulder Creek.
The study is the first to demonstrate that the concentrations of these antidepressants in stream waters do not necessarily correlate with the concentrations or presence of antidepressants found in fish tissue, according to a statement by the U.S. Geological Survey, which funded and helped lead the research.
During the last decade, as concerns have grown about rising levels of antidepressants in our water supply, studies have confirmed that antidepressants enter the water supply via wastewater treatment plants.
However, little is known about how much is released or accumulates after leaving the treatment plant, what types of antidepressants are released and where these chemicals end up.
A team of researchers that included David O. Norris and Alan M. Vajda, University of Colorado professor and associate professor of integrative physiology at Boulder and integrative biology at Denver, respectively, recently published findings that shed more light on concentrations of antidepressants found downstream from wastewater outflow.
The study, published in the March edition of the journal Environmental Science & Technology, was led by Melissa M. Schultz, a chemist at the College of Wooster, and Edward T. Furlong, a research chemist at the U.S. Geological Survey. The team included researchers from St. Cloud State University and several USGS offices.
The study focuses on two sites, Boulder Creek in Colorado and Fourmile Creek in Iowa. The study aimed “to determine the fate and distribution of a wide range of commonly prescribed antidepressant pharmaceuticals and select degradates in water, sediment and fish brain tissue as a result of discharge of wastewater effluent into two streams.”
Ten antidepressants were targeted for all samples of stream water, sediment and fish brain tissue. All 10 antidepressants were detected in at least one sample of stream water, and most samples contained at least eight different varieties.
Effexor, Lexapro and Wellbutrin were the three antidepressants found in the highest concentrations downstream of the wastewater treatment plants. As the researchers note, these three are among the most commonly prescribed antidepressants.
Pre-wastewater-treatment-plant stream water was also tested, but those samples did not show significant levels of any antidepressants. Researchers suggest that the wastewater treatment plant was a point source of antidepressants.
The data found that the stream water of Boulder Creek generally carried more antidepressants than Fourmile Creek in Iowa.
The sediment samples retrieved from Boulder Creek contained eight of the 10 targeted antidepressants. Not found were Luvox and Cymbalta.
There were significant differences between stream water and sediment samples.
First, antidepressants were measured in the sediment upstream from the wastewater plant. The researchers determined that, “A small WWTP facility in Nederland, Colo., discharges effluent 38.5 km upstream from the Boulder WWTP and may provide a source of sediment-associated antidepressants that are not reflected in the water samples collected just upstream from the Boulder WWTP discharge.”
The second difference was that the highest concentrations of antidepressants in the sediment were found further downstream when compared to the stream water.
As a reason for this inconsistency, they surmise: “The transit time for a parcel of water through this reach is on the order of a few hours, whereas the sediment deposits sampled in this study may accumulate over substantially longer periods.”
The primary responsibility of the CU academics, Norris and Vajda, was to provide white sucker fish brain tissue for analysis of antidepressants.
This line of research is nothing new for the pair, who, along with CU Professor John Woodling, previously conducted a study focusing on three wastewater treatment plants.
“In 2000, my colleagues and I decided to examine Boulder Creek below the wastewater treatment plant, the South Platte below the city of Denver WWTP and Fountain Creek below the Colorado Springs WWTP and discovered reproductive disruption. Our emphasis in this work was on the effects of environmental estrogens,” explains Norris.
The white sucker brain tissue collected for this study contained eight of the 10 antidepressants. But there were different concentrations and types of antidepressants in sediment vs. stream water.
Whereas the sediment and water contained high concentrations of Effexor and Lexapro, the fish brain tissue showed Zoloft, Prozac and their degradates to have the highest concentrations. Though the reasons for these differences are not known, it is an indication of a selective uptake process in the fish, the authors said.
For Norris, one of the most striking findings of the study was the “verification that these animals are accumulating these chemicals.” This confirmation has vast implications for the health of the wildlife and the natural ecosystems, he said.
“We published a previous paper in cooperation with our colleagues in Minnesota that shows how exposure to the same anti-depressants we found in white sucker brains affects the escape behavior of young fathead minnows at concentrations shown to be present in streams,” he said.
“Man-made chemicals now are interfering with ancient signaling mechanisms capable of disrupting the biology of animals at extremely low concentrations (parts per billion or parts per trillion),” he said. “The burgeoning human population is not only fouling its nest but is fouling the nests of all other creatures as well.”
In a statement posted by the USGS, Furlong concurred: “The most important observation in our study is that you cannot necessarily predict which antidepressants are present in aquatic tissue from antidepressant concentrations in the water the organisms are living in. This study clearly documents selective uptake of specific antidepressants into fish brain tissue that were minor components in corresponding water samples.”
And echoing Norris’ observation about the escape behavior of minnows, Furlong said, “A slower response to predators is probably not helpful when you are on the lower end of the food chain.”
To learn more about Norris’ research, see “Gender-bending fish get break from Boulder plant.”