Excessive Amounts Of Fluoride Research Articles

A new probabilistic assessment process for human health risk (HHR) in groundwater with extensive fluoride and nitrate optimized by non parametric estimation method.

Excessive amounts of fluoride (F-) and nitrate (NO3-) in groundwater pose a significant threat to human health. However, a quantitative approach to assessing the human health risks caused by these harmful substances is lacking. To optimize the probabilistic assessment process for human health risk (HHR), this study introduced kernel density estimation (KDE) into the stochastic simulation of F- and NO3- content in groundwater samples. The potential HHRs caused by F- and NO3- in Songyuan City were summarized by combining the probabilistic and deterministic assessments. This study found that the concentrations of F- and NO3- did not follow common probability density functions (PDFs), but the KDE method passed the Kolmogorov-Smirnov test with the critical value of 0.067 and 0.062, showing high fitting accuracy. Monte Carlo simulation indicated that the probability of NO3- for children and adult exceeding the standard is 21.95% and 15.14%, respectively, which is comparable with the results of the deterministic assessment, but the probabilistic assessment emphasized lower probability of HHRs in children caused by excess F-(4.14%). Global sensitivity analysis revealed that excessive NO3- in groundwater has the highest sensitivity of the HHR (>0.1), followed by other factors representing water use habits (>0.01). This study presents a refined probabilistic assessment method for HHR and provides a scientific reference for understanding the state of groundwater environments.

REMOVAL OF FLUORIDE FROM DRINKING WATER THROUGH LOW-COST TECHNIQUES

Fluoride ions (F-) from natural sources or industrial wastewater are the main cause of many pathological conditions in people living in more than 25 countries. Thus, removing F- from drinking water is pivotal for preventing serious health consequences. The WHO recommends a limit of 1,5 mg/L for fluoride in drinking. Excessive amounts of fluoride in drinking water are prevalent in Pakistan, leading to related health risks. Low-cost techniques for the defluoridation of drinking water can be used. In this study, the removal of fluoride from drinking water by an adsorption method using low-cost materials/adsorbents, such as marble chips, wheat husks, rice husks, egg shells, concrete, fuller earth, fly ash, freshly fired bricks, and charcoal, at different contact times and different bed thicknesses were investigated. A batch sampling technique was used for sample collection. On average, marble chips, wheat husks, rice husks, egg shells, concrete, fuller earth, fly ash, freshly fired bricks, and activated charcoal (rice husk) resulted in 71,99 %; 90,99 %; 66,73 %; 90,99 %; 63,30 %; 71,99 %; 22,60 %; 49,67 %; and 90,13 % fluoride removal, respectively. Therefore, defluoridation using these materials is desirable. The performance of adsorbents depends on parameters such as contact time, depth of the adsorbent media, and pH. The bed thickness of the adsorbent has a minor effect on fluoride removal. The major contributors to fluoride removal from water are contact time and adsorbent composition.

High-efficiency N-doped activated carbon-based defluoridation adsorbent prepared from itaconic acid fermentation waste liquid

Excessive amounts of fluoride in water cause irreversible harm to people and seriously threaten human health.

Utilization of Community-Level Fluoride-Filtered Water and its Associated Factors in Dugda Woreda of East Shewa Zone, Oromia Region, Ethiopia.

