Distribution and Toxic Effects of Antibiotics on Impacted Inland and Coastal Waters

Antibiotics are among the most significant medical discoveries of the 20th century. However, their extensive use and persistence in the environment have contributed to the emergence and dissemination of antibiotic resistance, causing increasing global concern. This study investigates the occurrence of antibiotics in aquatic environments to assess their ecological impact. Samples from rivers, seas and areas around wastewater treatment plants (WWTPs) in Barcelona, Valencia (Spain), Paris (France) and Helsinki (Finland), areas with different anthropogenic impacts and climate conditions, were examined to determine the occurrence of antibiotics using liquid chromatography coupled to high-resolution mass spectrometry (HPLC-HRMS). Target analysis focused on 18 compounds, alongside suspect screening for the identification of other drugs. The results were further analysed using multivariate statistical approaches, and ecotoxicological risk was assessed using the Hazard Quotient (HQ). Those most frequently detected and with the highest risk were sulfamethoxazole, metronidazole, azithromycin and tetracycline, with maximum concentration values of 69.6, 12.3, 119.1, and 12.6 µg/L, and maximum HQ values of 116,136, 6268, and 207, respectively. The highest concentrations occurred near WWTPs, while sea samples had the lowest concentrations. Overall, many compounds exceed environmental risk thresholds, demonstrating the need for improved removal treatments and stricter environmental regulation.