FLUORINE IN WATER SUPPLIES—VAN BURKALOW 209 
At the suggestion of W. D. Collins, chemist in charge, Quality of 
Water Division, United States Geological Survey, a visit was made 
to the Washington office of the Survey, where access was kindly granted 
to the files of unpublished water analyses. About 1,500 additional 
analyses were derived from this source. 
MAP SUMMARY OF QUANTITY OF AVAILABLE DATA 
These sources yielded some 12,000 analyses showing the fluorine 
content of water supplies. As a preliminary to the preparation of a 
fluorine map of the United States it was desirable to see how the data 
were distributed. For this purpose a map (A on pl. 1) was prepared 
showing in a general way the amount of information available for 
each county in the country. <A distinction was drawn between the 
counties for which five analyses or more were available, those for which 
one to four analyses were available, and those for which no analyses 
were available. A few areas were shown as being covered by a “gen- 
eral statement.” ‘This means that, although our collection does not 
include any analyses from these areas, some have been made, and on 
the basis of them a public-health or sanitary officer has given a general 
statement about the fluorine content of the waters. 
This arbitrary classification of the abundance of data in terms of 
number of analyses per county does not take into consideration the 
sizes of the counties, which differ greatly, and therefore does not give 
a true picture of the number of analyses in proportion to area. Five 
analyses represent the conditions in one of the large western counties 
less truly than in a small eastern county. Nevertheless, the map does 
reveal the relative amount of attention that has been given to the 
problem in different parts of the country. The areas most thoroughly 
studied are the Great Plains and the Southwest. Comparison with 
C and D on plate 1 shows that these are the areas where the problem 
of excessive fluorine is most widespread. 
Apparently public interest has been aroused, and health officers have 
been stirred to action, more widely by the dangers of fluorine excesses 
than by those of fluorine deficiencies. This interpretation is supported 
by several circumstances. Although a relationship between fluorine 
and dental caries was suggested at least half a century ago,’ no at- 
tention was given to the fluorine content of water supplies until 1932, 
after a high content had been definitely identified as the cause of 
mottled enamel. From that time on, and beginning in the States most 
afflicted with the malady, recognition of the importance of fluorine 
t Dean, H. Trendiey, Domestic water and dental caries, Journ. Amer. Water Works Assoc., 
vol. 35, pp. 1161-1186, 1943. 
§ Churchill, H. V., Occurrence of fluorides in some waters of the United States, Ind. and 
Eng. Chem., vol. 23, pp. 996-998, 1931; Smith, M. C., Lantz, E. M., and Smith, H. V., The 
cause of mottled enamel, a defect of human teeth, Univ. Arizona Agr. Exp. Stat. Techr. 
Bull. No. 32, 1931, reprinted 1937 ; and many later papers. 
