© 2025 American Dental Association l 11
Fluoridation Facts
3. What is water fluoridation?
Answer
Water fluoridation is the controlled adjustment of the natural fluoride concentration in
community water supplies to the concentration recommended for optimal dental health.
Fluoridation helps prevent tooth decay in children and adults.
Fact
In 2015, the HHS, using the best available science, established the recommended concentration for
fluoride in the water in the United States at 0.7 mg/L.39 This level effectively reduces tooth decay
while minimizing dental fluorosis.
The level of fluoride in water is measured in milligrams per liter (mg/L) or parts per million (ppm).
When referring to water, a concentration in mg/L is the same as ppm and the notations can be
used interchangeably. Thus, 0.7 mg/L of fluoride in water is identical to 0.7 ppm. The preferred
notation is mg/L.
At 0.7 mg/L, there are seven-tenths of one part of fluoride mixed with 999,999.3 parts of water.
While not exact, the following comparisons can be of assistance in comprehending 0.7 mg/L:
• 1 inch in approximately 23 miles
• 1 minute in approximately 1,000 days
• 1 cent in approximately $14,000
• 1 seat in more than 34 Wrigley Field baseball stadiums (seating capacity 41,268)
The following terms and definitions are used in this publication:
• Community water fluoridation is the controlled adjustment of the natural fluoride
concentration in water up to 0.7 mg/L, the level recommended for optimal dental health.
Other terms used interchangeably are water fluoridation, fluoridation, and optimally fluoridated
water. Optimal levels of fluoride can be present in the water naturally or by adjusted means.
• Sub-optimally fluoridated water is water that naturally contains less than the optimal
level (below 0.7 mg/L) of fluoride. Other terms used are non-fluoridated water and fluoride-
deficient water.
Additional information on this topic can be found in this Section, Question 6.
The level of fluoride in water is measured in milligrams per liter (mg/L) or parts
per million (ppm). When referring to water, a concentration in mg/L is identical
to ppm and the notations can be used interchangeably. Thus, 0.7 mg/L of fluoride
in water is identical to 0.7 ppm. The preferred notation is mg/L.
Fluoridation Facts
3. What is water fluoridation?
Answer
Water fluoridation is the controlled adjustment of the natural fluoride concentration in
community water supplies to the concentration recommended for optimal dental health.
Fluoridation helps prevent tooth decay in children and adults.
Fact
In 2015, the HHS, using the best available science, established the recommended concentration for
fluoride in the water in the United States at 0.7 mg/L.39 This level effectively reduces tooth decay
while minimizing dental fluorosis.
The level of fluoride in water is measured in milligrams per liter (mg/L) or parts per million (ppm).
When referring to water, a concentration in mg/L is the same as ppm and the notations can be
used interchangeably. Thus, 0.7 mg/L of fluoride in water is identical to 0.7 ppm. The preferred
notation is mg/L.
At 0.7 mg/L, there are seven-tenths of one part of fluoride mixed with 999,999.3 parts of water.
While not exact, the following comparisons can be of assistance in comprehending 0.7 mg/L:
• 1 inch in approximately 23 miles
• 1 minute in approximately 1,000 days
• 1 cent in approximately $14,000
• 1 seat in more than 34 Wrigley Field baseball stadiums (seating capacity 41,268)
The following terms and definitions are used in this publication:
• Community water fluoridation is the controlled adjustment of the natural fluoride
concentration in water up to 0.7 mg/L, the level recommended for optimal dental health.
Other terms used interchangeably are water fluoridation, fluoridation, and optimally fluoridated
water. Optimal levels of fluoride can be present in the water naturally or by adjusted means.
• Sub-optimally fluoridated water is water that naturally contains less than the optimal
level (below 0.7 mg/L) of fluoride. Other terms used are non-fluoridated water and fluoride-
deficient water.
Additional information on this topic can be found in this Section, Question 6.
The level of fluoride in water is measured in milligrams per liter (mg/L) or parts
per million (ppm). When referring to water, a concentration in mg/L is identical
to ppm and the notations can be used interchangeably. Thus, 0.7 mg/L of fluoride
in water is identical to 0.7 ppm. The preferred notation is mg/L.
