Water Fluoridation (Grand Rapids study, 10-year results)

In the 1930s the only treatment for tooth decay was individual: dentists drilled and filled. The idea of a community-wide measure grew out of a stain. Frederick McKay, a dentist in Colorado Springs from 1901, studied the brown mottling on local teeth with G. V. Black and found that mottled teeth were unusually resistant to decay; he suspected the water. In 1931 an Alcoa chemist, H. V. Churchill, identified high fluoride in water from a town with mottled teeth. H. Trendley Dean of the National Institute of Health then found that about 1 part per million in water caused little or no mottling.

The Grand Rapids trial, launched in January 1945, was designed to test whether adding fluoride at that level would prevent decay. Grand Rapids, Michigan, became the first city in the world to deliberately adjust its municipal water supply to 1 ppm fluoride. Muskegon, Michigan, was the unfluoridated control city, and Aurora, Illinois, a community with naturally occurring fluoride at that concentration, provided a third comparison. Francis A. Arnold Jr. led the study, which the National Institute of Dental Research took over after its founding in 1948. Dentists examined Grand Rapids schoolchildren once a year, and almost 30,000 children were followed.

The ten-year results, published in Public Health Reports in 1956, showed that the caries rate among Grand Rapids children born after fluoridation began had fallen by about 60 percent. By then Muskegon was no longer a clean control: after early results showed fewer cavities in Grand Rapids, Muskegon began fluoridating its own water in 1951. The four paired-city trials begun in 1945, in Michigan, New York, Illinois and Ontario, found caries reduced by 50 to 70 percent after 13 to 15 years.

The Public Health Service did not wait for the full decade of data. On interim results, it backed fluoridation at 1 ppm in 1950, six years before the ten-year report. In 1951 only 3.3 percent of Americans drank fluoridated water, but municipal utilities across the country soon began adjusting fluoride levels. Opponents, active from 1950 onward, objected to medicating whole populations and claimed links to cancer and other diseases; the Public Health Service and the American Dental Association kept their endorsements.

In 1999 the CDC listed fluoridation of drinking water among ten great public health achievements of the twentieth century in the United States, alongside vaccination, motor-vehicle safety, and control of infectious diseases. In 2022, 72.3 percent of Americans served by community water systems received fluoridated water. Recent studies suggest a smaller benefit than in the early trials, typically 25 to 35 percent, largely because fluoride toothpaste and other sources are now common.