Optimal Fluoride Concentration Research Articles

Fluoride-assisted liquid chromatography-tandem mass spectrometry method for simultaneous analysis of propofol and its metabolites without derivatization in urine

The misuse of propofol for recreational purposes has become a serious social issue. Accordingly, practical and sensitive analytical methods to investigate the chronic abuse and toxicity of propofol are required. However, current propofol determination methods using liquid chromatography-mass spectrometry (LC-MS/MS) suffer from problems associated with loss in sample preparation due to its volatility and its poor ionization efficiency and collision-induced dissociation in mass spectrometry. Herein, we have developed a sensitive and accurate fluoride-assisted LC-MS/MS method combined with direct-injection for propofol determination. Ionization via fluoride-ion attachment/induced deprotonation, effected by ammonium fluoride in the mobile phase, was found to dramatically improve the sensitivity of propofol without derivatization. Furthermore, direct injection without derivatization enables the simultaneous analysis of propofol and its phase II metabolites without analyte loss. The optimal concentration of ammonium fluoride in the mobile phase was found to be 1 mM under methanol conditions. The linearity is good (R2 ≥ 0.999) and the intra- and inter-day precisions for propofol determination are between 1.9 and 8.7%. The accuracies range from 87.5% to 105.4% and the limits of detection and quantitation for propofol in urine are 0.15 and 0.44 ng mL−1, respectively. The present method was successfully applied to human urine and showed a sufficient sensitivity to determine propofol and five phase II metabolites over 48 h in human urine after administration. Consequently, the fluoride-assisted LC-MS/MS method was demonstrated to be sensitive, accurate, and practical for the determination of propofol and its metabolites.

Fluoride exposure and factors affecting dental caries in preschool children living in two areas with different natural levels of fluorides

BackgroundSuccessful oral health interventions must be based on the specific needs of the population that they serve. Evaluation of habits related to dental caries development and estimation of fluoride exposure in a target group of young patients helps to plan effective and safe caries prevention strategies. ObjectivesThe study aimed to evaluate factors affecting dental caries experience and sources of fluoride exposure in preschool children living in two areas: with optimal and low natural content of fluoride in drinking water. Materials and methodsThe study included a group of 73 children of both sexes aged 4–7 years attending two kindergartens in Środa Wielkopolska and Turek (Wielkopolska Voivodeship, Poland), where the content of fluoride in drinking water according to data obtained in the sanitary station ranged from 0.68 to 0.74 mg/L (optimal concentration of fluoride) and from 0.19 to 0.30 mg/L (low concentration of fluoride), respectively. Parents of patients completed a survey about diet, hygiene, and dental care, taking into account the child's fluoride exposure. The calibrated dentist assessed the oral health condition using a mirror, a CPI probe, and a headlamp. Oral hygiene was recorded using the Silness and Löe plaque index, caries experience by calculating the numbers of decayed, missing, and filled primary, and permanent teeth (dmf and DMF, respectively) while caries frequency by calculating the percentage of children with caries experience above 0. In order to assess the fluoride concentrations in urine and drinking water, parents were asked to provide a urine sample collected on fasting and a tap water sample. Fluoride concentrations were assessed using a 09–37 (MARAT) fluoride ion-selective electrode and a RAE 111 silver-chloride reference electrode. Statistical analysis was conducted using the data analysis software system Statistica (version 12, StatSoft, Inc. 2014), assuming a statistical significance level p < 0.05. ResultsNo statistically significant differences were found between caries indices of the examined children in each kindergarten (p > 0.05). Urinary fluoride levels were higher in children who tended to swallow toothpaste or used fluoride rinses and positively correlated with fluoride concentrations in the drinking water. Dental caries experience in the examined children depended on the effectiveness and frequency of oral hygiene procedures and dietary habits. ConclusionsThe strategy aimed at improving the oral health of the examined group of children should include accomplishing oral hygiene, promoting a non-cariogenic diet, and, finally, controlling fluoride exposure from at-home fluoride products. Caries prevention program ought to be adjusted to individual characteristics of each child, taking into consideration oral hygiene practices, dietary habits and total fluoride intake.

The impact of stopping or reducing the level of fluoride in public water supplies on dental fluorosis: a systematic review.

