Comparison of the toxicity of fluoridation compounds in the nematode Caenorhabditis elegans

Fluorides are commonly added to drinking water in the United States to decrease the incidence of dental caries. Silicofluorides, such as sodium hexafluorosilicate (Na2 SiF6 ) and fluorosilicic acid (H2 SiF6 ), are mainly used for fluoridation, although fluoride salts such as sodium fluoride (NaF) are also used. Interestingly, only the toxicity of NaF has been examined and not that of the more often used silicofluorides. In the present study, the toxicities of NaF, Na2 SiF6 , and H2 SiF6 were compared. The toxicity of these fluorides on the growth, feeding, and reproduction in the alternative toxicological testing organism Caenorhabditis elegans was examined. Exposure to these compounds produced classic concentration-response toxicity profiles. Although the effects of the fluoride compounds varied among the 3 biological endpoints, no differences were found between the 3 compounds, relative to the fluoride ion concentration, in any of the assays. This suggests that silicofluorides have similar toxicity to NaF.