Application of international regulations and standards on natural radioactivity in ceramic tiles

Only a few countries worldwide have regulations to control the radioactivity of ceramic tiles and other building materials (mainly the European Union, China, and Russia). Annual external exposure is assessed using indices based on activity concentrations of 226 Ra, 232 Th, and 40 K. This study reviews international regulations and standards related to radioactive indices of building materials, including covering materials such as ceramic tiles. These indices were estimated theoretically for the main types of ceramic tiles produced in Spain, taking into account the activity concentration of the raw materials used in the production of their bodies (atomized) and glazes. These results were compared with gamma-ray spectrometry measurements of real ceramic tiles from Spain and Asian countries, including India, China, and Iran. Ceramic tiles with zircon content above 3–4% could exceed regulatory levels because there is a linear relationship between this content and the index. However, Chinese tiles with lower zircon content could exceed the reference levels because of higher 232 Th activity concentrations. So this linear relationship depends on the manufacturing country, due to the origin of the raw materials used in production. Despite several tiles being close to or exceeding the EU index threshold, none exceed the maximum external dose of 1 mSv y −1 , so they can be used as covering materials without restrictions.