172-7 Radon, the Invisible Geologic Hazard: Measuring Soil Levels in Kentucky

Session: Environmental Geochemistry and Health (Part II)

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Radon gas is a geogenic Class A human carcinogen produced from the radioactive decay of naturally occurring uranium and thorium in the ground. Radon is known to be the second leading cause of lung cancer in the United States and the number one cause among nonsmokers. The National Institute of Environmental Health Sciences is funding a collaboration between the Kentucky Geological Survey and the University of Kentucky College of Nursing to investigate the phenomenon known as the limestone paradox, where higher indoor radon levels are statistically linked to geologic map units in Kentucky with lower uranium potential. Isolating the geologic and atmospheric variables that lead to spikes in soil radon and resulting indoor radon levels is a major focus in the advancing field of geology and health, or geohealth, with the aim of reducing lung cancer deaths and better understanding geologic pathways for this deadly natural hazard. In 2025, the Kentucky Geological Survey deployed state-of-the-art Durridge radon monitoring equipment to measure soil radon gas levels at several locations across the Bluegrass region of Kentucky using optimized soil gas testing methods developed after rigorous field testing. A soil sample was also collected from each site, and total uranium content was quantified using inductively coupled plasma mass spectrometry at the University of Kentucky. The preliminary data showed a weak positive correlation between in-situ soil radon and total uranium in the soil (R² = 0.15) and a slightly higher positive correlation between expected surficial uranium concentrations and total measured uranium in the soil (R² = 0.18). It was also found that measured soil radon values were not always consistent within the same localized testing areas. The early results of this multiyear study suggest that there are complex processes involved in the spatial distribution of soil radon, more than previously hypothesized. More data points are needed to bolster the statistical significance of these relationships and to fine-tune the sample collection methodology to account for elevated soil heterogeneity during future soil gas testing. 

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