Geospatial monitoring and human health risk assessment of pharmaceutical residues in groundwater and surface water in Kampala and Mbarara Districts, Uganda

Abstract

This study investigated the occurrence, concentration and human health risks of five pharmaceutical residues-metronidazole, sulfamethoxazole, ciprofloxacin, carbamazepine, and caffeine-in groundwater and surface water samples from Kampala and Mbarara districts of Uganda. The present study also employed techniques of remote sensing and geographic information system (GIS); thereby, emphasizing the importance of thematic mapping, land use classification, and spatial buffering to evaluate pharmaceutical contaminants in an environmental setting. The risk quotient (RQ) approach was also employed to assess the risk of exposure to the pharmaceutical contaminants. Caffeine was found with the highest average concentration in groundwater (53.515 µg/L), whereas carbamazepine had the highest average concentration in surface water (48.635 µg/L) during the dry season. Ciprofloxacin consistently recorded the lowest average concentrations in both groundwater and surface water across all seasons. Overall, the data revealed high concentrations of pharmaceutical residues in surface water compared to groundwater during both seasons, except for caffeine which was not detected in surface water across the seasons. Notable seasonal changes were also observed in caffeine and metronidazole concentrations, indicating the role of human activities and environmental factors in influencing contamination patterns during specific seasons. The factor analysis revealed that consumption rate of pharmaceuticals and anthropogenic activities are the main factors responsible for the contamination of groundwater and surface water. Moreover, results revealed that the risk of adverse human health effects for carbamazepine and metronidazole during both seasons were high (RQ > 1), thereby highlighting the prioritization of frequent monitoring by the environmental protection agencies. Given that the combined risk of exposure for all the pharmaceuticals exceeded one, adopting stringent pharmaceutical disposal and control measures are essential for mitigating potential human health risks associated with their exposure. Further investigation into optimal and effective pharmaceutical remediation strategies for both groundwater and surface water are highly recommended.

Keywords: Contamination; Health risk assessment; Pharmaceuticals; Remote sensing; Spatial distribution.