Silica exposure in the glass industry and human health risk assessment

Abstract

Introduction: Among adverse effects in mines and industries, silica dust often been the subject of many controversies. Its severe and incurable side effects call for special attention to as well as assessment and control in workplaces. This study aims to determine the rate of silica concentration in the breathing zones of the glass industry in a comparison to standard limits in order to improve the safety of workers exposed to these particles. Materials and Methods: Being conducted in a glass factory in Tehran, this research employed a sampling method to measure the silica dust diffusion in six consecutive years from 2005 to 2010. The most effective method of dust level measurement in a workplace is to take samples in the breathing zone of workers exposed to it. In the subject factory, the sampling was performed in four sectors with the highest level of occupational exposure to the respirable dust. (1) Material charging unit, Excavator Operator. (2) Miscellaneous material weighing Operator (mixer). (3) Material charging, loading unit Operator. (4) Discharge (unloading) zone. The silica compound sampling and measur was conducted via the method by National Institute of US Occupational Health and Safety (NIOSH). By this method, the silica particles in the air were collected on the sorbent tube containing activated carbon (coconut shell) SKC-USA No. 226-01 and the sampling pump Model 222 ml/count, SKC with a flow rate of two liters per minute in the active method for 30 minutes. Then, observing necessary conditions and the chain of cold (Stored at 4΀C), the samples were transferred to the laboratory. The breathing zone samples were also collected from the four mentioned sectors by the sampling pump. Samples were analyzed with the Flame Ionization Detector, when they were transferred to the laboratory by Gas Chromatography Apparatus with the Flame. Results: Time-weighted a Average (TWA) exposure was at its highest level in 2009 and at its lowest level in 2008. Findings of the study also revealed that the amount of environmental silica dust threshold limit value in the material charging Unit of loading and Excavator Operators in the discharge zone was higher than the threshold limit value. After determining the dispersion density of suspended silica particles, TLV, TWA, and the non-cancer risk ratio of the particles in the mentioned sectors, control strategies and corrective suggestions were proposed. Conclusions: Results showed that, the silica concentration in the breathing zone of the glass industry was higher than the threshold limit value. Silica is a carcinogenic material causes chronic respiratory diseases and silicosis, therefore it is recommended to observe the safety principles and use wet silica in stead. The concentration of silica is at its highest level in the loading and unloading units, thus the engineering and managing controls should be utilized to avoid the direct exposure to these suspended particles. Moreover, the workers in these sectors should be well-trained regarding the exposure to silica and use of individual protective equipment.