Hydrated kaolinite (d(001) = 10 Å) can be synthesized by mild heating of a kaolinite-organic suspension, allowing time for the clay to be intercalated by the organic solvent, and then dissolving a fluoride salt in the liquid. After mild heating of the suspension, the salt and organic solvent are removed by repeated water washings. The kaolinite retains interlayer water in the form of a 10-Å kaolinite hydrate. The influence of the intercalating agent, type of salt, concentration of salt, and the time of treatment on the synthesis of 10-Å hydrate was examined for several kaolinites. The most effective salt is NH4F; much smaller yields were obtained using KF and RbF. Not all organic molecules gave high yields of the hydrate; dimethyl sulfoxide, formamide, and hydrazine worked well but N-methyl formamide did not. The reaction between clay and salt resulted in the replacement of some hydroxyls by fluoride. This replacement was rapid; after 1 min of fluoride treatment a substantial yield of hydrate was obtained. The intercalation step separated the layers and also disordered the kaolinite, facilitating the F for OH replacement at or near crystallite edges. This replacement weakens the interlayer bonding at the edges and thereby reduces the possibility of layer collapse and attendant dehydration.

Smectites are one of the most important groups of phyllosilicates found in soils and sediments, and certainly one of the most difficult to study. New information about the formation mechanisms, impact of structural features on surface properties, and long-term stability of smectites can best be gained from the systematic study of single-phase specimens. In most instances, these specimens can only be obtained through synthesis under controlled conditions. Syntheses of smectites have been attempted (1) at ambient pressure and low-temperature (<100°C), (2) under moderate hydrothermal conditions (100–1000°C, pressures to several kbars), (3) under extreme hydrothermal conditions (>1000°C or pressures >10 kbars), and (4) in the presence of fluoride. Of these approaches, syntheses performed under moderate hydrothermal conditions are the most numerous and the most successful in terms of smectite yield and phase-purity. Using hydrothermal techniques, high phase-purity can be obtained for beidellites and several transition-metal smectites. However, synthesis of montmorillonite in high purity remains difficult. Starting materials for hydrothermal syntheses include gels, glasses, and other aluminosilicate minerals. The presence of Mg2+ seems to be essential for the formation of smectites, even for phases such as montmorillonite which contain low amounts of Mg. Highly crystalline smectites can be obtained when extreme temperatures or pressures are used, but other crystalline impurities are always present. Although the correlation between synthesis stability fields and thermodynamic stability fields is good in many instances, metastable phases are often formed. Few studies, however, include the additional experiments (approach from under-and over-saturation, reversal experiments) needed to ascertain the conditions for formation of thermody-namically stable phases. Thorough characterization of synthetic products by modern instrumental and molecular-scale techniques is also needed to better understand the processes leading to smectite formation.

Using 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, we show that most of the fluoride present in the KGa-lb reference kaolinite from Washington County, Georgia, occurs as a surface-adsorbed species bonded to Al. This surface fluoride can be removed from the <2 µm fraction by acid wash, but is largely retained in the coarse fraction. Correlation of integrated 19F NMR peak intensities with fluoride sorption experiments indicates a bulk F content of ∼144 ppm for KGa-1b, of which ∼30% substitutes for hydroxyl sites in the mineral structure and the remaining 70% occurs adsorbed on particle surfaces, corresponding to an edge surface fluoride density of ∼0.7 F− nm−2. 19F{27Al} TRAPDOR (TRAnsfer of Populations in DOuble Resonance) NMR data for the original kaolinite and for products of F− sorption experiments at pH 4 show that all of the observed 19F signals arise from fluoride bonded to Al atoms. Furthermore, bridging Al-F-Al sites and terminal Al-F give distinctly different TRAPDOR fractions allowing assignment of resolved peaks based on the number of Al in the first coordination sphere. This result was confirmed for fluoride adsorbed to the surface of gibbsite from aqueous suspension. No evidence was found for Si-F-type environments on the kaolinite surfaces.

