Fluoride, a naturally occurring element, exists in combination with other elements as a fluoride compound and is found as a constituent of minerals in rocks and soil. When water passes through and over the soil and rock formations containing fluoride, it dissolves these compounds, resulting in the small amounts of soluble fluoride present in virtually all water sources. For more information, see the Fluoride Dental Health Fact Sheet P-44532 (PDF, 11 KB).
The widespread use of fluorides in various forms (water, milk, salt, dentifrices, gels, rinses, tablets, drops, etc.) is in large part responsible for the significant declines in tooth decay. The right amount of fluoride in drinking water can reduce cavities in children by 20 to 40 percent. Many Wisconsin communities add fluoride to public drinking water supplies that do not have enough naturally occurring fluoride. However, there are many Wisconsin children whose drinking water comes from a private well that may or may not contain enough fluoride for maximum dental health.
The two maps on this page show the average natural fluoride concentrations in private wells in Wisconsin by zip code and by county. The data was obtained from water sample testing (1998-2003) of private wells by the State Laboratory of Hygiene. The maps indicate that higher levels of natural fluoride generally occur in eastern, northeastern and central areas of Wisconsin. Families with children should have the water from their private well tested for natural fluoride content. Children on private wells deficient in fluoride should receive dietary fluoride supplements. It is essential that a patient's individual private well source of drinking water be tested for fluoride content prior to prescribing fluoride supplements. The maps show average natural fluoride levels for zip code and county areas and are not specific to individual wells. For more information, see the Fluoride Supplementation fact sheet P-44531 (PDF, 111 KB).
Although fluoride has a beneficial effect within a range of low concentrations, at higher concentrations it may cause fluorosis. Dental fluorosis is a hypoplasia or hypomineralization of the dental enamel caused by the consumption of excessive amounts of fluoride during the years of tooth calcification. The prevalence and severity of fluorosis has been shown to increase when the concentration of fluoride in drinking water is above 2.0 ppm.
Source: Wisconsin Department of Health Services and the Wisconsin State Laboratory of Hygiene, July 2003. Average fluoride concentrations in parts per million (ppm). n=9999
Wisconsin Average Natural Fluoride Content in Wells by County
Source: Wisconsin Department of Health Services and the Wisconsin State Laboratory of Hygiene, July 2003.
Average fluoride concentrations in parts per million (ppm). n=42087
- Centers for Disease Control and Prevention. Recommendations for using fluoride to prevent and control dental caries in the United States. MMWR 2001;50 (No.RR-14).
- Ekstrand J, Fejerskov O, and Silverstone L. Fluoride in dentistry. Copenhagen: Munksgaard, 1988.