Exposure from Thoron, Radon and Modelling Indoor Gamma Radiation Dose in Homa Bay County, Kenya

Simple item page
dc.contributor.advisorMargaret W. Chegeen_US
dc.contributor.advisorNadir Hashinaen_US
dc.contributor.advisorShinji Tekonamien_US
dc.contributor.authorOdongo, Willis Otieno Gor
dc.date.accessioned2023-08-09T08:56:27Z
dc.date.available2023-08-09T08:56:27Z
dc.date.issued2023
dc.descriptionThesis Submitted in Fulfillment of the Requirements for the Award of the Degree of Doctor of Philosophy (Nuclear Physics) in the School of Pure and Applied Science of Kenyatta University July, 2023en_US
dc.description.abstractHoma and Ruri hills in Homa Bay County, Kenya, are associated with high background radiation levels. Presently, they are experiencing high human settlement. Maize is the major food crop and Lake Victoria is the major water source. There is no sufficient data on radiation exposure from indoor gamma, air (222Rn and 220Rn) crops and water. The main objective of this research is to determine human exposure to ionizing radiation associated with natural radioactivity in dwellings, water and crops, besides assessing the risk of heavy metals from contamination of Lake Victoria waters and modeling indoor gamma absorbed dose due to non-secular equilibrium in 232Th decay series. Terrestrial radioactivity measurements were done using NaI (Tl) detector. Indoor 222Rn, 220Rn, and 220Rn progenies were measured using RADUET and EETC monitors while 222Rn in water was measured using big bottle system coupled with RAD7. For heavy metal analysis, AAS was used. A mathematical model on absorbed gamma dose was developed and validated. The modelled and measured absorbed doses in the dwellings registered a reasonable agreement. The modelled absorbed dose was 15% less than the experimental one, which considers secular equilibrium in the 232Th decay series. The total annual effective dose from indoor air in Ruri was 4.9±0.7 mSv/y1, nearly 1.5 times that of Homa. The average 222Rn concentration in Lake Victoria in Homa was 14.8 Bq/L, 10% higher than in Ruri. The average 222Rn ingested annual effective dose was 60% lower than the recommended WHO reference level of 100 μSv/y1 in both regions. Arguably, heavy-metal lead was the main contaminant in Lake Victoria around the study region as the average incremental lifetime cancer risk for heavy metals was above the WHO limit of 1 × 10-4 by a factor of 5 for adults in both Ruri and Homa, respectively. The total annual effective dose from indoor air, building materials, food stuff maize, and Lake Victoria in Homa was 45% lower than Ruri, which was 12.6±2.1 mSv/y, each contributing about 45%, 30%, 24%, and 1% of the dose respectively in both regions. These results indicate potential health risk of human exposure to ionizing radiations in these regions as the reported values in some of the considered dwellings and maize samples were above the ICRP and WHO safe limits. Indoor air was the major contributor to radiation exposure; thus, houses in the regions should be properly ventilated. Non-secular equilibrium in the 232Th decay series should be considered in determining absorbed gamma dose in earthen dwellings to avoid overestimation.en_US
dc.description.sponsorshipKenyatta Universityen_US
dc.identifier.urihttp://ir-library.ku.ac.ke/handle/123456789/26675
dc.language.isoenen_US
dc.publisherKenyatta Universityen_US
dc.subjectExposure from Thoronen_US
dc.subjectRadon and Modelling Indoor Gamma Radiation Doseen_US
dc.subjectHoma Bay Countyen_US
dc.subjectKenyaen_US
dc.titleExposure from Thoron, Radon and Modelling Indoor Gamma Radiation Dose in Homa Bay County, Kenyaen_US
dc.typeThesisen_US
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Exposure from Thoron, Radon and Modelling Indoor Gamma Radiation Dose in Homa Bay County, Kenya.pdf
Size:
3.87 MB
Format:
Adobe Portable Document Format
Description:
Full text Thesis
Download
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
1.71 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
PHD-Department of Physics