Multi-residue analysis of pharmaceuticals in water samples by liquid chromatography- mass spectrometry: Quality assessment and application to the risk assessment of urban-influenced surface waters in a metropolitan area of Central America

The occurrence of pharmaceuticals in surface water has been barely studied in Latin America. This work aimed to i) develop a multi-residue liquid chromatography- triple quadrupole mass spectrometry (LC–MS/MS) method for the determination of pharmaceutical active compounds (PhACs); ii) monitor 70 PhACs in three urban-influenced rivers in San José, Costa Rica; and iii) perform the risk assessment of detected compounds and ecotoxicological evaluation on water samples. Caffeine, 1,7-dimethylxanthine, naproxen, gemfibrozil and ibuprofen were the most frequent among 23 detected compounds. Concentrations ranged from 0.013 μg/L to 53.8 μg/L (62 % detections between 0.1 μg/L–1 μg/L), and the highest values corresponded to caffeine, 1,7-dimethylxanthine, ofloxacin, gemfibrozil and cephalexin. The environmental risk estimated using the hazard quotient (HQ) approach, revealed four and eleven compounds with medium and high risk, respectively. The highest risk (HQ >10) was determined for diphenhydramine, risperidone, fluoxetine, trimethoprim, ofloxacin and azithromycin; nonetheless, high risk (HQ >1) was also estimated for caffeine, diclofenac, clarithromycin, gemfibrozil and ibuprofen. Total HQ sample values (ΣHQ), calculated as the sum of individual HQs for each detected compound, revealed the highest hazard in surface water near wastewater treatment plant discharges, followed by the locations of higher urban influence (in the Virilla river). Ecotoxicological evaluation showed no acute toxicity towards Daphnia magna and Vibrio fischeri in surface water samples; on the contrary, toxicity towards Lactuca sativa (germination tests) showed a similar pattern to that determined with the ΣHQ, although the highest toxicity was observed downstream with respect to the urban influence of the metropolitan area. These findings help to visualize the importance of pharmaceutical residues in the overall toxicity of surface water samples, and remark the relevance of monitoring these compounds, as an input for the implementation of future mitigation actions.