Fluoride Removal Using Nanofiltration-Ranged Polyamide Thin-Film Nanocomposite Membrane Incorporated Titanium Oxide Nanosheets

Drinking water defluoridation has attracted significant attention in the scientific community, from which membrane technology, by exploring thin film nanocomposite (TFN) membranes, has demonstrated a great potential for treating fluoride-contaminated water. This study investigates the development of a TFN membrane by integrating titanium oxide nanosheets (TiO2 NSs) into the polyamide (PA) layer using interfacial polymerization. The characterization results suggest that successfully incorporating TiO2 NSs into the PA layer of the TFN membrane led to a surface with a high negative charge, hydrophilic properties, and a smooth surface at the nanoscale. The TFN membrane, containing 80 ppm of TiO2 NSs, demonstrated a notably high fluoride rejection rate of 98%. The Donnan-steric-pore-model-dielectric-exclusion model was employed to analyze the effect of embedding TiO2 NSs into the PA layer of TFN on membrane properties, including charge density (Xd), the pore radius (rp), and pore dielectric constant (εp). The results indicated that embedding TiO2 NSs increased Xd and decreased the εp by less than the TFC membrane without significantly affecting the rp. The resulting TFN membrane demonstrates promising potential for application in water treatment systems, providing an effective and sustainable solution for fluoride remediation in drinking water.

Exogenous Auxin and Gibberellin on Fluoride Phytoremediation by Eichhornia crassipes

High rates of fluorosis were reported worldwide as a result of human consumption of water with fluoride contents. Adjusting fluoride concentration in water as recommended by the World Health Organization (<1.5 mg L^-1) is a concern and it needs to be conducted through inexpensive, but efficient techniques, such as phytoremediation. The application of phytohormones was investigated as a strategy to improve this process. Thus, the main goal of this research was to evaluate the effect of exogenous auxin and gibberellin on the tropical duckweed Eichhornia crassipes performance for fluoride phytoremediation. Definitive screening and central composite rotatable designs were used for experiments where fluoride concentration (5~15 mg L^-1), phosphorus concentration (1~10 mg L^-1), and pH (5~9) were assessed as well throughout 10 days. Fluoride contents were determined in solution and plant tissues by potentiometry. Higher concentrations of fluoride reflected on greater absorptions by plants, though in relative terms removal efficiencies were quite similar for all treatments (~60%). Auxin and acidic conditions favored fluoride removals per mass of plant. Fluoride accumulated mostly in leaves and auxin probably alleviated toxic effects on E. crassipes while gibberellin showed no effect. Therefore, E. crassipes could be employed as a fluoride accumulator plant for water treatment and exogenous auxin may be used to improve the process.

Template-Free Synthesis of Magnetic La-Mn-Fe Tri-Metal Oxide Nanofibers for Efficient Fluoride Remediation: Kinetics, Isotherms, Thermodynamics and Reusability

The occurrence of fluoride contamination in drinking water has gained substantial concern owing to its serious threat to human health. Traditional adsorbents have shortcomings such as low adsorption capacity and poor selectivity, so it is urgent to develop new adsorbents with high adsorption capacity, renewable and no secondary pollution. In this work, magnetic electrospun La-Mn-Fe tri-metal oxide nanofibers (LMF NFs) for fluoride recovery were developed via electrospinning and heat treatment, and its defluoridation property was evaluated in batch trials. Modern analytical tools (SEM, BET, XRD, FTIR) were adopted to characterize the properties of the optimized adsorbent, i.e., LMF11 NFs with a La:Mn molar ratio of 1:1. The surface area calculated via BET method and pH_pzc assessed using pH drift method of LMF11 NFs were 55.81 m² g^-1 and 6.47, respectively. The results indicated that the adsorption amount was highly dependent on the pH of the solution, and reached the highest value at pH = 3. The kinetic behavior of defluoridation on LMF11 NFs was dominated by the PSO model with the highest fitted determination coefficients of 0.9999. Compared with the other three isotherm models, the Langmuir model described defluoridation characteristics well with larger correlation coefficients of 0.9997, 0.9990, 0.9987 and 0.9976 at 15 °C, 25 °C, 35 °C and 45 °C, respectively. The optimized LMF11 NFs exhibited superior monolayer defluoridation capacities for 173.30-199.60 mg F^-/g at pH 3 at 15-45 °C according to the Langmuir isotherm model. A thermodynamic study proved that the defluoridation by LMF11 NFs is a spontaneous, endothermic along with entropy increase process. In addition, the LMF11 NFs still showed high defluoridation performance after three reused cycles. These findings unveil that the synthesized LMF11 NFs adsorbent is a good adsorbent for fluoride remediation from wastewater owing to its low cost, high defluoridation performance and easy operation.

