Vol.:(0123456789) 1 3 Earth Systems and Environment (2018) 2:95–102 https://doi.org/10.1007/s41748-018-0039-9 ORIGINAL ARTICLE Indoor External Radiation Risk in Densely Populated Regions of Southern Nigeria Oluwatobi O. Ife‑Adediran 1  · Iyobosa B. Uwadiae 2 Received: 30 August 2017 / Accepted: 7 February 2018 / Published online: 15 February 2018 © Springer International Publishing AG, part of Springer Nature 2018 Abstract It is known that certain types of building materials contain signifcant concentrations of natural radionuclides; consequently, exposure to indoor background radiation is from the combined radioactivity from the soil as well as building materials; indoor exposures therefore have higher radiation hazard potentials than outdoor exposures in this regard and hence, need to be monitored. In this paper, an evaluation of background ionizing radiation from diferent buildings in Lagos and Ibadan, Southwestern Nigeria was carried out to determine the exposure rate of the general public to indoor ionizing radiation. 630 in situ measurements from the diferent buildings were taken using a Geiger Muller counter (model GQ-320 Plus). The indoor dose rates (i.e., 50–120 nGy/h) were within the world average values while the Annual Efective Dose for most of the buildings were above the world average AED for indoor gamma exposure from building materials. The mean AED for Lagos and Ibadan due to indoor exposures were 0.37 and 0.39 mSv/y with Excess Lifetime Cancer Risk of 0.99E−3 and 1.05E−3, respectively. Keywords Indoor external radiation · Dose rate · Annual efective dose · Excess lifetime cancer risk 1 Introduction The main sources of radiation exposure to human beings are natural and artifcial radionuclides (UNSCEAR 2008). Natural radioactivity is widely spread in the earth’s environ- ment and it exists in various geological formations like soils, rocks, plants, water and air (Nikolaev 1999) and as such, the human body is exposed to radiation from these diferent sources (Jitka and van Barnet 2002). All building materials are mostly composed of rock and soil and these two raw materials contain natural radioactive isotopes such as 232 Th and 238 U decay series and 40 K (IAEA 2008; El-Taher 2010). The concentrations of the radioisotopes in the earth’s crust and in building materials, determine the dose of natural radi- ation, both outside and inside of building (Ademola 2009). Ambient dose rates of natural radiation could be infuenced by soil composition, atmospheric conditions, topography and vegetation (Bossew et al. 2017; Ljiljana and Lidija 2017). Natural radionuclides in building materials may cause both external exposure caused by their direct gamma radiation and also internal exposure from radon gas. The gamma radiation arising from the walls, foors and ceilings, as well as 222 Rn and 220 Rn and their progeny are the major sources of radiation exposures. More specifcally, natural environmental radioactivity due to gamma radiation depends primarily on the geological and geographical conditions, and appears at diferent levels in the soils of each region in the world (UNSCEAR 2000). External irradiation from radio- nuclides naturally present in the environment is an important component of the exposure of human populations (Otwoma et al. 2013). As individuals spend more than 80% of their time indoors the internal and external radiation exposure from building materials creates prolonged exposure situ- ations (Senthilkumar et al. 2014). The worldwide average indoor efective dose due to gamma rays from building mate- rials is estimated to be about 0.4 mSv per year (UNSCEAR 2000). 222 Rn, a decay product of uranium with a half-life of 3.82 days is of concern for indoor background ionizing radiation and contributes an annual exposure of 1.15 mSv * Oluwatobi O. Ife-Adediran tobireliable@yahoo.com Iyobosa B. Uwadiae iyobosa.uwadiae@physics.org 1 Department of Physics, Federal University of Technology Akure, Akure, Ondo State, Nigeria 2 Department of Radiation Oncology, University College Hospital, Ibadan, Nigeria