Skeletal fluorosis

Toxicology. Fluoride causes irritation of the eyes and respiratory tract and gastrointestinal effects absorption of excessive amounts of fluoride over a long period of time results in skeletal fluorosis. 

Repeated exposure to excessive concentrations of fluoride over a period of years results in increased radiographic density of bone and eventually may cause skeletal fluorosis. Crip-... 

Another much discussed concern is the potential effect on bone, with conditions such as skeletal fluorosis, osteosarcomas, osteoporosis and greater incidence of fractures being considered. 

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. 

Skeletal fluorosis can be defined as excessive deposition of fluoride in bone. This is a pathological condition that is by far the most important aspect of chronic exposure to elevated levels of fluoride, either by inhalation or by ingestion. The skeletal deformities may be associated with or accentuated by nutritional deficiencies or even malnutrition and hard manual work or, possibly, other conditions found in areas of long-term social and nutritional deprivation [6]. See, for instance Fig. 1 of [54]. The situation is specific also for populations consuming large volumes of water, such as athletes or people with certain medical conditions or... 

Endemic crippling skeletal fluorosis is confined in temperate climates to individuals exposed continuously over many years to very high levels of fluoride these cases are associated with industrial situations, with unusually high levels of fluoride in drinking water (e.g., 10 mg/L) or the use of high fluoride coal for cooking and drying foodstuffs indoors [6,17,55]. 

Most epidemiological research has indicated that an intake of at least 10 mg/day for 10 or more years is needed to produce clinical signs of the milderforms of osteosclerosis [8]. Water fluoride concentrations of 4-8 mg/L in temperate climates have not been found to be associated with any signs or symptoms of skeletal fluorosis [6]. This data should be regarded with scepticism in view of reports from a number of developing countries that endemic skeletal fluorosis occurs in individuals whose drinking water contains more than 6 mg/L of fluoride [6]. 

Reliable analytical techniques are a prerequisite for accurate and precise determination of human exposure to fluoride. The goal is to monitor the intake of fluoride and maintain it at adequate levels so that optimal protection against dental caries is achieved, without excessive intake resulting in the appearance of dental or, in the worst case, skeletal fluorosis. 

Boron elfectively counteracts symptoms of fluoride intoxication in humans (Zhou etal. 1987) and in rabbits poisoned experimentally (Elsair et al. 1980a, 1980b, 1981). Humans suffering from skeletal fluorosis experienced 50 to 80% improvement after drinking solutions containing 300 to IKX) mg of borax per liter daily, 3 weeks a month for 3 months (Zhou et al. 1987). Boron enhances sequestration of fluoride from bone and excretion through kidneys and possibly the intestinal tract (Elsair et al. 1980a, 1981). 

CAUTION Fluorides are eye and respiratory tract irritants and chronic exposure may result in skeletal fluorosis Appropriate safety precautions and procedures should be adopted when handling this substance. 

Endemic fluorosis is known to be global in scope, occurring in all continents and affecting many millions of people. Cases of skeletal fluorosis have been... 

Federal regulations require that fluoride not exceed a concentration of 4.0 mg L"1 in drinking water. Chronic exposure to levels above 4.0 mg L-1 may result in some cases of crippling skeletal fluorosis, a serious bone disorder. Fluoride in children s drinking water at levels of approximately 1 mg L-1 reduces the number of dental cavities. Federal law also requires that notification take place when monitoring indicates that the fluoride exceeds 2.0 mg L 1. 

Additional problems of high F occur in some groundwaters from arid areas (notably northern China, Pakistan). This creates potential additional health problems from dental and skeletal fluorosis. However, the presence of one of these elements in the Asian aquifers is not necessarily an indication of the presence of the other since As is dependent on the presence of strongly reducing conditions, whilst F occurs where Na-HCOs groundwaters dominate and where Ca concentrations are comparatively low. 

In skeletal fluorosis, the affected bones lose their normal, hard, smooth luster and appear rough, porous, and chalky white. A generalized hyperostosis (excessive formation of bone tissue, especially in the skull) and, in some cases, exostotic lesions of the otherwise smooth, long bones can be observed (Figure 8.3). Exostosis refers to a spur or bony outgrowth from a bone. 

What are the characteristic features of skeletal fluorosis in animals intoxicated by fluoride ... 

List five factors that can influence the manifestation of dental and skeletal fluorosis in animals. 

Occupational exposure to inhaled fluoride dusts in cryolite workers during aluminum refining has resulted in severe bone abnormalities, but safety equipment now limits such exposure. No cases of skeletal fluorosis are attributed to use of controlled fluoridation of water supplies. However, skeletal fluorosis may occur in areas of the world where naturally occurring drinking water has high levels of fluoride, such as China and the Indian subcontinent. It is thought that exposure to fluoride intakes of 10 to 25mg/day for 10 years or more may result in skeletal fluorosis, but other nutritional factors may make these populations more susceptible. ... 

If the fluoride intake is maintained above 10 ppm, the inhibition of enolase (Sects. 16.2.2 and 16.3.1) inhibits both anaerobic and aerobic glycolysis. In addition, skeletal defects may be caused by improper collagen synthesis inhibiting proper bone formation in children. Skeletal fluorosis in children and fluoride poisoning in adults is therefore accompanied by... 

This case illustrates the problem of low level chronic hydrofluoric acid exposure and the insidious nature of osteosclerosis (chronic skeletal fluorosis). Source Wilkie J (1940). Two cases of fluorine osteosclerosis. British Journal of Radiology 13, 213-217.)... 

Controlling Dental Fluorosis and Skeletal Fluorosis due to Atmospheric Fluorine Pollution... 

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