Grey water footprint of pharmaceuticals and personal care products discharged via urban wastewater.

Urban wastewater is a significant source of micro- and macropollutants in aquatic ecosystems, posing a high potential risk to drinking water sources. Pharmaceuticals and personal care products (PPCPs) are widely recognized as contaminants of emerging concern, although their relative burden compared to traditional pollutants remains insufficiently quantified. This study presents a comprehensive assessment of 92 micropollutants together with conventional pollution represented by nutrients and organic pollutants across 19 municipalities in the catchment of the largest Czech drinking water reservoir. More than one hundred 24-hour composite measurements were analysed. The Grey Water Footprint methodology integrates ecotoxicological thresholds, enabling a consistent comparison across PPCPs, nutrients, and organic pollution. Results reveal that the most critical micropollutants released from centralized wastewater treatment plants are Ibuprofen or Diclofenac, depending on treatment technology and plant size. However, nitrogen remains the dominant stressor approximately one kilometer downstream of urban discharges. These findings highlight that despite the increasing attention to micropollutants, conventional pollutants still account for the largest share of pollution in recipients. The methodological framework applied in this study allows stakeholders to compare the risks of different types of pollutants in a specific region. It offers a transferable tool for prioritizing contaminants and treatments, and guiding local wastewater management strategies under the EU Water Framework Directive, risk assessments under the revised Urban Wastewater Treatment Directive, and beyond.