222 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1946: 
by this group was eliminated in the urine, which greatly reduces the 
probability of fluorine toxicosis when the fluorine concentration in 
the drinking water is 5.0 p. p. m. or less. For the effects of higher 
concentrations, and for other types of fluorosis, more studies are 
needed. 
In conclusion the need for better data on the fluorine content of 
potable and agricultural waters is urged upon county and State health 
departments. ‘Tests should be repeated on the same wells throughout 
the year to determine minimum as well as average and maximum val- 
ues. Tests should be correlated with depth of well, with populations 
using the supply (both human and animal), and, wherever possible, 
with rock analyses at well depths. A copy of this report will be 
mailed to each cooperating office, and correspondence will be contin- 
ued until the preliminary map can be redrawn and the study advanced 
to a more permanent basis, 
