While Florida calls itself the Sunshine State, from a geological and economic perspective, it could just as accurately be known as the Phosphate State.

The so-called Bone Valley of central Florida contains some of the largest phosphate deposits in the world, which supply global agriculture with one of its most important commodities: synthetic fertilizer. In the process, the mining industry leaves behind a scarred landscape denuded of vegetation and pocked with vividly colored waste disposal ponds that one writer described as “beautiful pools of pollution.”

Phosphate loaded by elevator at Port Tampa, FL in 1958.

Highly toxic hydrogen fluoride and silicon tetrafluoride gases are by-products of fertilizer production. Prior to the 1970s, these pollutants were vented into the atmosphere and gave central Florida some of the most noxious air pollution in the country.

During the 1960s, however, complaints by farmers and ranchers eventually forced reluctant manufacturers to invest in pollution abatement scrubbers that converted toxic vapors into fluorosilicic acid (FSA), a dangerous but more containable liquid waste.

A safety instructor checking fluoridation levels at the Fluoride Feed Station on Tinker Air Force Base in Oklahoma City, OK in 2016.

The U.S. National Institute for Occupational Safety and Health (OSHA) cautions that FSA, an inorganic fluoride compound, has dire health consequences for any worker that comes into contact with it. Breathing its fumes causes severe lung damage or death and an accidental splash on bare skin will lead to burning and excruciating pain. Fortunately, it can be contained in high-density cross-linked polyethylene storage tanks.

It is in such tanks that fluorosilicic acid has for the past half century been transported from Florida fertilizer factories to water reservoirs throughout the United States. Once there, it is drip fed into drinking water. This is a practice that the American Dental Association and numerous scientists and public health officials describe as “the precise adjustment of the existing naturally occurring fluoride levels in drinking water to an optimal fluoride level … for the prevention of dental decay.”

A worker watching the loading of powder fine phosphate in Mulberry, FL in 1947 (left). An 1892 map of phosphate deposits on the western edge of Florida (right).

The practice of adding fluoride compounds (mostly FSA and occasionally sodium fluoride) to drinking water is known as community water fluoridation. It has been a mainstay of American public health policy since 1950 and continues to enjoy the support of government health agencies, dentists, and numerous others in the medical and scientific community.

As with many chemical additives in the modern world, however, few people know much about it.

Many are surprised to learn that unlike the pharmaceutical grade fluoride in their toothpaste, the fluoride in their water is an untreated industrial waste product, one that contains trace elements of arsenic and lead. Without the phosphate industry’s effluent, water fluoridation would be prohibitively expensive. And without fluoridation, the phosphate industry would be stuck with an expensive waste disposal problem. 

A 2009 map depicting global fluoridated water usage with colors indicating the percentage of the population in each country with fluoridated water from natural and artificial sources.

Only a handful of countries fluoridate their water—such as Australia, Ireland, Singapore, and Brazil, in addition to the United States. Western European nations have largely rejected the practice. Nonetheless, dental decay in Western Europe has declined at the same rate as in the United States over the past half century. In fact, the more one looks at the history of fluoridation, the more it appears to be a relic of the sort of mid-20th century scientific incaution that gave us DDT, thalidomide, and other attempts at “better living through chemistry.”

This is not to vilify the early fluoridationists, who had legitimate reason to believe that they had found an easy and affordable way to counter a significant public health problem. However, the arguments and data used to justify fluoridation in the mid-20th century—as well as the fierce commitment to the practice—remain largely unchanged, failing to take into account a shifting environmental context that may well have rendered it unnecessary or worse.

An advertisement for the pesticide DDT from Time magazine in 1947 (left). An advertisement from the 1940s for children's wallpaper laced with DDT (right).

Ugly Smiles and Tough Teeth

Fluoride’s public health history is like a crime story with a twist. After following a trail of clues for many years, detectives finally catch their chief suspect and put him on trial. But it soon turns out that he has redeeming qualities that far outweigh the crime for which he was originally charged.

