(Updated September 2016)
Thousands of research studies and more than 60 years of experience have demonstrated that fluoridating public drinking water is not only safe and effective, it is the best method of improving oral health in a community. In fact, the Centers for Disease Control and Prevention (CDC) recognized drinking water fluoridation as one of the 10 great major public health achievements of the 20th century. 
Although tooth decay can be prevented, it still affects more children in the United States than any other chronic infectious disease.
Fluoridation of drinking water, proven to reduce tooth decay in both children and adults, is endorsed by the American Dental Association (ADA). Studies prove water fluoridation continues to be effective in reducing tooth decay by 20 to 40%, even in an era with widespread availability of fluoride from other sources.[3,4]
Along with the CDC and the ADA, the American Medical Association, the American Cancer Society, the American Academy of Pediatrics, the National Institutes of Health, the National Parents-Teachers Association, and the World Health Organization support drinking water fluoridation.
Based on these benefits, the Santa Clara Valley Water District Board (SCVWD) of Directors decided in November of 2011 to provide optimal levels of fluoride at its three water treatment plants. Implementation of fluoridation is expected to be completed in December 2016 for eastern Santa Clara County, and in 2020 for western Santa Clara County.
Despite fluoridation's proven record, many consumers may not be familiar with its benefits or may be concerned about adding a chemical to their drinking water. The answers to some of the more frequently asked questions about fluoride are provided below.
Frequently asked questions
Q1. What is fluoride?
Fluoride is the electrically charged atom (or "ion") that makes up the naturally occurring element fluorine. Although fluoride comes from fluorine, its properties are very different, just like chloride in common table salt is very different from chlorine. Most sources of drinking water contain some naturally occurring fluoride.
Q2. What is fluoridation?
Fluoridation is the addition of fluoride to a drinking water supply so that it contains the level recommended for optimal protection against tooth decay.
Q3. Why is Santa Clara Valley Water District fluoridating its water supplies?
Community water fluoridation is supported by most major national and international health service organizations. Supporters include: the American Dental Association, American Medical Association, American Academy of Pediatric Dentistry, U.S. Centers for Disease Control and Prevention, and the World Health Organization. After hearing information from many sides of the issue over several months, in 2011 the SCVWD Board of Directors voted to fluoridate at the district’s three water treatment plants.
As a drinking water wholesaler, the Santa Clara Valley Water District is exempt from the state law which mandates fluoridation; however, local health officials have advocated for large-scale fluoridation to be applied in order to maximize the public health benefits and minimize the cost of treating municipal water supplies. Fluoridation at our three drinking water treatment plants would be the most cost-effective means of providing this proven health benefit to Santa Clara Valley.
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Q4. How does fluoride protect teeth against tooth decay?
Tooth enamel and the material underneath are made mostly of two common minerals--calcium and phosphate. Tooth decay occurs when acids produced by bacteria in the mouth dissolve or "demineralize" the teeth. Fluoride protects against tooth decay by slowing down or stopping demineralization, promoting "remineralization" and keeping the bacteria from producing too much acid.
According to the American Dental Association, during tooth formation, ingested fluorides become incorporated into tooth structures. Fluorides ingested regularly during the time when teeth are developing are deposited throughout the entire tooth surface and provide longer-lasting protection than those applied topically. Ingested fluorides are also present in saliva, which continually bathes the teeth providing a reservoir of fluoride that can be incorporated into the tooth surface to prevent decay. 
Q5. What proof is there that fluoridated water prevents tooth decay?
According to the American Dental Association, the effectiveness of water fluoridation has been documented in scientific literature for more than 60 years. Thousands of studies have been done which continue to prove fluoride’s effectiveness in decay reduction.
A 1987 study of 40,000 schoolchildren showed that the decay rate was 25% lower in children with continuous residence in fluoridated communities when the data was adjusted to control for fluoride exposure from supplements and topical treatments. 
In 1993, the results of 113 published studies in 23 countries were analyzed. The analysis concluded that “community water fluoridation is one of the most successful public health disease prevention programs ever initiated. It has the potential to benefit all age groups and all socioeconomic strata, including the lowest, which has the highest caries prevalence and is least able to afford preventive and restorative services. Community water fluoridation is also the most cost-effective of all community-based caries preventive methods.” 
In 2015, the U.S. Department of Health and Human Services (HHS) reviewed all available evidence and recommended community water be fluoridated throughout the USA, where feasible, at an optimal concentration of 0.7 parts per million.
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Q6. If I use a fluoridated toothpaste, am I already getting enough fluoride to protect against decay?
The American Dental Association (ADA) states that a study of 6- and 7-year-old children who had moved from a fluoridated community to a nonfluoridated community saw an 11% increase in decayed, missing or filled tooth surfaces over a 3-year period from the time the children moved, reaffirming that relying only on topical forms of fluoride is not an effective or prudent public health practice.  Decay reductions are greatest where water fluoridation is available in addition to topical fluorides, such as fluoride toothpaste and fluoride rinses. The ADA concludes that “studies prove water fluoridation continues to be effective in reducing dental decay by 20-40%, even in an era with widespread availability of fluoride from other sources, such as fluoride toothpaste.” 