Background:Long-term consumption of water containing an excessive amount of fluoride causes dental and skeletal fluorosis. De-fluoridation options differ in terms of scale, efficacy, long-term viability, and user acceptance. Therefore, this study aimed to identify the challenges of using fluoride-filtered water and its associated factors among households.Methods:A cross-sectional study was conducted from April to May, 2018 among 405 randomly selected households in Dugda Woreda of Ethiopia Rift Valley East Shewa Zone, Oromia Region. A structured interviewer-administered questionnaire was used to collect the data. SPSS version 20 was used to enter and analyze the collected data. Logistic regression analysis was used to identify association between dependent and independent factors and explained by odds ratio with 95%CI.Results:A total of 228 (56.3%) households were found to utilize fluoride filtered water from community water supply schemes for drinking and cooking purposes. No family history of fluorosis (AOR = 44.4, 95%CI: 18.8, 104.74), monthly income of less than 1000 ETB (AOR = 0.03, 95%CI: 0.004, 0.23), good knowledge of community fluoride filter schemes (AOR = 5.93, 95%CI: 1.30, 26.9), and not afford to pay bill of ⩾0.50 ETB [AOR = 0.4, 95%CI: 0.20, 0.91] were factors significantly associated with utilization of community-level fluoride-filtered water.Conclusion:In this study, more than half of the households used fluoride filtered water. Family monthly income, affordability, presence of family members with the history of fluoride exposure, and knowledge about community fluoride filter schemes were factors significantly associated with utilization of community-level fluoride-filtered water.

Overview of fluoride removal from water using separation techniques

Fluoride contamination due to natural and anthropogenic activities has become the biggest threat to human health worldwide. Geological and anthropogenic factors are responsible for contaminating groundwater with fluoride. Excess amounts of fluoride in potable water may cause irreversible demineralization of bone and tooth tissues, a condition called fluorosis, and long-term damage to the brain, liver, thyroid, and kidney. For a long time there has been a need for fluoride removal from potable water to make it safe for human use. The present paper reviews the different methods used for defluoridation, for example, coagulation–precipitation, ion exchange, membrane separation, and adsorption. Among the methods, membrane and ion exchange are not regularly used in India due to their cost and high maintenance. On the other hand, coagulation–precipitation and adsorption are mostly used in India. Nalgonda method is used in developing nations like Kenya, Senegal, Tanzania, and India for fluoride removal. Comparatively, adsorption is broadly used for defluoridation because of its low cost and high efficiency in removal. This paper also discusses the merits and demerits of the methods. It is evident from literature study that different methods show unique potential for defluoridation. The most promising adsorbents tested so far from each category of adsorbents are also highlighted. In any circumstance, there is an urgent requirement to find the practical utility of such developed methods on a business scale and to initiate a change in contamination control. • Different methods for water defluoridation have been thoroughly discussed. • Nalgonda method used in several countries has been thoroughly discussed for fluoride removal. • The merits and demerits of the defluoridazation methods are discussed. • Adsorption is most preferred separation process for defluoridation because of its low cost and high efficiency.

Fluoride contributes to the shaping of microbial community in high fluoride groundwater in Qiji County, Yuncheng City, China

As a toxic element, excessive amounts of fluoride in environment can be harmful because of its antimicrobial activity, however little is known about the relationship between fluoride and the bacterial community in groundwater systems. Here, we use samples from a typical fluorosis area to test the hypothesis that fluoride concentration is a fundamental structuring factor for bacterial communities in groundwater. Thirteen groundwater samples were collected; high-throughput 16S rRNA gene sequencing and statistical analysis were conducted to compare the bacterial community composition in individual wells. The results showed that Proteobacteria, with most relative abundance in groundwater, decreased along the groundwater fluoride concentration. Additionally, relative abundances of 12 families were also statistically correlated with fluoride concentration. The bacterial community was significantly explained by TOC (P = 0.045) and fluoride concentration (P = 0.007) of groundwater. This suggests that fluoride and TOC likely plays an important role in shaping the microbial community structure in these groundwater systems. Our research suggest that fluoride concentration should be taken into consideration in future when evaluating microbial response to environmental conditions in groundwater system, especially for fluoride rich groundwater.

