Expert Commentary

Drugs in our rivers: Bugs on speed and Prozac in the food chain

When we flush, Prozac, cocaine and antibiotics trickle into the ecosystem. Researchers are just beginning to understand their effects.

David Trilling /
What's in your water? (David Trilling)

Legislation like the Clean Water Act has helped check the effluent flowing into rivers and streams. Though that fight is far from over, a new, all-too-modern danger has meanwhile seeped invisibly into waters around the world: legal and illegal drugs. And their effect on the ecosystem is poorly understood.

The United States is a heavily medicated country. Almost 70 percent of Americans took at least one prescription drug regularly in 2013, up from 44 percent in 2000, according to a Mayo Clinic study. Illicit drugs are common, too. Antidepressants and narcotics, hormones and amphetamines — we take these tonics in quantities unlike ever before.

They don’t disappear after entering our bodies. What we don’t metabolize we excrete through our urine and feces. Neither sewer-treatment systems nor drinking-water plants filter all these compounds from the water.

Scientists have found Prozac, speed and antibiotic-resistant sludge in the food chain. They have discovered higher-than-normal levels of cocaine in waterways after holidays and events like the Super Bowl. Many farmers treat their animals with antibiotics and hormones, which also enter rivers, lakes and reservoirs. And don’t forget non-prescription personal care products like sunscreen that wash off our bodies into the sewers.

Researchers are just beginning to query the dangers these contaminants may pose.

How are humans, for example, affected by eating fish on Prozac? In rivers in Colorado and Iowa, researchers have found Prozac and other antidepressants in the brain tissue of mullet, which is eaten by humans and other fish (such as walleye, trout and bass) that humans later consume. Other researchers have found that minnows exposed to antidepressants exhibit developmental delays.

Downstream from Baltimore — besides the morphine, caffeine and acetaminophen (the active ingredient in Tylenol) in the water — amphetamines (speed) seem to be encouraging an increase in aquatic insects (dipterans, such as lake flies and gnats) by 65 and 89 percent. In other words, the bugs are on speed and they’re mating like crazy.

Other researchers are concerned about the places that antibiotics — drugs like penicillin that kill bacteria like strep throat — are appearing. A 2016 study in Nature Microbiology noted the presence of dozens of antibiotic-resistant genes in bacteria along thousands of miles of the Chinese coast. Bacteria that have evolved protections against antibiotics could, in theory, cause an epidemic in livestock or humans. A 2007 study found such adapted bacteria widespread at Brazilian beaches, too. Scholars looking at India’s waters found antibiotic concentrations up to 40 times higher than in the West.

Still other scientists note that the hormone gestodene, which some women take as a contraceptive, appears to frustrate minnow reproduction by making the female fish behave more like males and the males less interested in breeding.

Listed below are some of the leading research papers on drugs in the water. In early 2017, the U.S. Geological Survey — the office of the Department of Interior tasked with scientific research — also released an eight-part study on “contaminants of emerging concern” in the water. The Survey defines CECs broadly as “any synthetic or naturally occurring chemical or any microorganism that is not commonly monitored in the environment but has the potential to enter the environment and cause known or suspected adverse ecological and/or human health effects. In some cases, release of emerging chemical or microbial contaminants to the environment has likely occurred for a long time, but may not have been recognized until new detection methods were developed. In other cases, synthesis of new chemicals or changes in use and disposal of existing chemicals can create new sources of emerging contaminants.”

Selected research:

“Continental-Scale Pollution of Estuaries with Antibiotic Resistance Genes.”
 Zhu, Yong-Guan; et al. Nature Microbiology, 2017. DOI: 10.1038/nmicrobiol.2016.270.
Abstract: “Antibiotic resistance genes (ARGs) have moved from the environmental resistome into human commensals and pathogens, driven by human selection with antimicrobial agents. These genes have increased in abundance in humans and domestic animals, to become common components of waste streams. Estuarine habitats lie between terrestrial/freshwater and marine ecosystems, acting as natural filtering points for pollutants. Here, we have profiled ARGs in sediments from 18 estuaries over 4,000 km of coastal China using high-throughput quantitative polymerase chain reaction, and investigated their relationship with bacterial communities, antibiotic residues and socio-economic factors. ARGs in estuarine sediments were diverse and abundant, with over 200 different resistance genes being detected, 18 of which were found in all 90 sediment samples. The strong correlations of identified resistance genes with known mobile elements, network analyses and partial redundancy analysis all led to the conclusion that human activity is responsible for the abundance and dissemination of these ARGs. […]”

