Occupational Exposures to Respirable Dust and Crystalline Silica Among Brick Workers in Kathmandu Valley, Nepal: An Expanded Analysis Across Job Categories, 2023–2025

Workers employed in clay brick manufacturing are at risk of developing chronic respiratory diseases stemming from work-related aerosol exposures. Prior studies characterize respirable dust and respirable silica (SiO2) exposures among brick workers in Nepal, but these assessments were based on relatively small sample sizes and incomplete representation of job categories with potentially high exposures. In this study we combine exposure data previously reported with data from two subsequent sampling periods. The expanded data set (N = 205) allowed for exposure characterization across ten common job categories. Partial-shift breathing zone respirable dust and respirable SiO2 exposures were measured using personal pump and cyclone samplers with a 4.0 µm aerodynamic diameter cut-point. Job categories that involved handling red (fired) bricks in any capacity, and top loading, are associated with geometric mean SiO2 exposure concentrations exceeding 25 µg/m3 that were significantly higher than job categories that did not handle red bricks (p < 0.01). Similarly, job categories where red bricks are handled in any capacity are associated with significantly higher respirable dust concentrations than other job categories (p < 0.01). Understanding task-specific exposure profiles may help prioritize interventions aimed at decreasing workers’ aerosol exposures, which may decrease chronic respiratory diseases in this population of workers.