Spatial Analysis of Pharmaceutical Waste Disposal Practices and Their Environmental Chemical Impact in Osun State Communities

Improper disposal of pharmaceutical waste by households, healthcare facilities, and pharmacies is an emerging environmental contamination concern in Nigeria. Pharmaceutical compounds detected in water and soil systems pose ecotoxicological risks and may contribute to environmental selection for antimicrobial resistance. This study characterised pharmaceutical waste disposal practices across urban, peri-urban, and rural communities in Osun State, South West Nigeria, and assessed the chemical impact on soil and water environments proximate to disposal sites. A cross-sectional survey assessed disposal practices at 300 households, 30 pharmacies, and 20 health facilities across Osogbo, Ile-Ife, and Ede. Soil and surface water samples from twelve identified disposal sites were analysed for pharmaceutical residues including antibiotics, analgesics, and antihypertensives using HPLC-MS/MS. Municipal waste dumping was the dominant disposal route across all settings. Antibiotic compounds including ciprofloxacin, sulfamethoxazole, and tetracycline were detected in soil and water adjacent to disposal sites, with ciprofloxacin concentrations reaching 48 micrograms per kilogram in soil. Urban disposal sites showed higher contamination intensities. Awareness of pharmaceutical waste hazards was very low among households and pharmacy staff. The study identifies pharmaceutical waste management as a critical gap in environmental health governance in Osun State and recommends implementation of a community pharmaceutical take-back programme integrated with existing waste management infrastructure. Keywords: pharmaceutical waste, environmental contamination, antibiotic residues, Osun State, HPLC-MS/MS.