40 l © 2025 American Dental Association
Section 2: Safety
In 2015, the USPHS published a final report establishing guidance for water systems that are actively
fluoridating or those that may initiate fluoridation in the future.39 For community water systems that
add fluoride to their water, the USPHS recommends a uniform fluoride concentration of 0.7 mg/L
(ppm) for the entire United States to maintain caries (tooth decay) prevention benefits and reduce
the risk of dental fluorosis.
The USPHS further noted that surveillance of dental caries (tooth decay), dental fluorosis, and fluoride
intake through the National Health and Nutrition Examination Survey (NHANES) will be done to monitor
changes that might occur following implementation of the recommendation.39
20. What is the recommendation for the maximum level of naturally
occurring fluoride in drinking water contained in the 2016 EPA
6-Year Review 3?
Answer
As established by the EPA, the maximum allowable level of naturally occurring fluoride in drinking
water is 4 mg/L (or ppm). Under the Maximum Contaminant Level (MCL) standard, if the naturally
occurring level of fluoride in a public w0ater supply exceeds the MCL, the water supplier is required
to lower the level of fluoride below the MCL—a process called defluoridation. The MCL is a federally
enforceable standard.197 (Additional details regarding the EPA maximum contaminant standards can
be found in Figure 3.)
Fact
Under the Safe Drinking Water Act (SDWA),197 the EPA is required to periodically review the existing
National Primary Drinking Water Regulations (NPDWRs) “not less often than every 6 years.” This
review is a routine part of the EPA’s operations as dictated by the SDWA.
In April 2002, the EPA announced the results of its preliminary “revise/not revise” decisions for 68
chemical NPDWRs as part of its first 6-Year Review of drinking water standards.198 Fluoride was one
of the 68 items reviewed. While the EPA determined that it fell under the “Not Appropriate for Revision
at this Time” category, the agency asked the National Academies to update the risk assessment for
fluoride. The NRC previously had completed a review of fluoride for the EPA, which was published
as Health Effects of Ingested Fluoride in 1993.25
The NRC’s Committee on Toxicology created the Subcommittee on Fluoride in Drinking Water,26 which
reviewed toxicologic, epidemiologic, and clinical findings published since 1993 and exposure data on
orally ingested fluoride from drinking water and other sources (e.g., foods and beverages, toothpaste,
dental rinses). Based on these reviews, the subcommittee evaluated independently the scientific and
technical basis of the EPA’s maximum contaminant level goal (MCLG) of 4 mg/L and the secondary
maximum contaminant level (SMCL) of 2 mg/L in drinking water (see Figure 3).
On March 22, 2006, almost 3 years after work began, the NRC issued a 500-page report titled
Fluoride in Drinking Water—A Scientific Review of the EPA’s Standards26 to advise the EPA on the
adequacy of its fluoride MCLG and SMCL to protect children and others from adverse effects.
(For additional information on the EPA maximum contaminant standards, refer to Figure 3.)
The report contained two major recommendations related to the MCLG:
Continued on page 52
Section 2: Safety
In 2015, the USPHS published a final report establishing guidance for water systems that are actively
fluoridating or those that may initiate fluoridation in the future.39 For community water systems that
add fluoride to their water, the USPHS recommends a uniform fluoride concentration of 0.7 mg/L
(ppm) for the entire United States to maintain caries (tooth decay) prevention benefits and reduce
the risk of dental fluorosis.
The USPHS further noted that surveillance of dental caries (tooth decay), dental fluorosis, and fluoride
intake through the National Health and Nutrition Examination Survey (NHANES) will be done to monitor
changes that might occur following implementation of the recommendation.39
20. What is the recommendation for the maximum level of naturally
occurring fluoride in drinking water contained in the 2016 EPA
6-Year Review 3?
Answer
As established by the EPA, the maximum allowable level of naturally occurring fluoride in drinking
water is 4 mg/L (or ppm). Under the Maximum Contaminant Level (MCL) standard, if the naturally
occurring level of fluoride in a public w0ater supply exceeds the MCL, the water supplier is required
to lower the level of fluoride below the MCL—a process called defluoridation. The MCL is a federally
enforceable standard.197 (Additional details regarding the EPA maximum contaminant standards can
be found in Figure 3.)
Fact
Under the Safe Drinking Water Act (SDWA),197 the EPA is required to periodically review the existing
National Primary Drinking Water Regulations (NPDWRs) “not less often than every 6 years.” This
review is a routine part of the EPA’s operations as dictated by the SDWA.
In April 2002, the EPA announced the results of its preliminary “revise/not revise” decisions for 68
chemical NPDWRs as part of its first 6-Year Review of drinking water standards.198 Fluoride was one
of the 68 items reviewed. While the EPA determined that it fell under the “Not Appropriate for Revision
at this Time” category, the agency asked the National Academies to update the risk assessment for
fluoride. The NRC previously had completed a review of fluoride for the EPA, which was published
as Health Effects of Ingested Fluoride in 1993.25
The NRC’s Committee on Toxicology created the Subcommittee on Fluoride in Drinking Water,26 which
reviewed toxicologic, epidemiologic, and clinical findings published since 1993 and exposure data on
orally ingested fluoride from drinking water and other sources (e.g., foods and beverages, toothpaste,
dental rinses). Based on these reviews, the subcommittee evaluated independently the scientific and
technical basis of the EPA’s maximum contaminant level goal (MCLG) of 4 mg/L and the secondary
maximum contaminant level (SMCL) of 2 mg/L in drinking water (see Figure 3).
On March 22, 2006, almost 3 years after work began, the NRC issued a 500-page report titled
Fluoride in Drinking Water—A Scientific Review of the EPA’s Standards26 to advise the EPA on the
adequacy of its fluoride MCLG and SMCL to protect children and others from adverse effects.
(For additional information on the EPA maximum contaminant standards, refer to Figure 3.)
The report contained two major recommendations related to the MCLG:
Continued on page 52
