“WARNING: Keep out of reach of children under 6 years of age. If you accidentally swallow more than used for brushing, seek professional help or contact a poison control center immediately.”
The FDA warning is necessary because relatively small doses of fluoride can induce symptoms of acute fluoride toxicity (i.e., poisoning). Early symptoms of fluoride poisoning include gastrointestinal pain, nausea, vomiting, and headaches. The minimum dose that can produce these symptoms is estimated to be 0.1 to 0.3 mg/kg of fluoride (i.e., 0.1 to 0.3 milligrams of fluoride for every kilogram of bodyweight). A child weighing 10 kilograms, therefore, can suffer symptoms of acute toxicity by ingesting just 1 to 3 milligrams of fluoride in a single sitting.
The practice of water fluoridation has been controversial from day one. It was first introduced in the U.S. in the 1940s, when Grand Rapids, Mich. added fluoride to its public water supply in the wake of wide evidence that fluoride helps strengthen teeth and supports oral health. Many of us use toothpaste with fluoride in it for this purpose, and organizations like the American Dental Association and the International Dental Federation believe that drinking water with added fluoride can help our teeth in much the same way that toothpaste does. After the World Health Organization’s 1969 endorsement, countries throughout the world began fluoridating their drinking water.
However, in the 1970s through the1990s, some European countries reversed their stance. Countries like Germany, Sweden, the Netherlands and Finland discontinued fluoridation, while France never even started. The exact reasons for the policy change depend on who you ask.
In high concentrations, soluble fluoride salts are toxic and skin or eye contact with high concentrations of many fluoride salts is dangerous. Referring to a common salt of fluoride, sodium fluoride (NaF), the lethal dose for most adult humans is estimated at 5 to 10 g (which is equivalent to 32 to 64 mg/kg elemental fluoride/kg body weight). Ingestion of fluoride can produce gastrointestinal discomfort at doses at least 15 to 20 times lower (0.2–0.3 mg/kg) than lethal doses. Although helpful for dental health in low dosage, chronic exposure to fluoride in large amounts interferes with bone formation. In this way, the greatest examples of fluoride poisoning arise from fluoride-rich ground water
In India an estimated 60 million people have been poisoned by well water contaminated by excessive fluoride, which is dissolved from the granite rocks. The effects are particularly evident in the bone deformations of children. Similar or larger problems are anticipated in other countries including China, Uzbekistan, and Ethiopia.
Historically, most cases of acute fluoride toxicity have followed accidental ingestion of sodium fluoride based insecticides or rodenticides. Currently, in advanced countries, most cases of fluoride exposure are due to the ingestion of dental fluoride products. Although exposure to these products does not often cause toxicity, in one study 30% of children exposed to fluoride dental products developed mild symptoms. Other sources include glass-etching or chrome-cleaning agents likeammonium bifluoride or hydrofluoric acid, industrial exposure to fluxes used to promote the flow of a molten metal on a solid surface, volcanic ejecta (for example, in cattle grazing after an 1845–1846 eruption of Hekla and the 1783–1784 flood basalt eruption of Laki), and metal cleaners. Malfunction of water fluoridation equipment has happened several times, including a notable incident in Alaska.
Children may experience gastrointestinal distress upon ingesting sufficient amounts of flavored toothpaste. Between 1990 and 1994, over 628 people, mostly children, were treated after ingesting too much fluoride-containing toothpaste. “While the outcomes were generally not serious,” gastrointestinal symptoms appear to be the most common problem reported
A meta analysis conducted on epidemiological studies conducted in China concluded that exposure to “high” levels of fluoride (variously defined) in childhood was associated with a reduction in IQ of about 7 points. The authors of the meta analysis noted that this research is not applicable to the safety of artificial water fluoridation because the adverse effects on IQ was found with fluoride levels that were much higher than typically found in artificially fluoridated water. The meta analysis has been criticized for failing to account for confounding factors. For example, in some of the studies fluoride exposure came from the burning of high fluoride content coal, and used a control group from an area in which wood was used as fuel.
Danish researcher Kaj Roholm published Fluorine Intoxication in 1937, which was praised in a 1938 review by dental researcher H. Trendley Dean as “probably the outstanding contribution to the literature of fluorine”. Since that time, the fluoridation of public water has been widely implemented and has been hailed as one of the top medical achievements of the 20th Century. The effects of fluoride-rich ground water became recognized in the 1990s.