Risk Assessment of Occupational Exposure to Crystalline Silica in Small Foundries in Pakdasht, Iran

Background: The term crystallized silica refers to the crystallized form of Sio2 and quartz, the most frequency composition in the earth's crust that can cause silicosis and lung cancer through occupational exposure and inhalation of its large quantities.

Methods: Occupational exposure of workers in Pakdasht, Iran, in 2011 was investigated in four different casting processes in small foundries with less than 10 workers. Sampling respirable dust was collected on MCE filter, using HD cyclone at a flow rate of 2.2 lit/min. The filters were analyzed for dust using NIOSH Method 7601. Gravimetric and visible absorption spectrophotometer was used to determine amounts of inhalable dust and free silica, respectively. Risk assessment techniques were also used to predict silicosis and lung cancer.

Results: Geometric means of occupational exposure to crystalline silica in 4 different casting processes were studied within the range of 0.009-0.04 mg/m(3). Mortality rate due to silicosis was in the range of 1-13.7 per 1000 persons exposed. Risk of mortality due to lung cancer in exposed workers in small casting workshops in Pakdasht, Iran ranged 4-16 per 1000 persons exposed based on geometric mean and 45 years of exposure. According to risk assessment, mortality due to silicosis, cumulative exposure of 96% of population was at an acceptable level of 1/1000.

Conclusion: Fifty percent of workers were exposed to crystalline silica dust in excess of Recommended Exposure Limit -NIOSH and Threshold Limit Value ACGIH (0.025 mg/m(3)). Several cases of silicosis and lung cancer are anticipated for this occupational group in near future.