Ask A Toxicologist > What is the toxicity of exposure to fluorides?

What is the toxicity of exposure to fluorides?

posted on 11:37 AM, August 1, 2016

What are fluorides?

Fluorides are compounds that contain the naturally occurring element fluorine, and one or more other elements. When added in small amounts to water or dental products, fluorides can be very beneficial because they strengthen bones and teeth. Examples of these compounds that are added to toothpastes include sodium fluoride, stannous fluoride (which is made of fluoride + tin), and sodium monofluorophosphate. To further strengthen teeth, compounds such as sodium fluoride, fluorosilic acid, and sodium fluorosilicate are added to water.. Conversely, too much fluoride, as is found naturally in the water in some parts of the world, can cause weak teeth and bones, and can place older adults at risk for fractures.  

Fluorine is incorporated into some medications including some antibiotics, some depression medications, some antifungal medicines, and some cancer medications in order to improve the therapeutic effects of the drug. Although no studies have demonstrated toxicity, some consumers remain concerned that the presence of fluorine in medications may cause toxicity.

Hydrogen fluoride is a gas that is irritating to the lungs, and workers who are exposed to large amounts in work places where hydrogen fluoride is used, such as in glass etching factories or in the chemical manufacturing industry, can have skin, eye, nose, and lung irritation. Fluorine gas is also very irritating to the lungs in large exposures to workers, which can occur in factories that make refrigerants and plastics. These effects can be avoided by using appropriate eye and respiratory protection (such as respirator masks).

Hydrofluoric acid and ammonium bifluoride are examples of liquid fluorides which are used in a number of products including glass etching, microchip etching, and tire cleaners, and can burn the eyes and skin, resulting in tissue damage. If skin contact occurs with very concentrated formulas, such as those used in the microchip industry, low levels of calcium in the body can develop which can cause abnormal heart rhythms and death.  

How does fluoride exposure occur?

Fluorides exist naturally in rocks, soil, and clay, and can be released into the air in large amounts during volcanic eruptions. Since these compounds are found in soil, water, air, animals, and plants, most humans are exposed to small amounts by eating food and drinking water. Some areas of the world including Africa, China, the Middle East, and India, have water with naturally high levels of fluoride, so adding fluoride to water or dental products is not needed. However many areas of the United States have water with low levels of fluoride, so fluoride is added to the water to help prevent dental cavities. The amount of fluoride added to drinking water is very small – 1 part of fluoride to every million parts of water, and the amount of fluoride in the air is even smaller: 1 millionth of a gram (about 1 millionth the weight of a paper clip) of fluoride in the amount of air that would fill a box made of sides that are each 1 meter (or about 3 feet).

The amount of fluoride in the air may be higher near power or industrial plants such as power plants that burn coal, smelting plants, and fertilizer plants. Workers in these industries may be at risk for toxicity. They should shower and change clothes before leaving work to protect themselves and their families. If there is a risk for workers to be exposed to fluorides in the air, or by contacting liquid fluoride compounds, appropriate protection should be used, including protective clothing, eye goggles, and masks.

However, for individuals who don’t work these industries, the most common exposure is through food, water, and dental products, where harmless exposure occurs every day. The amount of fluoride contained in toothpaste, fluoride gels, and some mouth rinses is about 1000 times the amount in air, yet these products are harmless if used properly. These products are not meant to be swallowed. Supervising children when brushing their teeth, and making sure children brush with a small amount of toothpaste can help prevent them from swallowing unsafe amounts of fluoride in toothpaste. Foods that contain higher levels of fluoride than others include brewed teas, instant iced-tea powders, canned crab, and canned shrimp. However, these foods are still harmless when consumed in moderation as part of a normal healthy diet.

What does fluoride do to the body?

Fluoride entering the body through the air or by consuming food or water will leave the body quickly in the urine. A small amount of fluoride, such as the amount the World Health Organization recommends for our drinking water (0.8-1.2 milligrams per liter), is stored in teeth and bones, and helps to prevent cavities and broken bones. Exposure to larger amounts of fluoride (above 1.5 milligrams per liter), such as is found in areas of the world where water naturally contains higher than the recommended amount of fluoride, can result in dental fluorosis, or discolored, fragile teeth in children. Exposure to very large amounts (over 10 mg/L, or about 8 times the recommended amount) for a period of at least 10 years in parts of the world where there is a naturally very high level of fluoride (such as parts of India, Turkey, and Afghanistan), can result in skeletal fluorosis, which causes brittle bones, joint pain, and spinal rigidity.

While a possible relationship between bone cancer and fluoridated water has been a source of debate for decades, animal studies have demonstrated no clear relationship between high doses of fluoride and cancers such as bone cancer.  

Hydrogen fluoride and fluorine gas act by directly irritating the surface tissues of the skin, nose, mouth, throat and lungs directly, causing mild pain and difficulty breathing.  Hydrofluoric acid and ammonium bifluoride act by moving deeply into the skin after contact, binding up the body’s calcium, and causing abnormal heart function by removing the calcium the heart depends on to beat normally.

How are fluoride exposures monitored?

Studies from around the world have demonstrated that having the right amount of fluoride in drinking water can significantly decrease tooth decay. US government and World Health Organization scientists recommend that drinking water contains between 0.7 and 1.2 grams (about the weight of a paper clip) per liter (1/4 gallon) of water in order to help prevent cavities. Since it is important to have just the right amount in water, the U.S. Environmental protection agency recommends that drinking water have no higher than 4 grams of fluoride per liter in order to prevent toxic effects such as bone and dental fluorosis.

Workplaces are monitored for air levels of fluoride which are regulated by government agencies such as the Centers for Disease Control, Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH).

Can I be tested for fluoride exposure?

Urine and blood tests can be performed to detect recent exposures to abnormally high levels of fluorides, such as large exposures in the industrial work setting. Since most fluoride leaves the body within a few days, testing that is being performed to confirm an exposure needs to be performed soon after the exposure. Even with elevated blood or urine levels, it is difficult to predict if individuals will develop bone or dental abnormalities from the exposure, so measuring fluoride levels is not recommended unless there is a very severe work place exposure. Testing is not needed in individuals with normal daily consumption of fluoride in foods, medications, or drinking water.


Agency for Toxic Substances and Disease Registry Toxicological Profile for Fluorides, Hydrogen Fluoride, and Fluorine.  Centers for Disease Control and Prevention, 2003.  Available at

Centers for Disease Control and Prevention Community Division of Oral Health, National Center for Chronic Disease Prevention and Health Promotion.  Water Fluoridation, 2015.  Available at

United States Department of Agriculture Agricultural Research Service National Fluoride Database of Selected Beverages and Foods.  Available at  Accessed February 19, 2016.

World Health Organization Water Sanitation and Health: Fluoride.  Available at: World Health Organization.  Accessed February 19, 2016.

Centers for Disease Control and Prevention National Institute for Occupational Safety and Health (NIOSH): Fluorine.  Available at CDC OSHA Fluorine.  Accessed February 19, 2016.