Mobile phone cases as hotspots for perfluoroalkyl substances and pathogenic bacteria: An analysis based on user...

Mobile phone cases, widely used personal items, may act as microenvironments for pathogenic bacteria and toxic chemical residues, with risks closely linked to user behavior. Here, we propose a "behavior-material-exposure" triad, based on a 285-day controlled cohort study, to examine how lifestyle habits (e.g., cosmetic use) drive polymer aging and contaminant enrichment on TPU phone case surfaces. Frequent cosmetic use and poor hygiene accelerated TPU oxidation (O/C ratio up to 0.1953) and increased the carbonyl index (up to 33.70), producing micro-fragmented niches that enhanced contaminant retention. Among 21 phone cases samples, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) reached 9.39 μg·cm⁻² and 0.164 μg·cm⁻², respectively. Density functional theory calculations showed stronger adsorption of PFOA (-253.44 eV) than PFOS (-246.33 eV), explaining its higher surface accumulation. PFAS residues acted as environmental stressors, shifting microbial assembly from stochastic to deterministic processes. High-exposure groups (A and B) exhibited reduced diversity and more interconnected networks dominated by opportunistic taxa such as Staphylococcaceae and Burkholderiaceae. Functional predictions revealed enrichment in ABC transporters (efflux systems) and biofilm formation pathways, suggesting adaptive responses that may further sequester PFAS and stabilize pathogenic taxa. Exposure assessment indicated that dermal uptake from aged phone cases contributes meaningfully to total PFAS burden; for frequent users, intake is comparable to indoor dust ingestion. Overall, these findings demonstrate that everyday behaviors drive coupled chemical-microbial dynamics on personal devices, highlighting phones-and other high-touch surfaces-as important interfaces for PFAS and microbial exposure, with implications for health risk management.