Fluorides are found throughout the environment and originate naturally from rocks and soil or from industrial processes. Toxic quantities of fluorides occur naturally. In certain areas, drinking water from deep wells may contain high levels of fluorides. Volcanic ash may be high in fluoride. Wastes from industrial processes, fertilizers, and mineral supplements are the most common causes of longterm fluoride poisoning. The fluoride-containing gases and dusts from manufacturing of fertilizers, mineral supplements, metal ores (steel and aluminum), and certain enamelling processes may contaminate forage crops.
Mouth or teeth-cleaning products with fluoride present a danger to pets, especially dogs. Sodium fluoride at a dosage of 5 to 10 milligrams per kilogram can be fatal, and toxic effects can occur at less than 1 milligram per kilogram. Fluoride is absorbed quickly (most within 90 minutes). The stomach and intestines become inflamed, and the heart beats rapidly and irregularly. Nervous signs may also be seen, followed by collapse and death within a few hours of fluoride ingestion.
At high levels, fluorides bind calcium and replace the mineral part of bone. Longterm ingestion of fluoride at lower levels can cause changes in the enamel of developing teeth, leading to mottling, staining, and rapid wear. Signs develop in many animals when fluoride builds up in the bone. This results in abnormal bony growths and the hardening and thickening of tissue (sclerosis). Growing bones in the young and the ribs, jaws, and long bones are most affected.
A developing fluoride poisoning can be recognized by the following criteria (from most to least reliable): 1) chemical analyses to determine the amount of fluoride in the diet, urine, bones, and teeth; 2) tooth effects, in animals exposed at time of permanent teeth development; 3) lameness, as the result of fluoride buildup in bone; and 4) overall signs of loss of appetite and energy, weight loss, muscular wasting, and general mental and physical debilitation.
Severe fluoride poisoning can be treated with calcium gluconate given intravenously and magnesium hydroxide or milk given by mouth. This can help bind the fluoride before it is absorbed. In longterm exposure, control is difficult unless animals are removed from affected areas. Feeding calcium carbonate, aluminum oxide, aluminum sulfate, magnesium metasilicate, or boron can decrease absorption or increase excretion of fluoride, offering some control of longterm fluoride poisoning under some conditions. However, no treatment has been shown to cure the longterm effects of fluoride toxicity.