The artificial nature of fluoridated water: between nations, knowledge, and material flows.

An exercise in "historical ontology," this paper charts the contrasting ways fluoridated water and its effects crystallized as objects of knowledge and concern in three quite different realms over the mid twentieth century. Among U.S. health officials and experts, fluoridated water emerged and stabilized as a public health goal, preventing tooth decay. Indian doctors and scientists defined it as a public health problem, causing "skeletal fluorosis." Fluoridated water also acquired an intense presence among laypeople in the United States, especially those voting in local referenda on fluoridation. More often than not rejecting it, suspecting bias and myopia in profluoridation expertise, they cobbled together a lay ontology that proved predictive of the varied and changing flows of fluoridated water itself. The paper concludes by suggesting a principle of environmental symmetry as an aid to this kind of comparative ontology.