Natural radioactivity in soils and medicinal plants of the Sundarban: Concomitant radiological risks and radionuclide transfer factor

The natural radioactivity (226Ra, 232Th, and 40K) levels of some medicinal plants and soils in the Sundarban mangrove ecosystem in Bangladesh were assessed for the first time using gamma-ray spectrometry. Depth-wise activity concentration variations for most of the soil cores indicate an increase in radiological contamination in recent years. Although some radiological hazard parameters for soils are higher than the global average values, excess lifetime cancer risk values are below the acceptable limit. The activity concentrations of 226Ra, 232Th, and 40K in the studied medicinal plant leaves varies from 9.03 f 3.01 to 66.9 f 8.2 Bq kg- 1, 25.3 f 5.0 to 155 f 16 Bq kg- 1, and 68.1 f 8.3 to 139 f 12 Bq kg- 1, respectively. For the studied medicinal plants, the soil-to-plant transfer factors of 226Ra, 232Th, and 40K ranged from 0.20 to 1.36, 0.27 to 2.08, and 0.036 to 0.108, respectively. This study indicates that people's consumption of medicinal plants is radiologically safe. The present study assessed radiological risks to develop new strategies to save the sensitive Sundarban ecosystem.