Natural radioactivity concentration in traditional Thai herbal medicine

The aim of this study is to create a database of radioactivity concentration and annual effective dose of the naturally occurring radionuclides: ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ²¹⁰Po in Thai medicinal herb plants. 99 types of popular Thai medicinal herb plants (total of 214 samples) such as Curcuma comosa Roxb., mucuna, white kwao krua, barbed grass, black galingale, lingzhi mushroom, Ginkgo biloba, jiaogulan, plu kaow, turmeric, ginger, safflower, moringa, gotu kola and garlic were randomly collected from drug stores and herbal fair. The activity concentration of ²²⁶Ra, ²²⁸Ra and ⁴⁰K in all herb samples was determined by gamma-ray spectrometry while that of ²¹⁰Po was determined by alpha spectrometry. The activity concentration was found to range from <0.20 to 89.92 Bq kg⁻¹ for ²²⁶Ra, from <0.10 to 39.62 Bq kg⁻¹ for ²²⁸Ra and from 4.83 to 2761.33 Bq kg⁻¹ for ⁴⁰K and from 0.32 to 47.13 Bq kg⁻¹ for ²¹⁰Po. The highest activities concentration of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ²¹⁰Po were found in the white kwao krua, jiaogulan, plu kaow and ginkgo, respectively. The average total annual effective dose due to ingestion of these herbal plants was assessed to range from 0.0001 to 0.0327 mSv y⁻¹, with highest dose found in jiaogulan. (paper)