Wisconsin Water Fluoride: Updated Statistics

Fluoride levels in Wisconsin’s drinking water have become a leading discussion point in recent years, fueled by changing municipal decisions and differing natural groundwater concentrations across the state. The statistics surrounding Wisconsin’s water fluoridation provide critical insights for anyone researching oral health trends, caries prevalence, and regional disparities.

This article compiles updated statistics on fluoridation coverage, community opt-outs, and the corresponding oral health impacts statewide. It also contextualizes Wisconsin’s data alongside neighboring states, enabling a broader comparison of current and historical trends. Read on for an in-depth, data-focused overview of where Wisconsin stands in 2025 and how its communities have shifted their fluoridation practices over the past two decades.

Despite no single statewide mandate, Wisconsin’s coverage levels have remained comparatively high but have declined steadily from early highs in 2005. Rural regions often rely on wells with naturally variable fluoride concentrations, which can be both above and below recommended ranges. This variability has generated a rich set of statistics that illustrate how dental health outcomes can correlate with local water fluoride levels.

Key Data Highlights

Below are a few core data points that underscore the fluoride situation in Wisconsin:

• From 2005 to 2024, the percentage of Wisconsin residents on fluoridated community water systems decreased from 92.4% to 83.6%.
• In rural, non-core counties, fluoridation rates dropped from 61.2% in 2011 to 54.8% by 2024.
• 28 communities ceased fluoridation between 2020 and 2024, impacting both small towns and mid-sized cities.
• Children in non-fluoridated Wisconsin areas experience a 32% higher prevalence of untreated cavities than those in fluoridated locations.

The sections below present a deeper dive into these statistics, showing how coverage rates have evolved, which demographics face the greatest disparities, and how Wisconsin’s numbers compare with those of neighboring states.

Historic Coverage Trends

These historical figures show how Wisconsin’s fluoridation efforts have shifted over time.

• In 2005, 92.4% of Wisconsin’s population on community water systems had access to fluoridated water.
• By 2015, coverage declined to 88.1%, driven largely by early opt-outs in some rural municipalities.
• Between 2020 and 2024, an additional 28 communities ended fluoridation programs.
• Declines outpaced national trends, where coverage remained near 72.3% overall.

Although Wisconsin once nearly matched or even exceeded coverage levels seen in many states, the statistics point to a gradual erosion of that early lead.

While these shifts involve multiple factors, the data confirm an accelerating downturn in public water fluoridation, especially over the past decade.

Current Coverage and Regional Disparities

The latest figures show a broad range of coverage levels depending on whether communities opt for artificial fluoridation or rely on naturally occurring fluoride.

• Statewide coverage stands at 83.6% as of 2024.
• Around 84.3% of water systems that remain fluoridated maintain optimal levels of 0.6–1.0 mg/L.
• Urban centers like Milwaukee and Madison report 94% compliance with recommended levels.
• Rural communities have shouldered the greatest declines, with some dropping below 55% coverage by 2024.

When groundwater fluoride levels are naturally low, many rural systems have chosen not to implement artificial supplementation, often citing cost and policy skepticism.

Factors like population density, municipal budgets, and local decision-making processes contribute to these disparities across Wisconsin’s diverse geography.

Comparisons with Neighboring States

Looking beyond Wisconsin helps contextualize how its fluoridation statistics align with regional norms.

• Minnesota maintains a 98.9% fluoridation rate, driven by a longstanding statewide requirement.
• Illinois holds a 95.3% coverage rate under a 2016 law standardizing 0.7 mg/L levels.
• Michigan’s coverage sits at 75.1%, balancing state guidelines and local discretion.
• Iowa closely resembles Wisconsin, with an estimated 82.4% coverage.

The statistical differences illustrate how policy approaches—whether mandated at the state level or left to municipalities—shape overall coverage rates.

This side-by-side breakdown underscores Wisconsin’s relatively high but gradually declining standing compared to its neighbors with stronger mandates.

Health Effects and Costs

Concrete statistics reveal significant oral health patterns tied to fluoridation levels in Wisconsin.

• Children in non-fluoridated Wisconsin areas see 32% more untreated cavities compared to fluoridated communities.
• Statewide, children’s dental caries rates are 18% higher than in Minnesota.
• Annual per-person savings on dental treatments average $61 in Wisconsin, compared to $89 in Minnesota, reflecting broader fluoride coverage there.
• Moderate to severe dental fluorosis remains under 3.1% in Wisconsin adolescents.

Overall, these findings highlight the balance between preventing caries and minimizing potential fluorosis when coverage is maintained within recommended ranges.

The data link higher fluoridation rates to lower treatment expenses and fewer emergency dental procedures, especially among low-income populations.

Groundwater and Natural Fluoride Variations

Wisconsin’s geology contributes another dimension to the fluoridation picture, as groundwater can have varying fluoride concentrations:

• Natural fluoride levels in some northeastern and rural Marathon County wells exceed 1.2 mg/L.
• Some groundwater sources measure fluoride content up to 4.2 mg/L in certain aquifers.
• These higher concentrations correlate with rare occurrences of skeletal fluorosis and joint pain in affected communities.
• Urban systems generally rely on controlled additions to keep levels at or around 0.7 mg/L.

As rural municipalities debate costs, they often weigh the presence of natural fluoride in their water sources when deciding whether to continue supplemental fluoridation.

Data show that naturally elevated levels reduce the need for added fluoride but can also raise concerns about overexposure if levels exceed the recommended range.

Key Statistics Summary

• 83.6% of Wisconsin residents now receive fluoridated water, down from 92.4% in 2005.
• Rural counties experienced a drop from 61.2% to 54.8% since 2011.
• Children in non-fluoridated parts of Wisconsin show a 32% higher rate of untreated cavities.
• Annual dental cost savings in Wisconsin average $61 per person with fluoridation.
• Some aquifers contain up to 4.2 mg/L of natural fluoride.

Overall, the data point to a notable decline in Wisconsin’s fluoridation coverage over the past two decades, especially in rural regions. These trends coincide with measurable shifts in dental health outcomes, demonstrating how fluctuating fluoride levels can influence both cost and caries rates. While neighboring states maintain higher rates of community water fluoridation through legal mandates, Wisconsin continues to balance local autonomy with public health considerations and natural groundwater variations.