(8-OHdG) [7–12]. The increased DNA damage and MN in peripheral lymphocytes from workers exposed to crystalline silica were found in some epidemiologic studies [13,14]. In addition, several studies in vitro demonstrated that BPs after specific activations were able to induce genotoxic effects. These genotoxic effects may be associated with oxidative stress induced by BPs. Geh et al. [15] reported that MN was slightly increased after exposure of human fibroblasts to active BPs (activated with HCL) in cytokinesis-block micronucleus (CBMN) assay, and the increased MN was related to reactive oxygen species generation induced by BPs. In our recent work, a signif- icant dose-related increase in DNA damage and MN induced by organic BPs (activated with alkyl quaternary ammonium salt) or active BPs (activated with H2SO4) in human B lymphoblast cells were observed using comet assay and CBMN assay [16,17]. Active BPs (activated with H2SO4) could induce higher levels of ROS gener- ation, superoxide dismutase [18] inhibition and malondialdehyde (MDA, a biomarker of lipid peroxidation) in cultures of human B lymphoblast cells, as compared with native BPs or gypsum control [19].