Community Water Fluoridation Levels to Promote Effectiveness and Safety in Oral Health

Morbidity and Mortality Weekly Report

Weekly / Vol. 72 / No. 22 June 2, 2023

U.S. Department of Health and Human Services

Centers for Disease Control and Prevention

Community Water Fluoridation Levels To Promote Effectiveness and

Safety in Oral Health — United States, 2016–2021

Theresa J. Boehmer

; Srdjan Lesaja, MS

; Lorena Espinoza, DDS

; Chandresh N. Ladva, PhD

Drinking water fluoridated at the level recommended by the

U.S. Public Health Service (USPHS) reduces dental caries (cav-

ities) by approximately 25% in children and adults (1). USPHS

recommends fluoride levels to achieve oral health benefits and

minimize risks associated with excess fluoride exposure. To

provide the benefits of community water fluoridation, water

systems should target a level of 0.7 mg/L and maintain levels

≥0.6 mg/L (2). The Environmental Protection Agency (EPA)

sets a safety standard at 2.0 mg/L to prevent mild or moderate

dental fluorosis, a condition that causes changes in the appear-

ance of tooth enamel caused by hypermineralization resulting

from excess fluoride intake during tooth-forming years (i.e.,

before age 8 years). During 2016–2021, fluoride measurements

for 16.3% of population-weighted monthly fluoride measure-

ments (person-months) reported by community water systems

to CDC’s Water Fluoridation Reporting System (WFRS)

were <0.6 mg/L; only 0.01% of person-months exceeded

2.0 mg/L. More than 80% of population-weighted fluoride

measurements from community water systems reporting to

WFRS were above 0.6 mg/L. Although 0.7 mg/L is the rec-

ommended optimal level, ≥0.6 mg/L is still effective for the

prevention of caries. A total of 4,080 community water systems

safely fluoridated water 99.99% of the time with levels below

the secondary safety standard of 2.0 mg/L. Water systems are

encouraged to work with their state programs to report their

fluoride data into WFRS and meet USPHS recommendations

to provide the full benefit of fluoridation for caries prevention.

Monthly data from WFRS during 2016–2021 were analyzed

for water systems that added fluoride (adjusting systems);

these systems provide monthly average fluoride levels in mg/L.

These monthly average fluoride levels were compared for two

goals: prevention and safety. For prevention, reported levels

were compared with 0.7 mg/L, the USPHS-recommended

optimal fluoride level for preventing caries (3). For safety

(i.e., to minimize potential fluorosis)* (4), reported fluoride

levels were compared with the EPA’s secondary maximum

contaminant level (SMCL), of 2.0 mg/L. All analyses were

conducted using SAS (version 9.4; SAS Institute) and R (ver-

sion 4.1.3; The R Foundation). This activity was reviewed by

CDC and was conducted consistent with applicable federal

law and CDC policy.

†

Water system populations were obtained from WFRS for

each year during 2016–2021 (5). These populations are

updated periodically by the states directly to WFRS or annually

* EPA also sets a maximum contaminant level (MCL) of 4.0 mg/L to prevent

bone disease and mottling of teeth from fluorosis.

†

5 C.F.R. part 46, 21 C.F.R. part 56; 42 U.S.C. Sect. 241(d); 5 U.S.C. Sect.

552a; 44 U.S.C. Sect. 3501 et seq.

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The MMWR series of publications is published by the Office of Science, Centers for Disease Control and Prevention (CDC), U.S. Department of Health and Human

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Centers for Disease Control and Prevention

Rochelle P. Walensky, MD, MPH, Director

Debra Houry, MD, MPH, Chief Medical Officer and Deputy Director for Program and Science

Rebecca Bunnell, PhD, MEd, Director, Office of Science

MMWR Editorial and Production Staff (Weekly)

Charlotte K. Kent, PhD, MPH, Editor in Chief

Rachel Gorwitz, MD, MPH, Acting Executive Editor

Jacqueline Gindler, MD, Editor

Debbie Dowell, MD, MPH, Guest Science Editor

Paul Z. Siegel, MD, MPH, Associate Editor

Mary Dott, MD, MPH, Online Editor

Terisa F. Rutledge, Managing Editor

Teresa M. Hood, MS, Lead Technical Writer-Editor

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Technical Writer-Editors

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Alexander J. Gottardy, Maureen A. Leahy,

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Visual Information Specialists

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Terraye M. Starr, Moua Yang,

Information Technology Specialists

MMWR Editorial Board

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Matthew L. Boulton, MD, MPH

Carolyn Brooks, ScD, MA

Virginia A. Caine, MD

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Jewel Mullen, MD, MPH, MPA

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Lead Health Communication Specialist

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Health Communication Specialists

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Visual Information Specialists

by CDC from EPA’s State Drinking Water Information System.

Population-weighted monthly fluoride levels (person-months)

were calculated by multiplying each average monthly fluoride

level by the size of the population served by each water system.

Data are typically reported to WFRS on a monthly, quar-

terly, or yearly basis. Participation across states varies based on

fluoride-reporting requirements, drinking water or oral health

program staffing limitations, and fluoridation program funding

status. Among approximately 54,000 water systems in WFRS,

a total of 5,888 adjust fluoride levels and serve a population

of more than 200 million persons (145 million directly and

an additional 55 million through water systems that purchase

fluoridated water from adjusted water systems). Among the

systems in WFRS, a total of 4,080, serving a population of

124,616,896, provided at least 1 month of data during the

study period. Among 7,936,442,898 person-months during

2016–2021, only 796,283 (0.01%) exceeded the SMCL

;

16.3% were below 0.6 mg/L, and 83.7% of person-months

operated between 0.6 mg/L and 2.0 mg/L with the largest peak

in data at the 0.7 mg/L target (Figure).