Characterization of a novel Fluoride resistant bacterial isolate and its capability of Fluoride bioremediation

A Gram positive rod shaped bacterium designated as isolate H1 with Fluoride resistance up to 4 g/L sodium fluoride (NaF) in LB (Luria-Bertani) agar was isolated from a ground water sample of Narketpally area, Nalgonda district, Telangana, India. The colonies of isolate H1 were off white in color. Growth patterns of isolate H1 were observed at two different concentrations, 100 and 250 ppm, of NaF and also without NaF in the medium. In cases where NaF was present in the media, the lag phases of the growth curves were extended when compared to the absence of NaF. Optimum pH required for the organism's growth was 8. Isolate H1 required a temperature of 37 °C with 150 rpm and 2% NaCl for its optimal growth in the medium without NaF. Meanwhile, isolate H1 could thrive in a diverse pH range, i.e., pH 5-10, and at an NaCl concentration of up to 11% in the medium with NaF. Based on morphological, biochemical and molecular characterization, isolate H1 was identified as belonging to the genus Bacillus. It showed 98.47% 16S rDNA gene sequence similarity with Bacillus australimaris NH71_1^T. Isolate H1 showed high fluoride removals of 22.5% and 38.2% with 100 and 250 mg/L of NaF in the LB broth when incubated at pH 8 and a temperature of 37 °C with 150 rpm for 3 day. Hence, this organism could be a promising isolate to apply for defluoridation of ground water in fluoride contaminthe ated areas.

Nanoarchitectonics and Kinetics Insights into Fluoride Removal from Drinking Water Using Magnetic Tea Biochar

Fluoride contamination in water is a key problem facing the world, leading to health problems such as dental and skeletal fluorosis. So, we used low-cost multifunctional tea biochar (TBC) and magnetic tea biochar (MTBC) prepared by facile one-step pyrolysis of waste tea leaves. The TBC and MTBC were characterized by XRD, SEM, FTIR, and VSM. Both TBC and MTBC contain high carbon contents of 63.45 and 63.75%, respectively. The surface area of MTBC (115.65 m²/g) was higher than TBC (81.64 m²/g). The modified biochar MTBC was further used to remediate the fluoride-contaminated water. The fluoride adsorption testing was conducted using the batch method at 298, 308, and 318 K. The maximum fluoride removal efficiency (E%) using MTBC was 98% when the adsorbent dosage was 0.5 g/L and the fluoride concentration was 50 mg/L. The experiment data for fluoride adsorption on MTBC best fit the pseudo 2nd order, rather than the pseudo 1st order. In addition, the intraparticle diffusion model predicts the boundary diffusion. Langmuir, Freundlich, Temkin, and Dubnin-Radushkevich isotherm models were fitted to explain the fluoride adsorption on MTBC. The Langmuir adsorption capacity of MTBC = 18.78 mg/g was recorded at 298 K and decreased as the temperature increased. The MTBC biochar was reused in ten cycles, and the E% was still 85%. The obtained biochar with a large pore size and high removal efficiency may be an effective and low-cost adsorbent for treating fluoride-containing water.

Evaluation of Scales of Tilapia Sp. and Sciaenops ocellatus as Low Cost and Green Adsorbent for fluoride Removal From Water

