Investigation of naturally occurring radionuclides in selected medicinal plants and associated soils, and calculation of soil-to-plant transfer factors

This study investigated the activity concentrations of 226Ra, 232Th, and 40K and their soil-to-plant transfer factors in some medicinal plants located in Nepal. The geometric mean values of soil-to-plant transfer factors (TFs) for 226Ra, 232Th, and 40K were 0.37, 0.96, and 3.50, respectively. This indicated that medicinal plants absorbed the highest amount of 40K from the soil, followed by 232Th, while 226Ra was absorbed the least. The average radium equivalent activities for medicinal plants (189 Bq/kg) and associated soils (182 Bq/kg) were within the international acceptable limit of 370 Bq/kg. According to the activity concentrations found in the medicinal plants, they do not present any radiological health hazards unless consumed in excessive quantities; however, continuous investigations are essential. •Medicinal plants absorbed the highest amount of 40K, followed by 232Th, and 226Ra.•The average Raeq for medicinal plants and soils were within safe limit of 370 Bq/kg.•The mean TF values for 226Ra, 232Th, and 40K were 0.37, 0.96, and 3.50, respectively.•Medicinal plants pose no radiological risk unless consumed in excessive amounts.