Synthesis and Study of an Efficient Metal-Organic Framework Adsorbent (MIL-96(Al)) for Fluoride Removal from Water

Long-term consumption of drinking water that contains excessive amounts of fluoride can endanger human health; therefore, the preparation and application of a high-efficiency defluorination adsorbent for advanced purification of drinking water are of significant interest. This study presents a metal-organic framework adsorbent (MIL-96(Al)) with the granular structure of rice, which was generated by hydrothermal reaction. The specific surface area of MIL-96(Al) was ~220 m2 g-1, and it showed a good thermal stability. Several experiments were conducted wherein conditions, including adsorbent dosage, initial concentration, pH, and coexisting anions, were varied to understand the defluorination performance of the material. Results showed that pH (6–9) and coexisting anions had little effect on the removal efficiency of fluoride. The adsorption isotherm can be described by the Langmuir model, and the theoretical fluoride adsorption capacity of MIL-96(Al) was up to 42.19 mg Fg-1 at 298 K, which is much higher than that of the commonly used activated alumina. The adsorption process of fluoride is endothermic and follows pseudo second-order kinetics. In addition, MIL-96(Al) was shown to still achieve ~61.8% of the adsorption capacity after seven regenerations. This study shows that MIL-96(Al) is a good application prospect and could be widely used to remove fluoride from water.

Diverse mechanisms drive fluoride enrichment in groundwater in two neighboring sites in northern China

Excessive amounts of fluoride in drinking groundwater are harmful to human health, but the mechanisms responsible for fluoride enrichment in groundwater are not fully understood. Samples from two neighboring areas with endemic fluorosis were collected to test the hypothesis that there are distinctly different mechanisms responsible for the enrichment of fluoride in these groundwater. Hydrochemistry, stable isotopes and geochemical simulation were conducted together to investigate the fluoride spatial distribution and the diversity of responsible mechanisms. Our results showed that the spatial distributions of fluoride are different: I) high [F] in fresh shallow groundwater (SGQJ) and II) medium [F] in fresh to brackish deep groundwater (DGQJ) in the Qiji area; and III) medium [F] in brackish shallow groundwater (SGYH) and IV) low [F] in fresh deep groundwater (DGYH) in the Yanhu area. We also found that the fluoride concentration in groundwater is primarily controlled by the dissolution equilibrium of fluorite, as suggested by the correlation between [F] and [Ca]. However, there are other significant mechanisms: 1) for SGQJ, fluoride-bearing minerals (such as fluorite) dissolution, along with moderate evaporation, cation exchange and the more alkaline conditions are the driving factors; 2) for SGYH, the contributing factors are strong evaporation, the salt effect, dissolution of evaporites, gypsum and dolomite, bicarbonate-fluoride competition and anthropogenic activity; 3) for DGQJ, cation exchange, alkaline conditions and competitive adsorption are major factors; and 4) dolomite dissolution promotes the [F] increase in DGYH. Our findings suggest that the hydrogeochemical conditions play key roles in the enrichment of fluoride and that caution should be taken in the future when evaluating fluoride occurrence in groundwater, even in nearby areas.

Effect of fluoride on the cell viability, cell organelle potential, and photosynthetic capacity of freshwater and soil algae

Although fluoride occurs naturally in the environment, excessive amounts of fluoride in freshwater and terrestrial ecosystems can be harmful. We evaluated the toxicity of fluoride compounds on the growth, viability, and photosynthetic capacity of freshwater (Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata) and terrestrial (Chlorococcum infusionum) algae. To measure algal growth inhibition, a flow cytometric method was adopted (i.e., cell size, granularity, and auto-fluorescence measurements), and algal yield was calculated to assess cell viability. Rhodamine123 and fluorescein diacetate were used to evaluate mitochondrial membrane potential (MMA, ΔΨm) and cell permeability. Nine parameters related to the photosynthetic capacity of algae were also evaluated. The results indicated that high concentrations of fluoride compounds affected cell viability, cell organelle potential, and photosynthetic functions. The cell viability measurements of the three algal species decreased, but apoptosis was only observed in C. infusionum. The MMA (ΔΨm) of cells exposed to fluoride varied among species, and the cell permeability of the three species generally decreased. The decrease in the photosynthetic activity of algae may be attributable to the combination of fluoride ions (F−) with magnesium ions (Mg2+) in chlorophyll. Our results therefore provide strong evidence for the potential risks of fluoride compounds to microflora and microfauna in freshwater and terrestrial ecosystems.

