Radioprotection, vol. 46,n ◦ 6 (2011) S137–S143 C  EDP Sciences, 2011 DOI: 10.1051 / radiopro / 20116898s Assessment of direct radiological risk and indirect associated toxic risks originated by Coal-Fired Power Plants M.L. Dinis 1 , A. Fiúza 1 , J. Góis 1 , J.S. de Carvalho 1 and A.C.M. Castro 1,2 1 Geo-Environment and Resources Research Center (CIGAR), Engineering Faculty, Porto University (FEUP), R. Dr. Roberto Frias, 4200-465 Porto, Portugal 2 School of Engineering, Polytechnic of Porto (ISEP), R. Dr. António Bernardino de Almeida, 431, 4200-072 Porto, Portugal Abstract. Over the past few decades there has been some discussion concerning the increase of the natural background radiation originated by coal-fired power plants, due to the uranium and thorium content present in combustion ashes. The radioactive decay products of uranium and thorium, such as radium, radon, polonium, bismuth and lead, are also released in addition to a significant amount of 40 K. Since the measurement of radioactive elements released by the gaseous emissions of coal power plants is not compulsory, there is a gap of information concerning this situation. Consequently, the prediction of dispersion and mobility of these elements in the environment, after their release, is based on limited data and the radiological impact from the exposure to these radioactive elements is unknown. This paper describes the methodology that is being developed to assess the radiological impact due to the raise in the natural background radiation level originated by the release and dispersion of the emitted radionuclides. The current investigation is part of a research project that is undergoing in the vicinity of Sines coal-fired power plant (south of Portugal) until 2013. Data from preliminary stages are already available and possible of interpretation. 1. INTRODUCTION Over the past few decades there has been some discussion about the elevated natural background radiation in areas near to coal-fired power plants. Coal contains trace quantities of the naturally occurring radionuclides like uranium (1 to 10 ppm) and thorium (3 to 25 ppm), as well as their radioactive decay products and 40 K. When coal is burned, minerals, including most of the radionuclides, do not burn and concentrate in the ash. These materials increase the radiation output. They may also accumulate in the environment or be continually dispersed in millions of tons of coal combustion by-products. As radiological impact is usually considered to be related to nuclear energy or atomic bombs, most of the research on radiation protection has been focused on artificial radionuclides and radioactive waste. Far less attention has been paid to the risk caused by the exposure to natural materials in which radioactive elements concentration is enhanced. Since radioactive elements from coal power plants emissions are not obligatory measured parameters, there is no measured data or concentration estimative for the radioactive elements released. Consequently, predicting dispersion and mobility of these elements in the environment, after their release, is based on limited data and the radiological impact from the exposure to these radioactive elements is most of the times unknown. People living near coal power plants may be exposed to increasing quantities of radioactive isotopes through air, water movement and food chain transfer. Because the half-lives of these radionuclides are practically infinite in terms of human lifetimes, the accumulation of these species in the biosphere is directly proportional to the length of time that a quantity of coal is burned. The Oak Ridge National Laboratory (ORNL) gives statistics on the levels of radioactive material given off by a coal fired plant: to run an average 1000MW coal-fired power plant, it is needed to burn