Preliminary survey of radioactivity level in Thai medicinal herb plants

In this research, the natural radioactivity concentrations and their respective annual effective dose of the naturally occurring radionuclides Ra-226, Ra-228 and K-40 in selected medicinal herb plants were investigated. Seven kinds of popular Thai medicinal herb plants had been studied: turmeric, ginger, safflower, moringa, gotu kola, garlic and alexandria senna. The radiological risk associated with the use of these medicinal plants was assessed. The activity concentrations of Ra-226, Ra-228 and K-40 were determined using the gamma-ray spectrometry technique. The radioactivity concentrations were found to range from less than 0.20 to 6.67 Bqkg(-1) for Ra-226, less than 0.10 to 9.69 Bqkg(-1) for Ra-228, and from 159.42 to 1216.25 Bqkg(-1) for K-40. Gotu kola showed the highest activity concentrations of Ra-226 and Ra-228, while ginger showed the highest activity concentration of K-40. The total annual effective dose due to ingestion of these herb plants were found to range from 0.0028 to 0.0097 mSvy(-1) with an average value of 0.0060 +/- 0.0001 mSvy(-1). The results conclude that the Thai medicinal herb plants samples from this research are considered safe in terms of the radiological hazard.