Effects of Fluoride on the Expression of Beclin1 and mTOR in Ameloblasts

Exposure to high levels of fluoride (F^-) can result in dental fluorosis in different individuals, but the mechanism of dental fluorosis remains unclear. Autophagy is a highly conserved intracellular digestion process that degrades damaged organelles and protein aggregates. This study examined the effect of sodium fluoride (NaF) on the expression of Beclin1 and mTOR to elucidate the development mechanisms of dental fluorosis. HAT-7 cells were incubated with various concentrations of NaF, and autophagic vacuoles were studied by transmission electron microscopy. At both mRNA and protein level, expression of Beclin1, which is required for autophagosome formation and decreases the expression of mTOR, an autophagy-related complex, was increased at 1.2 mmol/l NaF compared to baseline (0 mmol/l NaF). Additionally, immunohistochemical analysis was performed on paraffin-embedded rat incisor sections to identify the expression of Beclin1 and mTOR proteins in vitro. Highly significant differences were detected compared to controls. In summary, our results demonstrate unequivocally that excessive amounts of fluoride cause autophagy of HAT-7 cells, indicating that autophagy is involved in dental fluorosis.

Analysis of the Role of Insulin Signaling in Bone Turnover Induced by Fluoride.

The role of insulin signaling on the mechanism underlying fluoride induced osteopathology was studied. We analyzed the expression of genes related with bone turnover and insulin signaling in rats treated by varying dose of fluoride with or without streptozotocin (STZ) in vivo. Furthermore, insulin receptor (InR) expression in MC3T3-E1 cells (pre-osteoblast cell line) was interfered with small interfering RNA (siRNA), and genes related with osteoblastic and osteoclastic differentiation were investigated in cells exposed to fluoride in vitro for 2days. The in vivo study indicated the possible role of insulin in bone lesion induced by excessive amount of fluoride. Fluoride activated the InR and Insulin-like growth factor 1 (IGF1) signaling, which were involved in the mechanism underlying fluoride induced bone turnover. The TGFβ1 and Wnt10/β-catenin pathway took part in the mechanism of bone lesion induced by fluoride, and insulin probably modulated the TGFβ1 and β-catenin to exert action on bone turnover during the development of bone lesion. The in vitro study showed the concomitant decrease of OPG, osterix and OCN with inhibition of InR expression in osteoblast, and three genes still was low in cells co-treated with fluoride and InR siRNA, which suggested that fluoride probably stimulated the expression of OPG, osterix and OCN through InR signaling. In conclusion, insulin played the important role in bone lesion induced by excessive amount of fluoride through mediating InR receptor signaling, and IGF1 signaling probably exerted action on bone turnover caused by overdose of fluoride.

Influence of chronic fluorosis on the expression of mitochondrial fission protein dynamin-related 1 in the cortical neurons of rats

