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CAN FLUORIDATION AFFECT LEAD (II) IN POTABLE WATER? HEXAFLUOROSILICATE AND FLUORIDE EQUILIBRIA IN AQUEOUS SOLUTION
Citation:
Urbansky*, E T. AND M R. Schock*. CAN FLUORIDATION AFFECT LEAD (II) IN POTABLE WATER? HEXAFLUOROSILICATE AND FLUORIDE EQUILIBRIA IN AQUEOUS SOLUTION. INTERNATIONAL JOURNAL OF ENVIRONMENTAL STUDIES B. Overseas Publishers Association, Amsterdam, Netherlands, 57:597-637, (2000).
Description:
Recent reports have attempted to show that fluoridating potable water is linked to increased levels of lead(II) in the blood. We examine these claims in light of the established science and critically evaluate their significance. The completeness of hexafluorosilicate hydrolysis is of paramount importance in ensuring that water quality is maintained. The possible impacts of such complexes as PbII-F-SiF5 or PbFx(2-x) are discussed as are the contributions of fluoridation byproducts to total acid content. We calculate the fractional distribution of aqueous species based on known chemical equilibria and show the species concentrations for several different model tap waters. We discuss and quantitatively show the effects of other complexing anions, such as carbonate or hydroxide. Overall, we conclude that no credit evidence exists to show that water fluoridation has any quantitatable effects on the solubility, bioavailability, bioaccumulation, or reactivity of lead(O) or lead(II) compounds. The governing factors are the concentrations of a number of other species, such as (bi)carbonate, hydroxide, or chloride, whose effects far exceed those of fluoride or fluorosilicates under drinking water conditions. Lastly, we consider some previous epidemiological studies of lead(II) exposure and how recent papers fare methodologically.