Water<unk>  is the controlled addition of fluoride to a public water supply to reduce tooth decay, and is handled differently by<unk> . Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride. Fluoridated water operates on tooth surfaces: in the mouth it creates low levels of fluoride in saliva, which reduces the rate at which tooth enamel demineralizes and increases the rate at which it remineralizes in the early stages of cavities. Typically a fluoridated compound is added to drinking water, a process that in the U.S. costs an average of about $ per person-year. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. In 2011 the World Health Organization suggested a level of fluoride from 0.5 to 1.5 mg/L (milligrams per litre), depending on climate, local environment, and other sources of fluoride. Bottled water typically has unknown fluoride levels. Dental caries remains a major public health concern in most industrialized<unk> es, affecting 60–90% of schoolchildren and the vast majority of adults. Water<unk>  reduces cavities in children, while efficacy in adults is less clear. A Cochrane review estimates a reduction in cavities when water<unk>  was used by children who had no access to other sources of fluoride to be 35% in baby teeth and 26% in permanent teeth. Most European<unk> es have experienced substantial declines in tooth decay without its use. Recent studies suggest that water<unk> , particularly in industrialized<unk> es, may be unnecessary because topical fluorides (such as in toothpaste) are widely used and caries rates have become low. For this reason, some scientists consider<unk>  to be unethical due to "the debilitating effects of fluoride toxicity" and the lack of informed consent. Although<unk>  can cause dental fluorosis, which can alter the appearance of developing teeth or enamel fluorosis, the differences are mild and usually not considered to be of aesthetic or public-health concern. There is no clear evidence of other adverse effects from water<unk> , as revealed by the York review from 2000. A 2007 Australian systematic review used the same inclusion criteria as York's, plus one additional study. This did not affect the York conclusions. Fluoride's effects depend on the total daily intake of fluoride from all sources. Drinking water is typically the largest source; other methods of fluoride therapy include<unk>  of toothpaste, salt, and milk. The views on the most effective method for community prevention of tooth decay are mixed. The Australian government states that water<unk>  is the most effective means of achieving fluoride exposure that is community-wide. The World Health Organization states water<unk> , when feasible and culturally acceptable, has substantial advantages, especially for subgroups at high risk, while the European Commission finds no advantage to water<unk>  compared with topical use. Currently about 372 million people (around 5.7% of the world population) receive artificially-fluoridated water in about 24<unk> es, including Australia, Brazil, Canada, Chile, Republic of Ireland, Malaysia, the U.S., and Vietnam. 57.4 million people receive naturally occurring fluoridated water at or above optimal levels in<unk> es such as Sweden, China, Sri Lanka, Finland, Zimbabwe and Gabon. Community water<unk>  is rare in Continental Europe, with 97–98% choosing not to fluoridate drinking water. Fluoridated salt and milk is promoted in some European<unk> es instead. Water<unk>  has been replaced by other modes in many<unk> es where water supplies are too decentralized for it to be a practical choice, or existing natural fluoride levels were already ample, including Germany, Finland, Japan, Netherlands, Sweden, Switzerland, Denmark and at a time Israel. Cessation of water<unk>  has been demonstrated in scientific studies such as a recent one in Calgary, Alberta, to result in increased rates of dental decay. While<unk>  can result in mild dental fluorosis, this effect is barely detectable and causes no concerns with the appearance or health of teeth.<unk> es practicing artificial water<unk>  vary in their recommended fluoride levels according to what health authorities in each have determined to be most effective for its citizens. The US recently reset the recommended optimal level of fluoride in drinking water, lowering it slightly, because of observed increased Fluorosis levels, likely due to additional fluoride sources like toothpaste and mouthwash which were not present when this level was originally set.
Water fluoridation by country
Human milk banking in North America
Safety of electronic cigarettes
Nutrition facts label
EPA list of extremely hazardous substances
Recommended maximum intake of alcoholic beverages
Water fluoridation controversy
Single use medical device reprocessing