Fluoride ions fluorosis

Because of the corrosive effects and discomfort associated with inhalation of fluorine, chronic toxicity does not occur. Although the metaboHc fate of fluorine is not clear, it does not seem that much is converted to fluoride ion in the body (107). Therefore comparisons to effects of fluoride ion poisoning, known as fluorosis, are probably incorrect. 

Fluorides ia small (1 ppm ia water, 0.1% ia dentifrices) quantities have been shown to provide dramatic reduction ia dental decay. Fluorides also show promise for bone treatment and ia pharmaceuticals (qv) (see also Chemotherapeutics, anticancer Steroids). However, larger quantities of fluorides can lead to dental fluorosis, bone fracture, and even death. The oral LD q for free fluoride ion ia rats appears to be 50 to 100 mg/kg body weight based on LD q values for several fluorides. 

Health and Safety Factors. The low solubiUty of calcium fluoride reduces the potential problem of fluoride-related toxicity. Water saturated with calcium fluoride has a fluoride concentration of 8.1 ppm as compared to the recommended water fluoridation level of 1 ppm fluoride ion. However, because the solubiUty of calcium fluoride ia stomach acid is higher, continued oral ingestion of calcium fluoride could produce symptoms of fluorosis. The adopted TWA limit for fluorides as F is 2.5 mg/m (68,69). 

This paper is written with the aim of providing sufficient background to help understand the mechanism of action of fluoride ion on humans. The main focus is on the effects of fluoride on dental health, in-depth discussion of skeletal fluorosis and use of fluoride for treating osteoporosis being outside the scope of this paper. Current information on the main sources of human exposure to fluoride and current recommendations for adequate intake (Al) of fluoride, as well as methods for assessing exposure, will be reviewed. 

The toxic nature of fluoride ion, F, is not confined to its presence in HF. It is toxic in soluble fluoride salts, such as NaF. At relatively low levels, such as about 1 ppm, used in some drinking water supplies, fluoride prevents tooth decay. At excessive levels, fluoride causes fluorosis, a condition characterized by bone abnormalities and mottled, soft teeth. Livestock are especially susceptible to poisoning from fluoride fallout on grazing land as a result of industrial pollution. In severe cases, the animals become lame and even die. 

The fluoride ion can replace the hydroxide ion in a crystal without significantly altering its structure, an isomorphous ion replacement. Fluoride also affects the enzymes involved in enamel formation, causing mottled enamel, a severe example of enamel fluorosis. White opaque patches on the normally translucent enamel indicate mild fluorosis. Fluorosis is measured on a grade of 0-5 where 1 through 3 indicate an increased cover of opaque white patches on the tooth surface, and 4 and 5 indicate an increased mottling. The two worst affected teeth make up an individual s score. The community s index of fluoridation is the mean score for all individuals. As the natural or artificial fluoride concentration of the water supply increases to 1 ppm, the mean number of cavities in 10-12 year-old children decreases from 7 to 3. Above 1 ppm fluoride, caries does not decrease much more, but the index of fluorosis increases markedly. This is the reason why public water supplies are fluoridated to only 1 ppm and not more or less. 

In addition to alkenyl fluorosi lanes, alkenyl(alkoxy)silanes also undergo the crosscoupling reaction with the aid of a palladium catalyst and fluoride ion activator [Eq.(ll)] [9]. 

B. Fluoride Appropriate concentrations of fluoride ion in drinking water (0.5-1 ppm) or as a dentifrice additive have a well-documented ability to reduce dental caries. Chronic exposure to the ion, especially in high concentrations, may increase new bone synthesis. It is not clear, however, whether this new bone is normal in strength. Clinical trials of fluoride in patients with osteoporosis have not demonstrated a reduction in fracmres. Acute toxicity of fluoride (usually caused by ingestion of rat poison) is manifested by gastrointestinal and neurologic symptoms. Chronic toxicity (fluorosis) includes ectopic bone formation and exostoses. 

Clinical manifestations of fluorosis often occur in the hard tissues of animals, such as bones and teeth, as a result of long-term intake of elevated levels of fluoride, mainly due to industrial fluoride pollution. Evidence also indicates harmful effects of fluoride on soft tissues such as lung, kidney, testis, fiver and brain. Generally, fluorine, in the form of the fluoride ion (F ), is present in soil and water in low concentrations, but it may cause a threat to public and occupational health when its presence in the environment increases due to natural or anthropogenic sources. Excessive intake of F via drinking water is an endemic problem in a number of countries including China, India,... 

The recommended daily dose of fluorine for children under 6 months ranges from 0.1 to 0.5 mg, for children from 6 months to 1 year this dose is 0.2-1.0 mg, for children from 1 to 3 years 0.5-1.5 mg, for children 4-10 years old 1.0-2.5 mg and 1.5 to 4.0 mg for adults. Insufficient intake of fluorine in the diet and drinking water increases tooth decay and can lead to osteoporosis. When long-term elevated fluoride doses (20-80 mg per day) are taken, symptoms of poisoning (fluorosis) appear, which leads to damage of the teeth, bones, kidney and nervous system as fluoride ions act as inhibitors of some enzymes. 

The synergistic action of aluminum ions with fluoride may be the underlying mechanism of the observed neurotoxic effects of fluoride. Chronic exposure of humans to A1FX begins in the fetus. Elevated fluoride content was found in embryonic brain tissues obtained from required abortions in areas where fluorosis was prevalent [78, 124]. These studies showed poor differentiation of brain nerve cells and delayed brain development. High fluoride exposure appears to weaken mental function among children, as well as adults [125, 126]. 

Anions, such as fluoride, chloride, and phosphate, play critical roles in a range of biological processes and are implicated in a number of diseased states, ranging from fluorosis to cystic fibrosis [41]. Therefore, the exploitation of new luminescent chemosensors for anions is very important. The main design approach for lanthanide complexes as luminescent chemosensors for anions is to utilize the specific interaction between the anions and the lanthanide ion to realize the detection of the anions. 

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