Fluoride, the tooth health-boosting mineral that conjures images of dentists' offices for many, has been a standard additive to municipal water sources since the 1940s.

Naturally occurring in water, soil, plants, rocks and even the air, fluoride was discovered as a useful tool for preventing cavities and tooth decay by the late 1930s. In 1945, Grand Rapids, Michigan became the first city to fluoridate its community water, adjusting existing levels in the supply to the therapeutic 1.0 parts-per-million (ppm).

Since then, the levels have been adjusted to a maximum of 0.7 ppm or 0.7 milligrams of fluoride per liter of water which is considered optimal for preventing tooth decay.

According to the U.S. Centers for Disease Control and Prevention (CDC), 72.7% of the U.S. population on a community water source received fluoridated water as of 2020. This percentage has remained relatively consistent since 2008, according to CDC data, fluctuating between 72.4% at the lowest and 74.6% at the highest.

Last week, KFF Health reported that as the fluoride bans proliferate, the issue has divided communities.

While the CDC maintains that fluoridated water is both safe and cost-effective, questions as to potential hazards introduced by water fluoridation have existed as long as the practice has been popular.

Fluoride divide:As bans spread, fluoride in drinking water divides communities across the US

Communities concerned about fluoride risks

The potential for fluoride toxicity does technically exist, for example, but would require consuming an amount of fluoridated water that would kill a human via water intoxication before the amount of fluoride could become harmful or deadly, according to the Cleveland Clinic.

Other arguments have included a theorized connection between fluoridated water and increased cancer risk, a topic studied extensively. According to the National Cancer Institute, the most recent population-based studies found no evidence of an association between fluoride in drinking water and an increased risk of bone cancer, though past results have been mixed.

Other topics have been explored as science has evolved, including the impact of fluoride consumption on pregnancy, arthritis, IQ, and kidney disease. Again, results have been mixed and scientists say more research needs to be done to come to any strong conclusions.

Is fluoridated water still needed in the modern age?

Some have begun to speculate about the need for fluoridated water with so many dental hygiene products now available in stores. Detractors argue that there is no need to add more of the compound on top of what naturally occurs in water and that distributing it via drinking water is an imprecise and uncontrolled way of dosing residents.

The CDC says, however, that while hygiene products can help reduce tooth decay, the greatest protection comes when they are used in tandem with fluoridated water. Still, groups across the U.S. have taken up the cause of getting fluoride removed or banned from community water, saying the consumption of the mineral should be an individual choice.

Currently, a federal case in the California courts could change the practice, forcing the Environmental Protection Agency (EPA) to regulate or ban the use of fluoride in drinking water nationwide.

U.S. communities implement bans on fluoridated water

The Flouride Action Network, an anti-fluoride group, has tracked the ongoing battle in U.S. communities. As of 2023, the network says, more than 240 communities in the world have rejected the use of fluoridated water since 2010, more than 170 of which are in the U.S.

Some of these communities, like Weston, Georgia, have as few as 80 affected residents. Others, however, like Portland, Oregon have roughly 900,000.

According to the Flouride Action Network data, the overall number of U.S. residents not receiving fluoridated water after a community rejection, rule or ban went into place has steadily increased since 2010, with large gains between 2010 and 2014, followed by a less dramatic but still upward trend.

4.2 million Americans lived in communities without fluoridated water last year

In January 2011, the U.S. Department of Health and Human Services (HHS) announced plans to reduce the recommended fluoride level in drinking water, saying the U.S. has seen increased incidences of dental fluorosis in children, a tooth condition that can occur when exposed to too much fluoride, prompting some existing detractors to double down on their beliefs about fluoridated water.

Several official agencies acknowledged the increased consumption of fluoride through other means beyond water at this time, citing this fact as another reason for reducing the levels in drinking water.

In 2015, federal recommendations were simplified to make 0.7 pm the standard level at which fluoride should be present in community water.

According to the Flouride Action Network data, more than 4.2 million Americans lived in a community without fluoridated water in 2023, up from just 219,900 in 2010.

Not all states agree on fluoride

Some areas of the U.S. have been more aggressive than others in riding its community waters of added fluoride. The Fluoride Action Network data reported 16 states without any bans or removals of fluoridated water on record.

The rest of the states saw varying levels of rejection, with some like Alaska, Arizona, Idaho, Kansas, Louisana, Maine, Maryland, Montana, New Mexico, North Carolina, Ohio, Oregon, South Carolina, Vermont, West Virginia and Wyoming only reporting one or two counties in which fluoride had been removed from water.

Other states, however, like Pennsylvania, California, Florida, Tenessee, Missouri, and Wisconsin had well over five counties reporting such bans or removals. Pennsylvania had the most with 17 counties containing 647,232 residents, followed by Tennessee with 15 counties and Missouri with 10.

Others, like Oregon, New Mexico and Kansas had higher overall populations affected by a lack of fluoride in drinking water despite few counties participating; Oregon, for example, had 914,120 people represented by only two counties.

The fluoride fight continues

As Americans wait out the conclusion of the California case, it appears fluoride will remain a community issue.

The decision to omit added fluoride from community water is often made at local government assemblies and via a vote among sometimes hyperlocal government lines, meaning one community may make a decision that the bordering one does not.

While official health agencies have reaffirmed the assertion that fluoride continues to be safe, effective and even necessary, the movement's growth indicates what was once considered a fringe opinion has become more mainstream.