Fate of fluorosilicate drinking water additives

Fluoride-Induced Mitochondrial Dysfunction and Approaches for Its Intervention

Fluoride is present everywhere in nature. The primary way that individuals are exposed to fluoride is by drinking water. It's interesting to note that while low fluoride levels are good for bone and tooth growth, prolonged fluoride exposure is bad for human health. Additionally, preclinical studies link oxidative stress, inflammation, and programmed cell death to fluoride toxicity. Moreover, mitochondria play a crucial role in the production of reactive oxygen species (ROS). On the other hand, little is known about fluoride's impact on mitophagy, biogenesis, and mitochondrial dynamics. These actions control the growth, composition, and organisation of mitochondria, and the purification of mitochondrial DNA helps to inhibit the production of reactive oxygen species and the release of cytochrome c, which enables cells to survive the effects of fluoride poisoning. In this review, we discuss the different pathways involved in mitochondrial toxicity and dysfunction induced by fluoride. For therapeutic approaches, we discussed different phytochemical and pharmacological agents which reduce the toxicity of fluoride via maintained by imbalanced cellular processes, mitochondrial dynamics, and scavenging the ROS.

Recent advances in cellular effects of fluoride: an update on its signalling pathway and targeted therapeutic approaches

Fluoride is a natural element essential in minute quantities in human's to maintain dental and skeletal health. However, the disease fluorosis manifests itself due to excessive fluoride intake mostly through drinking water and sometimes through food. At the cellular energetics level, fluoride is a known inhibitor of glycolysis. At the tissue level, the effect of fluoride has been more pronounced in the musculoskeletal systems due to its ability to retain fluoride. Fluoride alters dentinogenesis, thereby affecting the tooth enamel formation. In bones, fluoride alters the osteogenesis by replacing calcium, thus resulting in bone deformities. In skeletal muscles, high concentration and long term exposure to fluoride causes loss of muscle proteins leading to atrophy. Although fluorosis is quite a familiar problem, the exact molecular pathway is not yet clear. Extensive research on the effects of fluoride on various organs and its toxicity was reported. Indeed, it is clear that high and chronic exposure to fluoride causes cellular apoptosis. Accordingly, in this review, we have highlighted fluoride-mediated apoptosis via two vital pathways, mitochondrial-mediated and endoplasmic reticulum stress pathways. This review also elaborates on new cellular energetic, apoptotic pathways and therapeutic strategies targeted to treat fluorosis.

ECNU-36: A Quasi-Pure Polymorph CH Beta Silicate Composed of Hierarchical Nanosheet Crystals for Effective VOCs Adsorption

A quasi-pure C_H polymorph of microporous zeolite beta, named ECNU-36, was obtained as a highly crystalline silicate using 1,5-bis(tetramethylimidazolium) hydroxide as organic structure-directing agent (OSDA) in fluoride media. An appropriate concentration of free fluoride in the synthetic mother liquor was crucial to purify the C_H -phase. The framework structure of ECNU-36 consists of polymorph C_H (>95 %) and polymorph B, elucidated by a combination of PXRD data, DIFFaX simulation, EDT, and HRTEM techniques. For the first time, the framework structure of beta C_H polymorph was directly confirmed and solved using electron diffraction data. The pure-silica ECNU-36 showed an unusual crystal morphology, composed of stacked nanosheets, with typical 17 nm thickness and exposed {100} facets, which exhibited attractive adsorption performance for hydrocarbons and aromatics.

Binding consistency of anions by the effect of aromatic meta-substitution of bis-urea receptors: entrapment of hexafluorosilicate clusters

The solid as well as solution state preferential and discriminating binding of hexafluorosilicate anions depending on aromatic meta-substitution with respect to adjacent urea moieties by self-assembly of isomeric neutral bis-urea acyclic receptors.

