decay in communities. a 2015 cochrane review also found benefit in children. fluoride may also prevent cavities in adults of all ages. a 2007 meta-analysis by cdc researchers found that water fluoridation prevented an estimated 27% of cavities in adults, about the same fraction as prevented by exposure to any delivery method of fluoride (29% average). a 2011 european commission review found that the benefits of water fluoridation for adult in terms of reductions in decay are limited. 2015 cochrane review found no conclusive research in adults. most countries in europe have experienced substantial declines in cavities without the use of water fluoridation. for example, in finland and germany, tooth decay rates remained stable or continued to decline after water fluoridation stopped. fluoridation may be useful in the u.s. because unlike most european countries, the u.s. does not have school-based dental care, many children do not visit a dentist regularly, and for many u.s. children water fluoridation is the prime source of exposure to fluoride. the effectiveness of water fluoridation can vary according to circumstances such as whether preventive dental care is free to all children. ethics water fluoridation pits the common good against individual rights. some say the common good overrides individual rights, and equate it to vaccination and food fortification. others say that individual rights override the common good, and say that individuals have no choice in the water that they drink, unless they drink more expensive bottled water, and some argue unequivocally that it does not stand up to scrutiny relative to the nuremberg code and other codes of medical ethics. those who emphasize the public good emphasize the medical consensus that appropriate levels of water fluoridation are safe and effective to prevent cavities and see it as a public health intervention, replicating the benefits of naturally fluoridated water, which can free people from the misery and expense of tooth decay and toothache, with the greatest benefit accruing to those least able to help themselves. this perspective suggests it would be unethical to withhold such treatment. in her book 50 health scares that fizzled, joan callahan writes that, "for lower-income people with no insurance, fluoridated water (like enriched flour and fortified milk) looks more like a free preventative health measure that a few elitists are trying to take away." those who emphasize individual or local choice, may view fluoridation as a violation of ethical or legal rules that prohibit medical treatment without medical supervision or informed consent or that prohibit administration of unlicensed medical substances, view it as "mass medication", or may even characterize it as a violation of the nuremberg code and the council of europe's biomedical convention of 1999. another journal article suggested applying the precautionary principle to this controversy, which calls for public policy to reflect a conservative approach to minimize risk in the setting where harm is possible (but not necessarily confirmed) and where the science is not settled. others have opposed it on the grounds of potential financial conflicts of interest driven by the chemical industry. a 2007 nuffield council on bioethics report reached a conclusion mainly on three points, stating that : the balance of benefit to risk ratio – is unclear due to the lack of good evidence for or against water fluoridation. alternatives to the practice exist – topical fluoride therapy (toothbrushing etc.) the role of consent – it gets priority when there are potential harms. the report therefore concluded that local and regional democratic procedures are the most appropriate way to decide whether to fluoridate. opposition groups and campaigns the controversy is propelled by a significant public opposition supported by a minority of professionals, including researchers, dental and medical professionals, alternative medical practitioners such as chiropractors, 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.: 219–254 opposition campaigns involve newspaper articles, talk radio, and public forums. media reporters are often poorly equipped to explain the scientific issues, and are motivated to present controversy regardless of the underlying scientific merits. websites, which are increasingly used by the public for health information, contain a wide range of material about fluoridation ranging from factual to fraudulent, with a disproportionate percentage opposed to fluoridation. antifluoridationist literature links fluoride exposure to a wide variety of effects, including aids, allergy, alzheimer's disease, arthritis, cancer, and low iq, along with diseases of the gastrointestinal tract, kidney, pineal gland, and thyroid, though there is no scientific evidence linking fluoridation to these adverse health effects. public opinion many people do not know that fluoridation is meant to prevent tooth decay, or that natural or bottled water can contain fluoride. as fluoridation does not appear to be an important issue for the general public in the u.s., the debate may reflect an argument between two relatively small lobbies for and against fluoridation. a survey of australians in 2009 found that 70% supported and 15% opposed fluoridation. those opposed were much more likely to score higher on outrage factors such as "unclear benefits". a study of focus groups from 16 european countries in 2003 found that fluoridation was opposed by a majority of focus group members in most of the countries, including france, germany, and the uk. a survey in sheffield, uk, performed in 1999 found that while a 62% majority favored water fluoridation in the city, the 31% who were opposed expressed their preference with greater intensity than supporters. every year in the u.s., pro- and anti-fluoridationists face off in referendums or other public decision-making processes: in most of them, fluoridation is rejected. use throughout the world main article: fluoridation by country despite support by public health organizations and dental authorities, the practice is controversial as a public health measure; some countries and communities have discontinued it, while others have expanded it. in the u.s., rejection in state and local communities is more likely when the decision is made by a public referendum; in europe, most decisions against fluoridation have been made administratively. neither side of the dispute appears to be weakening or willing to concede. water fluoridation is used in the united states, united