Limited knowledge is available on total fluoride exposure, excretion and retention in infants, despite the first year of human life being the critical period for dental development and risk of dental fluorosis. This study investigated total daily fluoride intake (TDFI), excretion (TDFE) and retention (TDFR) in infants living in fluoridated and non-fluoridated water areas at pre- and post-weaning stages of development. Healthy infants, aged 0–12 months, were recruited and their TDFI (mg/kg body weight (BW) per d), from diet and toothpaste ingestion, was assessed over a 3-d period using a dietary diary and tooth-brushing questionnaire. TDFE (mg/kg BW per d) was estimated by collecting 48-h urine and faeces. TDFR (mg/kg BW per d) was estimated by subtracting TDFE from TDFI. A total of forty-seven infants completed the study: sixteen at pre-weaning and thirty-one at post-weaning stages, with a mean age of 3·4 and 10·0 months, respectively. TDFI was lower in the non-fluoridated area (P<0·001) and at the pre-weaning stage (P=0·002) but higher in formula-fed infants (P<0·001). TDFE was mainly affected by type of feeding, with higher excretion in formula-fed infants (P<0·001). TDFR was lower in the non-fluoridated area (P<0·001) and at the pre-weaning stage (P<0·001) but higher in formula-fed infants (P=0·001). In conclusion, a relatively large proportion of fluoride intake is retained in the body in weaned infants. This is an important consideration in fluoride-based prevention programmes, with goals to maximise caries prevention while minimising the risk of dental fluorosis.

The new mineral oskarssonite (IMA2012-088), with ideal formula AlF3, was found in August 2009 at the surface of fumaroles on the Eldfell volcano, Heimaey Island, Iceland (GPS coordinates 63°25′58.9″N 20°14′50.3″W). It occurs as sub-micron-sized crystals forming a white powder in association with anhydrite, bassanite, gypsum, jarosite, anatase, hematite, opal, ralstonite, jakobssonite and meniaylovite. Chemical analyses by energy-dispersive spectrometry with a scanning electronmicroscope produced the following mean elemental composition: Al, 31.70; F, 58.41; O, 9.22; total 99.33 wt.%. The empirical chemical formula is AlF2.6(OH)0.5 which suggests partial substitution of F by OH. Oskarssonite is rhombohedral, space group Rc, with ah = 4.9817(4) Å, c = 12.387(1) Å, Vuc = 266.23(5) Å3, Z = 6. The five strongest lines in the powder diffraction diagram [d in Å(I) (hkl)] are as follows: 3.54 (100) (012), 2.131 (13) (113), 1.771 (20) (024), 1.59 (15) (116), 1.574 (10) (122). Rietveld refinement confirms the identity of oskarssonite with the synthetic rhombohedral form of AlF3. Its structure can be described as a rhombohedral deformation of the idealized cubic perovskitetype octahedral framework of corner-sharing AlF6 groups. Oskarssonite appears in the surface part of the fumaroles where fluorides are abundant. At greater depths (below 10 cm) sulfates dominate among the fumarolic minerals. In accordance with its occurrence, we surmise that oskarssonite forms in the later stages of the fumarolic activity in an environment poor in alkalies and Mg. Ralstonite (NaxMgxAl1−xF3(H2O)y), which, unlike oskarssonite, contains Na and Mg as important constituents, dominated in the first-formed fumaroles, but now, 41 years after the eruption of Eldfell, is only a minor phase. The new mineral is named after the Icelandic volcanologist Niels Oskarsson.