Sodium fluoride induced skeletal muscle changes: Degradation of proteins and signaling mechanism

Fluoride is a well-known compound for its usefulness in healing dental caries. Similarly, fluoride is also known for its toxicity to various tissues in animals and humans. It causes skeletal fluorosis leading to osteoporosis of the bones. We hypothesized that when bones are affected by fluoride, the skeletal muscles are also likely to be affected by underlying molecular events involving myogenic differentiation. Murine myoblasts C2C12 were cultured in differentiation media with or without NaF (1 ppm-5 ppm) for four days. The effects of NaF on myoblasts and myotubes when exposed to low (1.5 ppm) and high concentration (5 ppm) were assessed based on the proliferation, alteration in gene expression, ROS production, and production of inflammatory cytokines. Changes based on morphology, multinucleated myotube formation, expression of MyHC1 and signaling pathways were also investigated. Concentrations of NaF tested had no effects on cell viability. NaF at low concentration (1.5 ppm) caused myoblast proliferation and when subjected to myogenic differentiation it induced hypertrophy of the myotubes by activating the IGF-1/AKT pathway. NaF at higher concentration (5 ppm), significantly inhibited myotube formation, increased skeletal muscle catabolism, generated reactive oxygen species (ROS) and inflammatory cytokines (TNF-α and IL-6) in C2C12 cells. NaF also enhanced the production of muscle atrophy-related genes, myostatin, and atrogin-1. The data suggest that NaF at low concentration can be used as muscle enhancing factor (hypertrophy), and at higher concentration, it accelerates skeletal muscle atrophy by activating the ubiquitin-proteosome pathway.

Synthesis of polymorph A-enriched beta zeolites in a HF-concentrated system

Polymorph A-enriched beta zeolites were synthesized by employing high HF concentrations in the synthesis medium. The polymorphic compositions of the synthesized beta zeolites were determined by the complementary characterization methods (19)F NMR analysis and PXRD simulation. With a variety of SDAs, a high HF concentration (HF/SDA > 1.0) in the synthesis medium results in the A-rich feature (55-65% A) of beta zeolites, while a moderate HF concentration only results in typical beta zeolites. A systematic study on the synthesis conditions reveals the existence of a buffered system of H(+) and F(-) formed in the highly HF-concentrated medium. This buffer results in a small but continuous supply of F(-) during zeolite crystallization, in contrast to the conventional fluoride route where all F(-) are discharged all-at-once at the initial stage.

Dual modes of binding on the hexafluorosilicate anion by a C3v symmetric flexible tripodal amide ligand in solid state

A para-nitrophenyl functionalized C_3v symmetric flexible tripodal amide ligand, L, shows remarkable solvent dependent dual binding behaviour towards the octahedral hexafluorosilicate anion in solid state.

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.

Differential Expression ESTs Associated with Fluorosis in Rats Liver

The fluoride has volcanic activity and abundantly exists in environment combining with other elements as fluoride compounds. Recent researches indicated that the molecular mechanisms of intracellular fluoride toxicity were very complex. However, the molecular mechanisms underlying the effects on gene expression of chronic fluoride-induced damage is unknown, especially the detailed regulatory process of mitochondria. In the present study, we screened the differential expression ESTs associated with fluorosis by DDRT-PCR in rat liver. We gained 8 genes, 3 new ESTs, and 1 unknown function sequence and firstly demonstrated that microsomal glutathione S-transferase 1 (MGST1), ATP synthase H⁺ transporting mitochondrial F₀ complex subunit C1, selenoprotein S, mitochondrial IF1 protein, and mitochondrial succinyl-CoA synthetase alpha subunit were participated in mitochondria metabolism, functional and structural damage process caused by chronic fluorosis. This information will be very helpful for understanding the molecular mechanisms of fluorosis.

A critical study on borosilicate glassware and silica-based QMA's in nucleophilic substitution with [18F]fluoride: influence of aluminum, boron and silicon on the reactivity of [18F]fluoride

Leachables of borosilicate glassware and silica-based anion exchange columns (QMAs) may influence nucleophilic substitution with [(18)F]fluoride ([(18)F]F(-)). Aluminum, boron and silicon, all constituents of borosilicate glass, were found as water soluble leachables in a typical PET synthesis setup. Relevant ranges of the leachable quantities were studied based on an experimental design, in which species of the three elements were added to the labeling of the precursor for anti-1-amino-3-[(18)F]fluorocyclobutyl-1-carboxylic acid ([(18)F]FACBC). Levels of 0.4-2 ppm aluminum as AlCl(3) had a strong negative influence on labeling yield while 4-20 ppm of boron as KBO(2) and 50-250 ppm of silicon as Na(2)SiO(3) did not have a significant impact. Interesting interaction effects between the elements were observed, where particularly KBO(2) reduced the negative effect of AlCl(3) on labeling yield. It can be concluded that leachables of borosilicate glassware easily can influence nucleophilic substitution with n.c.a. [(18)F]F(-) and give variable yields.

