Industrial processing of materials containing quartz induces physico-chemical modifications that contribute to the variability of quartz hazard in different plants. Here, modifications affecting a quartz-rich sand during cast iron production, have been investigated. Composition, morphology, presence of radicals associated to quartz and reactivity in free radical generation were studied on a raw sand and on a dust recovered after mould dismantling. Additionally, cytotoxicity of the processed dust and ROS and NO generation were evaluated on MH-S macrophages. Particle morphology and size were marginally affected by casting processing, which caused only a slight increase of the amount of respirable fraction. The raw sand was able to catalyze (OH)-O-center dot and CO2 center dot-. generation in cell-free test, even if in a lesser extent than the reference quartz (Min-U-Sil), and shows h(AJ) radicals, conventionally found in any quartz-bearing raw materials. Enrichment in iron and extensive coverage with amorphous carbon were observed during processing. They likely contributed, respectively, to increasing the ability of processed dust to release CO2- and to suppressing (OH)-O-center dot generation respect to the raw sand. Carbon coverage and repeated thermal treatments during industrial processing also caused annealing of radiogenic h(Al) defects. Finally, no cellular responses were observed with the respirable fraction of the processed powder. (C) 2016 Elsevier B.V. All rights reserved.