Mapping Radionuclide Exposure Through Marine Gastropods in Coastal Waters of Kerala, South-West India

Abstract

Naturally occurring radionuclides in marine food webs are an important radiation exposure pathway for coastal populations, especially in high-background natural radiation areas (HBNRAs). This study investigated the accumulation, spatial distribution, ecological controls, and radiological implications of ²³⁸U, ²³²Th, ²¹⁰Po, and ²¹⁰Pb in 15 commercially and ecologically important gastropod species collected along the heavy mineral-rich Kollam coast of southwest India. The activity concentrations ranged from BDL(≤ 0.5)–1.8 Bq kg⁻¹ for ²³⁸U, 0.62–4.1 Bq kg⁻¹ for ²³²Th, 14.7–76.4 Bq kg⁻¹ for ²¹⁰Po, and 3.2–56.4 Bq kg⁻¹ for ²¹⁰Pb, with overall accumulation following ²¹⁰Po ≫ ²¹⁰Pb ≫ ²³²Th > ²³⁸U. Significant differences were observed among species, taxonomy, feeding guilds, and stations for ²¹⁰Po and ²¹⁰Pb (Kruskal–Wallis, p < 0.01), whereas ²³⁸U and ²³²Th showed limited biological variability. Strong positive correlations between ²¹⁰Po and ²¹⁰Pb (r > 0.80, p < 0.001) and elevated ²¹⁰Po/²¹⁰Pb ratios (1.09–4.59) indicated preferential enrichment and retention of ²¹⁰Po. The annual committed effective dose (A_CED) was estimated to vary between 62.5 and 229.5 µSv y⁻¹, with an average value of 178 µSv y⁻¹. Although the carcinogenic risk to the general public was minimal, the results highlight the importance of thorough tailored species-specific ecological monitoring, guidelines for human consumption, and strategies for sustainable management.