eng Science and Education Publishing Journal of Environment Pollution and Human Health 2334-3494 2021-09-24 9 2 64 70 10.12691/jephh-9-2-5 JEPHH2021925 article F. Omonya Wanjala feliwanjala@yahoo.com 1 N. O. Hashim 1 D. Otwoma 2 J. Kebwaro 3 M. Chege 3 C. Nyambura 3 Atieno Carmen 4 Kenyatta University, Physics Department, P. O. Box 43844-00100, Nairobi, Kenya National Commission for Science Technology and Innovation, P. O. Box 30623-00100, Nairobi Karatina University, School of Pure and Applied Sciences, P.O. Box 1957-10101, Karatina, Kenya Kenya Methodist University, Nairobi Campus, KEMU Building P.O BOX 45240-00100 Radon and thoron gases are produced by radioactive decay of soil and rocks containing uranium and thorium. Radon and thoron in dwellings constructed using soil and rocks rich in uranium and thorium are considered as a major causes of lung cancer especially for nonsmokers. Despite the dangers that these gases can cause to human health, extensive mapping of concentration of radon and thoron gases in Kenyan dwellings has not been done. This phenomenon leaves a large population at risk of exposure to these gases especially in rural areas where good ventilation is not considered in most of the housing design. In this study, indoor radon and thoron exposure were measured in 7 dwellings chosen using purposive sampling method in Ortum, West Pokot county, Kenya. The radon and thoron concentration in mud houses was determined using a passive radon and thoron discriminative detector (RADUET). The detectors were placed in mud houses at a height of about 2 meters above the ground for 3 months (103 days). The concentrations of radon and thoron were calculated and found to range from 16 ± 6 to 72 ±13 and 18 ±11 to 110 ±30 respectively. The average radon and thoron concentration were found to be 40 ± 19 Bq/m3 and 54 ± 30 Bq/m3 respectively, which is below the International Commission on Radiological Protection (ICRP) recommended lower and upper limit of 100 Bq/m3 and 300 Bq/m3 respectively. The annual effective dose was found to be 1.03 mSv/y for radon and 0.30 mSv/y for thoron which is within the 1.3 mSv average global annual effective dose due to radon, thoron and its progeny. http://pubs.sciepub.com/jephh/9/2/5/jephh-9-2-5.pdf radon thoron lung cancer radioactive gas indoor gases mud houses Ortum