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The Mystery of the Colorado Brown Stain and the History of Fluoride


The Center for Disease Control has called community water fluoridation one of the 10 great public health achievements of the 20th century. This is due to its effectiveness, and low cost. In fact, the American Dental Association, American Academy of Pediatrics, US Public Health Service, and World Health Organization all advocate for fluoridating community water supplies. But, we haven’t always reaped the oral-health benefits of fluoride. Actually, until recently, we haven’t even fully understood the full scope of fluoride. It wasn’t until the early 1900’s that we began studying fluoride, and incorporating it into our health toolbox.

Colorado Brown Stain

In 1901, a young dental school graduate named Frederick McKay moved to Colorado Springs, Colorado to open a dental practice. Upon his arrival, he was astounded to observe that many of the locals suffered from brown stains on their teeth. Sometimes, these stains were so dark that it appeared as if their teeth were caked in dark chocolate. After observing this, McKay frantically searched for information about the disorder causing the stains.

Teeth mottling (dental fluorosis)

McKay invited a renowned dental researcher named Dr. G.V. Black to help him get to the root of the stain affecting those in Colorado Springs. In 1909, Black accepted the invitation and arrived in Colorado. For six years, the two worked together and found that nearly 90% of children native to Colorado Springs suffered from the stain. They gave the brown stain a more technical name (tooth mottling, which was later changed to fluorosis) and were surprised to discover that mottled teeth were highly resistant to tooth decay. While they couldn’t identify a cause for tooth mottling, they noted the anti-cavity effects of the stain and moved on.

A Trip across the Rockies

McKay was ever-vigilant in his quest to solve the brown stain issue. So much so, that in 1923 he went from Colorado Springs to Oakley, Idaho to investigate a recent uptick in tooth mottling in Oakley. The parents told McKay that the stains began appearing shortly after Oakley constructed a communal water pipeline to a warm spring five miles away. After examining and finding the water to be normal, McKay advised town leaders to abandon the pipeline and use a nearby spring as their water source. The town obliged, and within a few years the brown stains disappeared.

McKay still hadn’t found the exact cause, but he isolated the source of tooth mottling.

An Arkansas Aluminum Town

McKay then travelled to Bauxite, Arkansas, a town owned by an aluminum plant called the Aluminum Company of America (ALCOA). The residents of Bauxite were afflicted with mottled teeth, but nearby towns were not. McKay asked the town to conduct a study on the water, and returned to Colorado.

ALCOA’s chief chemist, H.V. Churchill, analyzed the water with more powerful tools than available to McKay when he was in Oakley. Several days after the study was conducted, Churchill found high levels of fluoride in the water at Bauxite. At first, he couldn’t believe it, and order a new sample. The second test showed the same results and compelled Churchill to write a 5 page letter to McKay.

The letter informed McKay of the fluoride findings, and Churchill urged him to test samples from Colorado Spring and Oakley for increased levels of fluoride. McKay obliged, and within months, he found the answer to the brown stain problem: increased levels of fluoride were in fact staining teeth.

National Institute of Health

After learning of McKay and Churchill’s findings, the National Institute of Health (NIH) decided to investigate water-borne fluoride, and the effects on teeth. Drs Trendley Dean and Elias Elvove first came up with a method to measure fluoride levels in water. Together, they developed a state-of-the-art method to measure fluoride levels in water with an accuracy of 0.1 parts per million (ppm). By the late 1930’s the NIH concluded that fluoride levels up to 1.0 ppm could not cause enamel fluorosis.

What about Cavity Protection?

Upon finding that miniscule amounts of fluoride would not stain teeth, the NIH went back to McKay’s writings where he observed the cavity resistance of those with the brown stain. Dean wondered whether adding fluoride to drinking water at physically and cosmetically safe levels would help fight tooth decay. This hypothesis, Dean told his colleagues, would need to be tested. In 1945, Grand Rapids Michigan voted to add fluoride to its drinking water. The 15 year study would be the first of its kind. After just 11 years, Dean announced that the cavity rate among children in Grand Rapids had dropped more than 60%. This was a major scientific breakthrough and helped revolutionize dental care.

Fluoride Today and in the Future

Today, fluoride is widely acknowledged as a way to prevent cavities. In the United States, community water fluoridation costs just over 1 dollar per person every year, which is a low price to pay for better oral health. Check online to see if your town uses a fluoridated water source. If not, we suggest buying fluoridated toothpaste to get your daily dose of cavity-preventing fluoride.

2 Responses to “The Mystery of the Colorado Brown Stain and the History of Fluoride”

  1. nyscof

    On world oral health day, people need to know that most US water supplies add an unnecessary, ineffective and harmful chemical into the water supplies in a failed effort to reduce tooth decay in tap water drinkers. Politics, not science, keeps fluoridation afloat. Fluoridation began with the mistaken belief that ingested fluoride was an essential nutrient required to make teeth decay-resistant – but only up to age 9 when all permanent teeth were fully emerged. But those theories, while well-intentioned, are wrong.

    Fluoride is not a nutrient, essential or needed. Consuming a fluoride-free diet does not cause tooth decay. Rotten diets make rotten teeth and no amount of fluoride has changed that. This is why tooth decay crises are occurring in all fluoridated cities and states.

    The US Centers for Disease Control also admits that those early theories are wrong. They want you to know “It is not CDC’s task to determine what levels of fluoride in water are safe”

    The CDC explains: “In the earliest days of fluoride research, investigators hypothesized that fluoride affects enamel and inhibits dental caries (cavities) only when incorporated into developing dental enamel…” but now CDC admits that: “Fluoride works primarily after teeth have erupted…”

    CDC also admits that “The prevalence of dental caries in a population is not inversely related to the concentration of fluoride in enamel, and a higher concentration of enamel fluoride is not necessarily more efficacious in preventing dental caries.” and

    “Saliva is a major carrier of topical fluoride. The concentration of fluoride in ductal saliva, as it is secreted from salivary glands, is low — approximately 0.016 parts per million (ppm) in areas where drinking water is fluoridated and 0.006 ppm in nonfluoridated areas . This concentration of fluoride is not likely to affect cariogenic activity.” (So therefore, fluoridated water has no topical effect on tooth decay as well as no systemic effect)

    So why fluoridation. Follow the Money

    If your legislators allow fluoride to be added to your drinking water, tell them to cut it out!


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