Discussion

In this examination of the performance of U.S. water systems

reporting fluoride levels from the perspectives of preventing

caries and supporting established safety standards, the most

Fluoride levels rarely exceeded the MCL (0.002%).

common person-month fluoride level was the USPHS-

recommended level of 0.7 mg/L and fluoride levels rarely

exceeded the SMCL (0.01%). SMCL exceedances should be

minimized to reduce dental fluorosis. Dental caries are one of

the most common preventable chronic diseases among U.S.

children: approximately one in four children living below the

federal poverty level experiences untreated caries (6). Optimal

levels of water fluoridation prevent caries by providing frequent

and consistent contact with low levels of fluoride, ultimately

reducing tooth decay by 25% in children and adults (7). Water

systems that consistently and optimally fluoridate support the

reduction of tooth decay. Suboptimal water systems in which

fluoride concentrations are <0.6 mg/L are both ineffective in

using resources and in supporting the oral health of their com-

munities. Optimal fluoridation can be maintained with routine

maintenance and monitoring, which provide protection from

equipment malfunction, disruptions in fluoride supply, and

periodic system shutdowns.

Water fluoridation promotes health equity through its

proven effects on decreasing caries, reducing costs to families,

and being readily available at the tap. In light of these benefits,

Healthy People 2030, an ongoing initiative to improve popu-

lation health, set the objective to increase the proportion of

U.S. residents served by optimally fluoridated water systems

https://www.cdc.gov/mmwr/PDF/rr/rr4413.pdf

Morbidity and Mortality Weekly Report

MMWR / June 2, 2023 / Vol. 72 / No. 22 595

US Department of Health and Human Services/Centers for Disease Control and Prevention

FIGURE. Density estimation of population-weighted monthly average fluoride levels — United States, 2016–2021

0.5 1.00.0 1.5 2.0

Monthly average uoride level (mg/L)

987654321 100 11

Monthly average uoride level (mg/L)

Density of person-months

0.7 mg/L uoride target

2.0 mg/L uoride SMCL

Density of person-months

Abbreviation: SMCL = secondary maximum contamination level.

to 77.1% from 73.0% in 2018 (8). Currently, programs

nationwide receive a net savings of $6.5 billion per year by

averting direct dental treatment costs (tooth restorations and

extractions) and indirect costs (follow-up treatment and losses

of productivity) (9). After community water fluoridation was

discontinued in Juneau, Alaska, for example, a higher number

of caries-related procedures among persons aged <18 years was

documented, particularly in persons born after cessation of

Summary

What is already known about this topic?

Community water fluoridation delivers cavity-preventing

fluoride to everyone with access. The U.S. government sets

optimal fluoridation at 0.7 mg/L and a safety standard at

2.0 mg/L.

What is being added by this report?

During 2016–2021, a total of 4,080 community water systems

safely fluoridated water 99.99% of the time, with levels below

the secondary safety standard of 2.0 mg/L. However, 16.3% of

nearly 8 billion population-weighted monthly fluoride measure-

ments were <0.6 mg/L, placing the prevention of cavities

in jeopardy.

What are the implications for public health practice?

Water system managers are encouraged to work with their state

programs to report fluoride data to CDC and meet U.S. Public

Health Service recommendations to provide the full benefit of

cavity prevention through water fluoridation.

fluoridation, highlighting the long-term oral health benefits

of supporting access to fluoridated water (10).

The findings in this report are subject to at least two limita-

tions. First, CDC relies on state oral health and drinking water

programs to report operational information; 31% of adjust-

ing systems (5,888) did not report any fluoride levels during

2016–2021. Second, population values for all water systems

are obtained from EPA’s State Drinking Water Information

System federal database at the state’s discretion; however, addi-

tions and deletions of water systems and associated fluoridation

status must be received from the state programs. As a result,

counts of water system and information might differ from

other publicly available community water system databases.

Reporting in WFRS might be increased by improving data

sharing between state drinking water and oral health pro-

grams, especially in states where water system data are entered

into WFRS by the oral health program. Methods to increase

reporting can include creating a data-sharing memorandum of

understanding between the two programs and implementing

a state policy that requires water systems to conduct monthly

recording and reporting to the state.

Thousands of fluoride-adjusting community water systems

reach approximately 200 million persons in the United States.

To promote receipt of the full benefits of community water

fluoridation, water systems must manage resources to meet

the established 0.7 mg/L target consistently, especially those

Morbidity and Mortality Weekly Report

596 MMWR / June 2, 2023 / Vol. 72 / No. 22 US Department of Health and Human Services/Centers for Disease Control and Prevention

serving communities where fluoride measurements were

<0.6 mg/L. CDC carefully and continuously monitors emerg-

ing research about the benefits and risks of fluoride exposure

so that recommendations are evidence-based. CDC continues

to emphasize the importance of community water fluoridation

at the recommended level of 0.7 mg/L as the cornerstone of

dental caries prevention in the United States.** Water systems

are encouraged to work with their state programs to report their

fluoride data into WFRS and meet USPHS recommendations

to provide the full benefit of fluoride in caries prevention.

Maintaining and improving access to optimally fluoridated

water remains a vital, safe, and successful method for reduc-

ing dental caries and their associated costs for communities

and families.

** https://www.cdc.gov/fluoridation/guidelines/cdc-statement-on-community-

water-fluoridation.html

Corresponding author: Theresa J. Boehmer, [email protected].

Division of Oral Health, National Center for Chronic Disease Prevention and

Health Promotion, CDC;

DB Consulting Group, Inc., Bethesda, Maryland.

All authors have completed and submitted the International

Committee of Medical Journal Editors form for disclosure of potential

conflicts of interest. No potential conflicts of interest were disclosed.

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