Long-term vs. short-term measurements in indoor Rn concentration monitoring: Establishing a procedure for assessing exposure potential (RnEP)

Abstract

Radon (Rn-222 or Rn) is a naturally occurring chemical element that belongs to the progeny of U-238 released from soil and rocks into the atmosphere, whose impact on organisms is not negligible when it occurs inside confined spaces, such as mine shafts or low-ventilated buildings. The current methodologies for indoor radon assessment are based on passive and active detection. If passive detectors are mainly designed for long-term assessment, active detectors are electronic equipment that can allow on-time visualization of results and, therefore, faster decision-making on risk mitigation measures implementation. However, despite offering a prompt and informed decision, the uncertainty associated with active detector results may cast doubt on the quality of the measurements, which especially arises from the duration of the monitoring campaign. Since radon emanation from soils and rocks depends on a set of variables related to meteorological parameters and soil structure, the seasonal variation of these parameters impacts indoor radon concentration assessment, both on short-term and long-term measurements. Therefore, short-term monitoring campaigns lasting a month, a week, or a day may not produce a statistically representative description of indoor radon exposure for the monitored building. Accordingly, the study compares the reliability of short-term and long-term indoor radon measurements. It proposes a procedure for assessing the indoor Radon Exposure Potential (RnEP) based on in situ measurements through the analysis of the frequency of occurrence of results divided into three classes of potential exposure (low, moderate and high) to reduce occupants’ radon risk exposure.