kingdom, ireland, canada, australia, israel, hong kong and a handful of other countries. most countries failed to adopt fluoridation, yet experienced the same or greater decline in cavities as those countries that did fluoridate during the later half of the twentieth century. the following nations previously fluoridated their water, but stopped the practice, with the years when water fluoridation started and stopped in parentheses: federal republic of germany (1952–1971) sweden (1952–1971) netherlands (1953–1976) czechoslovakia (1955–1990) german democratic republic (1959–1990) soviet union (1960–1990) finland (1959–1993) japan (1952–1972) israel (1981–2014, 2016–) *mandatory by law since 2002. in the united kingdom a strategic health authority can direct a water company to fluoridate the water supply in an area if it is technically possible. the strategic health authority must consult with the local community and businesses in the affected area. the water company will act as a contractor in any new schemes and cannot refuse to fluoridate the supply. in areas with complex water sources, water fluoridation is more difficult and more costly. alternative fluoridation methods have been proposed, and implemented in some parts of the world. the world health organization (who) is currently assessing the effects of fluoridated toothpaste, milk fluoridation and salt fluoridation in africa, asia, and europe. the who supports fluoridation of water in some areas. in some other countries, sodium fluoride is added to table salt. as of 2012, 25 countries have artificial water fluoridation to varying degrees, 11 of them have more than 50% of their population drinking fluoridated water. a further 28 countries have water that is naturally fluoridated, though in many of them the fluoride is above the optimum level. as of 2012 about 435 million people worldwide received water fluoridated at the recommended level, about 211 million of them living in the united states. history main article: history of water fluoridation fluoridation began during a time of great optimism and faith in science and experts (the 1950s and 1960s), but even then, the public frequently objected. opponents drew on distrust of experts and unease about medicine and science. controversies include disputes over fluoridation's benefits and the strength of the evidence basis for these benefits, the difficulty of identifying harms, legal issues over whether water fluoride is a medicine, and the ethics of mass intervention. the first large fluoridation controversy occurred in wisconsin in 1950. fluoridation opponents questioned the ethics, safety, and efficacy of fluoridation. new zealand was the second country to fluoridate, and similar controversies arose there. fears about fluoride were likely exacerbated by the reputation of fluoride compounds as insect poisons and by early literature which tended to use terms such as "toxic" and "low grade chronic fluoride poisoning" to describe mottling from consumption of 6 mg/l of fluoride prior to tooth eruption, a level of consumption not expected to occur under controlled fluoridation. when voted upon, the outcomes tend to be negative, and thus fluoridation has had a history of gaining through administrative orders in north america. conspiracy theories involving fluoridation are common, and include claims that fluoridation was motivated by protecting the u.s. atomic bomb program from litigation, that (as famously parodied in the film dr. strangelove, where a deranged u.s. air force general claimed that it would "sap and impurify all of our precious bodily fluids") it is part of a communist or new world order plot to take over the world, that it was pioneered by a german chemical company to make people submissive to those in power, that behind the scenes it is promoted by the sugary food or phosphate fertilizer or aluminium industries, or that it is a smokescreen to cover failure to provide dental care to the poor. one such theory is that fluoridation was a public-relations ruse sponsored by fluoride polluters such as the aluminium maker alcoa and the manhattan project, with conspirators that included industrialist andrew mellon and the mellon institute's researcher gerald j. cox, the kettering laboratory of the university of cincinnati, the federal security agency's administrator oscar r. ewing, and public-relations strategist edward bernays. specific antifluoridation arguments change to match the spirit of the time. illustration in a 1955 flier by the keep america committee, alleging that fluoridation was a communist plot outside north america, water fluoridation was adopted in some european countries, but in the late 1970s and early 1980s, denmark and sweden banned fluoridation when government panels found insufficient evidence of safety, and the netherlands banned water fluoridation when "a group of medical practitioners presented evidence" that it caused negative effects in a percentage of the population. communist conspiracy theory (1940s–1960s) water fluoridation has frequently been the subject of conspiracy theories. during the "second red scare" in the united states during the late 1940s and 1950s, and to a lesser extent in the 1960s, activists on the far right of american politics routinely asserted that fluoridation was part of a far-reaching plot to impose a socialist or communist regime. these opponents believed it was "another aspect of president truman's drive to socialize medicine." they also opposed other public health programs, notably mass vaccination and mental health services. their views were influenced by opposition to a number of major social and political changes that had happened in recent years: the growth of internationalism, particularly the un and its programs; the introduction of social welfare provisions, particularly the various programs established by the new deal; and government efforts to reduce perceived inequalities in the social structure of the united states. others asserted the existence of "a communist plot to deplete the brainpower and sap the strength of a generation of american children". dr. charles betts, a prominent anti-fluoridationist, charged that fluoridation was "better than using the atom bomb because the atom bomb has to be made, has to be transported to the place it is to be set off while poisonous fluorine has been placed right beside the water supplies by the americans themselves ready to be dumped into the water mains whenever a communist desires!" similarly, a right-wing newsletter, the american capsule news, claimed that "the soviet general staff is