The contents of natural radionuclides (radium, uranium and potassium) were measured in the area of a phosphate fertilizer factory in central Croatia, as a part of extended and still ongoing monitoring program of radioactive contamination of human environment in Croatia that is performed by the Radiation Protection Unit of the Institute for Medical Research and Occupational Health in Zagreb. Activity concentrations in all analysed media (waste water, trickling water from piezometers, phosphogypsum deposit and final products) considerably fluctuated, especially in phosphogypsum and waste water. Mean Ra-226 activity concentration in waste phosphogypsum was measured to be 483 +/- 190 Bq kg(-1). Based on that value, it was estimated that 4 million m(3) of phosphogypsum that have been deposited up to now contain about 4.3 x 10(12) Bq, i.e. about 200 g of Ra-226. However, effective dose for an adult that would be incurred by consumption of water from nearby wells was estimated to be 5.3 +/- 1.3 mu Sv. The results show that Ra-226 activities cause effective doses, which are below the recommended maximum as the estimated annual Ra-226 effective dose does not exceed 0.1 mSv as recommended by the World Health Organization. (C) 2008 Elsevier B.V. All rights reserved.