Cancer Risks Associated with Exposure to Background Ionizing Radiation in Human Habitat, Soil, and Food in Kenya

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dc.contributor.advisorRichard Okoth Oduoren_US
dc.contributor.advisorMathew Piero Ngugien_US
dc.contributor.advisorSiphila Mumenya Wanjikuen_US
dc.contributor.authorOgola, Phillip Einstein
dc.date.accessioned2024-02-06T09:37:43Z
dc.date.available2024-02-06T09:37:43Z
dc.date.issued2023-10
dc.descriptionA Thesis Submitted in Fulfillment of the Requirement for the Award of the Degree of Doctor of Philosophy (Medical Biochemistry) in the School of Pure and Applied Sciences of Kenyatta Universityen_US
dc.description.abstractCancer is described as uncontrollable cell proliferation in the body. By spreading outside their borders and infiltrating neighbouring tissue, such cells can invade to other organs. Cancer is the third leading cause of mortality in Kenya, trailing only infectious and cardiovascular diseases, with an annual incidence increasing from 37,000 new cases in 2012 to 48,000 new cases in 2018. Similarly, annual cancer mortality increased from around 28,000 to 33,000 within the same time span. Cervical, breast, colorectal, prostate, and esophageal cancers are the most prevalent types of cancer in Kenya. According to the National Cancer Control Strategy 2011-2016, cancer arises from abnormal alterations resulting from interactions between genetic and environmental elements, which encompass physical carcinogens such as ionizing radiation. The GLOBOCAN 2020 estimates reported that in Kenya, there were 42,116 new cancer cases and 27,092 deaths attributed to cancer. Types of cancer linked to high radiation dose exposure include leukemia, breast, bladder, colon, liver, lung, esophagus, ovarian, multiple myeloma, and stomach cancers. Naturally Occurring Radioactive Materials (NORMs) are found in trace amounts in soil, water, food, and the atmosphere. While natural radioactivity is formed from primordial radionuclides spread throughout the earth's crust, human activities such as nuclear power generation and mining contribute to the release of additional radionuclides into the environment. Human exposure to radiation comes through external sources as well as consuming radionuclides through water and food ingestion or breathing of radioactive vapors. This research focused on establishing the cancer risks associated with exposure to background ionizing radiation in quarries, human premises, soils from agricultural zones, and tuber crops (cassava, sweet potatoes, and Irish potatoes) in Kisii, Kakamega and Busia Counties in Kenya. Ionizing radiation levels were detected using handheld radiation detectors in quarry sites and buildings, whereas 232Th, 40K, and 238U activity concentrations in soil and tuber crops were determined using high purity germanium detectors. In quarry sites, the calculated average annual effective dose (AED) was 1.702 mSv in Kisii County, 2.083 mSv in Kakamega County, and 2.016 mSv in Busia County. Furthermore, the mean excess lifetime cancer risk (ELCR) due to occupational exposure in quarry sites were 5.702×10-3 in Kisii County, 6.979×10-3 in Kakamega County, and 6.754×10- 3 in Busia County. The computed AED values in the premises were 1.369 mSv in Kisii County, 1.317 mSv in Kakamega County and 1.268 mSv in Busia County. Also, the lifetime cancer risk attributable to indoor background ionizing radiation exposure were 4.586×10-3 in Kisii County, 4.411×10-3 in Kakamega County and 4.247×10-3 in Busia County. From the findings, cancer risk associated with lifetime exposure to ionizing radiation in quarry sites and premises sampled herein was low. Moreover, the mean activity concentrations of 232Th, 238U, and 40K in soil samples were 83.58 Bq/kg, 28.6 Bq/kg, and 483.40 Bq/kg respectively in Kakamega County, 65.36 Bq/kg, 22.88 Bq/kg, and 176.72 Bq/kg respectively in Busia County and 106.6 Bq/kg, 46.08 Bq/kg, and 153.42 Bq/kg respectively in Kisii County. Additionaly, the mean activity concentrations of 232Th, 238U, and 40K in tuber crops sampled in this study were below the global average values. Furthermore, the estimated mean annual ingestion effective dose (AIED) values in tuber crops ranged from 0.049 mSv to 0.062 mSv for cassava, 0.027 mSv to 0.064 mSv for sweet potatoes, and 0.057 mSv to 0.153 mSv for Irish potato. Similarly, the computed radiation hazard indices in soil samples and tuber crops yielded values below the acceptable limits, indicating not only insignificant cancer risk associated with the general public's exposure to ionizing radiation from the soil samples but also safety in consumption of these tuber cropsen_US
dc.description.sponsorshipkenyatta universityen_US
dc.identifier.urihttps://ir-library.ku.ac.ke/handle/123456789/27568
dc.language.isoenen_US
dc.publisherkenyatta universityen_US
dc.subjectCancer Risksen_US
dc.subjectIonizing Radiationen_US
dc.subjectHuman Habitaten_US
dc.subjectSoilen_US
dc.subjectFooden_US
dc.subjectKenyaen_US
dc.titleCancer Risks Associated with Exposure to Background Ionizing Radiation in Human Habitat, Soil, and Food in Kenyaen_US
dc.typeThesisen_US
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