The indefatigable private eye in this case was a young Massachusetts-born dentist, Frederick McKay. After completing his training at the University of Pennsylvania School of Dentistry, McKay moved to Colorado Springs in 1901 to establish his first practice.

Dr. Frederick McKay in the early 20th century.

He soon became perplexed by the unsightly tea-colored stains that discolored many of his patients’ teeth, a condition that he was unable to find in the dental literature. McKay began calling it “brown stain” and “Colorado stain,” and nobody understood why many residents of that particular region suffered from it while those in neighboring counties did not. In the summer of 1909, McKay and some colleagues inspected the mouths of 2,945 Colorado Springs children and discovered that 87.5% suffered from the condition.

Upon further investigation, McKay determined that the Colorado Springs area was not unique. There were pockets of brown stain throughout the country. McKay began to conduct an informal epidemiological study. He examined the local diet, soil conditions, and air quality, but eventually decided that the culprit had to be the water.

“The evidence is so conclusive,” he wrote in 1927 to the Public Health Service (PHS) in Washington, D.C., “that it is futile to discuss it further from any other standpoint.” Despite testing numerous samples, however, he could not find anything unusual in the local water supply, which was clear, odorless, and agreeable to the taste. Nevertheless, he became increasingly convinced that some as yet undetected trace element in the water was responsible for the dental lesions.

A big step toward solving the mystery of brown stain occurred in 1931, when nervous chemists at the Aluminum Company of America (ALCOA) began to examine the water in Bauxite, Arkansas. The principle ore of aluminum, bauxite was vital to ALCOA’s production process. In 1909, the town’s growing population necessitated a new water supply, and ALCOA dug three deep wells to access the ample groundwater. In a few years, children in Bauxite began to be afflicted with brown stain. Initially, this was of no great concern to ALCOA. By the late 1920s, however, the company was fending off charges that its aluminum cookware was slowly poisoning the population.

The logo for the Aluminum Company of America (left). A mural of bauxite miners from the 1940s in Benton, AR (right).

ALCOA's chief chemist, H. V. Churchill, was concerned that any link between aluminum and brown stain would be a public relations disaster. So in 1930, he tested Bauxite’s water supply using the most advanced spectrographic equipment available at the time. The tests showed that the groundwater had unusually high levels of the element fluorine—15 parts per million (ppm), a result, he wrote McKay, “so unexpected in water that a new sample was taken with extreme precautions,” but showed the same outcome.

Soon after Churchill’s tests revealed the presence of fluoride compounds in water, animal experimentation by scientists at the University of Arizona firmly established a causal relationship between fluoride ingestion and stained teeth.

While McKay and Churchill were busy revealing fluoride’s undesirable effect on human teeth, a young Danish scientist, Kaj Roholm, was investigating the impact of industrial fluoride on human health.

A dentist examining children’s teeth at the Pine Ridge Indian Reservation in the 1940s or 1950s (left). Severe fluorosis, brown discoloration and mottled enamel, in an individual from an area of New Mexico with naturally occurring fluoride in the water (right).

In 1930, a dense layer of polluted fog settled over the Meuse Valley, a heavily industrial area in eastern Belgium, killing sixty people and sickening thousands. After lengthy and careful investigation, Roholm determined that gaseous fluoride compounds were responsible. Roholm also identified aluminum smelters as emitters of large quantities of fluoride gases.

In the mid-1930s, whether natural or anthropogenic, fluoride compounds were nothing but bad news for human and environmental health.

Just as fluoride’s negative image was beginning to crystalize in the minds of scientists and public health officials, however, a countervailing set of ideas began forming. Ironically, it also stemmed from the work of Frederick McKay.

Dr. Trendley H. Dean in the 1950s (left). An 1885 advertisement for cocaine for dental pain in children (right). 

As far as McKay could tell, the staining did not actually compromise the strength or physical health of teeth. On the contrary, people living in endemic brown-stain regions seemed to have fewer cavities than the general population.