To explore the changes of protein expression of mitochondrial fission gene dynamin-related 1(Drp 1) in the cortical neurons of rats with chronic fluorosis. A total of 120 one-month-old SD rats (each weighing approximately 100-120 g at the beginning of the experiment) were randomly divided into three groups, and fed with the different doses of fluoride containing in drinking water (untreated control containing 0 mg/L fluoride, and low-fluoride & high-fluoride supplemented with 10 and 50 mg/L fluoride,respectively). After 3 or 6 months exposure, 20 rats from each group were killed. Then the protein expression of mitochondrial fission gene, Drp1, was detected by immunohistochemistry and western-blotting method. Dental fluorosis and urinary fluorosis were obviously found in the rats exposed to fluoride. At the experiment period of 3 months, the numbers of positive cells of Drp1 detected by immunohistochemistry changed. Compared with the control group (36.3 ± 5.8), the changes in low-fluoride group (34.7 ± 4.1) showed no significant difference (t = 1.5, P > 0.05),but the increase in high-fluoride group (45.0 ± 4.7) had statistical significance (t = 8.8, P < 0.05). The western-blotting method had consistent results. Compared with the control group (0.59 ± 0.03), a significant increase of the average topical density in low- fluoride (0.62 ± 0.03) and high-fluoride (0.71 ± 0.02) groups were found (t = 0.02,0.11, P < 0.05). At the experiment period of 6 months, the numbers of positive cells of Drp1 detected by immunohistochemistry significantly changed. Compared with the control group (33.2 ± 4.4), the number in low- fluoride and high-fluoride groups were separately (36.6 ± 3.8) and (39.4 ± 4.2),both increased significantly (t = 3.5,6.3, P < 0.05). Same results could be found in western-blotting method,compared with the control group (0.65 ± 0.06), the average topical density in low- fluoride (0.80 ± 0.09) and high-fluoride (0.76 ± 0.08) groups both increased significantly (t = 0.1,0.1, P < 0.05). Taking excessive amount of fluoride might result in the changes of expression of Drp1, and the neurons damage from the chronic fluorosis might be associated with the hyperfunction of mitochondrial fusion.

Changed expression of mito-fusion 1 and mitochondrial fragmentation in the cortical neurons of rats with chronic fluorosis

To observe the mitochondrial fragmentation and the expression of mito-fusion 1 gene in the cortical neurons of rats with chronic fluorosis, and to reveal their roles in mitochondria damage to neurons due to chronic fluorosis. SD rats were divided randomly into three groups of 20 each (a half females and a half males housed individually in stainless-steel cages), and fed with the different doses of fluoride containing in drinking water (untreated control containing 0 mg/L fluoride, and low-fluoride and high supplemented with 10 and 50 mg/L fluoride, respectively). After 3 or 6 months exposure, the mitochondrial morphology of the neurons in rat brains were observed by transmission electron microscopy (TEM), then the expression of mitochondrial fusion gene, Mfn1, were detected by immunohistochemistry and western-blotting, respectively. Dental fluorosis was obvious in the rats exposed to excessive fluoride in their drinking water, that is, (16 rats out of 20) numbers of I° detal fluorosis in the low-fluoride group, and (11 rats out of 20) numbers of I° and (9 rats out of 20) numbers of II° detal fluorosis in the high-fluoride group were observed after 3 months exposure. Moreover, (14 rats out of 20) numbers of I° and (6 rats out of 20) numbers of II° detal fluorosis in the low-fluoride group and (6 rats out of 20) numbers of Io, (13 rats out of 20) numbers of II°, and (1 rats out of 20) numbers of III° detal fluorosis in the high-fluoride group were observed after 6 months exposure. And both of untreated controls without detal fluorosis were also observed. The urinary level of fluoride in the low-fluoride group (3.30 ± 1.18) mg/L and in the high-fluoride group (5.10 ± 0.35) were observed after 3 months exposure (F = 3.18, P < 0.05). Moreover, the urinary level of fluoride in the low-fluoride group (4.16 ± 1.39) mg/L and in the high-fluoride group (5.70 ± 1.70) mg/L were also observed after 6 months exposure (F = 3.17, P < 0.05). The normal mitochondrial morphology of neurons in rats without fluorosis was observed after 3 and 6 months, while the abnormal mitochondrial morphology of neurons with fluorosis was shown, presenting mitochondrial fragmentation with swollen cristae and even the fragmented, shortened or stacked punctuate membranes (section observation of three bullous mitochondrial-mitochondrial fission process) by TEM. As compared with controls (53.0 ± 4.54 and 1.21 ± 0.18) at the experiment period of 3 months, Mif1 protein analysis with immunocytochemical (the numbers of positive cells: 51.09 ± 6.25) and western-blotting (1.22 ± 0.26) were no significant difference for low fluoride group (t = 1.7, 1.1, P > 0.05); Mif1 protein analysis with immunocytochemical (the numbers of positive cells: 59.71 ± 5.64) and western-blotting (1.66 ± 0.20) were significantly increasing for high fluoride group (t = 2.1, 2.1, P < 0.05). As compared with controls (36.43 ± 4.04 and 1.00 ± 0.13) at the experiment period of 6 months, Mif1 protein analysis with immunocytochemical (the numbers of positive cells 20.05 ± 4.55 and 17.10 ± 3.86) and western-blotting (0.64 ± 0.08 and 0.39 ± 0.06) were significantly decreasing for the two fluoride group (t = 2.1, 2.2; 2.2, 2.2 respectively, all P value were < 0.05). Taking excessive amount of fluoride might result in the mitochondrial fragmentation for the changed expression of Mfn1, and the neurons damage from the chronic fluorosis might be associated with the dysfunction of mitochondrial fusion.

