hexafluorosilicic-acid and hexafluorosilicate

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.

Topics: Animals; Caenorhabditis elegans; Cariostatic Agents; Eating; Fluoridation; Fluorides; Reproduction; Silicic Acid; Sodium Fluoride

We determined the knowledge level of water plant operators who fluoridate drinking water, and we compared small and large water plants.. A pretested survey was sent to 2,381 water plant operators in 12 states that adjust the fluoride concentration of drinking water. A z-test for proportion was used to test for statistical difference between small and large plants at alpha = 0.05. Small water plants were those treating less than 1 million gallons of water daily.. Eight hundred small and 480 large water plant operators responded, resulting in a response rate of 54 percent. Two-thirds of water plant operators correctly identified the optimal fluoride level, but more than 20 percent used a poor source for choosing the optimal level. Only one-fourth of operators were able to maintain the fluoride concentration to within 0.1 mg/L of the optimal concentration. A significantly greater proportion of operators at large water plants than at small water plants reported that they were able to maintain a fluoride concentration to within 0.1 mg/L of the optimal concentration (33.5% vs 21.3%, z = 4.74, P < .05).. Although most operators correctly identified the optimal fluoride level, small water plant operators were less likely to use accurate reasoning for choosing that level and in maintaining fluoride concentrations within 0.1 mg/L of that level than large water plant operators.

Topics: Attitude to Health; Cariostatic Agents; Fluoridation; Fluorides; Health Education, Dental; Humans; Rural Population; Silicic Acid; Sodium Fluoride; Statistics as Topic; Surveys and Questionnaires; United States; Urban Population; Water Supply

This paper summaries the technical aspects of water fluoridation in the United States, and gives an overview of the engineering aspects of water fluoridation world-wide. The status of water fluoridation in the USA is summarised. Fluoride chemicals used in the USA are discussed, as well as the equipment used to deliver these chemicals. A brief overview of fluoridation engineering world-wide is also presented.

Topics: Asia; Central America; Fluoridation; Fluorides; Mexico; Silicic Acid; Sodium Fluoride; South America; United Kingdom; United States