Bacterial contamination of mask inner surfaces during prolonged use by paramedics in prehospital emergency care.
Scientific reports · 2026-06-26 · Observational study
Abstract
Paramedics are routinely exposed to respiratory secretions and aerosols in prehospital settings, necessitating prolonged or repeated mask use for infection prevention. However, evidence regarding time-dependent bacterial contamination of masks worn during extended prehospital duty remains limited. This within-subject repeated-measures study investigated bacterial contamination on the inner surface of KF94 masks worn by 24 Korean paramedics during routine duty. Mask samples were collected after 6, 12, and 24 h of wear. Bacterial contamination was quantified using colony-forming unit (CFU) counts, and bacterial species were identified via 16S rRNA gene sequencing. Differences across time points were analyzed using repeated-measures analysis of variance. Written informed consent was obtained from all participants, and institutional permission was secured from participating EMS agencies. Bacterial contamination increased significantly with prolonged mask-wearing duration (F(2,46) = 22.94, p < 0.001, partial η²=0.50). Mean CFU counts increased from 134.64 ± 131.30 CFU/mL at 6 h to 595.25 ± 153.23 CFU/mL at 24 h, approximately a 4.4-fold increase. Gram-positive bacteria predominated, including species from the Bacillaceae, Staphylococcaceae, and Micrococcaceae families. Attitudes toward mask use were positive overall (mean 3.89/5), alongside moderate perceived discomfort during prolonged wear. Prolonged mask use among paramedics is associated with significant, time-dependent bacterial accumulation on the inner surface of masks. These findings provide preliminary evidence that may inform the development of occupation-specific, evidence-based guidelines on mask replacement and PPE management in prehospital emergency care.