Assessment of natural radionuclides and health risks in Lannea discolor and its substrate from Limpopo Province, South Africa

Medicinal plants may accumulate naturally occurring radionuclides from the environment, raising safety concerns for long-term users. The study aimed to quantify the levels of naturally occurring radionuclides in commonly used Lannea discolor plant parts and their growing substrate, and to evaluate the associated radiological health risks to users. Plant and substrate samples were collected from Vuwani in the Vhembe Region of Limpopo Province, South Africa. Gamma-ray spectrometry with an AT6101DR spectrometer was used to determine the activity concentrations of the naturally occurring radionuclides 226 Ra, 232 Th, and 40 K. Radiological risk parameters such as radium equivalent activity (Ra eq ) external absorbed dose rate, and external and internal hazard index (H ex and H in ) were calculated to assess potential exposure risks. The activity concentrations of 226 Ra, 232 Th, and 40 K varied across plant parts and substrate. The highest 226 Ra activity was observed in the roots, ranging from 8.25 to 23.07 Bq/kg. 232 Th activity ranged from 0.38 to 0.77 Bq/kg, while 40 K concentrations varied from 0.48 to 0.93 Bq/kg. Calculated radiological parameters were as follows: radium equivalent activity ranged from 9.43 to 23.62 Bq/kg; external absorbed dose rate from 4.32 to 10.91 nGy/h; and external hazard index from 0.02 to 0.06. All values remained below the internationally accepted safety limits. The radiological assessment indicates that the levels of natural radionuclides in Lannea discolor and its substrate are low and do not pose significant health risks to users. This underscores the importance of routine radiological screening of medicinal plants to ensure their safe use. Further studies with larger sample sizes are recommended to validate these findings and inform regulatory guidelines for medicinal plant safety.