Radon exhalation rates from zircon sands and ceramic tiles in Italy

One of the most important use of zircon is within the ceramic industry for the production of ceramic tiles and sanitary ware. In porous fired tiles and sanitary ware, ceramic has a two-piece body made up of a clay-based ceramic body covered with a glaze to provide waterproofing, durability and decoration. Zircon, in the form of sand and/or flour, is added to the glaze as opacifyer, as well as to provide a white colour (15-20%). In contrast to porous fired tiles, porcelain stoneware tiles have a one-piece ceramic body composed of clays, quartz, feldspars together with zircon (1-5 %). The surface of these tiles may be glazed or unglazed. All zircon materials contain uranium and thorium in the crystal lattice. These primordial radionuclides substituted zirconium into the zircon lattice during the crystallization of the molten rocks. Basically two radiation exposure pathways are associated with ceramic tiles and other building materials: external exposure due to gamma-decay of naturally-occurring radionuclides, and internal exposure through inhalation of radon. This study reports the natural radioactivity and the radon exhalation rates from zircon materials, such as zircon sands and zircon flours, and commercial porcelain stoneware tiles in Italy.