Recently, Robert F. Kennedy Jr. affirmed his plans to advise water systems in the United States to remove fluoride from public water. As an individual expected to influence public health policy during the next administration, his comments created substantial controversy around the risks and benefits of fluoride in drinking water.   The story of fluoride begins in 1901 when a dentist noticed that his patients from Colorado Springs, Colo., frequently had brown stains on their teeth but were also less likely to suffer tooth decay — findings he and colleagues later understood to be due to high levels of fluoride naturally entering the water from rocks and soil. Over the next 40 years, research into the subject demonstrated that adding fluoride to drinking water prevents many cavities and is good for dental health. Since 1945, when Grand Rapids, Mich., became the first city in the world to add fluoride to its public drinking water, adding fluoride to water has become a cheap strategy that has helped people in communities across the country.   Preventing cavities has many benefits beyond avoiding pain and the cost of seeing a dentist. Cavities add billions of dollars every year to health care costs and may also increase the risk for heart disease later in life, resulting premature death.   Currently, about two-thirds of people living in the United States use water that contains fluoride. As such, adding fluoride into water systems is one of the great public health achievements of recent times. But new research has raised important questions about the safety of fluoride. New research shows that fluoride affects the brain of the fetus during pregnancy. Much of that research has come from countries outside the U.S. Fluoride exposure among pregnant women in Canada was linked to lower IQ among children ages 3 to 4 years old. Similarly, fluoride among pregnant women in Mexico was associated with lower IQ, an increase in attention-deficit/hyperactivity disorder, and reduced brain function among children 6-12 years old. Finally, a new article in the Journal of the American Medical Association showed that fluoride in pregnant women living in the United States was linked with nearly double the chance that preschool-aged children would have behavior problems.  Many questions remain. What amount of fluoride is safe for a pregnant woman and her baby? At what age does the impact of fluoride happen? How can and should policy makers weigh the benefits of preventing cavities — which can be serious and result in bad infections and even death — with the risks of poor brain function? There are not yet answers to many of those questions, but the conversation around adding fluoride to water has become dangerously politicized. Such division is like past discussions surrounding vaccine mandates during the COVID-19 pandemic. And like COVID-19, the science surrounding fluoride in water is changing. That means we will likely continue to learn more about how fluoride impacts the brain of babies that may again require a change in perspective. But at present, we are faced with mounting evidence that something once thought very safe might be harming our children, and we need to rely on elected officials to address the problem.  The fact that chemicals may harm children is not new. Skin care products sold for children were found to have harmful compounds as recently as this year. Lead-based paint and gasoline were widely used until it became clear lead caused learning problems. Cough medicine was prescribed to young children for decades until research showed it does not work well and has serious side effects. We cannot expect to avoid every dangerous chemical. But we can and must be able to review the science and make changes in public policy as quickly as possible. Public health officials, policy makers, scientists and community health advocates will need to work together to decide if and how much, fluoride is added to water.   Whether or not effective dialogue can happen depends on trust. Policy makers and public health officials must trust each other and be trusted by the public. However, trust in medical and public health institutions was another casualty of the COVID-19 pandemic. Regaining that trust is hard, but framing public health issues along political battle lines makes it more difficult, if not impossible, to earn the trust of people with different political beliefs. Further research is needed to understand the risks and benefits of adding fluoride to our drinking water. For the health of our children, sober and balanced dialogue is urgently needed.  Lao-Tzu Allan-Blitz, MD, MPH, is a pediatrician and adult medicine specialist at Harvard Medical School’s Brigham and Women’s Hospital. Jeffrey D. Klausner, MD, MPH, is a professor of population and public health sciences at USC’s Keck School of Medicine. He is a former CDC medical officer.