Civil Engineering Reference
In-Depth Information
CHAPTER 20
Fluoridation and Defluoridation
INTRODUCTION
The fluoride ion (reduced form of fluorine) is found in every water supply used for
drinking purposes.
1
It is required for the formation of bones and teeth, and is essential
to the normal growth and development of humans.
This chapter reviews the history of research on fluorides in drinking water, followed
by a description of the chemicals used for fluoridation and the techniques used for
fluoride addition to drinking water. Also, methods are described for the removal of
fluorides in situations where their concentration is too great to allow use as a potable
water supply.
FLUORIDE RESEARCH
During the 1800s, U.S. immigration officials noticed that people arriving from certain
parts of Europe were severely afflicted by a disfigurement of the teeth known as
mottled enamel or dental fluorosis. This led dental authorities to believe that the dis-
figurement was due to a local factor endemic to the immigrants' native land. Soon
after, reports began to appear of mottled enamel among people native to the United
States. These reports came largely from cities in the Great Plains and Rocky Mountain
states.
Substantial evidence that fluorides were the cause of mottled enamel was obtained
by H. V. Churchill in 1930.
2
The people of Bauxite, Arkansas, reported a high inci-
dence of mottled enamel. Churchill, by spectrographic analysis, found appreciable
amounts of fluoride ion in the Bauxite water supply. In collaboration with F. S. McKay,
a dentist, he studied waters from five areas where mottling was endemic and 40 areas
where it was not a problem. From these studies, it was concluded that excessive
fluoride levels in the drinking water caused the mottled enamel.
3
Further proof was
reported by Smith et al., who found that mottled enamel could be produced in white
rats by adding to their diets either small amounts of fluoride salts or the concentrated
residues from waters known to cause mottled teeth in humans.
4
Finally, Gottlieb in 1934 reported on the relationship between fluoride concentration
and mottling.
5
She found that in Kansas communities reporting mottled enamel, the
concentrations of fluoride in the public drinking water supplies were in excess of 2
mg/L.
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