Fluoride-liberating chemicals are found in some automobile wheel cleaners, rust removers, glass-etching solutions, pesticides, agents used in aluminum production, and vitamins and dietary supplements, and also in products used to prevent dental caries. Most toothpaste contains up to 5 mg of fluoride per teaspoon, and tea can contain 0.3–5.1 mg of fluoride per liter. Fluoride is commonly added to community drinking water and is a natural ground water contaminant in some parts of the world. It is also found in hydrofluoric acid (See Hydrogen Fluoride and Hydrofluoric Acid), which is used for etching glass and silicon chip products. Soluble fluoride salts are rapidly absorbed and are more acutely toxic (Table II–25).