for infants and children through age 8 years, and 10 mg/day thereafter. a rough estimate is that an adult in a temperate climate consumes 0.6 mg/day of fluoride without fluoridation, and 2 mg/day with fluoridation. however, these values differ greatly among the world's regions: for example, in sichuan, china the average daily fluoride intake is only 0.1 mg/day in drinking water but 8.9 mg/day in food and 0.7 mg/day directly from the air due to the use of high-fluoride soft coal for cooking and drying foodstuffs indoors. alternatives fluoride toothpaste is effective against cavities. it is widely used, but less so among the poor. fluoridated iodized salt sold in germany the views on the most effective method for community prevention of tooth decay are mixed. the australian government review states that water fluoridation is the most effective means of achieving fluoride exposure that is community-wide. the european commission review states "no obvious advantage appears in favour of water fluoridation compared with topical prevention". other fluoride therapies are also effective in preventing tooth decay; they include fluoride toothpaste, mouthwash, gel, and varnish, and fluoridation of salt and milk. dental sealants are effective as well, with estimates of prevented cavities ranging from 33% to 86%, depending on age of sealant and type of study. fluoride toothpaste is the most widely used and rigorously evaluated fluoride treatment. its introduction is considered the main reason for the decline in tooth decay in industrialized countries, and toothpaste appears to be the single common factor in countries where tooth decay has declined. toothpaste is the only realistic fluoride strategy in many low-income countries, where lack of infrastructure renders water or salt fluoridation infeasible. it relies on individual and family behavior, and its use is less likely among lower economic classes; in low-income countries it is unaffordable for the poor. fluoride toothpaste prevents about 25% of cavities in young permanent teeth, and its effectiveness is improved if higher concentrations of fluoride are used, or if the toothbrushing is supervised. fluoride mouthwash and gel are about as effective as fluoride toothpaste; fluoride varnish prevents about 45% of cavities. by comparison, brushing with a nonfluoride toothpaste has little effect on cavities. the effectiveness of salt fluoridation is about the same as that of water fluoridation, if most salt for human consumption is fluoridated. fluoridated salt reaches the consumer in salt at home, in meals at school and at large kitchens, and in bread. for example, jamaica has just one salt producer, but a complex public water supply; it started fluoridating all salt in 1987, achieving a decline in cavities. universal salt fluoridation is also practiced in colombia and the swiss canton of vaud; in germany fluoridated salt is widely used in households but unfluoridated salt is also available, giving consumers a choice. concentrations of fluoride in salt range from 90 to 350 mg/kg, with studies suggesting an optimal concentration of around 250 mg/kg. milk fluoridation is practiced by the borrow foundation in some parts of bulgaria, chile, peru, russia, macedonia, thailand and the uk. depending on location, the fluoride is added to milk, to powdered milk, or to yogurt. for example, milk powder fluoridation is used in rural chilean areas where water fluoridation is not technically feasible. these programs are aimed at children, and have neither targeted nor been evaluated for adults. a systematic review found low-quality evidence to support the practice, but also concluded that further studies were needed. other public-health strategies to control tooth decay, such as education to change behavior and diet, have lacked impressive results. although fluoride is the only well-documented agent which controls the rate at which cavities develop, it has been suggested that adding calcium to the water would reduce cavities further. other agents to prevent tooth decay include antibacterials such as chlorhexidine and sugar substitutes such as xylitol. xylitol-sweetened chewing gum has been recommended as a supplement to fluoride and other conventional treatments if the gum is not too costly. two proposed approaches, bacteria replacement therapy (probiotics) and caries vaccine, would share water fluoridation's advantage of requiring only minimal patient compliance, but have not been proven safe and effective. other experimental approaches include fluoridated sugar, polyphenols, and casein phosphopeptide–amorphous calcium phosphate nanocomplexes. a 2007 australian review concluded that water fluoridation is the most effective and socially the most equitable way to expose entire communities to fluoride's cavity-prevention effects. a 2002 u.s. review estimated that sealants decreased cavities by about 60% overall, compared to about 18–50% for fluoride. a 2007 italian review suggested that water fluoridation may not be needed, particularly in the industrialized countries where cavities have become rare, and concluded that toothpaste and other topical fluoride are the best way to prevent cavities worldwide. a 2004 world health organization review stated that water fluoridation, when it is culturally acceptable and technically feasible, has substantial advantages in preventing tooth decay, especially for subgroups at high risk. worldwide prevalence main article: fluoridation by country percentage of population receiving fluoridated water, including both artificial and natural fluoridation, as of 2012. 80–100% 60–80% 40–60% 20–40% 1–20% < 1% unknown as of november 2012, a total of about 378 million people worldwide received artificially fluoridated water. the majority of those were in the united states. about 40 million worldwide received water that was naturally fluoridated to recommended levels. much of the early work on establishing the connection between fluoride and dental health was performed by scientists in the u.s. during the early 20th century, and the u.s. was the first country to implement public water fluoridation on a wide scale. it has been introduced to varying degrees in many countries and territories outside the u.s., including argentina, australia, brazil, canada, chile, colombia, hong kong, ireland, israel, korea, malaysia, new zealand, the philippines, serbia, singapore, spain, the uk, and vietnam. in 2004, an estimated 13.7 million people in western europe and 194 million in the u.s. received artificially fluoridated water. in 2010, about 66% of the u.s. population was receiving fluoridated water. naturally fluoridated water is used by approximately 4% of the world's population, in countries including argentina, france, gabon, libya, mexico, senegal, sri lanka, tanzania, the u.s., and zimbabwe. in some locations, notably parts of africa, china, and india, natural fluoridation exceeds recommended levels. communities have discontinued water fluoridation in some countries, including finland, germany, japan, the netherlands, and switzerland. changes have been motivated by political opposition to water fluoridation, but sometimes the need for water fluoridation was met by alternative strategies. the use of fluoride in its various forms is the foundation of tooth decay prevention throughout europe; several countries have introduced fluoridated salt, with varying success: in switzerland and germany, fluoridated salt represents 65% to 70% of the domestic market, while in france the market share reached 60% in 1993 but dwindled to 14% in 2009; spain, in 1986 the second west european country to introduce fluoridation of table salt, reported a market share in 2006 of only 10%. in three other west european countries, greece, austria and the netherlands, the legal framework for production and marketing of fluoridated edible salt exists. at least six central european countries (hungary, czechia, slovakia, croatia, slovenia, romania) have shown some interest in salt fluoridation; however, significant usage of approximately 35% was only achieved in the czech republic. the slovak republic had the equipment to treat salt by 2005; in the other four countries attempts to introduce fluoridated salt were not successful. when israel implemented the 2014 dental health promotion program, that includes education, medical followup and the use of fluoride-containing products and supplements, it evaluated that mandatory water fluoridation was no longer necessary, stating "supply of fluoridated water forces those who do not so wish to also consume water with added fluoride. this approach is therefore not accepted in most countries in the world.". history