Q7. How much fluoride is used to treat drinking water supplies?
On April 27, 2015, the U.S. Department of Health and Human Services (HHS) finalized its recommendation for an optimal drinking water fluoride level of 0.7 milligrams per liter (mg/L) or parts per million (ppm). Following this announcement, California’s Division of Drinking Water (DDW) posted an advisory stating that public water systems practicing fluoridation could immediately implement the recommended optimal level of 0.7 ppm with a control range of 0.6 ppm to 1.2 ppm.
Q8. How much fluoride will be in my drinking water once SCVWD starts to fluoridate?
Santa Clara Valley Water District’s drinking water contains natural levels of fluoride of about 0.1 milligrams per liter (mg/L) or parts per million (ppm). Once SCVWD begins to fluoridate, drinking water levels will average about 0.7 ppm to 0.8 ppm. However, since SCVWD is a drinking water wholesaler, and many retail water agencies in Santa Clara County have more than one source of supply, the water delivered to your home may not come from SCVWD. Interested consumers should contact their water provider to find out how much fluoride, if any, is likely to be in their tap water.
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Q9. What chemical will SCVWD be using to fluoridate its supplies?
While there are three chemicals commonly used to fluoridate municipal drinking water, SCVWD selected fluorosilicic acid as the most cost-effective bulk chemical to be used in the district's treatment processes. This is the most commonly used fluoride additive by large water systems and is approved for use by the State Water Resources Control Board’s Division of Drinking Water (DDW), who regulates the drinking water that we serve . The selected fluorosilicic acid is certified for compliance with the American National Standards Institute (ANSI) and National Sanitation Foundation (NSF) Standard 60. ANSI/NSF Standard 60 ensures that chemicals used to treat drinking water do not contribute contaminants to the water that could cause adverse health effects.
Q10. What are SCVWD's costs to fluoridate at its treatment plants?
SCVWD's estimated cost to fluoridate its supplies is approximately $2.35 per acre-foot of water treated; which is roughly equal to an increased treatment cost of $1.45 a year per household. This cost is largely dependent on the cost of the fluoride additive.
Q11. Once SCVWD adds fluoride at its treatment plants, do its retailers still need to treat their supplies?
Any agency relying on SCVWD for 100 percent of its treated drinking water will benefit from fully optimized fluoride concentrations. If a water system blends SCVWD supplies with other non-fluoridated supplies, additional fluoride treatment would be necessary within its system to maintain optimal fluoride levels. If no additional fluoride is added in the blended system, fewer overall health benefits would be provided.
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Q12. Is fluoride harmful to my health?
There have been literally hundreds, if not thousands, of studies that have looked at whether fluoride in drinking water is harmful to human health. These studies have looked at whether there is a link between fluoride and cancer, bone fractures as well as adverse effects on the immune system, kidneys, digestive system and reproductive system. The American Dental Association concludes that “the overwhelming weight of credible scientific evidence has consistently indicated that the fluoridation of community water supplies is safe.” 
That doesn't mean that no studies have ever shown a link between an adverse health effect and fluoride in drinking water. Some of the studies that suggested a link looked at drinking water with fluoride levels 10 or more times higher than what will be in water fluoridated by SCVWD or recommended by public health officials. Other studies, when repeated, did not find any link, were inconclusive or suggested that fluoride actually reduced the rate of certain diseases. It is important to look at the whole body of scientific evidence and the quality of the studies. Fortunately, many studies have been performed, and the conclusions of the ADA are based on a review of the many studies that have been undertaken.
In 2015, the Water Research Foundation published “State of the Science: Community Water Fluoridation.” Among the conclusions was this: “Concerns with community water fluoridation (CWF) and fluoride exposure have been examined based on the latest science. Many concerns with CWF were health related. Each of these concerns was addressed and a balance of scientific studies showed that none of these issues poses a risk to public health at CWF levels” (p. 26)
Q13. How does SCVWD plan to guard against over-feeding fluoride into its water supply?
To prevent chemical overfeed, SCVWD will monitor its treatment plant product water on a continuous basis using on-line analyzers, and will verify the accuracy of these analyzers with daily "grab" samples.
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Q14. I heard that fluoride can cause teeth to become discolored or pitted, is that true?
Dental fluorosis—a condition that changes the appearance of the teeth—can be caused by ingesting too much fluoride in early childhood when teeth are forming. It can range from very mild to severe. Very mild fluorosis is characterized by small, opaque, paper-white areas covering less than 25% of the tooth surface. Most dental fluorosis in the United States is caused by the ingestion of topical fluoride products (such as toothpaste). This condition usually occurs at fluoride levels much higher than the drinking water control ranges. The recommended optimum water fluoride concentration was established to minimize the likelihood of even mild dental fluorosis.
