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.
History of municipal treatment of drinking water
As understanding of the bacteriological nature of disease became clearer in the late 19th century the need to filter and treat water became apparent. In Lowell, MA after a typhoid outbreak in 1890 William Thompson Sedgwick applied bacteriological methods to the investigation and was able to establish a link between contaminated water and the disease. The United States by this time had begun to introduce filtration into its municipal water supplies as a means of removing sediment form water in the 1870s through 90s. The United States also introduced the rapid sand filter which were a derivation of filters used in the paper making industry. The rapid filters and the slow sand filters engaged in competition as to which technology was superior. By the beginning of the 20th century, an increased knowledge in bacteriology led to improvements in the slow sand filters as well as the design of rapid filters. It soon became apparent that slow sand filters could remove typhoid germs.