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 t imes induces chromosome aberrations in human cells, human diploid fibr oblasts in the quiescent phase were treated with sodium fluoride (NaF) at 1-10 mu g/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 con taining 1% serum following overnight incubation of cells in the logari thmic phase. Significant levels of cytotoxicity, as determined by a de crease in the number of cells, were not induced by treatment of the ce lls with NaF at 5 or 10 mu g/ml for 1-3 weeks. No increase in the freq uency of chromosome aberrations was elicited in cultures treated fdr 1 -3 weeks with NaF over the range of doses examined. In contrast, a dos e-dependent increase in the frequency of chromosome aberrations was ob served in cultures treated with N-methyl-N'-nitro-N-nitrosoguanidine, used as a positive control. The results indicate that fluoride might b e not clastogenic to human fibroblasts when exposed at low levels, equ ivalent to those in the communal water supplies.