Water containing more than 1.5 mg/L of fluoride is considered toxic as it causes dental, kidney, and other health problems. With the purpose of helping alleviate these problems by exploring a treatment method for fluoride contamination, this study was to assess the suitability of scales of Tilapia Sp. and Sciaenops ocellatus as a cheaper source of adsorbent for the removal of fluoride from drinking water. The samples which were obtained from the Lapaz Market in Accra, Ghana, underwent treatment to eliminate any impurities. They were then ground into powder and treated with aluminum hydroxide [Al(OH)₃]. The treated samples were used for the removal of fluoride from spiked solutions prepared in the laboratory. Batch adsorption was performed by varying parameters such as adsorbent dose (1–8 g/L), initial concentration (2 mg/L to 10 mg/L), and contact time (30–300 min) at pH of 7. A one-way ANOVA was used to validate the significance of the defluoridation process with respect to the different experimental conditions. The optimum adsorbent dose, initial concentration, and contact time were found to be 4 g/L, 10 mg/L, and 300 min, respectively. The results revealed that the maximum percentage removal of fluoride was 76% by Tilapia Sp. and 70% by Sciaenops ocellatus at the optimum conditions. This is an indication that both Tilapia Sp. And Sciaenops ocellatus scales are suitable adsorbents for the removal of fluoride from water. The fluoride adsorption kinetics followed the pseudo-second-order model, and the adsorption isotherm fitted the Freundlich Isotherm model better than the Langmuir Isotherm model. The adsorption intensity and adsorption capacity for Tilapia Sp. were 3.484 L/mg and 0.065 mg/g, and that of Sciaenops ocellatus 3.195 L/mg and 0.045 mg/g respectively.

Enhanced Fluoride Uptake by Layered Double Hydroxides under Alkaline Conditions: Solid-State NMR Evidence of the Role of Surface >MgOH Sites

Layered double hydroxides (LDHs) are potential low-cost filter materials for use in fluoride removal from drinking water, but molecular-scale defluoridation mechanisms are lacking. In this research, we employed ¹⁹F solid-state NMR spectroscopy to identify fluoride sorption products on 2:1 MgAl LDH and to reveal the relationship between fluoride sorption and the LDH structure. A set of six ¹⁹F NMR peaks centered at -140, -148, -156, -163, -176, and -183 ppm was resolved. Combining quantum chemical calculations based on density function theory (DFT) and ¹⁹F{²⁷Al} transfer of populations in double resonance (TRAPDOR) analysis, we could assign the peaks at -140, -148, -156, and -163 ppm to Al-F (F coordinated to surface Al) and those at -176 and -183 ppm to Mg-F (F coordinated to surface Mg only). Interestingly, the spectroscopic data reveal that the formation of Al-F is the predominant mode of F^- sorption at low pH, whereas the formation of Mg-F is predominant at high pH (or a higher Mg/Al ratio). This finding supports the fact that the F^- uptake of 2:1 MgAl LDH was nearly six times that of activated alumina at pH 9. Overall, we explicitly revealed the different roles of the surface >MgOH and >AlOH sites of LDHs in defluoridation, which explained why the use of classic activated alumina for defluoridation is limited at high pH. The findings from this research may also provide new insights into material screening for potential filters for F^- removal under alkaline conditions.

Enhanced Defluoridation of Water Using Zirconium-Coated Pumice in Fixed-Bed Adsorption Columns

Millions of people across the globe suffer from health issues related to high fluoride levels in drinking water. The purpose of this study was to test modified pumice as an adsorbent for the purification of fluoride-containing waters. The adsorption of fluoride onto zirconium-coated pumice (Zr–Pu) adsorbent was examined in fixed-bed adsorption columns. The coating of zirconium on the surface of VPum was revealed by X-ray diffractometer (XRD), Inductively coupled plasma-optical emission spectroscopy (ICP-EOS), and X-ray fluorescence (XRF) techniques. The degree of surface modification with the enhanced porosity of Zr–Pu was evident from the recorded scanning electron microscope (SEM) micrographs. The Brunauer-Emmett-Teller (BET) analysis confirmed the enhancement of the specific surface area of VPum after modification. The Fourier transform infrared (FTIR) examinations of VPum and Zr–Pu before and after adsorption did not reveal any significant spectrum changes. The pH drift method showed that VPum and Zr–Pu have positive charges at pH_PZC lower than 7.3 and 6.5, respectively. Zr–Pu yielded a higher adsorption capacity of 225 mg/kg (2.05 times the adsorption capacity of VPum: 110 mg/kg), at pH = 2 and volumetric flow rate (Q_O) of 1.25 mL/min. Breakthrough time increases with decreasing pH and flow rate. The experimental adsorption data was well-matched by the Thomas and Adams-Bohart models with correlation coefficients (R²) of ≥ 0.980 (Zr–Pu) and ≥ 0.897 (VPum), confirming that both models are suitable tools to design fixed-bed column systems using volcanic rock materials. Overall, coating pumice with zirconium improved the defluoridation capacity of pumice; hence, a Zr–Pu-packed fixed-bed can be applied for defluoridation of excess fluoride from groundwater. However, additional investigations on, for instance, the influences of competing ions are advisable to draw explicit conclusions.

