Natural radioactivity and radiological hazard assessment of sand used for construction in South Korea.

Sand is widely used in concrete, mortar and plaster, but its natural radioactivity has received little systematic attention in South Korea. This study provides a descriptive, screening-oriented assessment of 50 construction sand samples obtained over approximately one year from multiple supply sites; regional identifiers were available for 33 samples and unavailable for 17 (34%). Mean activity concentrations were 31.2, 52.3 and 944.2 Bq/kg for 226Ra, 232Th and 40K, respectively. Mean radium equivalent activity was 178.7 Bq/kg, and 45 samples had Iγ ≤ 1. The model-based mean indoor annual effective dose and excess lifetime cancer risk were 0.79 mSv/y and 2.78 × 10-3, respectively; these are screening estimates, not measurements of personal exposure or cancer risk. 40K contributed 40.7% of mean radium equivalent activity and 46.7% of mean indoor absorbed dose rate. Nineteen samples had 40K above 1 Bq/g, two had 226Ra above 0.1 Bq/g and one had 232Th above 0.1 Bq/g; these are definition-level observations under Korean law, not stand-alone use limits or non-compliance determinations. None reached the separate registration concentration levels. At the default indoor occupancy factor of 0.8, 11 calculated AEDE values exceeded 1 mSv/y, but these generic-model results do not demonstrate finished-product non-compliance. Because sampling was not probability based and regional metadata were incomplete, the results characterize only the analyzed sample set and not nationwide averages.