Fluoride is an inorganic, monatomic anion of fluorine, with the chemical formula F−whose salts are typically white or colorless.
Fluoride salts typically have distinctive bitter tastes, and are odorless.
Its salts and minerals are important chemical reagents and industrial chemicals, mainly used in the production of hydrogen fluoride for fluorocarbons.
Fluoride is classified as a weak base.
It is concentrated fluoride is corrosive and can attack the skin.
Fluoride ions occur on Earth in several minerals, particularly fluorite, but are present only in trace quantities in bodies of water in nature.
Fluorine is estimated to be the 13th-most abundant element in Earth’s crust and is widely dispersed in nature, entirely in the form of fluorides.
Fluoride is naturally present in groundwater, fresh and saltwater sources, as well as in rainwater, particularly in urban areas.
In parts of Asia the groundwater can contain dangerously high levels of fluoride, leading to serious health problems.
Worldwide, 50 million people receive water from water supplies that naturally have close to the optimal level.
In other locations the level of fluoride is very low, sometimes leading to fluoridation of public water supplies to bring the level to around 0.7–1.2 ppm.
Mining can increase local fluoride levels.
All vegetation contains some fluoride, which is absorbed from soil and water.
All tea leaves contain fluoride; however, mature leaves contain as much as 10 to 20 times the fluoride levels of young leaves from the same plant.
Fluorine, in the form of fluoride, is considered to be a micronutrient for human health, necessary to prevent dental cavities, and to promote healthy bone growth.
Fluoride is the most bioavailable form of fluorine, and as such, tea is potentially a vehicle for fluoride dosing.
Approximately, 50% of absorbed fluoride is excreted renally with a twenty-four-hour period.
The remainder can be retained in the oral cavity, and lower digestive tract.
Fasting dramatically increases the rate of fluoride absorption to near 100%, from a 60% to 80% when taken with food.
Consumption of one liter of tea a day, can potentially supply the daily recommended intake of 4 mg per day.
Fasting can increase this to 150%.
Tea drinking communities are at an increased risk of dental and skeletal fluorosis, in the case where water fluoridation is in effect.
Fluoride ion in low doses in the mouth reduces tooth decay, and is used in toothpaste and water fluoridation.
At much higher doses and frequent exposure, fluoride causes health complications and can be toxic.
The main uses of fluoride, in terms of volume, are in the production of cryolite, Na3AlF6 used in aluminium smelting.
Fluoride is sold in tablets for cavity prevention.
Fluoride-containing compounds, such as sodium fluoride or sodium monofluorophosphate are used in topical and systemic fluoride therapy for preventing tooth decay.
They are used for water fluoridation and in many products associated with oral hygiene.
Originally, sodium fluoride was used to fluoridate water.
Hexafluorosilicic acid (H2SiF6) and its salt sodium hexafluorosilicate (Na2SiF6) are more commonly used additives, especially in the United States.
In some countries where large, centralized water systems are uncommon, fluoride is delivered to the populace by fluoridating table salt.
Meta-analysis show the efficacy of 500 ppm fluoride in toothpastes.
No beneficial effect can be detected when more than one fluoride source is used for daily oral care.
The current adequate intake (AI) for women 19 years and older is 3.0 mg/day (includes pregnancy and lactation).
The adequate intake for men is 4.0 mg/day.
The AI for children ages 1–18 increases from 0.7 to 3.0 mg/day.
The major known risk of fluoride deficiency appears to be an increased risk of bacteria-caused tooth cavities.
The tolerable upper intake level for fluoride the UL is 10 mg/day.
The European Food Safety Authority (EFSA) reviewed safety evidence and set an adult UL at 7.0 mg/day (lower for children).
Fluoride does not have a Daily Value and is not required to be shown on food labels.
Daily intakes of fluoride can vary significantly according to the various sources of exposure.
Values ranging from 0.46 to 5.4 mg/day have been reported in several studies.
In areas where water is fluoridated this can be expected to be a significant source of fluoride, however fluoride is also naturally present in virtually all foods and beverages at a wide range of concentrations.