Volcanic Rock Materials for Defluoridation of Water in Fixed-Bed Column Systems

Consumption of drinking water with a high concentration of fluoride (>1.5 mg/L) causes detrimental health problems and is a challenging issue in various regions around the globe. In this study, a continuous fixed-bed column adsorption system was employed for defluoridation of water using volcanic rocks, virgin pumice (VPum) and virgin scoria (VSco), as adsorbents. The XRD, SEM, FTIR, BET, XRF, ICP-OES, and pH Point of Zero Charges (pH_PZC) analysis were performed for both adsorbents to elucidate the adsorption mechanisms and the suitability for fluoride removal. The effects of particle size of adsorbents, solution pH, and flow rate on the adsorption performance of the column were assessed at room temperature, constant initial concentration, and bed depth. The maximum removal capacity of 110 mg/kg for VPum and 22 mg/kg for VSco were achieved at particle sizes of 0.075-0.425 mm and <0.075 mm, respectively, at a low solution pH (2.00) and flow rate (1.25 mL/min). The fluoride breakthrough occurred late and the treated water volume was higher at a low pH and flow rate for both adsorbents. The Thomas and Adams-Bohart models were utilized and fitted well with the experimental kinetic data and the entire breakthrough curves for both adsorbents. Overall, the results revealed that the developed column is effective in handling water containing excess fluoride. Additional testing of the adsorbents including regeneration options is, however, required to confirm that the defluoridation of groundwater employing volcanic rocks is a safe and sustainable method.

Evaluation of the feasibility of short-term electrodialysis for separating naturally occurring fluoride from instant brick tea infusion

BACKGROUND

Removing excessive naturally occurring fluoride from tea and/or infusions is difficult because the process has low efficiency and causes secondary pollution. In this study, a novel electrodialysis (ED) technology was developed. We examined the effect of crucial parameters (electrolyte concentration, operation voltage, ED duration and initial concentration of the tea infusion) on defluoridation performance using a highly efficient ion-exchange membrane with five-compartment cells.

RESULTS

The most effective ED system results were obtained at an electrolyte concentration of 10 g kg^-1 and operating voltage of 20 V. Moreover, the fluoride removal capacity (10.70-66.93%) was highly dependent on the ED duration (1-15 min) and initial concentration of the tea infusion (0.5-10 g kg^-1 ). The longer the ED duration and the lower the initial concentration, the higher was the defluoridation performance. During ED, limited loss of the main inclusions (total polyphenols, catechins, caffeine and selected ions) was observed. Furthermore, the D201 anion resin-filled ED stack (0.5-5 g) and improvement of concentrate compartment electrolyte (≥5 times the dilute compartment electrolyte) in the ED system enhanced the defluoridation rate significantly.

CONCLUSION

ED is a potentially effective method that can be used for defluoridation in the deep processing of tea products. © 2019 Society of Chemical Industry.

Optimization of defluoridation using Ficus benghalensis leaf biosorbent through Taguchi's method

Present research focuses on optimization of process parameters for defluoridation on novel Ficus benghalensis leaf biosorbent using Taguchi design tool. The maximum fluoride removal is obtained at pH 7, initial concentration 5 mg/L, contact time 120 min, adsorbent dose 10 g/L, and temperature 30°C, and its percentage contribution is found using ANOVA in the following order: pH 50.76% > initial concentration of adsorbate 44.76% > contact time 2.54% > adsorbent dose 1.17% > temperature 0.76%. It follows Langmuir isotherm with constants "a" and "b" obtained as 2.183 mg/g and 0.667 L/mg and fitting well with pseudo-second-order kinetic model. The thermodynamic study indicated the spontaneous and endothermic nature (ΔH = 15,530.55 J/mol). Advanced Analyses, viz., BET, FESEM-EDS, and FTIR are done to know the characteristics of Ficus benghalensis leaf biosorbent. Experiment on defluoridation of contaminated groundwater indicated over 90% removal efficacy, and the concentration of treated water satisfies drinking water standards for fluoride. PRACTITIONER POINTS: A fundamental research leading towards development of a novel biosorbent from Ficus benghalensis leaves waste for defluoridation. Necessary adsorption equilibrium, kinetic and thermodynamic studies to arrive at optimum operating parameters using Taguchi method and constants useful for designing defluoridation unit and advanced analysis mainly BET, FESM-EDS and FTIR to have better insight. Validation on real field samples to prove its technical feasibility of defluoridation using the novel biosorbent developed.

