Fluoride

Tiny things live in our world.

They are in rocks and water. Some rocks have them inside.

These things can taste bitter. They have no smell. They are often white or clear.

Plants take them from the soil. All tea leaves have them. Old leaves have more than young ones.

They help keep your teeth strong. This stops holes in your teeth. Many people put them in water.

They are also in toothpaste. This helps keep your mouth healthy. Do you brush your teeth?

Fluoride is a tiny part of a larger element called fluorine. It is often found in minerals like fluorite.

Fluoride salts are usually white or clear. They have a bitter taste but no smell. In nature, fluoride is found in many places. It is in groundwater and saltwater. It is even in rainwater. Some plants take fluoride from the soil. For example, all tea leaves contain fluoride. Mature tea leaves have much more than young ones.

Fluoride helps keep our bodies healthy. It is a micronutrient, which means our bodies need a little bit of it. It helps bones grow and prevents cavities in our teeth. Because it helps teeth, many people use it in toothpaste.

Some cities add fluoride to their public water. This helps stop tooth decay for many people. However, too much fluoride can be bad. High levels can cause health problems. Scientists say the right amount is key for staying healthy. Most people get the right amount from food and water.

Fluoride is a tiny part of the element fluorine. It is an inorganic, monatomic anion. This means it is a single atom with a negative charge. Most fluoride salts are white or colorless. They often have a bitter taste but no smell. Fluoride is a weak base. This means it does not change the way it acts much in water. However, concentrated fluoride can be corrosive. It can even attack the skin.

Fluoride moves through the world in a way called the fluorine cycle. This happens when rocks weather or humans do certain activities. It is the 13th-most abundant element in the Earth's crust. Most of it stays in mineral deposits. The most important mineral is called fluorite. Fluorite is made of calcium and fluoride.

Fluoride also travels through water. It is in groundwater, fresh water, and saltwater. It can even be found in rainwater. In urban areas, pollution can make the fluoride in rain go up.

Scientists study how fluoride acts in different places. In the ocean, fluoride levels are usually between 0.86 and 1.4 mg/L. This is much lower than chloride levels. In fresh water, levels change a lot. In some parts of Canada, levels are under 0.05 mg/L. In parts of China, they can reach 8 mg/L. In some parts of Asia, levels are high enough to cause health problems. Some people get water with the right amount of fluoride. About 50 million people use these supplies. In other places, cities add fluoride to water to keep it around 0.7 to 1.2 ppm.

Plants also play a role in the fluoride cycle. All vegetation contains some fluoride from the soil and water. Some plants take in more than others. For example, all tea leaves contain fluoride. Mature tea leaves have 10 to 20 times more fluoride than young leaves. Drinking tea can provide a lot of fluoride. A study found that one liter of tea a day might give a person 4 mg. This is the daily recommended amount. If a person drinks tea while fasting, they might absorb even more.

Fluoride is very useful for our health and industry. It is a micronutrient for humans. This means our bodies need a small amount. It helps bones grow and prevents cavities. Because of this, it is in toothpaste and water. The U.S. Centers for Disease Control says water fluoridation is a great public health achievement. It is also used to make metals like aluminum. It is used in steel-making to separate slag.

We also use it to make many drugs and polymers. It is a small thing that does many big jobs.

Fluoride is an inorganic, monatomic anion of the element fluorine. In chemistry, an anion is an atom that carries a negative charge. The chemical formula for the fluoride ion is F−. Most fluoride salts appear as white or colorless solids. These salts often have a distinctive bitter taste but no smell. Fluoride is classified as a weak base. This means it does not fully associate in a solution. However, concentrated fluoride is corrosive and can attack the skin.

The fluoride ion is the simplest form of a fluorine anion. In terms of its size and charge, it closely resembles the hydroxide ion. This similarity allows fluoride to act as a nucleophile in chemical reactions. In many inorganic solutions, fluoride ions exist alongside bifluoride ions, which are written as H2F+. Most fluoride salts are not very soluble in water without undergoing hydrolysis. This is a process where the salt reacts with water to change its chemical structure. In certain special environments, scientists can create "naked" fluoride. This refers to fluoride that is not surrounded by other atoms or solvents. A recent example from 2016 is imidazolium fluoride, which is a stable source of naked fluoride.

Fluoride is widely dispersed throughout the natural world. It is estimated to be the 13th-most abundant element in the Earth's crust. Most of this element exists entirely in the form of fluorides. These are found mostly in mineral deposits. The most commercially important mineral is fluorite, which has the formula CaF2.

Fluoride moves through the environment via the fluorine cycle. This cycle occurs through the natural weathering of rocks. Human activities also release fluorides into the biosphere. These activities can include mining or industrial processes.

Water sources contain varying amounts of fluoride depending on their location. Seawater fluoride levels usually range from 0.86 to 1.4 mg/L. The average concentration in the ocean is about 1.1 mg/L. This is much lower than the chloride concentration, which is about 19 g/L. In freshwater, the levels change significantly. Surface water in lakes and rivers typically contains between 0.01 and 0.3 mg/L. Groundwater levels vary based on local minerals. In Canada, natural levels can be under 0.05 mg/L. In China, levels can reach up to 8 mg/L. In some parts of Asia, groundwater can contain dangerously high levels. These high levels can lead to serious health problems for people.

Plants also absorb fluoride from the soil and water. All vegetation contains some amount of fluoride. Some plants are better at concentrating it than others. The tea plant, Camellia sinensis, is a notable accumulator. All tea leaves contain fluoride. Mature leaves can have 10 to 20 times more fluoride than young leaves. A 2013 study found that drinking one liter of tea daily might provide 4 mg of fluoride. This is the daily recommended intake for some adults. If a person is fasting, they may absorb even more. Fasting can increase absorption from 60–80% up to nearly 100%.

Fluoride is a vital micronutrient for human health. It is necessary to promote healthy bone growth and prevent dental cavities. Because of this, it is used in many oral hygiene products. Sodium fluoride and sodium monofluorophosphate are common ingredients in toothpaste. Some countries also add fluoride to table salt. In the United States, many cities use hexafluorosilicic acid to fluoridate public water. The U.S. Centers for Disease Control calls water fluoridation a great public health achievement.

The Institute of Medicine provides recommended amounts. The Adequate Intake for adult men is 4.0 mg/day. For adult women, it is 3.0 mg/day.

Industry relies heavily on fluoride for many different processes. Fluoride salts and hydrofluoric acid are highly valuable. One major use is in the production of cryolite, which is Na3AlF6. This chemical is essential for smelting aluminum. Mined fluorite is also used in steel-making to separate slag. Additionally, uranium hexafluoride is used to purify uranium isotopes. Fluoride is also used to create many drugs, polymers, and refrigerants. These are known as organofluorine compounds. In laboratories, fluoride salts are used to inhibit the activity of enzymes called phosphatases. This makes them very important tools for biological research.