The increased availability of fluoride and concern over the impact of fluorosis, have led to guidance suggesting a decrease or cease in the optimal concentration of fluoride in water fluoridation schemes. To date there have been no systematic reviews looking at both impact of fluoride reduction and total cessation. This review aimed to examine the impact of stopping or reducing the level of fluoride in public water supplies on dental fluorosis. Multiple databases were searched (MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials and the Web of Science). Two reviewers independently screened sources, extracted data and assessed study quality. Results were synthesised qualitatively and quantitatively. The main outcome measure was the prevalence of dental fluorosis. Six studies of cross-sectional design were included. Two studies were scored as evidence level B (moderate) and the remaining four publications were evidence level C (poor). Meta-analysis indicated fluorosis prevalence was significantly decreased following either a reduction in the concentration of fluoride or cessation of adding fluoride to the water supply (OR:6.68; 95% CI:2.48 to 18.00). The evidence suggests a significant decrease in the prevalence of fluorosis post cessation or reduction in the concentration of fluoride added to the water supply. However, this work demonstrates that when studies are subject to current expectations of methodological and experimental rigour, there is limited evidence with low methodological quality to determine the effect of stopping or reducing the concentration of fluoride in the water supply on dental fluorosis.

Water Fluoridation Basics: What Operators Need to Know

Fluoride can greatly reduce the incidence of tooth decay among children. However, to achieve fluoridation's maximum benefits, the optimal fluoride concentration in the water supply must be continuously maintained.

Two distinct mechanisms of fluoride enrichment and associated health risk in springs' water near an inactive volcano, southeast Iran.

Groundwater fluoride contamination is a major issue of water pollution in the world with health hazards such as dental and skeletal fluorosis. This research focused on exposure to the high concentration of fluoride in the springs water in the Bazman volcanic area, southeast Iran. The combination of chemical/isotopic analysis, geochemical modeling, health risk assessment and multivariate statistical methods were applied to investigate the contamination and sources of fluoride in the samples. Groundwater samples were collected from cold and thermal springs. Major ions, fluoride, trace elements and stable isotopes δ18O and δD were measured in the samples using standard methods, ICP-MS and OA-ICOS, respectively. Fluoride content in springs varied from 0.5 to 3.75mg/L with an average value of 1.66mg/L. The highest fluoride concentrations were observed in the eastern cold springs while thermal springs showed the minimum fluoride contents. The majority of samples showed F contents higher than the calculated optimal concentration of fluoride (0.75mg/L). Reaction of fluorite mineral with HCO3 and replacement of F in clay minerals and metal oxy-hydroxides with OH- in water were likely cause fluoride enrichment in the eastern springs. Whereas, in the western springs and thermal springs, origin of fluoride was related to weathering of muscovite, cryolite, apatite and fluoroapatite minerals. The δ18O and δ2H of the water samples displayed the impact on evaporation on fluoride enrichment in all spring water samples. The average value of contamination index (Cd) in the water samples was 1.94 categorizing medium risk level while springs S7, S8, S9 and S4 were above the threshold value of Cd index. The fluoride hazard quotient (HQ) showed that 25%, 44%, 56% and 0% of springs' water resources had high risk level for age group of adults, teenager, children and infants, respectively. Therefore, health risk of fluoride in drinking water resources were in the following order: children>teenager>adults>infants.

Enhanced simazine herbicide degradation by optimized fluoride concentrations in TiO2 nanotubes growth

The performance of simazine degradation using TiO2 nanotubes is strongly influenced by the morphology and structure of the nanotubes. TiO2 nanotubes were synthesized from pristine titanium foil in EG/NH4F/KOH solution using anodic oxidation technique. This study investigates the effect of fluoride concentration in the electrolytes on the efficiency of Simazine photodegradation. We found that the optimum NH4F concentration was 0.5 wt% resulted in 57.4% degradation rate of simazine after 240 min of UV illumination. The result was attributed to the well separated, ordered and uniform structure of TiO2 nanotubes. Having the optimum fluoride concentration in electrolyte is crucial as the photodegradation performance depends on the crystal structure, surface morphology, and phase stability of the TiO2 nanotubes.

