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This book evaluates the risk to human health and the environment posed by exposures to fluorides. It is widely known that fluoride has both positive and negative effects on human health and there is a narrow range between intakes that are associated with

"Groundwater researchers, educators, regulators, and water managers should have a general working knowledge of naturally occurring fluoride in groundwater. It often occurs at concentrations unfit for drinking when the aquifer rocks are silica-rich volcanics, granites, or phosphorous-rich marine sediments. This book introduces the reader to how our knowledge of fluoride in groundwater began, its effect on teeth and bones at high dosages, its distribution in groundwaters worldwide, natural processes causing high fluoride concentrations, examples of aquifers contaminated with unhealthy concentrations of fluoride and techniques used to treat excess fluoride in groundwater."--

This book describes in detail various aspects of fluoride toxicity in animals. Animals, like human beings, suffer from the toxic effects of excess fluoride intake. They show pathological changes in their teeth and bone, together with a marked reduction in appetite, productive and reproductive potentials, which can result in severe economic losses in the dairy industry. Laboratory and wild animals also suffer from this ailment. Animal suffering and economic losses alike can be minimized through early diagnosis of the problem and by adopting suitable preventive and therapeutic measures. The book details the susceptibility of different animal species, important sources of toxicity, clinical signs and symptoms, pathophysiology, diagnostic methods, preventive and therapeutic approaches. It offers a valuable resource for scientists working in the fields of toxicology, veterinary science, animal nutrition, and environmental science, as well as for public health workers, animal welfare activists, public health veterinarians, field veterinarians, medical professionals and all others interested in the subject.

Department of Chemistry, Ravishankar University, Raipur-492 010 Manuscript received 15 June 1987, revised 21 December 1987, accepted 30 December 1987 FLUORIDES occur in the industrial effluents1 and also in water flowing over fluoride-containing rocks and minerals. The TLV (threshold limit value) as recommended by the American Conference of Governmental lndustrial Hygienists is 3 ppm in drinking water2. The toxic effects of excess fluorides are well established2,3.

The discovery during the first half of the 20th century of the link between natural fl uoride, adjusted fl uoride levels in drinking water and reduced dental caries prevalence proved to be a stimulus for worldwide on-going research into the role of fl uoride in improving oral health. Epidemiological studies of fl uoridation programmes have confi rmed their safety and their effectiveness in controlling dental caries. Major advances in our knowledge of how fl uoride impacts the caries process have led to the development, assessment of effectiveness and promotion of other fl uoride vehicles including salt, milk, tablets, toothpaste, gels and varnishes. In 1993, the World Health Organization convened an Expert Committee to provide authoritative information on the role of fl uorides in the promotion of oral health throughout the world (WHO TRS 846, 1994). This present publication is a revision of the original 1994 document, again using the expertise of researchers from the extensive fi elds of knowledge required to successfully implement complex interventions such as the use of fl uorides to improve dental and oral health. Financial support for research into the development of these new fl uoride strategies has come from many sources including government health departments as well as international and national grant agencies. In addition, the unique role which industry has played in the development, formulation, assessment of effectiveness and promotion of the various fl uoride vehicles and strategies is noteworthy. This updated version of 'Fluoride and Oral Health' has adopted an evidence-based approach to its commentary on the different fl uoride vehicles and strategies and also to its recommendations. In this regard, full account is taken of the many recent systematic reviews published in peer reviewed literature.

1 Perspective and overview -- 1.1 Introduction -- 1.2 Optical fibre fundamentals -- 1.3 Loss mechanisms in optical fibre materials -- 1.4 Long wavelength fibre materials -- 1.5 Fluoride glasses and optical fibres -- 1.6 Applications for infrared optical fibres -- 1.7 Future prospects -- References -- 2 Properties of fluoride glasses -- 2.1 Introduction -- 2.2 Glass-forming systems, structure and crystallization -- 2.3 Thermal properties -- 2.4 Other properties -- 2.5 Optical properties -- References -- 3 Propagation in optical fibres -- 3.1 Introduction -- 3.2 Multimode fibres -- 3.3 Monomode fibres -- References -- 4 Manufacture of infrared fibres -- 4.1 Materials preparation -- 4.2 Melting techniques -- 4.3 Fibre fabrication -- 4.4 Problems -- 4.5 Fibre results -- References -- 5 Intrinsic loss measurements -- 5.1 Introduction -- 5.2 Rayleigh scattering -- 5.3 IR multiphonon edge -- 5.4 Minimum intrinsic loss -- 5.5 Longer wavelength transmitting fibres -- References -- 6 Extrinsic absorption -- 6.1 Introduction -- 6.2 Spectrometer measurements -- 6.3 Absorption due to water -- 6.4 Absorption due to transition metal ions -- 6.5 Absorption due to rare earth ions -- 6.6 Other impurities -- References -- 7 Extrinsic scattering -- 7.1 Introduction -- 7.2 Identification of scattering centres -- 7.3 Scattering theory -- 7.4 Scattering solutions for limiting cases -- 7.5 Solutions for metallic (absorbing) spheres -- 7.6 Applications to practical examples -- 7.7 Calculations of scattering loss -- 7.8 Scattering loss in fibres -- 7.9 Conclusions -- References -- 8 Measured losses in fibres -- 8.1 Introduction -- 8.2 Available techniques -- 8.3 Total loss -- 8.4 Absorption -- 8.5 Scattering -- 8.6 Recent results -- 8.7 Predicted minimum loss -- References -- 9 Mechanical properties -- 9.1 Introduction -- 9.2 Fracture and glass parameters -- 9.3 Strength measuring methods -- 9.4 Fibre strengths -- 9.5 Identification of flaws and effect on strength -- 9.6 Ultimate strength and maximum practical strength -- 9.7 Strength and homogeneous crystal growth -- 9.8 Durability -- 9.9 Conclusions -- References -- 10 Applications -- 10.1 Mid-IR communication systems -- 10.2 Active fibres -- 10.3 Laser surgery -- 10.4 Infrared fibre sensors -- References.

Critical of the fluoridation of drinking water in light of studies linking fluoride to bone cancer; US.