Activity concentrations of natural radionuclides and radiological risk evaluation in medicinal herbs and spices from Jazan, Saudi Arabia

This study aimed to measure the concentration of natural radionuclides ( 40 K, 238 U, and 232 Th) in medicinal herbs and spices collected from local markets in the Jazan region of southwestern Saudi Arabia, a region with high agricultural productivity and widespread consumption of herbal and spice, making it of particular interest for environmental and radiological assessment, and to evaluate their associated radiological risk. A total of 20 samples (10 medicinal herbs and 10 spices) were analyzed using a calibrated NaI(Tl) gamma spectrometry system. Radiological parameters, including absorbed dose rate, radium equivalent activity, annual effective dose, external and internal hazard indices, and gamma activity index, were calculated following IAEA and UNSCEAR guidelines. The results showed that 40 K exhibited the highest activity concentration, reaching up to 153.61 Bq.kg −1 while 238 U and 232 Th had average concentrations of 23.5 Bq.kg −1 and 1.9 Bq.kg −1 , respectively. The calculated values of radium equivalent for all samples were well below the recommended safety limit of 370 Bq.kg −1 . The estimated absorbed dose rates and corresponding annual effective doses were low under the assumed exposure conditions, with value on the order of 10 μSv/year, significantly below the public exposure limit of 1 mSv.y −1 (1000 μSv.y −1 ) recommended by WHO. It was found that AED in was always greater than AED out , indicating that ingestion was the main pathway of exposure. Statistical analysis, including normality testing, parametric and non-parametric comparisons, effect size assessment, and PCA, found no significant differences between medicinal herbs and spices, indicating their radionuclide distribution and associated radiological risk similarities. This study provides novel baseline data on natural radioactivity in commonly consumed medicinal herbs and spices in Jazan region. The findings indicate that these products are associated with a low level of radiological risk under the exposure scenarios and consumption assumptions considered in this study. However, continuous monitoring and the establishment of regulatory guideline are recommended to ensure long-term safety and to support public health protection in Saudi Arabia.