Reconsidering indoor radon monitoring strategies in Romanian medical buildings: a data-driven perspective

Abstract

Introduction Medical buildings are complex indoor environments with heterogeneous room functions, occupancy patterns and HVAC (especially ventilation) requirements. Although radon monitoring methodologies are applied across workplaces, healthcare facilities differ from residential buildings in air exchange, operational schedules and functional zoning. This study investigated indoor radon concentration in Romanian medical buildings and assessed whether current monitoring assumptions, including residential-derived seasonal correction factors, adequately reflect observed exposure patterns. Materials and methods A total of 1700 CR-39 detectors were installed for three-month measurements in 115 medical institutions from 40 localities across Romania. After retrieval, 1,651 valid measurements were included in the final analysis. Annual indoor radon activity concentration (AIRAC) was estimated using seasonal correction factors recommended by the Romanian methodology. Mixed-effects models were fitted separately for log-transformed uncorrected three-month radon concentrations and seasonally corrected AIRAC, with floor level, facility type and starting month as fixed effects and building code as a random intercept. Results Overall radon levels were low, with an arithmetic mean of 61 Bq/m 3 , a median of 40 Bq/m 3 and a geometric mean of 41 Bq/m 3 . Only 26 of the 1,651 valid measurements, representing 1.6%, exceeded the reference level of 300 Bq/m 3 . Exceedances were concentrated on lower levels: 25 occurred in basements, semi-basements or ground-floor rooms, whereas only one was found on upper floors. Higher median concentrations were observed in radiology clinics and dental offices, while hospitals and medical clinics showed lower values. For seasonally corrected AIRAC, the mixed-effects model indicated significant effects of floor level, facility type and starting month. However, starting month was not significant in the parallel model fitted to uncorrected three-month concentrations. Discussion Radon variability in medical buildings appears shaped by floor level, facility type and building-specific characteristics. The comparison between corrected and uncorrected seasonal patterns showed that the application of residential seasonal correction factors was associated with an amplified warm–cold contrast and a stronger starting-month pattern in AIRAC estimates. Conclusion This first large-scale assessment of indoor radon in Romanian medical buildings supports a risk-based and context-sensitive monitoring strategy. Detector allocation should prioritize lower levels and facility categories associated with higher concentrations, while the use of residential seasonal correction factors in medical buildings should be further evaluated through repeated seasonal measurements.

The authors' abstract, as published at the source. Frontiers in Public Health, 2026 · DOI ↗