Assessing historical residential radon exposure using a glass-based surface trap method in low radon level areas: a...

Retrospectively estimating residential radon exposure in epidemiological studies is challenging using conventional methods. This study aimed to compare a modified glass-based surface trap technique for assessing historical indoor radon exposure with conventional long-term radon detectors among pregnant women from areas with relatively low radon levels. Ten women during their first trimester pregnancy were recruited from a Columbia University Irving Medical Center-affiliated hospital. Each participant was asked to place one detector in the basement and another in a high-occupancy main-floor room until delivery, after which devices were returned by prepaid mail to a certified laboratory. In addition, we collected the cover glass from small picture-frames that participants placed in the main-floor living area of their current and previous homes. Each glass plate was mounted against TASTRAK alpha-particle-detecting plastic and stored at-20 °C in a radon-proof atmosphere for 37 d. Plastics were etched and analysed for alpha-particle track density over a 4 cm²area. Conventional detector measurements of indoor radon ranged from <14.8-133.2 Bq m^-3(<0.4-3.6 pCi l^-1), while the modified glass-based method yielded 641-1476 tracks (0.14-0.32 Bq m^-2). Spearman correlation (ρ) between these two measurements were 0.68 (main floor), 0.38 (basement), and 0.63 (average of both floors). After adjusting for detector exposure duration, the correlations were slightly increased to 0.72, 0.43, and 0.67, respectively. The modified glass-based surface trap method by assessing alpha-particle track counts demonstrated moderate-to-strong correlations with long-term radon detectors. While larger-scale studies are needed to confirm the findings, this technique may provide a practical alternative for reconstructing historical residential radon exposure, even in regions with relatively low radon levels.