Determination Using Gamma Spectroscopy of Natural Radionuclide Activity Concentrations and Annual Committed Effective Doses in Selected Thai Medicinal Plants

Abstract

Medicinal plants are widely used due to their pharmacological properties and less adverse side effects than laboratory-synthesized pharmaceutical drugs. However, possible elevated levels of natural radionuclides especially 226Ra, 232Th, and 40K in medicinal plants have raised concerns about radiological hazards from plant consumption. As a result, this work selected three medicinal plants that are popularly used in Thailand: Clitoria ternatea L., Zingiber montanum, and Andrographis paniculata (Burm.f.) Wall ex Nees to determine natural radionuclide activity concentrations, soil-to-plant transfer factors, and total annual committed effective doses. The results showed that 40K had the highest specific activities and soil-to-plant transfer factors (TFs) in all plants (339.49 - 950.77 Bq kg-1, 1.50 - 2.91, respectively), while leaves of Andrographis paniculata (Burm.f.) Wall ex Nees showed the highest activity concentration of all investigated radionuclides (7.54±0.61 Bq kg-1 for 226Ra, 1.71±0.14 Bq kg-1 for 232Th, and 950.77±89.44 Bq kg-1 for 40K). In terms of the total annual committed effective doses, all medicinal plants investigated in this work had the values from 6.23 - 15.12 mSv yr-1, far less than the average worldwide values of 290 mSv yr-1, indicating it was safe to use these medicinal plants without much danger of radiological hazards. The results were in agreement with previously reported values from other works, which reported the total annual committed effective doses ranging from 2.8 - 14.8 mSv yr-1.