EVALUATION OF GAMMA-EMITTING RADIONUCLIDES IN MEDICINAL HERBS USED FOR INFANT CARE IN IGBOKODA, SOUTHWESTERN NIGERIA.

Abstract

Concerns about the safety of herbal remedies used in infant care have increased, particularly regarding exposure to naturally occurring radionuclides. This study assessed the activity concentrations of uranium-238 (²³⁸U), thorium-232 (²³²Th), and potassium-40 (⁴⁰K) in medicinal herbs commonly used for infants in Igbokoda, Ondo State, Southwestern Nigeria. Twelve herb samples were selected based on traditional use for treating infant ailments. A thallium-doped sodium iodide gamma-ray spectrometry system (NaI(Tl)) was used to determine radionuclide concentrations. Radiological health indices, including absorbed dose rate, annual effective dose (AED), external and internal hazard indices (Hex and Hin), excess lifetime cancer risk (ELCR), and annual committed effective dose (Eave), were calculated and compared with international safety standards. The activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K ranged from 3.05–9.61, 1.26–5.94, and 43.16–256.24 Bq·kg⁻¹, respectively, remaining within UNSCEAR recommended limits. Carica papaya showed the highest absorbed dose rate (13.90 nGy·hr⁻¹), while Azadirachta indica recorded the lowest (5.66 nGy·hr⁻¹). AED values ranged from 0.028 to 0.068 mSv·yr⁻¹, representing only 2.8%–6.8% of the ICRP's public dose limit. Hazard indices (Hex: 0.041–0.087; Hin: 0.049–0.113) were below 1, and ELCR values ranged from 0.097 to 0.239. The mean Eave was 0.324 mSv·yr⁻¹. The results indicated no significant radiological risks to infants under normal herbal use. However, periodic monitoring is recommended, especially for Zingiber officinale and Carica papaya, which showed higher radionuclide uptake. These findings offer baseline data for radiological safety and public health policy.