Rapid and extremely high adsorption performance of porous MgO nanostructures for fluoride removal from water

Abstract Fluoride is a non-metal that can often be found in groundwater posing a serious environmental health hazard worldwide. So, it is very important to remove excess fluoride from drinking water to maintain the optimal concentration of fluoride. To address this issue, the synthesis of porous MgO nanostructures has been reported herein through the sol-gel and hydrothermal methods to use them as an effective adsorbent for removal of fluoride from water. The as-synthesized MgO nanostructures are porous, highly crystalline, and pure as confirmed by microscopic and diffractometric analysis. N2 gas adsorption-desorption study revealed that the BET surface areas of different MgO nanostructures are varied from 10.5 to 171 m2 g−1. The adsorption potential of MgO nanostructures is extremely high in the removal of fluoride from water with Langmuir adsorption capacity of 5716 to 15,691 mg g−1 at 303 K. The kinetic studies revealed that nearly 90% of fluoride were removed within 5 min. The adsorption process is thermodynamically favorable and is exothermic in nature. A maximum Langmuir adsorption capacity of 29,131 mg g−1 has been achieved at 313 K which is the highest for any adsorbent reported till now. The treatment of the experimental data with different isotherm and kinetic models suggests that these MgO nanostructures could be efficient, inexpensive, eco-friendly and convenient adsorbents for remediation of fluoride from water. The relative importance of test parameters such as the concentration of adsorbent, pH, and effect of co-existing ions on the adsorption performance of MgO nanostructures has been well investigated. The nanostructures are highly stable and are reusable up to the fifth cycle without losing too much of its adsorption performance.

Forecast optimal fluoride concentration data in drinking water according to the ambient temperature in Golestan, Iran

AbstractControlling fluoride concentrations in drinking water at optimal levels could be effective in preventing certain negative health effects in humans. This study investigated optimal fluoride concentrations in potable water in Golestan province, according the ambient temperatures in the province. The study used data on fluoride concentrations in drinking water supplied by the Water and Wastewater Company of Golestan Province. The annual mean maximum temperatures were extracted from a website that recorded daily ambient temperature. The optimal value of fluoride in drinking water for each county of Golestan province was calculated by the Galgan and Vermillion formula. The results show that all of the counties should contain fluoride concentrations ranging from 0.73 to 0.766 milligrams per liter (mg/L) according to the calculation formula, while fluoride concentrations were instead reported to range between 0.23 and 0.53 mg/L by the Water and Wastewater company. In addition, according to World Health Organization (WHO) recommendations, the concentrations of fluoride in potable in all of the cities in Golestan province fall below the WHO standard. In conclusion, we suggest that the fluoride concentrations in Golestan province's drinking water should be taken into account by the appropriate authorities and that optimal fluoride concentrations in drinking water according to ambient temperatures be set to avoiding negative health impacts.

Reduction of Fluoride in Water Phase by Micro-Nano Bubble Pretreatment Process.

Fluoride is important to aquatic environment and health aspects, and the optimal fluoride concentration in water is below 1 mg/L. In this study, the micro-nano bubble pretreatment was applied to remove fluoride ions in the water phase. The pH control by calcium hydroxide (Ca(OH)₂), and coagulation processes with poly aluminum chloride (PAC), aluminum sulfate (Alum), F900 and two kinds of polymer named as A-polymer and A430P polymer were applied for the pretreated wastewater. In results, the combination of PAC and A430P polymer with micro-nano bubble pretreated wastewater showed a higher fluoride removal than the case of other combinations. In chemical oxygen demand (COD) removal, the combination of Alum and A430P polymer with micro-nano bubble pretreated wastewater showed the best removal efficiency (64.6%) while the COD removal without pretreatment was 71.4% for fluoride and 57.2% for COD.

Optimal Fluoride Concentration in Drinking Water as a Function of Calcium Content

Fluoride (F-) is known to have both beneficial and adverse effects on humans, depending on the total intake. Drinking water, usually obtained from groundwater, is the primary source of fluoride intake. Estonian aquifer systems differ from each other in bedding conditions, hydraulic parameters and chemical composition and fluorides are released into the groundwater mostly through water-rock interaction. The present study bases on long term groundwater monitoring data and was undertaken to assess the occurrence of fluoride values in abstracted drinking water over the whole of Estonia and their relation to groundwater’s calcium content. Fluoride concentration in 4404 water samples ranges from 0 to 6.71 mg/l. Values higher than 1.5 mg/l were detected in 8 % of samples, mostly in Silurian-Ordovician aquifer system, composed of limestones and dolomites. Low fluoride area in southern Estonia coincides with the outcrop of Devonian sedimentary rocks, where the major source of drinking water is terrigenous Middle-Devonian aquifer system. The occurrence of fluorides is correlated to variations in groundwater chemical type, which is the function of the proportional content of main cations and anions. The highest F- values prevail in wells, which produce the water with low Ca2+ content and vice versa. Thus, the content of calcium ions in groundwater has an important effect on fluoride concentration, insofar as Ca is an element that removes F from water through CaF2 formation and precipitation. Generally, in terrigenous aquifer systems consisting of sand- and siltstones the optimal fluoride content (0.7-1.2 mg/l) is achieved at the calcium concentration within 30-120 mg/l, in carbonaceous Silurian-Ordovician aquifer calcium content which provides the optimal fluoride amount in carbonaceous aquifer system is 150-340 mg/l.