The maximum safe daily consumption of fluoride is 10 mg/day for an adult (U.S.) or 7 mg/day (European Union).
The upper limit of fluoride intake from all sources (fluoridated water, food, beverages, fluoride dental products and dietary fluoride supplements) is set at 0.10 mg/kg/day for infants, toddlers, and children through to 8 years old.
For older children and adults, who are no longer at risk for dental fluorosis, the upper limit of fluoride is set at 10 mg/day regardless of weight.
Fluoride Content of Selected Foods Food Milligrams per Serving
Tea, black, brewed, 1 cup 0.07 to 1.5* Coffee, brewed, 1 cup 0.22* Shrimp, canned, 3 ounces 0.17 Bottled water with added fluoride, 1 cup ≤0.17 Raisins, ¼ cup 0.08 Oatmeal, cooked, ½ cup 0.08* Grapefruit juice, ¾ cup 0.08 Potatoes, russet, baked, 1 medium 0.08 Rice, cooked, ½ cup 0.04* Cottage cheese, ½ cup 0.04 Pork chop, baked, 3 ounces 0.03 Yogurt, plain, low-fat, 1 cup 0.03 Lamb chop, cooked, 3 ounces 0.03 Tortilla, flour, 1 tortilla, approx. 10” diameter 0.02 Corn, canned, ½ cup 0.02 Beef, cooked, 3 ounces 0.02 Tuna, light, canned in water, 3 ounces 0.02 Cheese, cheddar, 1½ ounces 0.01 Bread, white or whole wheat, 1 slice 0.01 Asparagus, cooked, 4 spears 0.01 Chicken, cooked, 3 ounces 0.01 Milk, fat-free or 1%, 1 cup 0.01 Apple, raw, with skin, 1 medium 0.01 Avocado, raw, ½ cup sliced 0.01 Macaroni, plain, cooked, ½ cup 0.00* Tomato, raw, 1 medium 0.00 Banana, 1 medium 0.00 Egg, cooked, 1 large 0.00 Carrots, raw, 1 medium 0.00 Peanut butter, 1 tbsp 0.00
Raisins, seedless 2.34 small box, 43 g (1.5 oz) 0.101 Table wine 1.53 Bottle, 750 mL (26 imp fl oz) 1.150
Municipal tap-water, (Fluoridated) 0.81 Recommended daily intake, 3 litres (0.79 US gal) 2.433
Amounts of fluoride might vary by levels in the water used to prepare these foods and beverages.
In 1986, guidelines from the U.S. Environmental Protection Agency (EPA) established a maximum allowable concentration of 4.0 mg/L fluoride in public drinking water systems to prevent adverse effects from fluoride exposure, such as bone disease, and a recommended maximum concentration of 2.0 mg/L to prevent dental fluorosis.
Fluoridated municipal drinking water—including water that people drink as well as foods and beverages prepared using municipal drinking water—accounts for about 60% of fluoride intakes in the United States.
In 2020, 62.9% of the U.S. population had access to a fluoridated community water system.
The fluoride additives used to fluoridate drinking water in the United States are fluorosilicic acid, sodium fluorosilicate, and sodium fluoride
Fluoride is not typically added to bottled drinking waters.
However, when fluoride is added, the U.S. Food and Drug Administration (FDA) stipulates that the total amount of fluoride added plus naturally occurring) cannot exceed 0.7 mg/L.
Only a few dietary supplements contain fluoride, usually in the form of sodium fluoride.
Most are multivitamin/mineral supplements, multivitamins plus fluoride, or supplements containing trace minerals only.
Some fluoride supplements, for children, are in the form of drops.
The most common amount of fluoride in supplements is 0.25 mg, although a few products contain 0.5 or 1 mg per serving.
Most toothpaste sold in the United States contains fluoride in the form of sodium fluoride or monofluorophosphate, most commonly at a level of 1,000 to 1,100 mg/L, which is about 1.3 mg in a quarter teaspoon, a typical amount of toothpaste used for one brushing.
The amount of fluoride ingested from toothpaste depends on the amount used, the person’s swallowing control, and how often the person uses toothpaste.