Q15. Should I give fluoridated water to my infant?
The American Dental Association states that is safe to use fluoridated water to mix infant formula. “If your baby is primarily fed infant formula, using fluoridated water might increase the chance for mild enamel fluorosis, but enamel fluorosis does not affect the health of your child or the health of your child’s teeth. Parents and caregivers are encouraged to talk to their dentists about what’s best for their child.” The ADA offers the following recommendations to decrease the chances of your child’s teeth developing fluorosis:
You can breast feed. Breast milk is very low in fluoride. Nursing mothers or pregnant women who drink fluoridated water do not pass on significant amounts of fluoride to their child.
You can use ready-to-feed formula.
You can use powdered or liquid concentrate formula mixed with water that either is fluoride-free or has low concentrations of fluoride.[14
Similarly, the Centers for Disease Control and Prevention notes that “recent evidence suggests that mixing powdered or liquid infant formula concentrate with fluoridated water on a regular basis may increase the chance of a child developing the faint, white markings of very mild or mild enamel fluorosis.” The CDC suggests that “to lessen this chance, parents can use low-fluoride bottled water some of the time to mix infant formula.” 
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Q16. Will I miss the benefits from fluoridation if I drink bottled water, vended water or water from a "water store"? What about home filtration devices?
If you mostly drink bottled water, water from vending machines or water from water stores, you may miss the benefits of an optimally fluoridated water supply. That's because all of these alternatives typically contain fluoride levels that are below the optimal level for prevention of tooth decay.
Q17. I still would rather not drink water that has fluoride added to it, what choices do I have?
You have several choices. Many brands of bottled water contain some levels of fluoride. You can call the consumer information number on the bottle's label and ask about the level of fluoride and whether this level is naturally low. Other brands of bottled water take tap water and then further treat it. The additional treatment, if by reverse osmosis or distillation will remove a significant amount of both naturally occurring fluoride and any fluoride added through fluoridation. These bottled waters will say "purified" water on the label and should have very low levels of fluoride. Again, call the consumer service number on the bottle's label for more information about the level of fluoride.
If you are considering vended water or water from a water store, make sure the water has been treated by reverse osmosis or distillation. You can also use home treatment devices that are reverse osmosis systems or distillation units. For a list of state-certified devices, go to: http://www.waterboards.ca.gov/drinking_water/certlic/device/watertreatmentdevices.shtml. NSF International, a not-for-profit testing organization, also certifies certain reverse osmosis home treatment devices and distillation units for the reduction of fluoride. You can search on-line for NSF-certified products at: http://www.nsf.org/certified/DWTU/. Home filtration devices must be maintained according to the manufacturer's instructions in order to ensure their effectiveness.
Q18. Will fluoridated water harm my pets?
According to the Centers for Disease Control and Prevention, research findings do not support an association between fluoridation and negative health effects on animals.
Q19. Where can I get more information about fluoride?
The ADA and CDC both have web sites that provide very good information about fluoride and fluoridation. Go to www.ada.org/fluoride.aspx or www.cdc.gov/fluoridation/.
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- Centers for Disease Control and Prevention. Ten Great Public Health Achievements -- United States, 1900-1999. MMWR 1999;48(12):241-3. (Back)
- Centers for Disease Control and Prevention. Oral Health Resources. http://www.cdc.gov/oralhealth/ (accessed August 31, 2016). (Back)
- Newbrun E. Effectiveness of water fluoridation. J Public Health Dent 1989;49(5):279-89. (Back)
- Brunelle JA, Carlos JP. Recent trends in dental caries in U.S. children and the effect of water fluoridation. J Dent Res 1990;69(Spec Iss):723-7. (Back)
- American Dental Association. Fluoridation Facts. 2005:10. (Back)
- ADA 2005:13. (Back)
- Ripa LW. A half-century of community water fluoridation in the United States: review and commentary.
J Public Health Dent 1993;53(1):17-44. (Back)
- U.S. Public Health Service Recommendation for Fluoride Concentration in Drinking Water for the Prevention of Dental Caries.(accessed August 31, 2016). (Back)
- ADA 2005:15. (Back)
- ADA 2005:4. (Back)
- ADA 2005:4. (Back)
- Water Research Foundation. State of the Science: Community Water Fluoridation. http://www.waterrf.org/PublicReportLibrary/4641.pdf (accessed August 31, 2016). (Back)
- ADA 2005:29-30. (Back)
- American Dental Association. Fluoride and Infant Formula: Frequently Asked Questions (FAQ). http://www.ada.org/4052.aspx (accessed August 31, 2016). (Back)
- Centers for Disease Control and Prevention. Community Water Fluoridation—Overview: Infant Formula and Fluorosis. http://www.cdc.gov/Fluoridation/safety/infant_formula.htm (accessed August 31, 2016). (Back)
- Centers for Disease Control and Prevention. Community Water Fluoridation. http://www.cdc.gov/Fluoridation/safety/health_effects.htm (accessed August 31, 2016). (Back)