Fluoride: According to the Bureau of Indian Standards, the amount of fluoride in water should be 1 mg per liter. According to the report of the World Health Organization, the amount of fluoride in water should be half to one milligram per liter. Fluoride in excess quantity can harm health. Excessive amounts of fluoride can cause white spots on the teeth, which is called dental fluorosis. This problem affects children up to 8 years of age. Excessive amounts of fluoride can cause damage to bones and joints, which is called skeletal fluorosis. Reverse Osmosis (RO) filtration can be used to avoid fluoridated water. RO systems have a semipermeable membrane that separates water molecules from contaminants. Fluoride is a mineral found naturally in many foods and water. Fluoride helps prevent tooth decay .