181 Evaluation of respirable dust and respirable crystalline silica area concentrations in a clay brick factory using a field-based approach

Introduction Field-based monitoring methods have been developed for respirable dust and respirable crystalline silica (RCS) to enable exposure results to be obtained on the same day. This study aimed to use these field-based monitoring methods to evaluate respirable dust and RCS concentrations in the workplace air of a clay brick factory. Methodology Area monitoring was performed using NIOSH 7602 and the Nanozen DustCount 9000i. Both sampling trains were fixed to a tripod and placed in one of four work areas close to workers for a period of approximately five hours. A total of 13 sets of measurements were collected. Prior to analysis using infrared spectrometry (KBr pellet), 37 mm filters underwent direct-on-filter analysis for silica using a portable FT-IR instrument and NIOSH FAST software. Results Median time-weighted average (TWA) concentrations were 0.313 mg/m3 (max = 1.659 mg/m3) for respirable dust and 0.090 mg/m3 (max =0.289 mg/m3) for RCS. Significant positive relationships were found between the two methods for respirable dust (Spearman r = 0.853; p<0.01) and RCS (Spearman r = 0.934; p<0.0001). The direct-on-filter analysis of 37 mm filters also correlated strongly with infrared spectrometry (KBr pellet) (Spearman r = 0.990; p<0.0001). Additionally, the DustCount enabled the identification of peak concentrations (max = 7.548 mg/m3) and data showed that the dominant particle sizes were 0.375 µm and 0.468 µm. Conclusions The results of this study show on a small scale that field-based techniques can be combined with conventional monitoring techniques to obtain quicker exposure results and more detailed data to better understand exposure to for respirable dust and RCS.