Sodium fluoride and chromosome damage (in vitro human lymphocyte and in vivo micronucleus assays)

The clastogenic potential of sodium fluoride was determined both in vitro (using cultured human lymphocytes) and in vivo (using the rat bone-marrow micronucleus test). The incidence of chromosome aberrations in human lymphocyte cultures exposed to 20 or 40 micrograms/ml sodium fluoride (3 and 9% respectively) was significantly increased compared with control cultures (0.5%). However, the incidence of micronucleated polychromatic erythrocytes in male AP rats dosed 1000 mg/kg NaF (the maximum tolerated dose over 24 h) or 500 mg/kg NaF was similar to that in the animals dosed distilled water (vehicle control). Thus, sodium fluoride is clastogenic in vitro but not in vivo.