Background: Silica is the most common minerals on earth. Exposure to dusts containing free silica is associated with pulmonary diseases that finally may lead to silicosis. The present study was conducted to measure the duct concentration and its free silica at Emarat lead and zinc surface mine.

Materials and methods : For this descriptive study sampling was achieved according to the standard No. 7500 of NIOSH. The level of total exposure and respirable dust were measured by personal sampling. Then the level of dust was quantified by gravimetric method. The dust samples have been analyzed for free silica content by X-ray diffraction method.

Results : The mean exposure to respirable dust in the units of drilling and damping were 2.81±0.46 and 2.69±0.5 mg/m3. Meanwhile, the mean exposure to free silica respirable dust in these units were 0.51±0.12 and 0.47±0.9mg/m3. These averages are 5.1 and 4.7 times of standard of Iran (OEL) and 10.2 and 9.4 times of standard of ACGIH (TLV), respectively.

Conclusion : Unfortunately, the mean concentration of free silica in respirable dust of different units of the Emarat mine exceeds the allowed levels. This should be controlled.