In the early 1900s, a young dentist named Frederick McKay moved to a Colorado town where the residents’ teeth — though in some cases stained chocolate brown — had far less decay than was typical back then. He and other researchers eventually linked the phenomenon to fluoride in the town’s drinking water — a eureka moment that would usher in what is often called one of the 10 great public health achievements of the 20th century. Grand Rapids, Mich., in 1945 became the first city to fluoridate its water supplies. Today, two out of every three Americans receive drinking water containing the chemical, and the federal government is pushing to raise the numbers further.
Yet few substances found in drinking water trigger as emotional and polarized a public reaction as fluoride. In the fevered imaginations of conspiracy theorists, including members of the John Birch Society, fluoridation was denounced as a Communist plot, a view satirized in the film “Dr. Strangelove.”
It turns out that, when it comes to fluoride, there is a risk of getting too much. Abundant evidence suggests that while a small dose of the chemical can help prevent cavities, some American children are being exposed to amounts of fluoride that could be harmful to their teeth — and, possibly, even damaging to their brain development. A key reason is that our daily exposure to fluoride has been increasing for years, with the chemical used in everyday items such as bottled drinks, processed foods, toothpastes and mouthwashes, along with pesticide residues and even the air, thanks to industrial emissions.