The Centers for Disease Control and Prevention (CDC) says water fluoridation is one of the 10 greatest public health achievements of the 20th century.   Why? Because fluoridation helps to prevent the most common chronic disease in children: tooth decay.  In the early 1900s, people in Colorado Springs, Colo., got brown spots and mottled areas on their teeth from a mysterious dental disease named “Colorado Brown Stain.” This disease is actually fluorosis, which happens when developing teeth are exposed to excessive fluoride. The water they were drinking had extremely high natural levels of fluoride. However, scientists noted these Coloradans had very low rates of tooth decay.   Consequently, public health officials and dental scientists determined an optimal amount of fluoride to add to community water supplies.   Grand Rapids, Mich., was the world’s first city to fluoridate its water supply, in 1945. As evidence accumulated about the safety and effectiveness of water fluoridation, more cities worldwide followed suit. Clinical studies from the mid-20th century showed fluoridated water decreased tooth decay by 60-70 percent. Over time, especially with fluoridated toothpaste’s popularity, this impact diminished. Recent studies show fluoridated water still prevents up to 20-40 percent of cavities.   The decision to fluoridate water wasn’t, and still isn’t, taken lightly. Oral health experts continuously monitor and modify guidelines. The World Health Organization (WHO) endorses water fluoridation and recommends adding no more than 1.5 parts per million (ppm) fluoride. Studies of populations drinking natural water with fluoride levels far exceeding WHO’s recommendations found higher cancer and neurological diseases risk. But expert panels, including the CDC, categorize these studies as being low quality. The American Dental Association and U.S. Public Health Services recommend a maximum of 0.7ppm fluoride — the U.S. standard.   Fluoride isn’t the only additive in our water supplies: Other chemicals include aluminum sulfate, carbon dioxide, chlorine and ammonia. Imagine the toxic effects of too much of any of these chemicals. But we need them to make our drinking water safe and germ-free.   This exemplifies the therapeutic index: For any chemical (including medications), there’s an ideal dose, reminiscent of the Goldilocks fairy tale. Too little won’t have the desired effect, while too much can cause problems. Adding 0.7ppm fluoride is that “just right” amount; it helps prevent cavities without causing harmful effects.  Another public health intervention similar to water fluoridation is the addition of iodine to our table salt. In the early 1900s, many Americans were suffering the adverse health effects of iodine deficiency, including goiter. Once scientists identified therapeutic and safe levels of iodine, it was added to table salt starting in 1924. Within a few years, the prevalence of goiter drastically decreased. One hundred years later, table salt continues to be iodized. It’s important to note that excessive levels of iodine can cause thyroid disease and cancer. But when it’s added at a therapeutic level, it is safe and effective at preventing disease. This mirrors the situation with fluoride in our water and the disease of dental caries.  Despite the decades of evidence showing fluoride’s safety and effectiveness at preventing cavities, most New Jersey towns don’t fluoridate their water. This isn’t due to cost. Water fluoridation typically costs about $1 a person per year — a small investment compared with dental restorations costs. Public health research shows that for every $1 spent on preventing cavities, it saves the health system more than $50 in treatment costs for citizens who enrolled in Medicaid plans.  As of 2022, 16 percent of New Jersey residents had fluoridated water. The national average is almost 76 percent. This discrepancy sets up a natural experiment: If water fluoridation causes health problems, then New Jersey should be spared. But this isn’t the case. According to the CDC, New Jersey residents have higher cancer and autism rates than the national averages. A 2022 New Jersey Health Department survey found New Jersey children have higher untreated tooth decay rates than the national average. This higher decay rate might be partly because of the lack of water fluoridation.  Untreated tooth decay can cause tremendous pain and suffering. Studies show children with untreated tooth decay are three times more likely to miss school and children suffering from dental pain are four times more likely to have lower grades than their healthier peers. More than 2 million Americans go to emergency rooms each year with dental pain, burdening the health care system with billions of dollars in avoidable costs. In the worst-case scenarios, like that of 12-year-old Deamonte Driver, untreated dental decay can lead to fatal infections.   Tooth decay follows the same pattern as other chronic diseases, and certain marginalized populations suffer inequitable amounts. Children living in low-income households and racial minority children are nearly twice as likely to have cavities as their higher income, white peers. These children face barriers to accessing quality dental care, compounding their health problems and setting them up for a lifetime of poor oral health.   Water fluoridation is a powerful and equitable tool in the fight against tooth decay because household income and race don’t matter. The same optimally fluoridated water goes to every faucet in the municipality.   Arguably, any effort to remove fluoride from water supplies may be seen as a discriminatory policy. Research published after Calgary, Canada, stopped fluoridating their water supply showed higher amounts of tooth decay in all children. But low-income children had significantly more cavities than their higher income peers.  Removing fluoride from the water supply increases health care costs. The city of Juneau, Alaska, voted to stop fluoridating its water supply in 2007. By 2012, there was a significant increase in cavities in children living in Juneau. This increase in cavities led to increased treatment costs for children enrolled in Medicaid. This was especially pronounced in the youngest children (aged 0 to 5 years), for whom annual dental treatment costs increased 73 percent once fluoride was removed from the water.  A recent report published by the National Toxicology Program has caused a lot of concern over for the potential of fluoride in water to cause neurological damage. This report compiled data from studies conducted abroad, in areas where people were drinking water with naturally occurring fluoride at levels far greater than what the United States has in its intentionally fluoridated water supplies. Instead of weakening oral health measures based on sensationalized and misinterpreted data, we should focus on providing more cost-effective, evidence-based interventions such as water fluoridation.  Mary Beth Giacona is an assistant professor of pediatric dentistry at Rutgers School of Dental Medicine in Newark, N.J. She received her dental degree from Columbia University College of Dental Medicine and holds a master’s in public health from Yale University.