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

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 (ACED) 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.