Korea has enacted a law for natural radiation safety management to protect the public from natural radioactive materials.Phosphate fertilizer plant is one of the concerning areas because it may give rise to inhalation exposures to both workers and members of the general public.The objective of this study was to establish a database of information on the particle size distribution,density,shape,and radioactivity concentration at the largest phosphate fertilizer plant in Korea.Cascade impactors were employed to sample airborne particulates at various processing areas,including phosphate rock storage,rock screening,granulator,product screening,control room,and gypsum areas.Airborne particle concentrations varied by approximately one to three orders of magnitude among sampling areas.Airborne particle mass loadings were highest at the storage during bulldozer operation and lowest at the control room.Airborne particle mass concentrations increased with particle size,reached at the maximum at particle sizes of 5 – 8 um,and then decreased.Average densities of phosphate rocks,phosphogypsums,and fertilizers were 3.2,2.6,and 1.7 g/cm3.Under electron microscopy,the airborne particles appear as spheroids or rough spherical fragments across all work areas and sampled size intervals.The uranium and thorium decay series in the particles were measured by alpha- and gamma-spectroscopy.Radionuclides in phosphate rocks were in equilibrium.However,the equilibrium was broken during the chemical process.Uranium was selectively concentrated on products while radium was concentrated in gypsum.Radioactivity concentration in phosphate rocks varied with producing areas,ranging 90 – 900 Bq/kg for uranium series and 0.7 – 9 Bq/kg for thorium series.Radioactivity concentrations in final products and gypsum varied depending on phosphate rocks used.The database of airborne particle characteristics established in this study can be used for inhalation dose assessment for workers and the general public.In addition,the database provides important information to both industry and regulators as they assess the need for any radiological protection measures.This study is supported by Grant 2011-00321888 from the National Research Foundation of Korea.Keywords eywordseywords: Phosphate industry