Quality of the water fluoridation and municipal-level indicators in a Brazilian metropolitan region

This study explored the relationship between water fluoridation quality and development indicators at municipal level. In addition, fluoride concentrations found were classified based on two criteria for interpreting the samples. A cross-sectional ecological exploratory study was carried out including all municipalities of the metropolitan region of Great Vitória, ES, Brazil. From May to October 2016, 648 samples of water were collected covering water treatment plants responsible for more than 80% of the population of each municipality. The fluoride concentration of each sample was determined using ion-specific electrode and the results were classified according to the federal act and the criterion proposed by the Collaborating Center of the Brazilian Ministry of Health for Oral Health Surveillance. The outcome was the rate of values included in the optimal concentration interval and the independent variables were municipal-level indicators related to demographics, economics, sanitation, health conditions and human development characteristics. The Spearman test and Kappa statistic were used in the analysis. The percentage of samples presenting optimal fluoride concentration ranged from 68.1 to 81.4%, considering the two criteria used. The Kappa statistic between the criteria was 0.671 (p-value = 0.001). Human development, average coverage of supervised toothbrushing, and total population showed a strong positive correlation with the quality of fluoridation while infant mortality and tooth-extraction/dental procedures ratio showed a strong negative correlation. The plausibility of observed correlations encourages further investigations of potential causes.

Evaluation of fluoride concentration in water filter system for households

Drinking water that has good quality is important to sustain human life. If the sources of the drinking water have been contaminated by pollutants, it can give harmful effects to human. Besides of pollutants, good quality of drinking water should have optimum concentration of minerals and one of necessary minerals is fluoride. However, fluoride concentration is less emphasized in factor of purchasing the water filter system. In addition, Malaysians are not aware of the importance of optimum fluoride concentration in their drinking. Water filter system is installed to obtain the good quality of drinking water and needs the maintenance services to ensure the quality of drinking water accomplishes a constant protection. However, the performance of maintenance service is never being measured. Therefore, this study was conducted to measure the fluoride concentration in drinking water for household and evaluate the performance of maintenance service in water filter system. Two residential areas in Johor were involved in data collection. Fluoride concentrations at influent of water filter system were in range of 2.41 mg/L to 3.84 mg/L which were above the permissible limit except for USEPA standard. Concentrations at effluent for before maintenance service were reduced, in range of 0.89 mg/L to 1.28 mg/L, and thus water filter system is necessary to install in Malaysian household. However, very low concentrations were detected after maintenance service, in range of 0.08 mg/L and 0.12 mg/L, and thus the maintenance service needs to be revised to obtain the optimum fluoride concentration.

Hydrometallurgical Processing Technology of Titanomagnetite Ores

In this paper, we study the possibility of obtaining iron and titanium-vanadium concentrates with highest contents of iron and titanium, respectively, through hydrometallurgical processing of the titanomagnetite ores of the Chineisk deposit. We varied two key parameters to determine the efficiency of the process: (a) concentration of leaching solution (ammonium fluoride); and (b) acidity of solution. Ammonium fluoride concentration was varied from 0.08 mol/L to 4.2 mol/L with the other fixed parameters. It was shown that optimum ammonium fluoride concentration for leaching the ore is 0.42 mol/L; at these concentrations iron and titanium contents are about 62.8 wt % and 3.5 wt % in solid phase, respectively. The acidity of solution was changed by adding of hydrofluoric acid with varied concentration (from 0.86 mol/L to 4.07 mol/L) to ammonium fluoride solution with fixed concentration of 0.42 mol/L. The best results (degree of titanium extraction = 63.7%) were obtained when using a solution of hydrofluoric acid with concentration 4.07 mol/L. In this case, the addition of acid makes it possible to increase the Fe/Ti ratio by 3.4 times in comparison with the original ore. Thus, we conclude that acidity and the concentration of ammonium fluoride solution significantly influences the selectivity of the hydrometallurgical process.

