Originally published November, 2009. Updated July, 2015.
In April of this year (2015) the Department of Health and Human Services (HHS) recommended lowering the levels of fluoride in drinking water, the first change it has suggested since 1962. The new recommended limit is 0.7 milligrams (mg) of fluoride per liter of water, down from the previous range of 0.7 to 1.2 mg per liter. The rationale for the change is that we now have many more sources of fluoride than were available in 1962, including fluoridated toothpaste, mouth rinses and sealants.
In addition, the HHS recommendation was made to counter an increased incidence in white spots on tooth enamel caused by fluoridation, a risk I’ve written about on this site in response to earlier questions. Known as fluorosis, this spotting occurs only in children eight years old and younger as a result of too much fluoride intake while permanent teeth are developing under the gums. To prevent it, the U.S. Centers for Disease Control and Prevention (CDC) recommends using an alternative source of water for children aged 8 years and younger if your primary drinking water contains greater than 2 mg/L of fluoride. You may be able to find out how much fluoride is in your drinking water by accessing the CDC site "My Water’s Fluoride"
Most states provide information to this site on fluoride levels in their drinking water, but some do not. The CDC also recommends avoiding fluoridated toothpaste in children under age two and using only a pea-sized amount for kids between the age of 2 and 6. Also, instruct little kids to spit out toothpaste rather than swallow it, as young children are inclined to do.
Overall, fluoridation of community water supplies has been a tremendous success, having dramatically reduced tooth decay in both children and adults.
As for bone cancer, every year about 400 children and adolescents (boys and girls) in the U.S. are diagnosed with osteosarcoma, a rare disease. In 2006, Harvard researchers reported an association between fluoride in drinking water and the incidence of osteosarcoma in boys (not girls).
In a review of the more recent research, the American Cancer Society noted that the second part of the Harvard study, published in 2011, compared the fluoride levels in bones near tumors in people with osteosarcoma to levels in people with other types of bone tumors. No difference was seen between the fluoride levels in the two groups.
According to the ACS, two more recent studies compared the rates of osteosarcoma in areas with higher versus lower levels of fluoridation in Ireland and the United States. Neither one found an increased risk of the disease in areas with fluoridated water.
While this case isn’t closed, so far we have no hard evidence supporting a link between fluoridation and bone cancer.
Andrew Weil, M.D.
"Water Fluoridation and Cancer Risk," American Cancer Society, accessed April 28, 2014, http://www.cancer.org/cancer/cancercauses/othercarcinogens/athome/water-fluoridation-and-cancer-risk
"HHS issues final recommendation for community water fluoridation," U.S. Department of Health and Human Services, accessed April 28, 2015, http://www.hhs.gov/news/press/2015pres/04/20150427a.html