The water fluoridation controversy arises from moral, ethical, political, and safety concerns regarding the fluoridation of public water supplies. The controversy occurs mainly in English-speaking countries, as Continental Europe does not practice water fluoridation. Those opposed argue that water fluoridation may cause serious health problems, is not effective enough to justify the costs, and has a dosage that cannot be precisely controlled. In some countries, fluoride is added to table salt.
At the dosage recommended for water fluoridation, the only known adverse effect is dental fluorosis, which can alter the appearance of children's teeth during tooth development. Dental fluorosis is considered cosmetic and unlikely to represent any other effect on public health. Despite opponents' concerns, water fluoridation has been effective at reducing cavities in both children and adults.
Opposition to fluoridation has existed since its initiation in the 1940s. During the 1950s and 1960s, some opponents of water fluoridation suggested that fluoridation was a communist plot to undermine public health.