Municipal wastewater treatment plants are failing to remove many common pharmaceuticals, including the antidepressant fluoxetine (Prozac), allowing these drugs to enter rivers, lakes, and streams and potentially harm aquatic organisms.
A new study led by Paulina Chaber-Jarlachowicz of the Institute of Environmental Protection – National Research Institute in Warsaw, Poland, published September 24, 2025 in PLOS One, highlights the limitations of conventional wastewater treatment processes in addressing pharmaceutical pollution.
Ineffective removal of drugs
Most wastewater treatment plants rely on microbial processes to break down organic compounds, which are then removed as activated sludge. While these methods are effective for many conventional pollutants, they often fail to degrade pharmaceutical compounds.
The researchers collected samples from six municipal wastewater treatment plants across Poland. They analyzed the inflow, treated water, and sludge for over a dozen widely used drugs. They discovered that only a few drugs were effectively removed. These included the pain relievers naproxen and ketoprofen, as well as the antihistamine salicylic acid.
For other drugs, including fluoxetine, diclofenac, and the anti-seizure medication carbamazepine, levels in discharged water were sometimes higher than in the incoming wastewater. Fluoxetine and loratadine (Claritin) were identified as posing the highest risk to aquatic life. They have the potential to disrupt hormonal signaling and development even at low concentrations.
Ecological implications
“Municipal wastewater treatment facilities using conventional mechanical-biological processes (CAS) are ineffective at removing pharmaceuticals from wastewater,” the authors write. Their analysis estimated that the annual discharge of pharmaceuticals from the plants in the study region totaled at least 40 megagrams. Ketoprofen, sulfamethoxazole, carbamazepine, and fluoxetine contributed most to the total mass.
The findings add to growing evidence that standard wastewater treatment is a significant source of pharmaceutical pollution in the environment. Aquatic organisms exposed to these drugs can experience hormone disruption. They can also face altered development and other ecological effects. These effects occur even at very low concentrations.
Next steps
The researchers call for further studies into methods that can effectively degrade pharmaceutical compounds in sewage and sludge. This includes addressing their breakdown products. These methods may potentially involve advanced chemical, physical, or biological treatments.
This research underscores the need to update wastewater treatment practices to address the growing environmental challenge posed by pharmaceuticals.