Pharmacokinetics of ingested fluoride: lack of effect of chemical compound

Fluoride in drinking water may be present from natural sources or added as sodium fluoride (NaF), sodium silicofluoride (Na(2)SiF(6)) or fluorosilicic acid (H(2)SiF(6)). Results from an early study with rats suggested that, when ingested as Na(2)SiF(6), the absorption and excretion of fluoride were greater than when ingested as NaF.

OBJECTIVE

The present single-blind, crossover study with 10 adults was done to determine three key pharmacokinetic parameters: the maximum plasma fluoride concentrations (C(max)), the elapsed time to reach the maximum concentrations (T(max)) and the 6-h areas under the time-plasma concentration curves (AUCs) after ingestion of 500 mL of water containing 0.67 or 5.45 mg F/L present naturally or added as NaF or H(2)SiF(6).

DESIGN

Blood was collected prior to and at nine time points during 6h after ingestion of the test solutions. Plasma was analysed by electrode after HMDS-facilitated diffusion and the data were analysed for statistically significant differences using repeated measures ANOVA.

RESULTS

The C(max), T(max) and AUC values after ingestion of the solutions containing natural fluoride, NaF or H(2)SiF(6) did not differ significantly at either dose level. Further, the T(max) values associated with the 0.67 and 5.45 mg/L solutions did not differ significantly indicating that the absorption, distribution and elimination rates were not affected by the dose size.

CONCLUSIONS

Considered together with published reports, the present findings support the conclusion that the major features of fluoride metabolism are not affected differently by the chemical compounds commonly used to fluoridate water nor are they affected by whether the fluoride is present naturally or added artificially.

Confirmation of and explanations for elevated blood lead and other disorders in children exposed to water disinfection and fluoridation chemicals

Silicofluorides (SiFs), fluosilicic acid (FSA) and sodium fluosilicate (NaFSA), are used to fluoridate over 90% of US fluoridated municipal water supplies. Living in communities with silicofluoride treated water (SiFW) is associated with two neurotoxic effects: (1) Prevalence of children with elevated blood lead (PbB>10microg/dL) is about double that in non-fluoridated communities (Risk Ratio 2, chi2p<0.01). SiFW is associated with serious corrosion of lead-bearing brass plumbing, producing elevated water lead (PbW) at the faucet. New data refute the long-prevailing belief that PbW contributes little to children's blood lead (PbB), it is likely to contribute 50% or more. (2) SiFW has been shown to interfere with cholinergic function. Unlike the fully ionized state of fluoride (F-) in water treated with sodium fluoride (NaFW), the SiF anion, [SiF6]2- in SiFW releases F- in a complicated dissociation process. Small amounts of incompletely dissociated [SiF6]2- or low molecular weight (LMW) silicic acid (SA) oligomers may remain in SiFW. A German PhD study found that SiFW is a more powerful inhibitor of acetylcholinesterase (AChE) than NaFW. It is proposed here that SiFW induces protein mis-folding via a mechanism that would affect polypeptides in general, and explain dental fluorosis, a tooth enamel defect that is not merely "cosmetic" but a "canary in the mine" foretelling other adverse, albeit subtle, health and behavioral effects. Efforts to refute evidence of such effects are analyzed and rebutted. In 1999 and 2000, senior EPA personnel admitted they knew of no health effects studies of SiFs. In 2002 SiFs were nominated for NTP animal testing. In 2006 an NRC Fluoride Study Committee recommended such studies. It is not known at this writing whether any had begun.

Effects of fluoridation and disinfection agent combinations on lead leaching from leaded-brass parts

