Abstract:
The occurrence of naturally-occurring radionuclides, including Thorium-232, Uranium238, and Potassium-40, in various environmental matrices such as soil, water, rocks, and
food, is the primary cause of exposure to ionizing radiation. Radionuclides possess the
capability to induce deleterious effects on human health through inhalation, ingestion or
crops consumption, leading to detrimental impacts on living cells or DNA of the body.
Higher radiation doses cause mutagenesis, which results in lung cancer, pediatric
leukemia, kidney damage and death. Through the use of Gamma-ray Spectrometric
analysis, this study investigated the natural activity concentration levels of Potassium-40,
Thorium-232, and Uranium-238 in construction rocks from the 15 selected quarries in the
County of Kericho, Kenya. Based on the geological distribution of the rocks used in
building, quarries from each sub-county were selected. To improve the representation and
the quality of the data, two samples were taken from each quarry. From sample collection
through preparation and measurement, IAEA protocols were followed. In order to attain
secular equilibrium between Radium-226 and Thorium-232, samples were collected,
crushed, oven dried (105 °C), weighed, and put in airtight containers and were then
preserved for four weeks. The determination of radiological parameters, including specific
activity concentration, radium equivalent, annual effective dose rate, absorbed dose rate,
external hazard index, internal hazard index, and activity utilization index, was done to
determine the extent of radiation exposure to various groups of people who were
constantly in contact with rock fragments, such as miners, transporters, masons, residents
of homes constructed from these rocks, and even the general public. 232Th, 238U, and 40K
had average activity concentrations of 101± 5.08 Bq/kg, 56± 2.81 Bq/kg, and 1100 ±55.03
Bq/kg respectively and varied from 41± 2.07 to 138± 6.91 Bq/kg, 26 ±1.34 to 116 ±5.80
Bq/kg and 256±12.82 to 1919 ±95.99 Bq/kg respectively. The mean activity
concentrations of 238U, 232Th, and 40K were more than the global average values of 50
Bq/kg, 50 Bq/kg and 500 Bq/kg respectively. The Absorbed Daose Rate was greater than
the global recommended value of 60 nGy/h but lower than the permissible threshold value
of 1500 nGy/h, ranging from 83± 4.16 nGy/h to 152± 7.60 nGy/h with an average value of
138 ±6.94 nGy/h. The mean effective dose rates for indoor and outdoor environments were
0.6 ±0.03 mSv/y and 0.1±0 mSv/y respectively and were below the 1 mSv/y global
recommendation. The mean activity utilization, internal hazard, and external hazard
indices were 2.1±0.1, 0.9±0.04 and 0.8±0.04 mSv/y respectively. The average Radium
equivalent value of 285 ±14.28 Bq/kg, which was below the permissible limit of 370
Bq/kg and ranged from 165 ±8.25 Bq/kg to 309 ±15.47 Bq/kg, indicated that the excavated
rocks for construction from the chosen quarries in Kericho county pose negligible health
risks to those who are in constant contact with the rock fragments and the general public.
