The water fluoridation controversy arises from political, ethical, economic, and health considerations regarding the fluoridation of public water supplies. For deprived groups in both maturing and matured countries, international and national agencies and dental associations across the world support the safety and effectiveness of water fluoridation. Proponents of water fluoridation see it as a question of public health policy and equate the issue to vaccination and food fortification, claiming significant benefits to dental health and minimal risks. In contrast, opponents of water fluoridation view it as an infringement of individual rights, if not an outright violation of medical ethics, on the basis that individuals have no choice in the water that they drink, unless they drink more expensive bottled water. A small minority of scientists have challenged the medical consensus, variously claiming that water fluoridation has no or little cariostatic benefits, may cause serious health problems, is not effective enough to justify the costs, and is pharmacologically obsolete. Opposition to fluoridation has existed since its initiation in the 1940s. During the 1950s and 1960s, conspiracy theorists claimed that fluoridation was a communist plot to undermine American public health. In recent years, water fluoridation has become a prevalent health and political issue in many countries, resulting in some countries and communities discontinuing its use while others have expanded it. The controversy is propelled by a significant public opposition supported by a minority of professionals, which include researchers, dental and medical professionals, alternative medical practitioners, health food enthusiasts, a few religious groups (mostly Christian Scientists in the U.S.), and occasionally consumer groups and environmentalists. Organized political opposition has come from libertarians, the John Birch Society, and from groups like the Green parties in the UK and New Zealand.