The new mineral jakobssonite, ideally CaAlF5, was first found in crusts collected in 1988 from a fumarole on the Eldfell volcano, Heimaey Island, Iceland. It was subsequently found in similar crusts collected in 1991 from a fumarole on the Hekla volcano, Iceland. It is associated with leonardsenite (IMA2011-059), ralstonite, heklaite, anhydrite, gypsum, jarosite, hematite, opal and several fluoride minerals that have not been fully characterized. Jakobssonite occurs as soft white fragile crusts of acicular crystals <50 μm long. Its calculated density is 2.89 g cm–3. Chemical analyses by energy-dispersive spectrometry on a scanning electron microscope produced a mean elemental composition as follows: Ca, 18.99; Al, 18.55; Mg, 1.33; Na, 0.33; F, 50.20; O, 10.39; total 99.79 wt.%. The empirical chemical formula, calculated on the basis of 7 atoms per formula unit with all of the oxygen as OH, is (Ca0.73Mg0.09Na0.02)Σ0.84Al1.06F4.09(OH)1.01. Jakobssonite is monoclinic, space group C2/c, with a = 8.601(1), b = 6.2903(6), c = 7.2190(7) Å, β = 114.61(1)o, V = 355.09(8) Å3and Z = 4. The crystal structure contains chains of [AlF6] octahedra which run parallel to the c axis. These chains are interconnected by chains of [CaF7] pentagonal bipyramids. Jakobssonite is isostructural with several other CaMIIIF5 compounds. The eight strongest lines in the powder diffraction diagram [d in Å (I) (hkl)] are as follows: 4.91 (18) (110), 3.92 (76) (200), 3.15 (68) (020), 3.13 (100) (1), 2.27 (22) (2), 1.957 (21) (400), 1.814 (20) (1), 1.805 (22) (20). The chemical and crystal-structure analyses of jakobssonite are similar to synthetic CaAlF5 with minor substitutions of light elements (e.g. Na) or vacancies for Ca, and OH for F.

Arsenic and fluoride in groundwater from Quaternary loess deposits in Argentina pose major health concerns. Common sources for arsenic and fluoride have been suggested but the processes of mobilization are disputed, and distributions in groundwater are largely unresolved at a sample density >1/50 km2. At Los Pereyras in Tucumán Province, northern Argentina, we have evaluated distributions and hydrochemical associations of arsenic and fluoride with a sample density of 0.75 per km2 over an area of 75 km2, to a depth of 230 m. Groundwater in the loess is oxic and alkaline. Fluoride is restricted to the upper 20 m of the Quaternary loess, where it reaches 8.3 mg/1. Arsenic has a vertical layering consistent with that of fluoride, ranging from 20 to 760 μg/1 in the upper 20 m and 58—163 μg/l below this. There are two sources of arsenic, one unrelated to the fluoride source. Positive correlations between arsenic and fluoride with pH, but not with alkalinity, support desorption from iron oxyhydroxides as the likely mechanism of release to groundwater for arsenic and fluoride, rather than the weathering of silicate minerals. Stratigraphic and/or palaeohydrological controls may explain the observed depth distributions within the loess aquifer.

Moraskoite, a new natural phosphate of composition Na2Mg(PO4)F, has been found in the Morasko IAB-MG iron meteorite. The new phosphate occurs in a graphite-troilite inclusion enclosed in a kamacite-taenite matrix. Associated minerals in the inclusions are chlorapatite, buchwaldite, brianite, merrillite, a new phosphate phase of composition Na4MgCa3(PO4)4, chromite, enstatite (bronzite), kosmochlor, kosmochlor–augite, olivine, albite, orthoclase, quartz, cohenite, schreibersite, nickelphosphide, altaite, pyrrhotite, sphalerite, daubreelite, djerfischerite, whitlockite and native Cu. The inclusions are rimmed by a schreibersite-cohenite halo. Moraskoite forms aggregates up to 1.5 mm in size, with individual grains 20–300 μm across. It is colourless and transparent, with a white streak and vitreous lustre; fluorescence is weak blue in ultraviolet radiation (254 and 360 nm); hardness is 4–5; it has irregular, conchoidal fracture and cleavage is rarely observed. Calculated density (using the empirical formula) is 2.925 g cm–3. The moraskoite structure (Pbcn, a = 5.2117(10), b = 13.711(3), c = 11.665(2) Å, V = 833.6(3) Å3 and Z = 8) is similar to that of its synthetic analogue. The strongest diffraction lines of the moraskoite powder diffraction pattern are as follows (dhkl, I): 3.909(75), 3.382(52), 2.955(90), 2.606(100), 2.571(96), 2.545(68), 1.691 (67). In the Raman spectrum, the following characteristic bands are distinguished (cm–1, strong bands bold): 1114, 1027, 962, 589, 438, 336, 308, 279, 262, 244, 193, 184, 147 and 131. The Raman data prove the absence of H2O and CO2. Moraskoite is interpreted as being a primary phosphate, which crystallized together with graphite, troilite and other accessories inside the nodule.

