60 l © 2025 American Dental Association
Section 2: Safety
Chronic fluoride toxicity can develop after 10 or more years of exposure to very high levels of fluoride,
levels much higher than what is associated with drinking water fluoridated at recommended levels.
The primary functional adverse effect associated with long-term excess fluoride intake is skeletal
fluorosis.146,207 The development of skeletal fluorosis and its severity are directly related to the level and
duration of fluoride intake. For example, the ingestion of water naturally fluoridated at approximately
5 mg/L or greater for 10 years or more is needed to produce clinical signs of osteosclerosis (a mild form
of skeletal fluorosis that can be seen as a change in bone density on x-rays) in the general population.
In areas naturally fluoridated at 5 mg/L, daily fluoride intake of 10 mg/day would not be uncommon.146
A survey of x-rays from 170,000 people in Texas and Oklahoma whose drinking water had naturally
occurring fluoride levels of 4–8 ppm revealed only 23 cases of osteosclerosis and no cases of crippling
skeletal fluorosis.276 Evidence of advanced skeletal fluorosis, or crippling skeletal fluorosis, was not seen
in US communities where water supplies contained up to 20 mg/L of naturally occurring fluoride.146,277
In these communities, “daily fluoride intake of 20 mg/day would not have been uncommon.”146
Crippling skeletal fluorosis is extremely rare in the United States and is not associated with water
fluoridated at the recommended level.146,207
Additional information on this topic can be found in this Section, Question 26.
While large doses of fluoride could be toxic, it is important to recognize the difference in the effect
of a massive dose of an extremely high level of fluoride versus the recommended amount of fluoride
found in optimally fluoridated water. The implication that fluoride in large doses and fluoride in trace
amounts have the same effect is completely unfounded. Many substances in widespread use are very
beneficial in small amounts while toxic in large quantities.
The possibility of adverse health effects from continuous low-level consumption of fluoride over long
periods has been studied extensively. As with other nutrients, fluoride is safe and effective when used
and consumed properly. No charge against the safety of fluoridation has ever been substantiated
by generally accepted scientific knowledge. After more than 80 years of research and practical
experience, the best available scientific evidence indicates that fluoridation of community water
supplies is safe.
After more than 80 years of research and practical experience, the best available
scientific evidence indicates that fluoridation of community water supplies is safe.
Section 2: Safety
Chronic fluoride toxicity can develop after 10 or more years of exposure to very high levels of fluoride,
levels much higher than what is associated with drinking water fluoridated at recommended levels.
The primary functional adverse effect associated with long-term excess fluoride intake is skeletal
fluorosis.146,207 The development of skeletal fluorosis and its severity are directly related to the level and
duration of fluoride intake. For example, the ingestion of water naturally fluoridated at approximately
5 mg/L or greater for 10 years or more is needed to produce clinical signs of osteosclerosis (a mild form
of skeletal fluorosis that can be seen as a change in bone density on x-rays) in the general population.
In areas naturally fluoridated at 5 mg/L, daily fluoride intake of 10 mg/day would not be uncommon.146
A survey of x-rays from 170,000 people in Texas and Oklahoma whose drinking water had naturally
occurring fluoride levels of 4–8 ppm revealed only 23 cases of osteosclerosis and no cases of crippling
skeletal fluorosis.276 Evidence of advanced skeletal fluorosis, or crippling skeletal fluorosis, was not seen
in US communities where water supplies contained up to 20 mg/L of naturally occurring fluoride.146,277
In these communities, “daily fluoride intake of 20 mg/day would not have been uncommon.”146
Crippling skeletal fluorosis is extremely rare in the United States and is not associated with water
fluoridated at the recommended level.146,207
Additional information on this topic can be found in this Section, Question 26.
While large doses of fluoride could be toxic, it is important to recognize the difference in the effect
of a massive dose of an extremely high level of fluoride versus the recommended amount of fluoride
found in optimally fluoridated water. The implication that fluoride in large doses and fluoride in trace
amounts have the same effect is completely unfounded. Many substances in widespread use are very
beneficial in small amounts while toxic in large quantities.
The possibility of adverse health effects from continuous low-level consumption of fluoride over long
periods has been studied extensively. As with other nutrients, fluoride is safe and effective when used
and consumed properly. No charge against the safety of fluoridation has ever been substantiated
by generally accepted scientific knowledge. After more than 80 years of research and practical
experience, the best available scientific evidence indicates that fluoridation of community water
supplies is safe.
After more than 80 years of research and practical experience, the best available
scientific evidence indicates that fluoridation of community water supplies is safe.
