DETECTION OF MINERAL-DUST-INDUCED DNA-DAMAGE IN 2 MAMMALIAN-CELL LINES USING THE ALKALINE SINGLE-CELL GEL COMET ASSAY/

It has been estimated that over three million workers in the USA are p otentially exposed to silica or other mineral dusts. Results of epidem iological studies evaluating whether silica or glass fibers increase l ung cancer risk to the exposed workers are inconclusive. Detection of DNA damage in cells exposed to genotoxic agents is being used to asses s the carcinogenic potential of environmental agents. The alkaline (pH > 13) single cell gel/comet (SCG) assay was used to determine and com pare DNA damage in cultured Chinese hamster lung fibroblasts (V79 cell s) and human embryonic lung fibroblasts (Hel 299 cells) exposed to cry stalline silica (Min-U-Sil 5), amorphous silica (Spherisorb), carbon b lack, and glass fibers (AAA-10). V79 or Hel 299 cells were exposed to these mineral dusts for 3 h at various concentrations. Min-U-Sil 5 and AAA-10, at almost all concentrations tested, caused a significant inc rease in DNA migration measured as tail length in both V79 and Hel 299 exposed cells. However, the increase was much higher in V79 then in H el 299 cells for Min-U-Sil 5. Tail length was also increased relative to controls after amorphous silica treatment, but not to the same exte nt as that induced by crystalline silica. Exposure to carbon black did not induce DNA migration at any of the concentrations tested. These r esults indicate that silica and glass fibers, but not carbon black, ca n induce DNA damage in mammalian cells, and that crystalline silica ha s a higher DNA-damaging activity than amorphous silica. For glass fibe rs, induction of DNA damage in both V79 and Hel 299 cells was observed even at a concentration 10 times lower than silica and the response w as similar in both cell lines. These results suggest that the SCG/come t assay is useful for the detection of DNA damage caused by occupation ally related dusts/particles. (C) 1997 Elsevier Science B.V.