RESUMEN
Silica is an inorganic material that found in the nature in various forms. The hazards of crystal of silica or ?-quartz [free silica] is greater than other forms. Exposure to dust that contains free silica result to pulmonary injury and result to silicosis and death finally. The present research was conducted in order to evaluate the level of workers exposure to free silica in air of Khaf Iron stone quarries. The exposure level to total and respiratory dust measured based on personal and environmental sampling methods and concentration of dust determined based on gravimetric method. For determination of amounts of free silica, dust samples analyses based on X-ray diffraction [XRD] method, and results compared with standard levels. The maximum amount of total dust and free silica measured in stone breaking station [800 +/- 155mg/m3 and 26.11 +/- 6.7 mg/m3] and minimum of them measured in official and safeguarding station [8.28 +/- 2.2 mg/m3 and 0.012 +/- 0.0019 mg/m3]. The maximum amount of respiratory dust and free silica measured in red mound digging number 1 [66.14 +/- 13.45 mg/m3 and 1.48 +/- 0.39 mg/m3] and minimum of them measured in air hammer machine station [5.26 +/- 2.62 mg/m3 and 0.01 +/- 0.005 mg/m3]. Amount of total dust only in official and safeguarding station was lower than standard levels of Iran. Amount of respiratory dust in all stations was greater than Iran standard levels. Furthermore the level of respiratory free silica only in airy hammer machine station was lower than standard level of Iran. Regarding to this amounts it is so essential to that with applying different methods generation and emission of dust protected