Radiological profiling of modern building materials: A case study of natural radionuclides in vitrified tiles from Tamil Nadu, India and their health implications

Abstract

The activity concentrations of naturally occurring radioactive materials (NORM), specifically radium-226 (²²⁶Ra), thorium-232(²³²Th), and potassium-40 (⁴⁰K), in vitrified tiles widely used as modern building materials in Tamil Nadu, India, have been investigated. Since the global concern regarding radiation exposure from construction materials is increasing, a comprehensive radiological assessment was conducted to evaluate potential health hazards associated with these tiles. The analysis revealed mean activity concentrations of 68 ± 5 Bq kg⁻¹ for ²²⁶Ra, 116 ± 8 Bq kg⁻¹ for ²³²Th, and 540 ± 40 Bq kg⁻¹ for ⁴⁰K. These concentrations are notably higher than the corresponding world average values of 50 Bq kg⁻¹ for ²²⁶Ra, 50 Bq kg⁻¹ for ²³²Th, and 500 Bq kg⁻¹ for ⁴⁰K reported by UNSCEAR. Consequently, the calculated average indoor gamma absorbed dose rate of 124 nGy h⁻¹ and the estimated excess lifetime cancer risk of 2.13 × 10⁻³ mSv y⁻¹ associated with these tiles slightly exceed the global average values proposed by UNSCEAR. While the overall radiological hazard for most indices remains within acceptable international limits, these observed elevations in specific parameters highlight the importance of continued vigilance. To further understand the distribution patterns and interrelationships of these radionuclides, multivariate statistical analyses, including Pearson's correlation, hierarchical cluster analysis, and principal component analysis/factor analysis, were performed. These analyses consistently demonstrated that ²²⁶Ra and ²³²Th are the primary contributors to the calculated radiological hazard indices, as evidenced by their strong positive correlations with parameters such as radium equivalent activity, absorbed gamma dose rate, and excess lifetime cancer risk. In contrast, ⁴⁰K exhibited a distinct behavior, contributing less significantly to the potential health hazards associated with these tiles. The research findings highlight the need for region-specific radiological assessments of building materials and suggest the potential need for regulatory guidance in selecting and using raw materials for tile manufacturing to ensure public radiation safety.