This study concerns effects on water-borne lead from combinations of chlorine (CL) or chloramines (CA) with fluosilicic acid (FSA) or sodium fluoride (NaF). CL is known to corrode brass, releasing lead from plumbing devices. It is known that CA and CL in different ratios with ammonia (NH) mobilize copper from brass, which we have found also enhances elution of lead from leaded brass alloys. Phase I involved leaded-brass 1/4 in. elbows pre-conditioned in DI water and soaked in static solutions containing various combinations of CL, CA, FSA, NaF, and ammonium fluosilicate. In Phase II 20 leaded-brass alloy water meters were installed in pipe loops. After pre-conditioning the meters with 200 flushings with 1.0 ppm CL water, seven different solutions were pumped for a period of 6 weeks. Water samples were taken for lead analysis three times per week after a 16-h stagnation period. In the static testing with brass elbows, exposure to the waters with CA+50% excess NH3+FSA, with CA and ammonium fluosilicate, and with CA+FSA resulted in the highest estimated lead concentrations. In the flow-through brass meter tests, waters with CL+FSA, with CL+NaF, and with CL alone produced the highest average lead concentration for the first 3-week period. Over the last 3 weeks the highest lead concentrations were produced by CL+NaF, followed by CL alone and CA+NH3+FSA. Over the first test week (after CL flushing concentrations were increased from 1.0 to 2.0 ppm) lead concentrations nearly doubled (from about 100 to nearly 200 ppb), but when FSA was also included, lead concentrations spiked to over 900 ppb. Lead concentrations from the CL-based waters appeared to be decreasing over the study period, while for the CA+NH3+FSA combination, lead concentrations seemed to be increasing with time.

Two new “onium” fluorosilicates, the products of interaction of fluorosilicic acid with 12-membered macrocycles: structures and spectroscopic properties

Two novel compounds, (L(1)H)(2)[SiF(6)] x 2H(2)O (1) and (L(2)H)(2)[SiF(5)(H(2)O)](2) x 3H(2)O (2), resulting from the reactions of H(2)SiF(6) with 4'-aminobenzo-12-crown-4 (L(1)) and monoaza-12-crown-4 (L(2)), respectively, were studied by X-ray diffraction and characterised by IR and (19)F NMR spectroscopic methods. Both complexes have ionic structures due to the proton transfer from the fluorosilicic acid to the primary amine group in L(1) and secondary amine group incorporated into the macrocycle L(2). The structure of 1 is composed of [SiF(6)](2-) centrosymmetric anions, N-protonated cations (L(1)H)(+), and two water molecules, all components being bound in the layer through a system of NH[...]F, NH[...]O and OH[...]F hydrogen bonds. The [SiF(6)](2-) anions and water molecules are assembled into inorganic negatively-charged layers via OH[dot dot dot]F hydrogen bonds. The structure of 2 is a rare example of stabilisation of the complex anion [SiF(5)(H(2)O)](-), the labile product of hydrolytic transformations of the [SiF(6)](2-) anion in an aqueous solution. The components of 2, i.e., [SiF(5)(H(2)O)](-), (L(2)H)(+), and water molecules, are linked by a system of NH[...]F, NH[...]O, OH[...]F, OH[dot dot dot]O hydrogen bonds. In a way similar to 1, the [SiF(5)(H(2)O)](-) anions and water molecules in 2 are combined into an inorganic negatively-charged layer through OH[...]F and OH[...]O interactions.

Reexamination of hexafluorosilicate hydrolysis by 19F NMR and pH measurement

The dissociation of hexafluorosilicate has been reinvestigated due to recent suggestions that fluorosilicate intermediates may be present in appreciable concentrations in drinking water. 19F NMR spectroscopy has been used to search for intermediates in the hydrolysis of hexafluorosilicate. No intermediates were observable at 10(-5) M concentrations under excess fluoride forcing conditions over the pH range of 3.5-5. A single intermediate species, assigned as SiF5(-) or its hydrate, was detected below pH 3.5. At moderate pH values of 4 and 5 silica oligomerization in the solutions studied made it difficult to directly determine the hexafluorosilicate equilibrium constant. Under more acidic conditions the average pKd, or negative log of the dissociation constant Kd, determined by 19F NMR measurements, was 30.6. We also investigated the behavior of hexafluorosilicate in common biological buffer reagents including phosphate/citrate, veronal/HCI buffers, and Ringer's solution. The buffer capacity of all of these systems was found to be insufficient to prevent acidic shifts in pH when hexafluorosilicate was added. The pH change is sufficient explanation for the observed inhibition of acetylcholinesterase that was previously attributed to hexafluorosilicate hydrolysis intermediates.

Water fluoridation and the environment: current perspective in the United States

Evidence of water fluoridation's effects on plants, animals, and humans is considered based on reviews by scientific groups and individual communities, including Fort Collins, CO, Port Angeles, WA, and Tacoma-Pierce County, WA. The potential for corrosion of pipes and the use of fluoridation chemicals, particularly fluorosilicic acid, are considered, as is the debate about whether fluoridation increases lead in water, with the conclusion that there is no such increase. The arguments of anti-fluoridationists and fluoridation proponents are examined with respect to the politics of the issue.