Radiation Levels in Building Materials along Kangundo Road, Nairobi City County, Kenya
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Date
2025-04
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Kenyatta University
Abstract
The primary contributor to human exposure to ionizing radiation is from Natural Radiation Sources (NRS). This type of radiation comes mainly from terrestrial sources and accounts for a significant portion of the radiation humans receive on a daily basis. Terrestrial radiation is emitted from naturally occurring radioactive materials in the Earth's crust, such as radon gas, uranium, thorium, and potassium. To date, there has been no investigation into the concentration of radioactivity in construction materials found along Kangundo Road in Nairobi City County. This research aimed at assessing the environmental impact and human exposure to ionizing radiation from building materials found along Kangundo road in Nairobi. A purposive random sampling method was deployed in this work to collect samples of building materials for analysis. The radioactivity concentration levels in the sampled building materials were determined using a NaI(TI) spectrometer at Kenyatta University laboratory. The activity concentrations measured for 40K ranged from 151 ± 8 to 2392 ± 120 Bq/kg, while 238U exhibited values between 27 ± 2 and 412 ± 21 Bq/kg, and 232Th showed a range from 54 ± 3 to 612 ± 31 Bq/kg. The radioactivity levels for most of the radionuclides exceeded the global average values of 420 Bq/Kg, 33 Bq/kg, and 45 Bq/Kg for 40K, 238U, and 232Th respectively. The absorbed dose rate was found to vary from 65 ± 3 to 616 ± 31 nGyh-1 , which remains below the international safety threshold of 1500 nGyh-1 . The Radium Equivalent values were recorded between 138.18 ± 7 Bq/Kg and 1344 ± 67 Bq/Kg, with sample K3 presenting the highest Radium Equivalent value, surpassing the global safety limit of 370 Bq/Kg. The annual effective dose rate exhibited a range from 0.16 ± 0.01 mSvy-1 to 1.51 ± 0.02 mSvy-1 , with the highest measurement recorded in sample K3, surpassing the globally accepted maximum dose limit of 1 mSvy-1 . This elevated annual effective dose rate may be attributed to the samples being sourced from regions characterized by a significant presence of igneous rocks. The computed Gamma index (Hazard Index) values for the samples varied, with a minimum of 0.31 ± 0.02 mSvy-1 and a maximum of 3.63 ± 0.14 mSvy-1 , where six samples exceeded the permissible safety threshold of 1 mSvy-1 . The average Hazard Index determined in this study was calculated to be 1.01 ± 0.08 mSvy-1 which is within the range of world permissible limit of 1 mSvy-1 . This study adds to our understanding of radiation exposure levels and the related health hazards for construction workers, residents, and occupants of buildings made from materials with high radiation levels.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the Award of the Degree of Master of Science (Physics) in the School of Pure and Applied Sciences of Kenyatta University, April 2025.
Supervisor
1. Nadir O. Hashim
2. Felix Wanjala Omonya