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Abstract:

Fluorine rarely occurs in its free state in nature. It combines chemically to form fluorides. Fluorides are widely distributed in nature and various amounts are universally present in soil, water, the atmosphere, vegetation, and animal tissue (National Academy of Sciences, 1971). The terms "fluorine" and "fluoride" are often used interchangeably in the literature in referring to fluoride compounds or to the element fluorine (F). Animals routinely ingest small amounts of fluoride with no adverse effects (National Academy of Sciences, 1974; Shupe, 1967). Small amounts of fluoride may be beneficial, but greater amounts induce fluoride toxicosis (McClure, 1970; Roholm, 1937; Schmidt et al., 1954; Shupe, 1972; Shupe and Alther, 1966; Shupe and Olson, 1971; WHO, 1970). Wild as well as domestic animals are susceptible to potential undesirable effects during prolonged ingestion of elevated levels of fluorides (Karstad, 1967; Newman and Yu, 1967; Shupe et al., 1972). The most common sources of excessive fluoride emitted in excess quantities by nearby industrial operations; water with a naturally high fluoride content; forages contaminated by soils with high concentrations of fluoride; feed supplements and mineral mixtures containing too much fluoride; or any combination of these. Figure 1 illustrates possible routes in which animals encounter fluorides.In some industrial operations, ores of moderate to high fluoride content are ground and/or heated during processing. Unless control mechanisms are installed and functioning properly, some of the fluorides may escape into the environment as hydrogen fluoride and particulate matter, which can contaminate vegetation eaten by animals.Some waters, most often those from geothermal sources, contain higher than tolerable concentrations of fluorides (Neely and Harbaugh, 1954; Rand and Schmidt, 1952). The current impetus to locate, develop, and utilize geothermal energy sources will very likely increase water-associated environmental fluoride hazards that previously existed only with certain springs and geysers. Data in Table 1 indicate that geothermal waters of the western United States tend to have a high fluoride content. A total of 68% of the samples contained more that 2.1 mg/l of fluoride.Some soils throughout the world have a high natural fluoride content (Hobbs and Merriman, 1962; Merriman and Hobbs, 1962). Vegetation growing on these soils may be contaminated by windblown or rain-splashed soil. In such cases, most of the fluorides remain on the surface of the vegetation and are not incorporated within it. However, some plant species are able to translocate appreciable amounts of fluoride from the soil. This ability varies with the plant and soil conditions. Wild and domestic animals have access to such sources of fluoride.Excessive levels of fluoride in some mineral mixes used as livestock feed supplements have been incriminated in some cases of fluoride toxicosis in domestic animals. These mixes would not normally be available to wildlife.

Notes:

Found at Yellowstone Research LibraryNatureBib ID: 49273

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