Naturally occurring fluoride is frequently present in drinking water sources throughout Washington State. Public water systems that have naturally occurring fluoride above 0.7 mg/l (milligrams of fluoride per liter of water) serve approximately 300,000 people.
The treatment process of adjusting fluoride to meet a therapeutic fluoride level in a public water system is regulated by Chapter 246-290-460 Washington Administrative Code and subject to enforcement by the Washington State Department of Health's Division of Drinking Water.
Systems that adjust fluoride must meet monitoring and reporting requirements, and are required by law to maintain the fluoride level in a water system at a concentration of 0.8 to 1.3mg/l throughout the distribution system.
View the Washington Administrative Code (WAC) Chapter 246-290-460, "Fluoridation of drinking water."
King County water systems currently being fluoridated:
- City of Kent
- King County Water District 111
- City of Redmond
- City of Renton
- Seattle Public Utilities
This list should not be used for the purpose of writing fluoride prescriptions for children. To do so could result in over-prescribing or under-prescribing fluoride supplements.
Public Health recommends that health practitioners or their patients contact their local water systems for more current and precise information on water fluoridation.