“Exposure to the Contraceptive Progestin, Gestodene, Alters Reproductive Behavior, Arrests Egg Deposition, and Masculinizes Development in the Fathead Minnow (Pimephales promelas)”
Frankel, Tyler E.; et al. Environmental Science and Technology, 2016. DOI: 10.1021/acs.est.6b00799.
Abstract: “Endogenous progestogens and pharmaceutical progestins enter the environment through wastewater treatment plant effluent and agricultural field runoff. Lab studies demonstrate strong, negative exposure effects of these chemicals on aquatic vertebrate reproduction. Behavior can be a sensitive, early indicator of exposure to environmental contaminants associated with altered reproduction yet is rarely examined in ecotoxicology studies. Gestodene is a human contraceptive progestin and a potent activator of fish androgen receptors. Our objective was to test the effects of gestodene on reproductive behavior and associated egg deposition in the fathead minnow. After only 1 day, males exposed to ng/L of gestodene were more aggressive and less interested in courtship and mating, and exposed females displayed less female courtship behavior. Interestingly, 25 percent of the gestodene tanks contained a female that drove the male out of the breeding tile and displayed male-typical courtship behaviors toward the other female. […]  the rapid and profound alterations of the reproductive biology of gestodene-exposed fish suggest that wild populations could be similarly affected.”

“A Review of the Occurrence of Pharmaceuticals and Personal Care Products in Indian Water Bodies.”
Balakrishna, Keshava; et al. Ecotoxicology and Environmental Safety, 2017. DOI: 10.1016/j.ecoenv.2016.11.014.
Abstract: “Little information exists on the occurrence and the ultimate fate of pharmaceuticals in the water bodies in India despite being one of the world leaders in pharmaceutical production and consumption. This paper has reviewed 19 published reports of pharmaceutical occurrence in the aquatic environment in India [conventional activated sludge wastewater treatment plants (WTPs), hospital WTPs, rivers, and groundwater]. Carbamazepine (antipsychoactive), atenolol (antihypertensive), triclocarban and triclosan (antimicrobials), trimethoprim and sulfamethoxazole (antibacterials), ibuprofen and acetaminophen (analgesics), and caffeine (stimulant) are the most commonly detected at higher concentrations in Indian WTPs that treat predominantly the domestic sewage. The concentration of ciprofloxacin, sulfamethoxazole, amoxicillin, norfloxacin, and ofloxacin in Indian WTPs were up to 40 times higher than that in other countries in Europe, Australia, Asia, and North America. […]”

“Antimicrobial Resistance and Species Composition of Enterococcus Species Isolated from Waters and Sands of Marine Recreational Beaches in Southeastern Brazil.”
Fernandes Cardoso de Oliveira, Ana Julia; Watanabe Pinhata, Juliana Maira. Water Research, 2008. DOI: 10.1016/j.watres.2007.12.002.
Abstract: “Density, species composition and antimicrobial resistance in bacteria of the Enterococcus genus were evaluated in seawater and sands from two marine recreational beaches with different levels of pollution. […] These results show that water and sands from beaches with high indexes of fecal contamination of human origin may be potential sources of contamination by pathogens and contribute to the dissemination of bacterial resistance.”

