Because dental products are generally not swallowed (except, perhaps, by younger children), they cause less concern for possible health issues.Water fluoridation began in some parts of the United States in 1945, after scientists noted that people living in areas with higher water fluoride levels had fewer cavities.Natural drinking water sources in the US also have some fluoride in them, although the levels are much higher in some places than in others.Fluoride is not required in all drinking water sources in the United States, but the levels of fluoride in water are regulated by several government agencies.(Natural drinking water sources in the US have an average fluoride level of about 0.2 mg/L, although in some places it can be much higher.) The US Environmental Protection Agency (EPA) has set a maximum amount of fluoride allowable in drinking water of 4.0 mg/L.
This recommendation was updated in 2015 to a fluoride level of 0.7 mg/L, The change was made in part to account for the fact that people now get more fluoride from other sources (such as toothpaste) than in the past.
Fluorides are compounds that combine the element fluorine with another substance, usually a metal.
Examples include sodium fluoride, stannous fluoride, and fluoride monofluorophosphate (MFP fluoride).
Some of the controversy about the possible link stems from a study of lab animals reported by the US National Toxicology Program (NTP) in 1990.
The researchers found “equivocal” (uncertain) evidence of cancer-causing potential of fluoridated drinking water in male rats, based on a higher than expected number of cases of osteosarcoma (a type of bone cancer).
Many decades after fluoride was first added to drinking water in some parts of the United States, there is still controversy about the possible health effects of drinking water fluoridation.