[en] It is known that TPP operation is connected with the manmade increase in nature radiation background and a respective exposure of the population living in near - by regions. A more specific problem in this respect is the use of low-calorie coil, which is typical of the biggest Bulgarian TPP ^Maritsa-Iztok^. The Ra -equivalent of coal is approximately 69 Bq/kg. In this type of fuel, the required quantity for power production sharply increases, thus leading to an increased impact upon environment. On the other hand, the applied methods and obtained results concerning the filtration of aerosol products, released from TPP operation, assume still greater importance. The Ra - equivalent of the slag is approximately 183 Bq/kg and for the dust - approximately 370 Bq/kg