Daily Archives: March 14, 2015

Can Fluoride “Risks” be Balanced with “Benefits”? Only on paper.

The harmful effects of fluoride (dental fluorosis) can be directly observed by inspection. But the “benefits” claimed with regard to carries reduction cannot be directly measured, but are inferred from ecologic studies of populations. Such study designs do not support dogmatic cause and effect attributions as have been made for fluoride. This paper’s suggestion that somehow the “risks” can be balanced with the “benefits” fluoride is wishful thinking, misleading at best.

Bergamo ET, Barbana M, Terada RS, Cury JA, Fujimaki M. Fluoride concentrations in the water of Maringá, Brazil, considering the benefit/risk balance of caries and fluorosis. Brazilian Oral Research 2015 Mar;29(1):1-6. doi: 10.1590/1807-3107BOR-2015.vol29.0047.

Current Brazilian law regarding water fluoridation classification is dichotomous with respect to the risks of and benefits for oral diseases, and fluoride (F) concentrations less than 0.6 or above 0.8 mg F/L are considered outside the normal limits. Thus, the law does not consider that both caries and fluorosis are dependent on the dosage and duration of fluoride exposure because they are both chronic diseases. Therefore, this study evaluated the quality of water fluoridation in Maringá, PR, Brazil, considering a new classification for the concentration of F in water the supply, based on the anticaries benefit and risk of fluorosis (CECOL/USP, 2011). Water samples (n = 325) were collected monthly over one year from 28 distribution water networks: 20 from treatment plants and 8 from artesian wells. F concentrations were determined using a specific ion electrode. The average F concentration was 0.77 mg F/L (ppm F), ranging from 0.44 to 1.22 mg F/L. Considering all of the water samples analyzed, 83.7% of them presented from 0.55 to 0.84 mg F/L, and according to the new classification used, they would provide maximum anticaries benefit with a low risk of fluorosis. This percentage was lower (75.4%) in the water samples supplied from artesian wells than from those distributed by the treatment plant (86%). In conclusion, based on the new classification of water F concentrations, the quality of water fluoridation in Maringá is adequate and is within the range of the best balance between risk and benefit.

Paper is here. (Open Access)

Aquatic Toxicity of Fluoride

Pearcy K, Elphick J, Burnett-Seidel C. Toxicity of fluoride to aquatic species and evaluation of toxicity modifying factors. Environmental Toxicology and Chemistry. 2015 Mar 2. doi: 10.1002/etc.2963.

A study was performed to investigate the toxicity of fluoride to a variety of freshwater aquatic organisms and to establish whether water quality variables contribute substantively to modifying its toxicity. Water hardness, chloride and alkalinity were tested as possible toxicity modifying factors for fluoride using acute toxicity tests with Hyalella azteca and Oncorhynchus mykiss. Chloride appeared to be the major toxicity modifying factor for fluoride in these acute toxicity tests. The chronic toxicity of fluoride was evaluated with a variety of species, including three fish (Pimephales promelas, O. mykiss and Salvelinus namaycush), three invertebrates (Ceriodaphnia dubia, H. azteca and Chironomus dilutus), one plant (Lemna minor) and one alga (Pseudokirchneriella subcapitata). H. azteca was the most sensitive species overall, and O. mykiss was the most sensitive species of fish. The role of chloride as a toxicity modifying factor was inconsistent between species in the chronic toxicity tests.