“Occurrence and Potential Biological Effects of Amphetamine on Stream Communities.”
Lee, Sylvia S.; et al. Environmental Science and Technology, 2016. DOI: 10.1021/acs.est.6b03717.
Abstract: “The presence of pharmaceuticals, including illicit drugs in aquatic systems, is a topic of environmental significance because of their global occurrence and potential effects on aquatic ecosystems and human health, but few studies have examined the ecological effects of illicit drugs. We conducted a survey of several drug residues, including the potentially illicit drug amphetamine, at 6 stream sites along an urban to rural gradient in Baltimore, Maryland, USA. We detected numerous drugs, including amphetamine (3 to 630 ng L-1), in all stream sites. We examined the fate and ecological effects of amphetamine on biofilm, seston, and aquatic insect communities in artificial streams exposed to an environmentally relevant concentration (1 μg L-1) of amphetamine. […] Exposing streams to amphetamine also changed the composition of bacterial and diatom communities in biofilms at day 21 and increased cumulative dipteran emergence by 65 percent and 89 percent during the first and third weeks of the experiment, respectively. This study demonstrates that amphetamine and other biologically active drugs are present in urban streams and have the potential to affect both structure and function of stream communities.”

“Antidepressant Pharmaceuticals in Two U.S. Effluent-Impacted Streams: Occurrence and Fate in Water and Sediment, and Selective Uptake in Fish Neural Tissue.”
Schultz, Melissa M.; et al. Environmental Science and Technology, 2010. DOI: 10.1021/es9022706.
Abstract: “Antidepressant pharmaceuticals are widely prescribed in the United States; release of municipal wastewater effluent is a primary route introducing them to aquatic environments, where little is known about their distribution and fate. Water, bed sediment, and brain tissue from native white suckers (Catostomus commersoni) were collected upstream and at points progressively downstream from outfalls discharging to two effluent-impacted streams, Boulder Creek (Colorado) and Fourmile Creek (Iowa). […] This study documents that wastewater effluent can be a point source of antidepressants to stream ecosystems and that the qualitative composition of antidepressants in brain tissue from exposed fish differs substantially from the compositions observed in stream water and sediment, suggesting selective uptake.”

“Temporal Variability of Pharmaceuticals and Illicit Drugs in Wastewater and the Effects of a Major Sporting Event.”
Gerrity, Daniel; et al. Water Research, 2011. DOI: 10.1016/j.watres.2011.07.020.
Abstract: “This study characterizes the temporal variability associated with a major sporting event using flow data and corresponding mass loadings of a suite of prescription pharmaceuticals, potential endocrine disrupting compounds (EDCs), and illicit drugs. Wastewater influent and finished effluent samples were collected during the National Football League’s Super Bowl, which is a significant weekend for tourism in the study area. Data from a baseline weekend is also provided to illustrate flows and TOrC loadings during “normal” operational conditions. Some compounds exhibited interesting temporal variations (e.g., atenolol), and several compounds demonstrated different loading profiles during the Super Bowl and baseline weekends (e.g., the primary cocaine metabolite benzoylecgonine). Interestingly, the influent mass loadings of prescription pharmaceuticals were generally similar in magnitude to those of the illicit drugs and their metabolites. However, conventional wastewater treatment was more effective in removing the illicit drugs and their metabolites.”

“Antidepressants in Stream Ecosystems: Influence of Selective Serotonin Reuptake Inhibitors (SSRIs) on Algal Production and Insect Emergence.”
Richmond, E. K.; et al. Freshwater Science, 2016. DOI: 10.1086/687841.
Abstract: “The effects of pharmaceuticals on aquatic ecosystems are the subject of increasing environmental concern. Of particular interest are a suite of drugs known as selective serotonin reuptake inhibitors (SSRIs), commonly prescribed to treat depression. SSRIs are now detected in the environment worldwide, but their effects on ecosystems are not well understood. We conducted replicated experiments testing for an ecosystem effect of SSRIs in streams. We used artificial stream mesocosms to expose natural biofilms and aquatic insect communities to concentrations (20 µg/L) of fluoxetine or citalopram or a mix of both (totaling 40 µg/L). […] Total biomass of emerged adults at day 14 was greater in the SSRI-exposed streams, suggesting that fluoxetine and citalopram may influence developmental processes in some stream insects. Ecosystem function and invertebrate population dynamics are sensitive to pharmaceuticals. Our study demonstrates that chronic exposure to fluoxetine and citalopram has the potential to affect aquatic biota and ecosystem function.”

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