According to the Iranian Social Security Organization, construction industries have high rates of occupational injuries and health hazards due to unsafe work environment. The high rates of death and disability were recorded in these industries in Iran. Exposure to silica dust may be considered an important hazard in the demolition sites and construction activities. Also, building demolition workers may be at increased risk for asbestos-related disease . The international Agency for Research on Cancer classified some types of crystalline silica such as quartz and cristobalite as Group 1 (known human lung carcinogen) of carcinogens . The current and previous threshold limit values for respirable silica dust are 0.025 mg/m3 and 0.05 mg/m3, respectively . Rappaport et al reported that numerous of workers have been overexposed to crystalline silica dust in construction sites and the highest exposure was found in painters (1.28 mg/m3. Concentrations of respirable silica dust in breathing-zone air of exposed individuals and duration of exposure are the most potent risk factors for developing of silicosis .