Estimated typical amounts of fluoride ingested daily from toothpaste are 0.1 mg to 0.25 mg for infants and children age 0 to 5 years, 0.2 to 0.3 mg for children age 6 to 12 years, and 0.1 mg for adults.
Fluoride in toothpaste, regardless of its form, is well absorbed
Other dental products that provide fluoride include mouth rinses for home use, topical fluoride preparations applied in dentists’ offices or through school-based programs, and dental devices-orthodontic bracket adhesives, glass-ionomer and some composite resin dental restorative materials, and some dental sealants and cavity liners.
Gels used by dentists are typically applied one to four times a year and can lead to ingestions of 1.3 to 31.2 mg fluoride each time; varnishes are least likely to produce a high bolus of fluoride.
Some prescription medications contain fluoride, but not as the active ingredient.
Fluoride is a constituent of voriconazole and long-term use of this medication can lead to high fluoride concentrations in serum and plasma.
Fluoride Intakes and Status
Most people in the United States consume adequate amounts of fluoride through foods containing naturally occurring fluoride, fluoridated tap water, and food products made with fluoridated tap water.
The typical daily fluoride intakes in the United States from foods and beverages, including fluoridated drinking water, are 1.2 to 1.6 mg for infants and toddlers younger than 4 years, 2.0 to 2.2 mg for children age 4–11 years, 2.4 mg for those age 11–14 years, and 2.9 mg for adults .
The highest level of daily nutrient intake that is likely to pose no risk of adverse health effects is 10 mg/day for most people, corresponding to 10 L of fluoridated water with no risk.
For young children the values are smaller, ranging from 0.7 mg/d to 2.2 mg/d for infants.
Water and food sources of fluoride include community water fluoridation, seafood, tea, and gelatin.
Soluble fluoride salts, of which sodium fluoride is the most common, are toxic, and have resulted in both accidental and self-inflicted deaths from acute poisoning.
The lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg elemental fluoride per kg body weight.
Treatment may involve oral administration of dilute calcium hydroxide or calcium chloride to prevent further absorption, and injection of calcium gluconate to increase the calcium levels in the blood.
Hydrogen fluoride is more dangerous than salts such as NaF because it is corrosive and volatile, and can result in fatal exposure through inhalation or upon contact with the skin.
Wi high doses used to treat osteoporosis, sodium fluoride can cause pain in the legs and incomplete stress fractures, and it also irritates the stomach, sometimes so severely as to cause ulcers.
Slow-release and enteric-coated versions of sodium fluoride do not have gastric side effects,and have milder and less frequent complications in the bones.
In the lower doses that areused for water fluoridation, the only noted adverse effect is dental fluorosis.
Dental fluorosis can alter the appearance of children’s teeth during tooth development; but this is mostly mild and is unlikely to represent any real effect on aesthetic appearance or on public health.
Fluoride was known to enhance bone mineral density at the lumbar spine, but it was not effective for vertebral fractures and provoked more nonvertebral fractures.
In areas that have naturally occurring high levels of fluoride in groundwater which is used for drinking water, both dental and skeletal fluorosis can be prevalent and severe.
Around one-third of the human population drinks water from groundwater resources.
Of this, about 10%, approximately 300 million people, obtain water from groundwater resources that are heavily contaminated with arsenic or fluoride.
Concentrated fluoride solutions are corrosive.
Health authorities have declared that community water fluoridation, reaching over 400 million worldwide—is safe.
Higher fluoride exposure in pregnant women was associated with lower IQ scores in young children, critics attacked the methodology of the study and discounted the significance of the results.
Health authorities continue to conclude that fluoride is unequivocally safe, despite four well-conducted studies over the last 3 years consistently linking fluoride exposure in pregnancy with adverse neurodevelopmental effects in offspring, males>females.
Today, about three-fourths of people in the United States and one-third of Canadians have fluoride added to their drinking water.
Fluoride offers no benefits to the fetus.
The beneficial effects of fluoride predominantly occur at the tooth surface, after the teeth have erupted.
The Canadian Pediatric Society and the American Academy of Pediatrics advise against fluoride supplements during the first 6 months of life.