Environmental Monitoring and Risk Assessment of Pharmaceutical Residues Discharged from Large Livestock Complex in the Geum River Basin, South Korea

Abstract

This study aims to collect water samples from two tributaries within the Geum River basin in South Korea, where large-scale livestock complexes are located, to quantify the measured environmental concentration (MEC) of pharmaceutical residues using a multiresidue analytical method developed with liquid chromatography–tandem mass spectrometry (LC-MS/MS), and to evaluate the environmental risks posed by the detected pharmaceuticals to aquatic organisms. The water samples were collected at a total of 17 points, including up-, middle-, and downstream of the Seoksong and Nonsan-Gangkyoung streams connected to the Geum River, from October 2018 to March 2019. A multiresidue analytical method using LC-MS/MS was developed to quantify 49 pharmaceuticals with hydrophilic lipophilic balance using solid phase extraction. The recovery rates varied between 67.23% and 136.98%, while the limits of quantification were from 3.99 to 46.32 ng/L. Ecotoxicological information on acute and chronic effect endpoints (e.g., EC50, NOEC, etc.) was obtained from the U.S. EPA ECOTOX Knowledgebase. Considering the worst-case scenario, the lowest observed effect endpoint (mainly NOEC) of the most sensitive species was selected, and predicted no effect concentration (PNEC) values were calculated by dividing the endpoint by an assessment factor (AF). The mean, minimum, and maximum MECs of pharmaceuticals were divided by PNECs to calculate risk quotient (RQ). Caffeine was detected in all sampling sites with a detection frequency of 100%. High levels of pharmaceuticals (9.212 μg/L of sulfathiazole, 8.479 μg/L of acetaminophen, and 5.885 μg/L of florfenicol) were detected. The RQ values exceeded 1 and reached up to 84.79 (high risk category) for acetaminophen, and were between 0.11 and 0.83 (moderate risk) for carbamazepine, etc. The RQs for the rest of the 15 substances were below 1 (low risk). In the future, further studies should be conducted to monitor other micropollutants, including industrial chemicals, pesticides, etc., at different locations of the Geum River basin, including livestock farms, pharmaceutical manufacturing facilities, wastewater treatment plants, and other facilities, for long-term period.