Electrochemical behaviors of Ti(III) in molten NaCl-KCl under various contents of fluoride

In order to investigate an optimal concentration of fluoride in alkali chloride melt which the Ti(III) can be reduced into metallic titanium in one step, a systematic study of the electrochemical properties of Ti(III) was carried out in molten NaCl-KCl. KF was used as a source of fluoride ions, and the molar ratio of fluoride ions and titanium ([F−]/[Tin+] ratio) was employed as a parameter to illustrate the influence of fluoride anions on the electrochemical behaviors of Ti(III). The experiments were carried out with various concentrations of fluoride ions using a glassy carbon electrode at a temperature of 1023K. Transient electrochemical techniques, such as cyclic voltammetry and square wave voltammetry, were performed to reveal the reduction steps and reduction potentials of the electroactive species. Results suggest that there are two steps for Ti(III) ion reduction in molten NaCl-KCl: Ti(III)→Ti(II) and Ti(II)→Ti. Ti(III) can be reduced directly to Ti in one step when KF was added in the melt in increasing amount.

Dentin Erosion: Method Validation and Efficacy of Fluoride Protection.

The aging population experiences more gingival recession and root exposure which increases the opportunity for dentin erosion. This study tested the use of transverse microradiography (TMR) methods to assess dentin erosion and the interaction between fluoride and citric acid on the amount of erosion in the dentin samples. In a 4 × 3 interaction experimental design, four fluoride concentrations (0.00, 25.0, 50.0, and 100.0 mg/L) and three citric acid concentrations (0.0, 0.25, and 1.00%) were combined to form 12 experimental solutions. Forty-eight dentin samples were placed in the experimental solutions for 1 and 4 h and the amount of surface lost was determined by TMR methods. The resolution of the TMR method was 0.9 μm per pixel with a 0.1% and a 5% confidence interval of ±4.2 μm. Dentin erosion increased with the concentration of citric acid and time, the erosion decreased when concentration of fluoride was increased. Effects due to fluoride and citric acid concentrations individually, and their interaction on the amount of erosion observed was statistically significant (p < 0.0001). This study found that TMR methods are appropriate and that 25.0 mg/L was the optimal fluoride concentration to protect dentin from a 1.00% citric acid challenge.

Effects of fluoride-modified titanium surfaces with the similar roughness on RUNX2 gene expression of osteoblast-like MG63 cells.

Chemical modification of titanium surfaces by hydrofluoric acid (HF) is an effective method to improve bone responses on titanium implant surfaces. In this study, titanium disks were sandblasted with titanium oxide grits and modified with 0.2% and 0.4% of diluted HF under different exposure times of 40 and 60 s. Surface characteristics, such as surface chemical composition, surface topography, and surface wettability, were investigated. To examine MG63 osteoblast-like cell responses to fluoride-modified titanium surfaces with roughness similar to that of nonmodified surfaces, a cell proliferation assay was performed and gene expression levels of Runx2 were evaluated using real-time PCR. Fluoride-modified titanium surfaces revealed no significant roughness difference but with hydrophilic properties than control group SB. Moreover, the relative atomic concentration percentages of fluoride were 0.7, 1.5, and 2.8. As fluoride concentrations increased, surface wettability increased and cell proliferation began earlier. However, the gene expression levels of Runx2 increased earlier on surfaces with 1.5% fluoride, with significantly high surface skewness. There seems to be an optimal fluoride concentration percentage when gene expression levels of Runx2 were taken into consideration. In addition, surface parameters, such as surface wettability and surface skewness, seem to be important factors in the enhancement of osteoblast differentiation by HF. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3102-3109, 2017.

Geographical distribution of fluoride in the public water supply in the province of Tucumán, Argentina

This work studied the geographical distribution of fluoride content in the public water supply in the province of Tucumán, Argentina. A total of 1,210 samples were collected in 190 localities of the 17 departments of the province during the 2008-2012 period. The analytical determination was performed using the SPADNS method and QGis 2.16 was used for processing the information. The fluoride content requirements in the studied localities were determined according to the Argentine Food Code. The results showed that 94% of population studied consumed water with fluoride concentrations below the recommended limits, 5% were exposed to fluoride concentrations above the required maximum limit and 1% consumed water at optimal fluoride concentrations. The maps showed a heterogeneous geographical distribution of fluorides, in which areas with deficit, excess and recommended values of fluorides can be differentiated; in some departments an inverse relationship between the density of the hydrological network and fluoride concentration can be observed. In the capital of the province, the average value found was 0.32 mg/l, presenting a homogeneous geographical distribution. The information obtained is indispensable for the proper management of fluoride, so as to improve public health through policy.