The 3-d food diary method (3-d FD) or the 2-d duplicate plate (2-d DP) method have been used to measure dietary fluoride (F) intake by many studies. This study aimed to compare daily dietary F intake (DDFI) estimated by the 3-d FD and 2-d DP methods at group and individual levels. Dietary data for sixty-one healthy children aged 4–6 years were collected using 3-d FD and 2-d DP methods with a 1-week gap between each collection. Food diary data were analysed for F using the Weighed Intake Analysis Software Package, whereas duplicate diets were analysed by an acid diffusion method using an F ion-selective electrode. Paired t test and linear regression were used to compare dietary data at the group and individual levels, respectively. At the group level, mean DDFI was 0·025 (sd 0·016) and 0·028 (sd 0·013) mg/kg body weight (bw) per d estimated by 3-d FD and 2-d DP, respectively. No statistically significant difference (P=0·10) was observed in estimated DDFI by each method at the group level. At an individual level, the agreement in estimating F intake (mg/kg bw per d) using the 3-d FD method compared with the 2-d DP method was within ±0·011 (95 % CI 0·009, 0·013) mg/kg bw per d. At the group level, DDFI data obtained by either the 2-d DP method or the 3-d FD method can be replaced. At an individual level, the typical error and the narrow margin between optimal and excessive F intake suggested that the DDFI data obtained by one method cannot replace the dietary data estimated from the other method.

Remineralization of hard dental tissues is thought to be a tool that could close the gap between prevention and surgical procedures in clinical dentistry. The purpose of this study was to examine the remineralizing potential of different toothpaste formulations: toothpastes containing bioactive glass, hydroxyapatite, or strontium acetate with fluoride, when applied to demineralized enamel. Results obtained by scanning electron microscopy (SEM) and SEM/energy dispersive X-ray analyses proved that the hydroxyapatite and bioactive glass-containing toothpastes were highly efficient in promoting enamel remineralization by formation of deposits and a protective layer on the surface of the demineralized enamel, whereas the toothpaste containing 8% strontium acetate and 1040 ppm fluoride as NaF had little, if any, remineralization potential. In conclusion, the treatment of demineralized teeth with toothpastes containing hydroxyapatite or bioactive glass resulted in repair of the damaged tissue.

F is an important trace element for bones and teeth. The protective effect of F against dental caries is well established. Urine is the prime vehicle for the excretion of F from the body; however, the relationship between F intake and excretion is complex: the derived fractional urinary F excretion (FUFE) aids understanding of this in different age groups. The present study aimed to investigate the relationships between (1) total daily F intake (TDFI) and daily urinary F excretion (DUFE), and (2) TDFI and FUFE in 6–7-year-olds, recruited in low-F and naturally fluoridated (natural-F) areas in north-east England. TDFI from diet and toothbrushing and DUFE were assessed through F analysis of duplicate dietary plate, toothbrushing expectorate and urine samples using a F-ion-selective electrode. FUFE was calculated as the ratio between DUFE and TDFI. Pearson's correlation and regression analysis were used to investigate the relationship between TDFI and FUFE. A group of thirty-three children completed the study; twenty-one receiving low-F water (0·30 mg F/l) and twelve receiving natural-F water (1·06 mg F/l) at school. The mean TDFI was 0·076 (sd 0·038) and 0·038 (sd 0·027) mg/kg per d for the natural-F and low-F groups, respectively. The mean DUFE was 0·017 (sd 0·007) and 0·012 (sd 0·006) mg/kg per d for the natural-F and low-F groups, respectively. FUFE was lower in the natural-F group (30 %) compared with the low-F group (40 %). Pearson's correlation coefficient for (1) TDFI and DUFE was +0·22 (P= 0·22) and for (2) TDFI and FUFE was − 0·63 (P< 0·001). In conclusion, there was no correlation between TDFI and DUFE. However, there was a statistically significant negative correlation between FUFE and TDFI.

