Types of Fluoride Additives

 

Community water systems in the United States use one of three additives for water fluoridation. Decisions on which additive to use are based on cost of product, product-handling requirements, space availability, and equipment.

 

The Three Additives Are:

 

• Fluorosilicic acid: a water-based solution used by most water systems in the United States. Fluorosilicic acid is also referred to as hydrofluorosilicate, FSA, or HFS.

• Sodium fluorosilicate: a dry additive, dissolved into a solution before being added to water.

• Sodium fluoride: a dry additive, typically used in small water systems, dissolved into a solution before being added to water.

 

 

Sources of Fluoride Additives

CDC.gov

 

Most fluoride additives used in the United States are produced from phosphorite rock. Phosphorite is mainly used for manufacturing phosphate fertilizer. Phosphorite contains calcium phosphate mixed with limestone (calcium carbonates) minerals and apatite—a mineral with high phosphate and fluoride content. It is refluxed (heated) with sulfuric acid to produce a phosphoric acid-gypsum (calcium sulfate-CaSO4) slurry.

 

The heating process releases hydrogen fluoride (HF) and silicon tetrafluoride (SiF4) gasses, which are captured by vacuum evaporators. These gasses are then condensed to a water-based solution of approximately 23% FSA.

 

Approximately 95% of FSA used for water fluoridation comes from this process. The remaining 5% of FSA is produced in manufacturing hydrogen fluoride or from the use of hydrogen fluoride to etch silicates and glasses when manufacturing solar panels and electronics.

Since the early 1950s, FSA has been the main additive used for water fluoridation in the United States. The favorable cost and high purity of FSA make it a popular additive. Sodium fluorosilicate and sodium fluoride are dry additives that come from FSA.

 

FSA can be partially neutralized by either table salt (sodium chloride) or caustic soda to get sodium fluorosilicate. If enough caustic soda is added to completely neutralize the fluorosilicate, the result is sodium fluoride. About 90% of the sodium fluoride used in the United States comes from FSA. Sodium fluoride is also produced by mixing caustic soda with hydrogen fluoride.

 

Regulatory Scope on Additives

 

The U.S. Environmental Protection Agency (EPA) has authority over safe community drinking water, as specified in the Safe Drinking Water Act. On the basis of the scientific study of potential harmful health effects from contaminated water, the EPA sets a Maximum Contaminant Level (MCL) concentration allowed for various organisms or substances.

 

Although the EPA does not specifically regulate levels of "direct additives," which are additives added to water in the course of treatment, it does specify that the addition of chemicals as part of the treatment process should not be more than the MCL concentration for regulated substances. This MCL limit includes the levels naturally occurring in the source water, plus the contribution from direct additives. In 1979, EPA executed a Memorandum of Understanding with the U.S. Food and Drug Administration (FDA) to establish and clarify areas of authority in controlling additives in drinking water. FDA has regulatory oversight for food additives, which includes bottled water, and EPA has regulatory oversight of direct additives in public drinking water supplies.

 

Because of the decision to transfer the additives program to the private sector, EPA declared a moratorium in 1980 on issuing new advisory opinions on additives. EPA awarded a cooperative agreement to a group of nonprofit, nongovernmental organizations led by the National Sanitation Foundation (NSF) in 1985 (now NSF International) to develop a new additives program. Three years later, EPA announced that the new National Sanitation Foundation/American National Standards Institute (NSF/ANSI) Standard 60 was in operation.

 

How Many Types of Fluoride are There?

 

A lot. A whole lot. When the element of fluoride is combined with something else, it becomes a fluoride compound. There is a vast range of fluorine-containing compounds because fluorine has the capability of forming compounds with nearly all the elements.

 

Here Are Some Of The Common Forms:

 

Sodium Fluoride

 

Used in most toothpaste, mouthwashes, dental varnish, dental preparations and nutritional supplements. This same form of fluoride is used as an insecticide and pesticide, as a preservative in glues, as a growth inhibitor for bacteria, fungi, and mold. Sodium fluoride is also used in making steel and aluminum products. Added to molten metal, sodium fluoride creates a more uniform metal.

 

Other industrial uses for sodium fluoride include glass frosting and wood preservatives. Sodium Fluoride is also used in the manufacture of chemical and biological weapons. Although this form of fluoride can be used for water fluoridation, the next two forms listed are almost always used due to cost.

 

Calcium Fluoride (CaF2)

 

The compound of calcium and fluorine which occurs naturally as the mineral fluorite – also called fluorspar. Most of the world’s fluorine comes from calcium fluoride. 

 

Fluorides, in general, are toxic to humans, however, CaF2 is considered the least toxic, and even relatively harmless due to its extreme insolubility. Moreover, calcium is a well-known antidote for fluoride poisoning.

 

When an antidote exists in combination with a poison, it makes the poison far less toxic to the body. Calcium fluoride is the form of fluoride commonly found in natural, untreated waters.

 

Cryolite

 

Or Sodium Aluminum Fluoride is commonly used for aluminum smelting, though is also a pesticide often applied directly to field crops, resulting in permitted fluoride residues in and on fresh fruits and vegetables.

 

Fluorosilicic Acid (H2SiF6)

 

Commonly used for water fluoridation. This form of fluoride is a toxic liquid by-product, acquired by scrubbing the chimney stacks of phosphate fertilizer manufacture. Other names for it are hexafluorosilicic,  hexafluosilicic,  hydrofluosilicic,  and silicofluoric acid.

 

Sodium Fluorosilicate (Na2SiF6)

 

Primarily added to public drinking water as a fluoridation agent. This same compound is also used as an insecticide and a wood preservative.

 

It is a classified hazardous waste by-product of phosphate fertilizer manufacture which, if not put into our drinking water, must be disposed of at hazardous waste facilities.

 

Other names for it are Sodium Fluosilicate and Sodium Silica Fluoride.

 

Stannous Fluoride

 

A popular name that is given to Tin (II) fluoride. Stannous Fluoride is an additive to many kinds of toothpaste because it does not become biologically inactive in the presence of calcium, as sodium fluoride does. (http://en.wikipedia.org/wiki/Tin%28II%29_fluoride)

 

Sulfuryl Fluoride

 

Applied as a gas fumigant to kill insects and rodents. Using sulfuryl fluoride around food products was not allowed due to its toxicity. In 2004 the EPA reversed this policy (following long lobbying efforts by the manufacturer) and allowed its use on food. This opened the doors for food processing companies nationwide to fumigate their facilities with sulfuryl fluoride, leaving high levels of fluoride in and on foods and even food packaging.

 

It has become acceptable for sulfuryl fluoride fumigations to produce fluoride residues of 70 ppm “in or on” processed foods and 130 ppm “in or on” wheat.

 

There have been no labeling requirements for foods treated with sulfuryl fluoride, meaning that consumers have had no way of knowing which foods are treated. On January 2011 this decision was reversed.