FLUORINE IN WATER SUPPLIES—VAN BURKALOW 211 
CLASSIFICATION OF WATER SUPPLIES IN TERMS OF USE 
Many of the analyses included on the map just described are of 
the waters of private wells, used by an unknown but usually small 
number of people or for irrigation, stock, and so on. If the data 
assembled by this study are to be of maximum value in studies of 
endemic dental fluorosis and dental caries, it is important to know 
how many people use a given water supply for drinking. For this 
reason Dr. Dean suggested that the water supplies represented on 
the first map be classified in terms of the use to which they are put. 
For this purpose two main types of water supply may be distin- 
guished, communal and noncommunal. 
Communal water supplies are those used as sources of drinking 
water by a large part or all of a community. They include supplies 
with such labels as “water companies” and “public,” “municipal,” 
“town,” or “city” waterworks. For epidemiological studies these 
will be the most useful, since it is possible to ascertain approximately 
how many people use them. The emphasis is on use rather than 
ownership. Sometimes the communal water supply comes from a 
well or spring owned by a private individual. On the other hand, 
some publicly owned wells are used only for industrial purposes. 
Such would not be classed as communal. 
Water supplies listed as “noncommunal” comprise privately owned 
wells and springs used for domestic purposes by one or two families, 
school and prison wells, and wells owned either publicly or privately 
but used for such purposes as irrigation, stock, industry, swimming 
pools, fishponds, and parks. 
When the use to which a water supply is put is not clear, it is 
classified as “unidentified.” 
All the water supplies for which fluorine analyses are available 
have been classified in this way. The distribution of the resulting 
three types, communal, noncommunal, and unidentified, is shown in 
B on plate 1. 
MAPPING THE FLUORINE CONTENT 
As was mentioned above, inclusion of a fluorine test in water anal- 
ysis is a recent development (1932 on) and has not yet become univer- 
sal. This means that all earlier analyses and many of the more recent 
ones make no mention of fluorine. Incompleteness of data is therefore 
one of the major problems to be faced in making a map of the fluorine 
content of United States water supplies. Plate 1, A, shows that for 
many counties, sometimes for most of a State, no information is 
available. For many other counties there are available fewer than 
five water analyses that include a fluorine test. Analyses of many 
more water supplies are needed before a complete map of the country 
will be possible. 
