Presence of emerging organic contaminants and microbial indicators in surface water and groundwater in urban India

This study presents a first combined assessment of emerging organic contaminants (EOC) and antimicrobial resistance (AMR) indicators in the South Indian city of Bengaluru from multiple sources, addressing a knowledge gap on EOCs and AMR occurrences and relationships in different water sources in urban India. A unique approach in this study was to combine the detection of EOCs with an assessment of the AMR-indicating class 1 integron-integrase gene, intI1. Twenty-five samples collected from groundwater, local surface waters, and tap water imported from the Cauvery Basin were screened for 1499 EOCs. A total of 125 EOCs were detected at concentrations per compound of up to 314 μg/L. Concentrations for a range of contaminants were higher than those previously detected in Indian groundwaters. High concentrations of Per- and polyfluoroalkyl substances (PFAS) were detected with up to 1.8 μg/L in surface water and up to 0.9 μg/L in groundwater. Calculated risk quotients indicated potential AMR development caused by high concentrations of azithromycin, fluconazole, and sulfanilamide in surface waters that have little protection against sewage inflows. Surface waters that have recently undergone environmental restoration (e.g., removing silted bottom layers and enhancing protection against encroachments and sewage inflows) had lower EOC detections and risk of AMR development. Specific EOC detections, e.g., the ubiquitous detection of the sweetener sucralose (in use since ∼2000), indicated recent groundwater recharge and a contribution of imported Cauvery River water for recharge. This study highlights the need for monitoring and water protection, the role of EOCs as potential drivers of AMR, and the success of surface water protection measures to improve freshwater quality.