The Arizona Daily Star’s Centennial salute to science in Arizona runs all summer. Each day, for 100 days, we’ll record a milestone in the state’s scientific history.
We can thank University of Arizona researcher Margaret Cammack Smith for the addition of fluorine to much of the nation’s drinking-water supply – a development that the U.S. Centers for Disease Control and Prevention calls “one of the 10 great public health achievements of the 20th century.”
That’s despite the fact that Smith crusaded against putting fluoride compounds in water.
Smith, an agricultural chemist at the Agricultural Research Station in Tucson, performed the field studies and laboratory experiments that proved a link between levels of fluorine and the integrity of tooth enamel.
She was searching for the cause of “mottled teeth” in children of several Arizona communities in the 1930s. She settled on St. David in Cochise County, where she found a large population of children with pitted and discolored teeth, linking it to water with fluorine levels of 1.6 to 4.0 parts per million.
She later induced mottled teeth in rats and dogs by giving them fluorine-rich water.
Her research, some done in conjunction with her husband and colleague H.V. Smith, also noted that the children had fewer cavities than normal, but she argued at an American Journal of Public Health conference in 1940 that the difference between harmful and beneficial levels of fluorine in water was too small to allow for unregulated consumption.
“A word of warning is thus offered to any plan to build caries resistance into teeth by addition of fluorides to public water supplies as a public health procedure,” she said.
Fluoridation of drinking water began in the United States in the mid-1940s and by the end of the century had reduced childhood cavities by an estimated 40 to 70 percent, according to the Centers for Disease Control.
Recommended levels were lowered recently by federal agencies to guard against fluorosis – the “mottled teeth” of Smith’s day. Fluoride is not added to Tucson’s water but occurs naturally at levels within EPA guidelines.
On StarNet: Covering topics from the cosmos to the invisible world of nanotechnology: the Scientific Bent blog at azstarnet.com/ scientificbent