Zircon is naturally radioactive, containing small amounts of uranium, thorium and radium in its crystalline structure. Ceramic industry is one of the major consumers of zirconium compounds which are used as an ingredient about 10-20% by weight in glaze. In this study seven different ceramic factories have been investigated regarding the presence of radioactive elements with focus on natural radioactivity. The overall objective of this investigation is to provide information regarding the radiation exposure to workers in ceramic industry due to NORM. This objective is met by collecting existing radiological data specific to glaze production and generating new data from sampling activities. The sampling effort involves all the process of glaze production. External exposures are monitored using portable gamma ray spectrometer and environmental thermoluminescent dosimeters with time studies. Internal routs of exposure (mainly inhalation) are studied using air sampling, gross alpha and beta counting. Measurement of radon gas and its progeny is performed by continuous radon gas monitors that using pulse ionization chambers. Natural radioactivity due to the presence of ~(238)U, ~(232)Th and ~(40)K in zirconium compounds, glazes and other samples is measured by gamma spectrometry system with a high pure germanium detector. The average concentrations of ~(238)U, ~(232)Th observed in the zirconium compounds are >3300 and >550, respectively. The specific activities of other samples are much lower than in zirconium compounds. Gamma radiation levels had a mean value of approximately 0.13 mSv y-1. Dust sampling revealed greatest values in the process of powdering site and hand weighing places. In these plants, the annual average effective dose from inhalation of long lived airborne was 0.226 mSv. ~(222)Rn gas concentrations in the glaze production plant and storage warehouse were found to range from 10 Bq m~(-3) to 213 Bq m~(-3). In this study, the estimated annual effective doses to exposed workers were below 1 mSv y~(-1).
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