High concentrations of fluoride (F) in powdered milk (formula milk) can have adverse health effects on the body. The F concentration in powdered milk was analysed in Iran in 2010. A total of twelve commercial brands of highly consumed powdered milk were selected to analyse the F content through the standard F ion-selective electrode method. From each brand, three samples with different production dates were selected. The means and standard deviation for F concentration in all the samples was 1·73 (sd 0·3) μg F/g. The minimum and maximum F content in powdered milk brands Humana2 and Humana3 was 1·32 (sd 0·1) and 2·36 (sd 0·3) μg F/g, respectively. The study revealed that there was no significant difference in F concentration in the samples that belonged to various dates. Humana3 had a high F concentration (with an average of 2·36 (sd 0·3) μg F/g), which can be a risk factor for increased dental fluorosis, especially when being prepared using water with a high content of F.

Previous papers in this series noted a positive association between aluminum water concentrations and a measure of mental impairment, and a negative association between fluoride concentrations and the same measure of mental impairment. The results obtained were qualitatively similar to the corresponding associations obtained from death certificate data that list Alzheimer's disease as the underlying cause of death. In addition, the results were also qualitatively similar to the results obtained in a number of other studies carried out at different times, in different areas and using different outcome measures for the measure of mental impairment. The present study concerns the role of iron concentrations and specifically, whether when taking iron concentrations into account, the previously noted associations involving aluminum are maintained. The results show that this seems to be the case and also suggest that iron can compete with aluminum, and can both increase or decrease the likelihood of showing signs of mental impairment. The results do not indicate consistently that by modifying the methods of water purification, using iron instead of aluminum, the treated water will be less biotoxic, although there could be instances, particularly when the aluminum concentrations are relatively high, when the use of iron compounds is beneficial.

Using data from the Ontario Longitudinal Study of Aging (LSA) and data for aluminum and fluoride water concentration in areas where the LSA subjects resided, a preliminary analysis suggests that persons who show no indications of impaired mental functioning are more likely to have resided in areas where the aluminum concentrations (in drinking water) are relatively low and where fluoride concentrations (in drinking water) are relatively high. The difficulties in analyses of this type include the likelihood that many persons who are affected by impaired mental functioning do not respond to surveys, the identification of impaired mental functioning, and obtaining good exposure estimates of fluoride and aluminum drinking water concentrations.

Previous studies in this series of papers investigated the associations between aluminum (Al) water concentrations and relatively high risks of a measure of mental impairment and also various possible other drinking water characteristics, particularly pH, turbidity, fluoride and silica. The results were based on one measure of mental impairment, which would not be expected to give the same results as the more definitive endpoint (outcome variable) of a record of Alzheimer's Disease (AD) as the underlying cause of death on a death certificate. The present paper therefore investigates the relevant associations, based both on the measure of mental impairment and on death certificates in which AD and presenile dementia are listed as the underlying causes of death. As expected, the associations were not identical, but they were similar. More specifically, Al water concentrations were strongly associated with the recording of AD on death certificates, as were pH, fluoride, and silica concentrations. The implications of these results are discussed, and it is suggested that the evidence is sufficiently strong for methods of water purification to be modified, at least on a trial basis, because of the likelihood that this will reduce the incidence of AD.

Previous papers reported on the associations between water quality and a measure of cognitive impairment, based on data of the Ontario Longitudinal Study of Aging (LSA). The present report summarizes the information on fluoride (F) and aluminum (Al) and provides additional information on the effects of pH. Specifically, our preliminary results suggest that a neutral pH, relatively low Al and relatively high F concentrations in drinking water decrease the odds of showing indications of cognitive impairment by a factor of about five, compared with other types of drinking water. The relevant chemical reaction is ascribed to an equilibrium involving Al complexes.