ارزیابی مواجهه شغلی با سیلیس آزاد در فرآیند تخریب ساختمان در شهر تهران

  Background and aims: The term "crystalline silica", refers to crystallized form of SiO2 and quartz, as the most abundant compound in earth crust.I It can cause silicosis and lung cancer following inhalation of large doses in course of occupational exposure. Silica exposure is unavoidable during demolition of buildings and therefore it can lead to many problems for demolition workers’ health. Theaim of this study was the assessment of workers respiratory exposure with crystalline silica during demolition of buildings in Tehran.   Methods: In this study, in order to assess the airborne crystalline silica exposure, four zones of Tehran (west ، east ، south ، center) were selected. Samples were collected on mixed cellulose filters, by using filter holder at flow rate of 2 l/min for a maximum volume of 800 liters. After transferring the samples to the laboratory, analysis of samples were performed using Visible absorption spectrometry (at 420-820nm) according to theNIOSH method No. 7601.   Results: The higher average of exposure to crystalline silica with geometric mean of 0.185 mg/m3 was related to south area, and center area with GM 0.085 mg/m3 had the lowest exposure with crystalline silica .The number of 48 samples (80%) of total samples were above the standard for crystalline silica (ACGIH 0.05mg/m3). The geometric mean of workers' exposure to crystalline silica was in the range of 0/085-0/0185 mg/m3. Conclusion:Based on the obtained results showing that the 80% of total sampleswere above the recommended threshold limit value (0.05mg/m3) and considering thehigh potential ofexposure to crystalline silica during demolition of buildings,, control of dust emission during demolition projects is required