Remote but not pristine anymore: pharmaceutical pollution challenges management of a high-elevation protected...

Remote ecosystems are often assumed to be insulated from chemical contamination; however, increasing human visitation may compromise this perception. We evaluated the occurrence, spatial distribution, and ecological implications of pharmaceutical active compounds (PhACs) in soils from the summit of Roraima-tepui, a high-elevation "sky island" in the Guiana Shield subjected to unregulated tourism and lacking sanitation infrastructure. Surface soils from anthropogenically influenced and naturogenic zones were analysed for 98 pharmaceuticals using HPLC-MS/MS, and potential risks were evaluated using environmental risk quotient (RQenv), cumulative and mixture-based approaches, and antimicrobial-resistance-specific thresholds (RQAMR). Eleven pharmaceuticals were detected, including antibiotics, antifungals, analgesics, and psychoactive compounds. Compounds associated with direct human use (e.g., ciprofloxacin, clarithromycin, acetaminophen) were primarily confined to anthropogenic areas, whereas others (notably fleroxacin, thiabendazole, pregabalin, and sulfadimethoxine) occurred more widely, including in naturogenic zones. These patterns suggest that heterogeneous inputs, compound-specific behaviour, intense rainfall, and shallow sandstone soils may interact to redistribute contaminants beyond their initial points of introduction. Ciprofloxacin reached concentrations up to 186 ng g⁻¹ and contributed substantially to cumulative environmental risk estimates. Several compounds exceeded predicted no-effect concentrations, and screening-level cumulative RQenv values indicated elevated potential environmental risk. Antimicrobial resistance assessment suggested pronounced selection potential for ciprofloxacin in tourist-impacted areas, although resistance genes or resistant bacteria were not directly measured. These findings indicate that tourism-related pharmaceutical residues can occur in remote high-elevation protected ecosystems under tourism pressure and highlight the need to integrate emerging contaminants into conservation and visitor management frameworks.