No increases in chromosome aberrations in human diploid fibroblasts following exposure to low concentrations of sodium fluoride for long times.

To study whether exposure to fluoride at low concentrations for long times induces chromosome aberrations in human cells, human diploid fibroblasts in the quiescent phase were treated with sodium fluoride (NaF) at 1-10 micrograms/ml (equivalent to fluoride ion at 0.45-4.5 ppm) for 1-3 weeks. Quiescent cells were obtained by a 10-day culture in medium containing 1% serum following overnight incubation of cells in the logarithmic phase. Significant levels of cytotoxicity, as determined by a decrease in the number of cells, were not induced by treatment of the cells with NaF at 5 or 10 micrograms/ml for 1-3 weeks. No increase in the frequency of chromosome aberrations was elicited in cultures treated for 1-3 weeks with NaF over the range of doses examined. In contrast, a dose-dependent increase in the frequency of chromosome aberrations was observed in cultures treated with N-methyl-N'-nitro-N-nitrosoguanidine, used as a positive control. The results indicate that fluoride might be not clastogenic to human fibroblasts when exposed at low levels, equivalent to those in the communal water supplies.