Mechanochemically Activated Aluminosilicate Clay Soils and their Application for Defluoridation and Pathogen Removal from Groundwater

In this study, aluminosilicate rich clay soils were prepared through mechanochemical activation. The chemical and mineralogical properties were investigated using X-Ray Fluorescence (XRF) and X-ray diffraction (XRD). The functional groups, morphology and surface area were evaluated using Fourier Transform Infra-Red (FTIR), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis. Batch experiments were used to evaluate its defluoridation efficiency while antibacterial activities were assessed using well diffusion method. Maximum adsorption capacity was found to be 1.87 mg/g with 32% fluoride removal. Fluoride adsorption was found to reduce in the presence of Cl^-, PO₄^2- and CO₃^2- while it increased in the presence of SO₄^2- and NO₃^-. Adsorption data fitted well to Freundlich isotherms, hence, confirming heterogeneous multilayer adsorption. Kinetic studies revealed that fluoride adsorption fitted well to pseudo-second order model. The sorption of F^- onto the clays' surface followed intra-particle diffusion mode. High correlation coefficient indicates that the sorption process was greatly controlled by particle diffusion while it is minimal in pore diffusion model. Antibacterial studies revealed no zone of inhibition for all the activated clays, hence indicating that they are not active against the bacterial strains of Escherichia coli used in this study. The results showed activated clays' potential for defluoridation. Its effectiveness in pathogen removal is limited. Hence further modifications of the clays' surfaces are hereby recommended.

Repeated Heat Regeneration of Bone Char for Sustainable Use in Fluoride Removal from Drinking Water

The effectiveness of regenerated chicken bone char (CBC) in fluoride removal was investigated in the present study. Heat treatment was studied as the regeneration method. Results revealed that the CBC regenerated at 673 K yielded the highest fluoride adsorption capacity, hence, 673 K was the best regenerating temperature. The study continued up to five regeneration cycles at the best regenerating temperature; 673 K. The CBC accounted to 16.1 mg F/g CBC as the total adsorption capacity after five regeneration cycles. The recovery percentage of CBC reduced from 79% at the first regeneration to 4% after five regeneration cycles. The hydroxyapatite structure of CBC was not changed during the fluoride adsorption by five regeneration cycles. The ion exchange incorporated with the chemical precipitation occurred during the fluoride adsorption. The repeated regeneration of CBC is possible and it could be used as a low cost defluoridation technique to minimize the wastage of bone char.

The Untold Story of Fluoridation: Revisiting the Changing Perspectives

The discovery of fluoride in dentistry has revolutionized treatment modalities with a new aspect of prevention and conservation of tooth structure coming into foreplay. Since then, there has been a lot of research on both topical and systemic fluoridation in an overzealous attempt to control the most debilitating dental problem of caries. Although topical fluoride is still being widely used as a preventive measure for dental caries, systemic administration of the same has gained major criticism worldwide due to the low margin of safety of fluoride and no control over the amount of individual intake when administered on a community level. This problem is more prevalent in countries with presence of natural fluoride belts that extend from Turkey to China and Japan through Iraq, Iran, and Afghanistan increasing the chances of both dental and skeletal fluorosis and hence increasing the focus toward defluoridation. This historical review highlights the distribution of fluoride worldwide and in India and also discusses about the various claims of the antifluoride lobby.

Removal of fluoride from wastewater using HCl-treated activated alumina in a ribbed hydrocyclone separator

Excessive fluoride concentration in wastewater is a major health concern worldwide. The main objective of wastewater treatment is to allow industrial effluents to be disposed of without danger to the human health and the natural environment. In this current study, experiments have been conducted to remove fluoride from aqueous solution using alumina and HCl (Hydrochloric acid) treated activated alumina in a continuous mode. A spiral rib was introduced in the cylindrical part of the conventional hydrocyclone to increase the performance, and the new hydrocyclone is dubbed as ribbed hydrocyclone. Experiments were carried out to analyze the performance of the ribbed hydrocyclone and compared the results with the conventional hydrocyclone of the same dimension. The efficiency of conventional and ribbed hydrocyclone at a slurry flow rate of 50 LPM (liter per minute) for the solid concentration of 1.4 wt% were 80% and 93.5% respectively. The cut size d₅₀ of the conventional and ribbed hydrocyclone was 18 µm and 13 µm respectively at a slurry velocity of 50 LPM. Fluoride removal efficiency using alumina and HCl-treated alumina was also investigated in a continuous mode by the ribbed hydrocyclone. Maximum fluoride removal efficiency was 49.5%, and 80% for alumina and HCl-treated alumina for the initial concentration of 10 mg/L at a slurry flow rate of 50 LPM.

