Occurrence, distribution and risk assessment of pharmaceuticals and personal care products in Djibouti aquifer

This study investigates the occurrence, distribution, and risks of 25 targeted pharmaceuticals and personal care products (PPCPs) in Djibouti’s aquifer, a critical water resource. Nine stations were sampled during the dry season (June 2024) to study the thermosaline groundwater of the Djibouti volcanic aquifer system. Only six PPCPs, caffeine (CAF), sulfamethoxazole (SMX), levofloxacin (LEV), propranolol (PPL), tramadol (TMD), and fluoxetine (FLX), were detected. Urban areas showed higher contamination due to inadequate wastewater treatment. CAF, a marker of domestic wastewater, was consistently present at a level ranging from 3.7 ± 0.1 ng/L to 13.2 ± 0.7 ng/L. While SMX and LEV exhibited the highest concentration of 23.6 ± 1.6 ng/L to 45.9 ± 1.2 ng/L and 119.7 ± 4.0 ng/L to 141.6 ± 3.7 ng/L respectively, reflecting their persistence and widespread use. Spatial analysis identified hotspots located near the Ambouli dry river area, with concentrations exceeding 200 ng/L, linked to urban activities. Ecological risk assessment identified moderate risks from PPCPs, particularly CAF and FLX, with Risk Quotient (RQ) values clustering around ecological thresholds. However, Mixture Risk Quotient (MRQ) values indicated significant cumulative risks at urban sites, driven by antibiotics like SMX and LEV, which also raise concerns about antimicrobial resistance and cocktail effect. Furthermore, human health risk analysis highlighted heightened vulnerabilities for infants and children, with CAF and SMX posing significant risks even at low water consumption rates. These findings underscore the need for improved wastewater management, targeted remediation strategies, and regular groundwater monitoring to safeguard public and environmental health.