Once hailed as a triumph of public health, water fluoridation is now under intense attack in the US.

Despite decades of data proving its efficacy at protecting teeth from decay—particularly children’s teeth—two states have now banned the use of fluoride in public water, and communities around the country have followed suit or are considering doing the same. The current US health secretary, Robert F. Kennedy Jr., who is known for his anti-vaccine advocacy and for peddling conspiracy theories, has pledged to remove fluoride from US water.