Assessment of Radiation Dose Levels in Tiles Used for Decoration in Bungoma County, Kenya.

International Journal of Research and Scientific Innovation (IJRSI) | Volume IX, Issue III, March 2022 | ISSN 2321–2705

Assessment of Radiation Dose Levels in Tiles Used for Decoration in Bungoma County, Kenya

John Simiyu Nalianya, Michael Nakitare Waswa, Francis Maingi and Conrad Khisa Wanyama
Department of Science, Technology and Engineering, Kibabii University

Abstract: The natural radioactive content of tiles used in Bungoma County, Kenya was assessed using gamma ray spectroscopy in this study. The amounts of certain radioisotopes found in 20 samples of decoration tiles used in Bungoma County, Kenya were estimated using a NaI(Tl) detector. The average activity concentrations of 226Ra, 232Th, and 40K for the tiles were determined to be 11±0.55, 109±5.85, and 1574±78.7Bq/kg respectively. Radiological hazard indices such as absorbed dose rate, radium equivalent activity, external Hazard Index (Hex), internal Hazard Index (Hin), Indoor and outdoor Annual Effective Dose (mSv/y), were determined as 140±7.03 nGyh-1; 288±14.44 Bq/kg, 0.7±0.03 mSv/y, 0.8±0.04 mSv/y; 0.5±0.02mSv/y; and 0.3±0.01mSv/yrespectively. The mean radium equivalent obtained in this investigation was lower than the worldwide reference value of 370 Bq/kg. Hence, use of tiles for decoration in Bungoma County, Kenya has minimal health threat to the population.

I. INTRODUCTION

Terrestrial gamma rays and cosmic rays are the two principal natural sources through which human civilization is exposed to radiation from the outside. Natural radionuclides from the 238U, 232Th, and 40K series found in the earth’s crust produce terrestrial gamma rays (1). These radionuclides (238U, 232Th, and 40K) are present in soils based on the distribution of these radionuclides in the rocks from which they originate, as well as the processes that concentrate the soils. Igneous rocks, such as granite, have higher radiation levels than sedimentary rocks, which have lower levels (2).The sorts of rocks from which soils are formed influence the amount of terrestrial background radiation. However, building materials such as tiles are derived from radioactive resources such as rocks, dirt, and so on. These isotopes can be found in all types of environments, but their activity levels are often higher in soils and rocks (3). However, the vast majority of these tiles are by-products of rocks and soils that contain varying levels of primordial radionuclides. Additional doses may be caused by increased or higher levels of natural radionuclides in building materials as a result of external and internal exposure (4). Radiation exposure is caused by naturally occurring radionuclides in building materials such as tiles in two ways: external radiation from the 238U and 232Th decay series, as well as 40K, and internal radiation from radon inhalation, which leads to deposition of its decay products in the respiratory tract (5). The monitoring of natural radioactivity in building materials has received a lot of interest in recent years, especially in European, Asian, and some African countries. The goal of this study is to assess radionuclide concentrations and associated hazard indices in tiles used in Bungoma County, Kenya in order to determine the radiation dose level for health safety.

II. MATERIALS AND METHODS

2.1 Study Area

The study was conducted using tiles commonly found in the hardware from Bungoma County being a representative of what is on the Kenyan market. The tiles that were considered were those from Egypt, India, Uganda and those which are locally manufactured, i.e the Twyford and saj tiles. The random sampling method was used to collect samples.

2.2. Sample Description and Preparation

To assess the radiological hazard in both the local and imported tiles, a total of 20 samples of commercial tiles were sampled. The names of different samples of ceramic tiles are (India: T1, T2,T3,T4. Uganda: T5,T6,T7,T8. Egypt: T9,T10,T11,T12,T13. Kenya Twyford: T13,T14,T15,T16. Kenya Saj: T17,T18,T19 and T20). For each country four samples were taken. These particular countries were considered because they were the ones available on the market. All samples were crushed (separately) to a fine powder and sieved through a 0.5mm mesh. Each sample was oven-dried at 110°C for 3hours to reduce the moisture content (6). Weighed samples of 200g were placed in polyethylene cylindrical beakers, of about 300ml each. These beakers were sealed to prevent the escape of gaseous 222Rn from the samples and stored for 30 days to attain secular equilibrium between 226Ra and 232Th and their decay products. At this point, the rate of decay of the progeny becomes equal to that of the parent (radium and thorium) within the volume and the progeny also remains in the sample (7).

2.3. Activity Concentration

The calculations of the activity concentration (Ac) values for the radionuclides from235U, 238U and 232Th series and 40K present in the selected tile samples was determined as shown by equation 2.1 (8)

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