In a February 1991 Public Health Service (PHS) report, the agency said it found no evidence of an association between fluoride and cancer in humans. The report, based on a review of more than 50 human epidemiological (population) studies produced over the past 40 years, concluded that optimal fluoridation of drinking water “does not pose a detectable cancer risk to humans” as evidenced by extensive human epidemiological data reported to date (
5).
In one of the studies reviewed for the PHS report, scientists at NCI evaluated the relationship between the fluoridation of drinking water and the number of deaths due to cancer in the United States during a 36-year period, and the relationship between water fluoridation and number of new cases of cancer during a 15-year period. After examining more than 2.2 million cancer death records and 125,000 cancer case records in counties using fluoridated water, the researchers found no indication of increased cancer risk associated with fluoridated drinking water (
6).
In 1993, the Subcommittee on Health Effects of Ingested Fluoride of the National Research Council, part of the National Academy of Sciences, conducted an extensive literature review concerning the association between fluoridated drinking water and increased cancer risk. The review included data from more than 50 human epidemiological studies and six animal studies. The Subcommittee concluded that none of the data demonstrated an association between fluoridated drinking water and cancer (
6). A 1999 report by the CDC supported these findings. The CDC report concluded that studies to date have produced “no credible evidence” of an association between fluoridated drinking water and an increased risk for cancer (
2). Subsequent interview studies of patients with osteosarcoma and their parents produced conflicting results, but with none showing clear evidence of a causal relationship between fluoride intake and risk of this tumor.
Recently, researchers examined the possible relationship between fluoride exposure and osteosarcoma in a new way: they measured fluoride concentration in samples of normal bone that were adjacent to a person’s tumor. Because fluoride naturally accumulates in bone, this method provides a more accurate measure of cumulative fluoride exposure than relying on the memory of study participants or municipal water treatment records. The analysis showed no difference in bone fluoride levels between people with osteosarcoma and people in a control group who had other malignant bone tumors (
7).
http://www.cancer.gov/cancertopics/factsheet/Risk/fluoridated-water