Levels Of Natural Radionuclides in Khat (Catha Edulis) Leaves and Soils in Selected Areas In Embu County, Kenya

VINDESIO NJAGI NGARI; Nadir Hashim; Abdalla Merenga

Authors

VINDESIO NJAGI NGARI Department of Physics, School of Pure and Applied Sciences at Kenyatta University, Nairobi, Kenya https://orcid.org/0000-0001-8341-5110
Dr Hashim Department of Physics, School of Pure and Applied Sciences at Kenyatta University, Nairobi, Kenya
Dr Merenga Department of Physics, School of Pure and Applied Sciences at Kenyatta University, Nairobi, Kenya

Keywords:

Radionuclide, Radioactivity, khat(Catha edulis), uranium, thorium, potassium, Embu

Abstract

Over the past years, khat (Catha edulis) has been the major cash crop grown in some parts of the Eastern side of Kenya.The leaves from this plant are chewed for their stimulating effect. However, some studies have reported detrimental effects on the users of khat. This research established the level of human exposure due to radiation by natural sources in the khat growing areas of Embu County by measuring the specific activities of ²³⁸U, ²³²Th and ⁴⁰K,estimate the dose rate absorbed and obtain the hazard indices due to these radionuclides. A total of 30 samples were collected from different areas distributed throughout Embu County, 15 for khat and 15 for soil samples. The samples were then prepared and analyzed using the Thallium activated Sodium Iodide Detector (NaI(Tl). Mean activities for khat leaves were obtained as 875.8±11 Bq/kg, 10.1±1 Bq/kg and 51.1±4 Bq/kg for ⁴⁰K, ²³⁸U and ²³²Th respectively. The activities of soil in the same region were obtained as 344±12 Bq/kg, 22±11 Bq/kg and 33±5 Bq/kg for ⁴⁰K, ²³⁸U and ²³²Th respectively. The mean absorbed dose rates obtained for soil was 44±0 nGyh^-1 while the average Annual Effective Dose (AED) for ingested radionuclides for khat was 0.45±0.19 mSv/y. Average values of soil hazard indices for soil 0.26, 0.32, 0.70 and 0.76 for external index (H_ex), internal index (H_in), gamma index (?) and Excess Lifetime Cancer Risk (ELCR) respectively. All the indices in this work were within the safe limit.

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