Background and objectives: Long term exposure to high levels of cement dust is one of the most important environmental risk factors in cement industries that adversely affect employee's respiratory system. Provided that achieving sustainable development mainly relies on healthy workers, this study aimed at assessing cement dust concentration and its free SiO₂ content in an Iranian Portland Cement Industry.

 Methods: In a cross - sectional study, airborne dust levels was investigated by collecting 64 personal and 35 environmental samples at both inhalable and respirable dust sizes. Dust concentrations were determined by deploying personal samplers in the breathing zone of workers. SiO₂ fractions were also measured in 4 samples collected from different part of the factory.

 Results: Arithmetic average concentrations of inhalable and respirable dust in personal sampling campaign were 58 and 13 mg m^-3, respectively. Respective values for inhalable and respirable dust in environmental sampling campaign were 154 and 27 mg m^-3. Dust concentrations in 90% of environmental samples and 80% of personal samples exceeded those occupational exposure limit values set for inert dusts i.e. Portland Cement. The average free SiO₂ fraction in analyzed samples was 2.86% varying from 2.33% in "packing and loading" area to 3.67 % in "raw mill" section.

  Conclusion: Free SiO₂ fraction as well as the concentrations of cement dust in this study is much higher than those of occupational exposure limit proposed by Iranian Technical Committee of Occupational Health.