[Comparative studies of the effect of quartz glass and quartz DQ-12 in inhalation tests in rats]

Fibrogenic effects of amorphous quartz dusts are discussed more and more during recent years. In order to study alterations due to amorphous silica (quartz glass VP 203-006) in comparison with crystalline quartz (DQ-12), an inhalation experiment in rats was carried out. Male Wistar rats were separated in two dust exposed groups (n = 35) and one control group (n = 30). The experiment was carried out in inhalation chambers with a slowly rotating animal cage for 12 months, 7 h per day, and 5 days per week. The dust concentration was 10 mg/m3. After 4 and after 8 months of inhalation, 5 animals of each group were sacrificed. After 12 months 15 rats of the dust exposed groups and 10 controls were euthanized. The remaining animals were kept for another 12 months post-inhalation period. Regarding the macroscopical appearance of the lungs, the relative organ weights and the histomorphological reaction pattern, marked dust depending differences are obvious. In the lungs of DQ-12-exposed animals diffuse structural changes occur, including fibrosis and severe reaction of macrophages. Histology of lungs from quartz glass exposed animals reveals only a slight and focally arranged cellular reaction with a few collagenous fibers. However, in both dust exposed groups the mediastinal lymph nodes are extremely enlarged with severe fibroses. Additionally, the following blood parameters were determined: lysozyme, ACE, GOT, GPT, and AP. The most pronounced changes are detectable in lysozyme and GOT after DQ-12 exposure. After quartz glass exposure, the levels of these parameters are similar to the controls. These results show that the amorphous quartz tested in this experiment (quartz-glass VP 203-006) has to be considered as a compound with certain biological effects. The establishing of occupational standards seems to be justified. But, assessing the effects, the different physical and/or chemical properties of various amorphous quartz dusts have to be considered.