Excessive fluoride induces endoplasmic reticulum stress and interferes enamel proteinases secretion

Protein retention in the enamel layer during tooth formation is well known to be associated with dental fluorosis but the underlying mechanism is unclear. The functions of the endoplasmic reticulum (ER) correlate directly with secreted protein metabolism. We used an ameloblast-derived cell line to determine whether excessive amounts of fluoride cause ER stress, and whether this interferes with the secretion of enamel matrix proteinases. ER stress activates a signaling network called the unfolded protein response (UPR). Here, we used real-time RT-PCR and immunofluorescence to study the effect of fluoride on the expression, translation, and secretion of UPR transcription factors in ameloblast-like cells. Measurement of both the gene and protein expression of UPR transcription factors indicated that high-dose fluoride increases the expression of UPR transcription factors in a dose-dependent manner. We also used ELISA to detect and quantify the enamel proteinases secreted by ameloblasts. We found a corresponding decrease in extracellular secretion of the enamel proteinases matrix metalloproteinase-20 and kallikrein-4, after exposure to fluoride. Furthermore, correlation analysis indicated that the expression of UPR transcription factors showed a strong inverse correlation with that of enamel proteinases. The results suggest that high-dose fluoride initiates an ER stress response in ameloblasts and induces the UPR, which interferes with the synthesis and secretion of enamel proteinases. Taken together, these results suggest that excessive ingestion of fluoride during tooth formation can decrease the secretion of proteinases, thus causing protein retention in the enamel layer, indicating that the ER stress response may be responsible for dental fluorosis.

Defluoridation in drinking waters

Although water supplies containing excessive amount of fluoride are generally very rare worldwide, there are locations in Turkey where drinking water contains very high fluoride concentrations. Especially in the middle and eastern part of Turkey, some mineral and drinking waters contain very high fluoride concentrations. It is a well known fact that drinking water exceeding the critical fluoride concentration (1 mg F−/L) may cause serious dental and skeletal damages. In this study, various techniques were evaluated to find the most suitable solution for defluoridation for these regions, which have high concentrations of fluoride in their water supplies. For this purpose, various chemical agents including locally produced alumina were investigated. Locally produced alumina gave promising and economically sound results in terms of defluoridation capacity and availability.

