Antidepressants and other psychoactive drugs are designed to affect the human brain. But after they enter the water system in excrement or unused drugs flushed down the drain, traces of these compounds can enter the environment in biosolids—the nutrient-rich material left over after wastewater treatment that is used as fertilizer. New research suggests an unexpected mitigation strategy: using wood-rotting fungi that can break down these chemicals before they reach soil, crops, and people.
Conventional wastewater treatment methods are effective at killing pathogens and reducing metals, but they are far less successful at neutralizing complex organic chemicals. This limitation prompted the research team to explore new, low-cost, and sustainable approaches to reducing pharmaceutical contamination before biosolids are applied to croplands.
“Even small concentrations of these compounds can have psychological effects when consumed, which is why they have become contaminants of concern.” — Kate Burgener
Researchers in the Johns Hopkins Department of Environmental Health and Engineering, which spans the Bloomberg School of Public Health and the Whiting School of Engineering, have shown that two species of white-rot fungi—oyster and turkey tail mushrooms—can degrade a wide range of psychoactive pharmaceuticals commonly found in biosolids.
The findings were published in ACS Environmental Au.
Biosolids are widely used across the United States as fertilizers and soil conditioners because they are rich in nitrogen, phosphorus, and organic matter. While some studies have shown that pharmaceuticals can be absorbed by plants grown in biosolids-amended soils or irrigated with wastewater, there is no conclusive evidence that these chemicals reach people who consume those crops.
Nonetheless, “Even small concentrations of these compounds can have psychological effects when consumed, which is why they have become contaminants of concern,” says Kate Burgener, a PhD candidate and lead author of the study.
The researchers focused on white-rot fungi, a group of fungi known for their ability to decompose lignin—the tough polymer that gives wood its rigidity. The two species—Pleurotus ostreatus (oyster mushroom) and Trametes versicolor (turkey tail)—are among the most studied and most widely available mushroom species. Biosolids from a municipal wastewater treatment plant were spiked with nine psychoactive drugs, including commonly used antidepressants such as citalopram and trazodone. The fungi were then allowed to grow directly on the biosolids for up to 60 days.
Both fungal species proved highly effective. Each degraded eight of the nine pharmaceuticals tested, with removal rates ranging from approximately 50% to nearly complete elimination after two months. Chemical analyses showed that the fungi were not simply trapping the drugs but chemically transforming them, often into less toxic products.
The study was co-authored by Carsten Prasse, associate professor in the Department of Environmental Health and Engineering, and supported by a U.S. Environmental Protection Agency National Priorities grant and Johns Hopkins University.
— DANIELLE UNDERFERTH