Pipe Dreams: America's Fluoride Controversy

Three satyrs wreak dental havoc in a Dutch caricature of tooth decay.

Three satyrs wreak dental havoc in a Dutch caricature of tooth decay. National Library of Medicine.

Chasing the Colorado Stain

The path to widespread fluoridation began a century ago and a continent away. In 1901, in Naples, Italy, a surgeon named John Eager worked for the U.S. Marine Hospital Service conducting medical examinations of prospective U.S. immigrants. Day after day he observed otherwise healthy men and women whose teeth had a mottled, brown stain. Other teeth had black lines running horizontally across them. The locals had named these conditions denti neri and denti scritti: respectively, “black teeth” and “written-upon teeth.” Eager had never seen anything like it. Neither had his superiors, who published the first scientific description of these mysterious blemishes. Remarkably, given the lack of any evidence, Eager hypothesized a connection between the affected denti and the local drinking water.

Eager never followed up on his intuition, but that same year Frederick McKay, a dentist in Colorado Springs, became fascinated by what he called “Colorado stain.” Like Eager, he had a high number of patients with stained and mottled teeth. As he investigated, he found similar defects in the teeth of 80% of the town’s schoolchildren. The staining wasn’t limited to Colorado Springs, one of the wealthiest cities in the United States at the time. Communities throughout Colorado exhibited the same defects. Rich or poor, it didn’t seem to matter.

McKay’s findings drew little notice until 1915. That year he collaborated with G. V. Black, dean of the dental school at Northwestern University. They published a series of five papers in Dental Cosmos about the defects, suggesting that they began early, as children’s teeth developed.

As McKay publicized similar stories from around the country, dental experts offered their own theories. Some speculated about deficiencies of calcium or too much iron; radioactivity and heredity also came under suspicion. McKay, though, homed in on drinking water as the culprit. On a 1927 visit to Naples, McKay discovered children in one district who no longer showed evidence of denti neri and denti scritti. Pozzuoli, the Neapolitan suburb now free of the stain, had switched the source of its water supply.

Though McKay believed he had conclusively linked Colorado stain to a variable in drinking water, he couldn’t identify it. At chemical labs water from stain-afflicted communities looked the same as that from nonstain areas.
It took H. V. Churchill, chief chemist of the Aluminum Mining Company of America (Alcoa), to find the culprit. In 1931 the Public Health Service called McKay to Bauxite, Arkansas, a well-water town, to examine the children’s stained teeth. Neighbors drinking from seemingly identical river water had no stains, but McKay still couldn’t decipher the puzzle. Bauxite, though, was an Alcoa company town. Anti-aluminum sentiment (a different set of public fears) was remarkably high; it was not a good time to be an aluminum company with a town full of black-toothed children. So Churchill ran his own tests, determined to identify all trace elements, which McKay’s instruments couldn’t reliably detect.

The results were obvious. The water contained fluoride concentrations of 13.2 parts per million (ppm)—around 26 times the average. Other afflicted communities also showed elevated fluoride levels. With further study the correlation became causation: after 30 years researchers had transformed “Colorado stain” into dental fluorosis.

The Paradox of Texas Teeth

Of course, if dental fluorosis were the only effect of high fluoride intake, no one would have ever suggested adding it to drinking water. In fact, early research often focused on removing it. But by 1928 McKay had noticed that mottled teeth had markedly fewer cavities.

This discovery planted seeds within the Public Health Service, especially with H. Trendley Dean, a dental researcher leading a long-term investigation of mottled teeth. He took a nationwide epidemiological approach, identifying pockets of fluorosis throughout the country. As he and his team compiled their data, the correspondence between mottling and resistance to decay became more and more obvious.

Dean’s findings reached the public in a 1942 Collier’s article, “The Town Without a Toothache.” The water in Hereford, Texas, the story revealed, had a fluoride concentration of 3 ppm—again well above the 0.5 ppm average and above Dean’s tentative threshold of 1.0 ppm. He believed at that concentration children got the maximum decay-resistance benefit without a significant increase in dental fluorosis. The Collier’s article was a feel-good story about fluoride’s benefits and never mentioned Hereford’s brown, mottled “Texas teeth.” Neither did subsequent reprints in national newspapers and Reader’s Digest. Suddenly press releases about fluoride research became front-page news, and a connection between the chemical and dental health became cemented in the public imagination.