Fluoride content of infant formulae in Australia

The prevalence of dental fluorosis in Australia and the United States of America has increased in both optimally fluoridated and non-fluoridated areas. This has been attributed to an increase in the fluoride level of food and beverages through processing with fluoridated water, inadvertent ingestion of fluoride toothpaste, and the inappropriate use of dietary supplements. A major source of fluoride in infancy is considered to be infant formula which has been implicated as a risk factor for fluorosis in a number of studies. In this study the fluoride content of the infant formulae commonly used in Australia was determined. The acid diffusible fluoride of each powdered formula was isolated by microdiffusion and measured using a fluoride ion-specific electrode. The fluoride content of milk-based formulae ranged from 0.23 to 3.71 micrograms F/g and for soy-based formulae from 1.08 to 2.86 micrograms F/g. When reconstituted, according to the manufacturer's directions, with water not containing fluoride, the formulae ranged in fluoride content from 0.031 to 0.532 ppm, with the average fluoride content 0.240 ppm. Using average infant body masses and suggested volumes of formula consumption for infants 1-12 months of age, possible fluoride ingestion per kg body mass was estimated. None of the formulae, if reconstituted using water containing up to 0.1 ppm F, should provide a daily fluoride intake above the suggested threshold for fluorosis of 0.1 mg F/kg body mass. However, if reconstituted with water containing 1.0 ppm F they should all provide a daily fluoride intake of above the suggested threshold for fluorosis with intakes up to 2-3 times the recommended upper 'optimal' limit of 0.07 mg/kg body mass. Under these conditions the water used to reconstitute the formulae would provide 65-97 percent of the fluoride ingested. These figures are likely to be overestimates due to the intake of nutrients from other sources reducing formulae consumption and also due to the lower bioavailability of fluoride from milk-based formulae. Further, it is generally believed that the maturation stage of enamel formation is the critical period for fluorosis development by chronic, above-threshold fluoride exposure. The maturation stage for the anterior permanent teeth, however, is after the first twelve months of life where fluoride intake from infant formula consumption per kg body mass is highest. The level of fluoride in the commonly used Australian formulae would suggest that infant formula consumption alone is unlikely to be a risk factor for dental fluorosis in a non-fluoridated community, but could make a major contribution to an infant's daily fluoride intake. However, prolonged consumption (beyond 12 months of age) of infant formula reconstituted with optimally-fluoridated water could result in excessive amounts of fluoride being ingested during enamel development of the anterior permanent teeth and therefore may be a risk factor for fluorosis of these teeth.

Clinicopathologic features of fluoride toxicosis in cattle.

Cattle normally ingest variable low-level amounts of fluorides with no known adverse effects, but when excessive amounts are ingested, adverse effects are induced. Several sources may contribute to the total fluoride intake. The many recognized factors that influence structural and functional responses of animals to fluorides are cited. Signs and lesions of fluoride toxicosis in cattle have been characterized. Major fluorotic lesions occur in the permanent teeth and in the bones. Dental lesions occur when excessive amounts of fluoride are ingested during the period of tooth formation and calcification. Bone effects can be induced at any time during an animal's life. A table relating structural changes and functional processes in cattle of various ages has been compiled as a guide for diagnosing and evaluating fluoride toxicosis. Recommended fluoride tolerance levels for cattle have been established. Prevention and control of fluoride toxicosis in cattle can be accomplished when the nature of the disease is realized; the symptomatology, lesions and pathogenesis are properly interpreted, correlated and evaluated; and the source(s) of excessive fluorides are eliminated.

Rapid Field Method for Determination of Fluoride in Plants

Abstract A colorimetric reaction, involving the cerium III-alizarin complexan reagent, is described for the simple, semiquantitative determination of excess amounts of fluoride. A method is outlined that may be used in the field for the determination of fluoride in plants in excess of 40 ppm.

Fluoridation as a Public Health Measure

Fluoridation remains a controversial point on many fronts, but perusal of this monograph should settle many questions which have bothered the profession and the lay public alike. The book is the third to be published by the AAAS on the public health aspects of fluoridation. The series of 11 papers also includes a medical study of a population using an excessive amount of fluoride (8 parts/M.) in a natural water supply. The series of papers is directed to the problem of effectiveness of water fluoridation in reducing dental caries and various elements are considered, namely; dental benefits, public health, engineering and chemical aspects, metabolism of inorganic fluorides, acute fluoride poisoning and crippling chronic fluorosis, among several.