New biological procedures for toxicological and hygienic risk evaluation of quartz dusts and quartz containing dusts - Presentation of the concept and first results

Quartz modifications may in industrial circumstances have a carcinogenic potential differing from that observed for Min-U-Sil or DQ12 in experimental studies. We established a new in vitro- and in vivo method for ranking quartz. The mechanism in quartz induced tumour formation is mainly the production of reactive oxygen species (ROS) causing DNA-damage by DNA adducts, such as 8-oxoguanine. Persistent elevated levels of 8-oxoguanine in proliferating cells can lead to mutations, which is critical for tumour formation. In the in vivo test (molecular dosimetry) primarily the content of 8-oxoguanine in the DNA of lung cells is determined by an immunohistochemical assay. The in vitro system (vector model) consists of the measurement of reactions of the phagocytosis of alveolar macrophages (AM) such as AM damage and AM secretions (mediators, ROS). Analysis of the vectors gives reaction patterns of high sensitivity and specificity. When comparing the biological activity of quartz samples most of the samples do not reach DQ 12 activity. Molecular dosimetry, showed for DQ12 up to 0.6 mg and for the other samples up to 7.5 mg no significant elevations in the levels of 8-oxoguanine. These investigations support the conception of a threshold for quartz mutagenicity, which is dependent on dose and type of quartz and demonstrate the utility of the presented methods.