Environmental, Economic, and Labour Burden of Time-related Sterility Maintenance and the Potential Reductions from Event-related Sterility Maintenance: A Single-Centre Gate-to-Gate Modelling Study.

BACKGROUND: Time-related sterility maintenance (TRSM) remains common in Japanese operating rooms, requiring re-sterilisation of unopened supplies at fixed intervals, although microbiological evidence indicates that sterility loss is event-driven, not time-driven. Its avoidable burden remains unquantified. AIM: To quantify the annual cost, carbon dioxide-equivalent (CO2e) emissions, water use, and labour from re-sterilising expired supplies under TRSM, and the upper-bound proportion avoidable by transition to event-related sterility maintenance (ERSM). METHODS: Single-centre observational and modelling study integrating a gate-to-gate environmental assessment (a partial boundary rather than a full cradle-to-grave life-cycle assessment), cost-consequence analysis, and discrete-event simulation (DES). A one-month census of expired supplies (746 items) was annualised with the institutional modality mix (steam:VH2O2:EO = 8:1:1) and literature-derived emission factors. As re-sterilisation is predominantly co-loaded, costs were allocated as a marginal increment by load factor. A competing-risk DES, with an event-related contamination hazard from five-year data, yielded a modelled upper bound; conservative scenarios retaining re-sterilisation for legitimate non-time triggers (damage, recall, audit, inventory checks) were added. Uncertainty was assessed by probabilistic (Monte Carlo, 5,000 iterations) sensitivity analysis. FINDINGS: An estimated 8,952 items were re-sterilised annually at one 643-bed centre. The avoidable fraction was a modelled upper bound of 99.9% (95% interval 99.6-100%); under conservative scenarios, 80-95% remained avoidable. At the upper bound, median avoidable burden was ¥1.24 million/year (≈US$8,300), 1,768 kg CO2e/year, 10,727 L water/year, and 147 hours/year. CONCLUSION: TRSM generated approximately 1.8 tonnes of avoidable CO2e, over ¥1 million, and up to 147 hours of avoidable labour annually, supporting evaluation of ERSM as a decarbonisation and efficiency measure.