An Emerging Technique For Deflouridation Of Water - A Nanotechnology

The de-fluoridation of simulated known concentration of fluoride solution (3 to 5 ppm) was studied using Al(OH)3 nano particles (0.5 gm/100 mL) as adsorbentsby a simple magnetic extraction method.Selective ion electrode method was adopted to analyze reduction of fluoride concentration in simulated solution before and after treatment. The result reveals that, the absorbance for the samples have been noticeable reduction in fluoride. Also it is evident that as the increase in fluoride content the reduction percentage also accelerated. The study showed 24.50 % reduction in absorbance for sample having fluoride 3ppm fluoride content, 21.93% reduction for 3.5ppm, 13.64% reduction for 4ppm fluoride concentration, 11.07% reduction for 4ppm fluoride concentration and 7.62% reduction in absorbance for the sample containing 5ppm of fluoride. I. Introduction More than 103 million people around the world live in areas where optimal fluoride concentrations occur naturally. In small amounts of fluoride is beneficial as it is believed to impart stability to bone and enamel, there by preventing dental carries and osteoporosis to some extent but its higher concentration is highly toxic to humans and animals alike. The permissible limit of fluoride in drinking water as recomended by WHO is 1.5 ppm. Chronic exposure to fluoride above the permissible limits causes a disease called Fluorosis which is an important clinical and public health problem in several parts of the world. This disease manifests itself in three forms, namely, dental, skeletal, and non-skeletal fluorosis. Even though extensive studies have been conducted, there seems to be no effective cure for these diseases, therefore, it is desirable to drink water having a fluoride concentration less than certain value. So it is essential to consider remedial measures of fluoride in potable water to control fluorosis. This paper deals with an overall, effective and low cost technique for defluoridation of water using nanotechnology.

Determining the Optimal Concentration of Fluoride in Drinking Water from the Republic of Macedonia

Aim: The aim of this study was to determine the optimal concentration of fluoride in drinking water from 11 cities located on different sites throughout the Republic of Macedonia. Method: The optimal level of fluoride in drinking water is universally calculated by applying the equation of Galagan and Vermillion, which permits the calculation of water as a function of temperature. Results: The annual mean maximum temperatures (AMMT) recorded during the last 5 years were collected from the meteorological centres of the 11 divisional headquarter stations. The optimal fluoride concentration in drinking water from different cities in Macedonia was calculated to be 0.84 mgF/L in Gevgelija, 0.83 mgF/L in Demir Kapija, 0.88 mgF/L in Strumica, 0.89 mgF/L in Shtip, 0.9 mgF/L in Skopje (Zajcev Rid), 0.92 mgF/L in Bitola, 0.94 mgF/L in Prilep and Ohrid, 0.95 mgF/L in Kriva Palanka, 1.00 mgF/L in Berovo and 1.09 mgF/L in Lazaropole. Conclusion: Determining the most appropriate concentration of fluoride in drinking water is crucial for communities. The optimal fluoride concentration in drinking water from different cities from the Republic of Macedonia was calculated to be between 0.84 -1.09 mg F/L.

Water Intake by Outdoor Temperature Among Children Aged 1-10 Years: Implications for Community Water Fluoridation in the U.S.

The U.S. water fluoridation recommendations, which have been in place since 1962, were based in part on findings from the 1950s that children's water intake increased with outdoor temperature. We examined whether or not water intake is associated with outdoor temperature. Using linked data from the National Health and Nutrition Examination Survey (NHANES) 1999-2004 and the National Oceanic and Atmospheric Administration, we examined reported 24-hour total and plain water intake in milliliters per kilogram of body weight per day of children aged 1-10 years by maximum outdoor temperature on the day of reported water intake, unadjusted and adjusted for age, sex, race/ethnicity, and poverty status. We applied linear regression methods that were used in previously reported analyses of data from NHANES 1988-1994 and from the 1950s. We found that total water intake was not associated with temperature. Plain water intake was weakly associated with temperature in unadjusted (coefficient 5 0.2, p=0.015) and adjusted (coefficient 5 0.2, p=0.013) linear regression models. However, these models explained little of the individual variation in plain water intake (unadjusted: R(2)=0.005; adjusted: R(2)=0.023). Optimal fluoride concentration in drinking water to prevent caries need not be based on outdoor temperature, given the lack of association between total water intake and outdoor temperature, the weak association between plain water intake and outdoor temperature, and the minimal amount of individual variance in plain water intake explained by outdoor temperature. These findings support the change in the U.S. Public Health Service recommendation for fluoride concentration in drinking water for the prevention of dental caries from temperature-related concentrations to a single concentration that is not related to outdoor temperature.