To fluoridate water means to add a small amount of fluoride (a natural mineral) to the public water supply to help prevent tooth decay. Many cities and towns fluoridate their drinking water because fluoride strengthens tooth enamel, the hard outer coating that protects teeth from cavities.

The practice started in the 1940s after scientists noticed that people living in areas with naturally fluoridated water had fewer cavities. Communities began adding fluoride to their water systems the same way they might add chlorine to kill germs. The amount added is tiny: about one part per million, roughly equal to one drop of water in a bathtub.

When you drink fluoridated water or brush your teeth with fluoride toothpaste, the fluoride helps repair weak spots in your enamel before cavities can form. Dentists and public health experts consider water fluoridation one of the most effective ways to reduce tooth decay across entire communities, especially for children whose teeth are still developing.

Some people debate whether water should be fluoridated, with supporters pointing to decades of cavity reduction and critics preferring individual choice about fluoride use. Most major health organizations support fluoridation as safe and beneficial, but communities ultimately decide whether to fluoridate their own water supplies.