مطالعه غلظت و نوع الیاف آزبست با روش میکروسکوپی فاز کنتراست و الکترونی روبشی به منظور تعیین مواجهه شغلی در یک صنعت سیمان- آزبست

  Background and aims : Asbestos minerals are divided into two main groups including serpentine and amphiboles and each has one or more subgroups. These minerals have been used in industrial products such as cement-asbestos sheet and pipe, brake shoe, clutch and insulation materials. Occupational and non - occupational exposures by this carcinogenic material have caused to develop several methods to evaluate airborne asbestos fibers. But in this way, NIOSH 7400 as the conventional method has some shortages that confirm necessity of studying of other microscopic methods in asbestos fibers evaluation.   Methods: In this study, 90 samples from different points of a cement- asbestos industry in Tehran (IRAN) have been collected on MCE filters. According to NIOSH 7400, half of each filter was prepared and then fiber counting was accomplished by phase contrast microscopy. The other part of filters were used for identification of asbestos fibers types by scanning electron microscopy.   Results : According to NIOSH 7400, fibers concentration range were determined 0.02 – 0.44 . The maximum concentration of airborne asbestos was 0.37±0.05 that was related to recycling process. Study of elemental composition of fibers by scanning electron microscopy confirmed that the type of fibers was chrysotile.   Conclusion: More than 50 percent of collected samples in this industry have concentrations above occupational exposure limits that may increase asbestos related diseases in the future. The preventive approaches in occupational health studies necessitate that in order to evaluate airborne asbestos fibers, the occupational hygienists need to be access to several methods. Therefore development of other microscopic methods such as scanning electron microscopy besides NIOSH 7400, must be considered.