Water fluoridation
Health and dental organizations worldwide have endorsed its safety and effectiveness. Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water. Further research showed that moderate fluoridation prevents tooth decay.
Defluoridation
Fluorosis was not identified as a problem until relatively recently. Few attempts to defluoridate water came before the 20th century. In the 1930s several nations began to investigate fluoride's negative effects and how best to remove it. An aluminum and sand filter that removes fluorine from water was devised by Dr. S. P. Kramer in 1933; in 1945 M. Kenneth received a French patent for a water defluoridation technique; and in 1952 a functioning activated alumina community defluoridation plant was commissioned in Bartlett, Texas, USA.