The man who played the most important role in transforming fluoride’s medical image from tooth disfigurer to a potential prophylactic against dental caries—cavities that require either filling or removing teeth—was Trendley H. Dean. A St. Louis dentist who had joined the Army Dental Corps in World War I, Dean went on to become a key figure in public health dentistry. In 1930, he was appointed chief scientist of the newly established Dental Research Section of the Nation Institutes of Health, and then in 1948 became the first director of the National Institute of Dental Research.

A dentist and patient in the 1910s or 1920s.

Dean was quick to realize that solving the mystery of mottled enamel, though useful, was of secondary importance compared to the broader public health implications of dental caries. In a letter to the U.S. Surgeon General in 1932, Dean repeated McKay’s earlier observation that “individuals in an endemic [brown-stain] area show a lesser incidence of caries than individuals in some nearby non-endemic areas. Consequently, the study of mottled enamel may disclose some lead applicable to the vastly more important problem, dental caries.”

Once it became clear that fluoride was the cause of brown stain—which Dean would soon label dental fluorosis—Dean shifted the focus of his research, and that of the government’s health bureaucracy, from eliminating fluorosis to combatting caries.

Optimizing Nature

Dental caries was perceived as one of America’s most widespread health problems in the early twentieth century. Since dentists were comparatively few and dental surveys virtually nonexistent, it is difficult to know just how pervasive the condition was and to what extent, if at all, it had gotten worse over time.

An advertisement for Klenzo, a dental creme, in The Saturday Evening Post in 1920.

Nonetheless, dentists themselves were convinced that it had reached epidemic proportions, a perception that appears to have been borne out by military fitness records. These show that in 1916, for example, one third of potential recruits failed their health exam due to caries-related problems. As a result, funds began to flow toward dental research, both from government sources and from corporate foundations.

Many dentists and medical scientists were convinced that Americans’ diets, particularly their fondness for refined flour and sugar, were largely to blame. But changing people’s dietary habits, then as now, seemed to be an insurmountable obstacle.

No wonder, then, that Dean and others were excited by the discovery of fluoride’s impact on teeth.

During the 1930s, Dean, McKay, and colleagues from the PHS and various university dental schools set about trying to demonstrate fluoride’s connection to both dental fluorosis and reduced rates of caries. Although nobody understood exactly how it worked—and nobody would for a long time—fluoride did indeed seem to change the structure of teeth in a way that offered some protection against the assaults of the 20th century American diet.

Embarking on a succession of epidemiological studies in towns that had fluoride-rich water supplies, Dean was able to gradually zero in on a ratio that appeared to offer considerable protection against caries while causing limited and barely discernable fluorosis. The magic number, he determined, was 1 part per million (1ppm).

A 2009 map depicting areas with groundwater fluoride concentrations above the recommended levels.

As the studies continued, Dean and his colleagues published a series of articles that would become the scientific bedrock of fluoridation. So although water naturally containing 1ppm fluoride existed in very few places, it nonetheless came to be seen as the optimal level, and water containing less was deemed “fluoride deficient.”

Dean himself did not advocate artificially augmenting the level of fluoride in drinking water, at least not during the 1930s and 1940s. A cautious and methodical researcher, he felt that many years of further investigation would be required before such a prospect could be contemplated. Even the American Dental Association, subsequently fluoridation’s most steadfast advocate, was reluctant to endorse the idea. However, some dental researchers were less circumspect.

The sculpture “Steel Water” commemorates Grand Rapid’s role as the first city to fluoridate its water supply (photo by Jyoti Srivastava).

In the early 1940s, Dean began to explore the possibility of testing artificial fluoridation in a handful of carefully chosen communities. After consulting with colleagues at the University of Michigan, Dean selected the towns of Grand Rapids and Muskegon to participate in a 15-year fluoridation trial. Both cities drew their water, which had virtually no natural fluoride, from Lake Michigan. In January 1945, with the enthusiastic cooperation of city officials, Grand Rapids began adding sodium fluoride—a waste product of aluminum production—to its water supply while Muskegon remained fluoride free.

But not everyone was prepared to wait fifteen years.