© 2025 American Dental Association l 85
Fluoridation Facts
on the health effects of fluoridation were completed in communities that were using the silicofluoride
additives, generally fluorosilicic acid.369–374
However, at that time, the additives used to fluoridate were not always identified in research reports.
As the body of research on fluoridation grew, it became evident that there were no adverse health
effects associated with water fluoridation regardless of which fluoride additive was used. Additionally,
over time, a number of comprehensive reviews of the health effects of fluoridation were published.
These reviews, which support the safety of water fluoridation, include many studies conducted in
large, fluoridated communities that used the silicofluoride additives.10,25,182,183,185,375–377
There is now more than 80 years of practical experience that supports the statement that the best
available science demonstrates that fluoridation is safe.
51. What is the source of the additives used to fluoridate water supplies
in the United States?
Answer
The majority of fluoridation additives used in the United States are derived from the mineral apatite
(a component of calcium phosphate).
Fact
About 95% of the fluoridation additives used in water fluoridation are byproducts that come from the
processing of calcium phosphate into phosphate fertilizer. About 4% are derived from the processing
of calcium fluoride, and the remaining 1% are from the production of high-purity silica.89
In the production of phosphate fertilizer, calcium phosphate ore (which contains apatite) is mixed
with sulfuric acid, resulting in a calcium sulfate (gypsum) slurry. The gaseous phosphoric acid released
from this process is collected by vacuum extraction, condensed, and then desiccated and formed
into phosphate fertilizer pellets. Fluoride is a trace constituent (3–7%) of the mineral apatite found in
calcium phosphate ore. Silica tetrafluoride is also released as a gas in the creation of the calcium sulfate
slurry and is collected by vacuum extraction along with the gaseous phosphoric acid. In about half of
US phosphate fertilizer plants, the silica tetrafluoride gas is condensed and processed along with the
phosphoric acid and becomes a trace component of the phosphate fertilizer. In the other plants, the
silica tetrafluoride gas is separated from the phosphoric acid. Roughly 60% of the fluoride recovered
from processing calcium phosphate ore is sold for use as a fluoridation additive. The fluoridation
additive produced by this process is fluorosilicic acid. While most of the product is sold as fluorosilicic
acid, some of the product is partially neutralized to sodium fluorosilicate salt and some is fully
neutralized to sodium fluoride salt. In the United States, about 77% of the fluoridation additives used
are fluorosilicic acid, 15% are sodium fluorosilicate, and 8% are sodium fluoride.89
About 4% of the fluoridation additives used are derived from the processing of calcium fluoride
into hydrogen fluoride using a gas separation technique to recover the fluorosilicic acid from the
hydrogen fluoride.89
About 1% of the fluoridation additives used are derived from the production of high-purity silica.
Fluorosilicic acid is produced as part of the purification of silica.89
Fluoridation Facts
on the health effects of fluoridation were completed in communities that were using the silicofluoride
additives, generally fluorosilicic acid.369–374
However, at that time, the additives used to fluoridate were not always identified in research reports.
As the body of research on fluoridation grew, it became evident that there were no adverse health
effects associated with water fluoridation regardless of which fluoride additive was used. Additionally,
over time, a number of comprehensive reviews of the health effects of fluoridation were published.
These reviews, which support the safety of water fluoridation, include many studies conducted in
large, fluoridated communities that used the silicofluoride additives.10,25,182,183,185,375–377
There is now more than 80 years of practical experience that supports the statement that the best
available science demonstrates that fluoridation is safe.
51. What is the source of the additives used to fluoridate water supplies
in the United States?
Answer
The majority of fluoridation additives used in the United States are derived from the mineral apatite
(a component of calcium phosphate).
Fact
About 95% of the fluoridation additives used in water fluoridation are byproducts that come from the
processing of calcium phosphate into phosphate fertilizer. About 4% are derived from the processing
of calcium fluoride, and the remaining 1% are from the production of high-purity silica.89
In the production of phosphate fertilizer, calcium phosphate ore (which contains apatite) is mixed
with sulfuric acid, resulting in a calcium sulfate (gypsum) slurry. The gaseous phosphoric acid released
from this process is collected by vacuum extraction, condensed, and then desiccated and formed
into phosphate fertilizer pellets. Fluoride is a trace constituent (3–7%) of the mineral apatite found in
calcium phosphate ore. Silica tetrafluoride is also released as a gas in the creation of the calcium sulfate
slurry and is collected by vacuum extraction along with the gaseous phosphoric acid. In about half of
US phosphate fertilizer plants, the silica tetrafluoride gas is condensed and processed along with the
phosphoric acid and becomes a trace component of the phosphate fertilizer. In the other plants, the
silica tetrafluoride gas is separated from the phosphoric acid. Roughly 60% of the fluoride recovered
from processing calcium phosphate ore is sold for use as a fluoridation additive. The fluoridation
additive produced by this process is fluorosilicic acid. While most of the product is sold as fluorosilicic
acid, some of the product is partially neutralized to sodium fluorosilicate salt and some is fully
neutralized to sodium fluoride salt. In the United States, about 77% of the fluoridation additives used
are fluorosilicic acid, 15% are sodium fluorosilicate, and 8% are sodium fluoride.89
About 4% of the fluoridation additives used are derived from the processing of calcium fluoride
into hydrogen fluoride using a gas separation technique to recover the fluorosilicic acid from the
hydrogen fluoride.89
About 1% of the fluoridation additives used are derived from the production of high-purity silica.
Fluorosilicic acid is produced as part of the purification of silica.89
