Influence of seasonal, technical, and lithological parameters on exposure to dust and crystalline silica in the French natural stone industry

European directives play a key role in establishing occupational exposure limit values within the European Union. Directive 98/24/EC and national regulations, such as French Decree 2021-1763, have recently introduced strict limits for exposure to non-specific dust, significantly impacting sectors such as natural stone processing. This study analyzes workers' exposure to inhalable and respirable dust across 8 representative industrial facilities in France, focusing on granite, hard limestone, soft limestone, and sandstone. Measurements were conducted to quantify exposure levels across 5 different processes, considering key parameters such as seasonal variations, wet and dry processes, as well as dust reduction measures. Results show significant seasonal fluctuations, with higher exposures in summer, particularly during granite finishing work, where inhalable dust concentrations exceeded regulatory thresholds by up to 120 times. Wet processes demonstrated effective dust reduction, decreasing concentrations by more than 90% compared to dry methods. However, exposure to crystalline silica frequently exceeds regulatory limits, highlighting a persistent health risk for workers. The study also assessed the effectiveness of technical devices, such as suction booths and water curtains, as well as the impact of wearing a mask on occupational exposure. If suction booths and hoses have proven to be highly effective, their performance remains limited during high-emission operations. In that case and in the absence of adequate engineering controls, filtering facepiece (FFP3) masks would be appropriate.