drinking water fluoridation and childrens health page



October 2007

The California Department of Public Health (CDPH) recommends suspending prescription fluoride supplements for one year in areas served by the Metropolitan Water District of Southern California.


Pursuant to Title 22, Section 64433.7 of the California Code of Regulations, this letter serves as official notice that the Metropolitan Water District of Southern California (MWD) will begin to increase the fluoride content of the treated water it supplies to its member agencies within Los Angeles, Orange, Riverside, San Diego, and Ventura counties.  The fluoride level in the water supplied from all five MWD treatment plants will be increased from the current levels of 0.1 - 0.4 ppm (mg/L) to 0.7 - 0.8 ppm starting October 29, 2007.  By adjusting the fluoride content of MWD's treated water supply, the MWD will supply its member agencies with water that contains the optimal level of fluoride.  This important preventive public health measure will help reduce the incidence of dental caries (tooth decay) for residents of all ages in our community.  


Local Public Water Systems

Local public water systems that use exclusively MWD water will be receiving, and thus delivering, optimally fluoridated water to their customers.  However, the MWD service delivery area is vast and some systems blend MWD water with their own local water sources before it is supplied to customers. This may result in the blended water having suboptimal fluoride levels (<0.6 ppm).  While suboptimal fluoridation still provides some benefit, the CDPH has requested local public water systems use a one-year period to determine the average fluoride level of the blended water supplied to customers.  


Prescription Fluoride Supplements

Prescribing fluoride supplements is at the professional discretion of health providers based on factors such as the current level of fluoride in the local public water system as well as a patient’s overall risk for dental disease. However, it is recommended that physicians and dentists suspend supplements for one year after the MWD implementation date in order to allow the local public water systems mentioned above time to record average fluoride levels in their water. Halting supplements during this one-year period will help ensure that consumers do not receive more fluoride than is necessary and will not affect tooth formation in children. After one year (October 29, 2008) and thereafter, we recommend providers resume verifying the fluoride level of local public water system using the CDPH website listed below. This will help guide physicians and dentists in providing updated fluoride supplement prescriptions to patients. If the average fluoride level of a local public water system is 0.6 ppm or greater, the CDPH and U.S. Centers for Disease Control & Prevention suggest you discontinue fluoride supplements for your patients.


To review fluoride levels in California public water systems, refer to the section entitled

“Fluoride Levels in Public Water Systems”

on the CDPH website at:





Fluoridation Resources

If you need further information, please refer to the following agencies:


  • Professional resources on fluoridation:

www.cdc.gov/fluoridation or



  • Information about the MWD fluoridation program: 

www.mwdh2o.com (click on the fluoridation link) or 1-800-354-4420


For all other information pertaining to local public water programs, check with your local public water system.


“The fact is that I started out as somewhat skeptical and cautious about fluoridation. But then I became a firm believer as proof was assembled by scientists that fluoridation of a water supply will reduce the production of tooth cavities (our most prevalent disease) by 60%, and, just as important, that no disease or defect is caused by this procedure. What particularly allayed my early doubts about adding a chemical to public water supplies was learning that fluoride has always occurred naturally in water supplies.” Dr. Benjamin Spock
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