Competitive adsorption of fluoride and natural organic matter onto activated alumina

Natural organic matter (NOM) is a major water constituent that affects the performance of water treatment processes. Several studies have shown that NOM can be adsorbed on the surface of oxides and may compete with other ions. The overall goal of this study was essentially to investigate the competitive adsorption between fluoride and NOM on activated alumina (AA). For this purpose, a humic acid (HA) was used as a model compound for NOM. The interaction of NOM with fluoride, the simultaneous competitive adsorption, and the effect of preloading AA with NOM were investigated. The specific absorbance of HA was determined at 254 nm. Size-exclusion chromatography measurements confirmed the adsorption of aromatic fractions of NOM onto AA. The presence of HA in the system inhibited fluoride sorption onto AA and the removal yield using fresh AA decreased from 70.4 % to 51.0 % in the presence of HA. The decrease was more pronounced using AA preloaded with HA, reaching 37.7 %. The interference of coexisting ions and their effect on fluoride removal capacity were evaluated, showing a severe impact of the presence of phosphate on the removal capacity unlike nitrates and sulfates, which slightly improved the fluoride sorption.

Multivariate optimization of process parameters in the synthesis of calcined Ca‒Al (NO3) LDH for defluoridation using 3(3) factorial, central composite and Box-Behnken design

Response surface methodology was applied for the first time in the optimization of the preparation of layered double hydroxide (LDH) for defluoridation. The influence of three vital process parameters (viz. pH, molar ratio and calcination temperature) in the synthesis of the adsorbent 'Calcined Ca‒Al (NO3) LDH' was thoroughly examined to maximize its fluoride scavenging potential. The process parameters were optimized using the 3(3) factorial, face centered central composite and Box-Behnken designs and a comparative assessment of the methods was conducted. The maximum fluoride removal efficiency was achieved at a calcination temperature of approximately 500ºC; however, the efficiency decreased with increasing pH and molar ratio. The outcome of the comparative assessment clearly delineates the case specific nature of the models. A better predictability over the entire experimental domain was obtained with the 3(3) factorial method, whereas the Box-Behnken design was found to be the most efficient model with lesser number of experimental runs. The desirability function technique was performed for optimizing the response, wherein face centered central composite design exhibited a maximum desirability. The calcined Ca‒Al (NO3) LDH, synthesized under the optimum conditions, demonstrated the removal efficiencies of 95% and 99% for the doses of 3 g L(-1) and 5 g L(-1), respectively.

Substance flow analysis: a case study of fluoride exposure through food and beverages in young children living in Ethiopia

CONTEXT

Dental and skeletal fluorosis is endemic in the Ethiopian Rift Valley. Children are especially vulnerable to excessive fluoride intake because their permanent teeth are still being formed. Strategies to reduce the total fluoride intake by children are thus warranted.

CASE PRESENTATION

By combining the results of field studies in Ethiopia, the relevant pathways for fluoride intake have been identified in 28 children 2-5 years of age living in two villages on the Wonji Shoa Sugar Estate in the Ethiopian Rift Valley. The focus of the present study was to simulate the fluoride intake of the children using the methods of material flow analysis (MFA) and substance flow analysis.

DISCUSSION

With a model based on MFA, we quantified the potential reduction in total fluoride intake given different scenarios-for example, by reducing the fluoride intake from drinking water and cooking water. The results show clearly that only by removing fluoride completely from both drinking and cooking water does the probability of remaining below the daily tolerable upper intake level exceed 50%. Both prepared food and food ingredients must be taken into consideration when assessing the total fluoride intake by children living in high-fluoride areas.

RELEVANCE

This knowledge will help health personnel, the government, and the food authorities to give scientifically based advice on strategies for reducing the total fluoride intake by children living in high-fluoride areas in the Ethiopian Rift Valley.