Fluoride is a naturally occurring mineral found in various environmental sources like rocks, soil, water, plants, and animals. Its historical application in public health, particularly since the discovery of its anti-caries effect in 1938, has significantly contributed to the reduction of dental decay. While beneficial for strengthening teeth, excessive exposure to fluoride can lead to potential health risks.
How People Encounter Fluoride
People encounter fluoride through several common pathways. Drinking water is a primary source, especially in communities where water supplies are fluoridated to prevent dental cavities. Naturally occurring fluoride concentrations in water vary significantly based on geological factors, with some areas having levels as high as 20 mg/litre.
Dental products also contribute to fluoride intake. Toothpastes for adults typically contain 1000 to 1500 µg/g of fluoride, while children’s toothpastes contain 250 to 500 µg/g. Mouthwashes also contain varying fluoride levels, depending on their intended frequency of use. Additionally, certain foods and beverages, such as fish and tea leaves, can contain elevated levels of fluoride because tea plants absorb the mineral from the soil. The fluoride content in foods is also impacted by the fluoride concentration of water used during preparation or processing, particularly for beverages and dry foodstuffs like powdered baby formula.
Well-Established Health Risks
Chronic excessive fluoride exposure is linked to two widely recognized health conditions: dental fluorosis and skeletal fluorosis. Dental fluorosis affects tooth enamel, occurring during tooth development, typically in children younger than eight years old. Its appearance ranges from subtle white spots or streaks on the enamel in mild cases to more noticeable brown stains, pitting, or rough surfaces in severe forms. While primarily a cosmetic concern, severe dental fluorosis can impact tooth function.
Skeletal fluorosis results from prolonged, very high fluoride intake over many years, often from drinking water with unsafe fluoride levels. This condition causes fluoride to accumulate in bones, leading to their hardening and reduced elasticity, which increases the frequency of fractures. Symptoms include painful damage to bones and joints, stiffness, impaired joint mobility, and in advanced stages, bone deformities and calcification of ligaments and cartilage. While rare in regions with regulated water fluoridation, skeletal fluorosis is more prevalent in areas with naturally high fluoride concentrations in groundwater, such as parts of India and China.
Other Reported Health Concerns
Beyond dental and skeletal fluorosis, other health concerns have been explored, though scientific consensus is less definitive. Some studies have investigated potential neurological effects, particularly concerning cognitive development in children. A systematic review by the National Toxicology Program concluded with moderate confidence that higher fluoride exposure, specifically from drinking water containing over 1.5 milligrams per liter, is associated with lower IQ in children. This association was primarily observed in epidemiology studies in countries like China, India, Iran, Pakistan, and Mexico, where populations had total fluoride exposures higher than 1.5 mg/L.
The National Toxicology Program’s review evaluated total fluoride exposure from all sources and did not specifically assess the effects of fluoridated drinking water alone at the currently recommended U.S. community levels of 0.7 mg/L. The review found insufficient data to determine if fluoride at this lower concentration negatively affects children’s IQ. Research also continues into fluoride’s potential impact on thyroid function and kidney issues.
Defining Safe Fluoride Levels
Safe fluoride levels are defined by established thresholds, with risks primarily associated with exceeding them. Regulatory bodies in many countries have set optimal fluoride levels for drinking water to balance cavity prevention with minimizing adverse effects. For instance, the U.S. Public Health Service recommends a fluoride concentration of 0.7 mg/L in community drinking water supplies.
While large doses of fluoride can be toxic, concentrations used in community water fluoridation are significantly lower and generally not considered harmful. For most individuals in areas with regulated fluoride levels, daily intake remains within safe limits. However, excessive cumulative exposure should be avoided, particularly for children whose developing teeth and bones absorb fluoride more efficiently than adults. This means monitoring all sources of fluoride intake to ensure total exposure does not exceed recommended guidelines.