High-volume samplers for the assessment of respirable silica content in metal mine dust via direct-on-filter analysis

Abstract

Exposure to crystalline silica in the mining industry around the world is a recognized occupational hazard and miners have the highest rate of silicosis related mortality of any industry. Mining operators are limited in assessing and monitoring exposure to silica by two main factors: 1) variability of the silica percent in the mining dust and 2) lengthy off-site laboratory analysis of collected samples. The collection of samples for short periods of time during the workers' shift and subsequent on-site silica quantification in the samples would allow the identification of high-risk tasks and appropriate dedicated control technologies. With the objective to find more timely silica monitoring solutions, the performance of five different samplers was investigated in a series of experiments in a calm air chamber. The respirable samples collected during each experiment were analyzed for collected respirable mass and respirable crystalline silica in the dust. The quantification of silica was conducted via Direct-on-Filter (DoF) analytical techniques, which have the potential to be employed at the mine site, and indirect techniques that are currently done at off-site laboratories (NIOSH 7500 method). Different experimental conditions were considered: respirable mass concentration, mass collected by the samplers, and environmental conditions. The experiments provided data for a statistical evaluation of the efficacy of collecting respirable mine dust and respirable crystalline silica by different samplers under different environmental conditions. In addition, the potential use of a DoF technique for the quantification of crystalline silica on respirable mine dust samples collected either with low-volume or high-volume samplers was assessed.