LOW-DOSE EFFECTS OF FIBROUS AND NONFIBROUS MINERAL DUSTS ON THE PROLIFERATION OF MAMMALIAN-CELLS IN-VITRO

This report presents preliminary results of studies on the growth stim ulating properties of mineral dusts. The studies were carried out with Syrian hamster diploid embryonic fibroblasts and Chinese hamster fibr oblasts, line B14F28. Toxicity testing was done by the determination o f the plating efficiency as a measure of growth and viability. The fol lowing dusts were used: the modified UICC asbestos fibres amosite, (AF F) crocidolite (KFF), chrysotile (KFF); in addition glass fibre (GFF), corundum and quartz DQ(12). Concentrations > 2 mu g/cm(2) of AFF, CFF , KFF and GFF depressed the plating efficiency of B14F28 cells in a do se-dependent manner, but all of the fibres and corundum increased colo ny sizes at concentrations of 0.16-0.33 mu g/cm(2), in the case of cor undum, AFF, KFF, and CFF also at up to 0.66 or 1.32 mu g/cm(2). DQ,, d id not enhance colony growth. The stimulation of proliferation could b e demonstrated both in terms of colony size (diameter) and cell number s. The factor(s) responsible for proliferation stimulation reside in t he supernatant, since the medium of dust-treated cell cultures was abl e to stimulate colony growth after removal of the dusts by filtration. The results indicate the induction of growth factors (cytokines) by l ow concentrations of the mineral dusts. Experiments concerning the eff ect of dusts on embryonic golden hamster fibroblasts yielded similar r esults. The plating efficiency was inhibited by concentrations of GFF and CFF > 0.25 mu g/cm(2) and by AFF, KFF, GFF and corundum at concent rations > 5 mu g/cm(2), but colony counts were significantly increased by AFF, KFF and corundum at concentrations of 0.25-3 mu g/cm(2). This biological reaction which was observed in different cell types appear s to be especially relevant in the context of environmental exposure w here low dust concentrations prevail. (C) 1998 Elsevier Science Irelan d Ltd. All rights reserved.