Several human epidemiological studies have found an association between fluoride in drinking water and the occurrence of osteosarcoma (bone cancer) in young males. (Bassin 2006; Cohn 1992; Hoover 1991). These studies are consistent with the National Toxicology Program’s (NTP) cancer bioassay which found that fluoride-treated male rats had an dose-dependent increase in osteosarcoma. (Bucher 1991). Although a number of studies have failed to detect an association between fluoride and osteosarcoma, none of these studies have measured the risk of fluoride at specific windows in time, which is the critical question with respect to fluoride and osteosarcoma.
As acknowledged by the NTP and most other observers, a fluoride/osteosarcoma connection is biologically plausible. The biological plausibility centers around three facts: 1) Bone is the principal site of fluoride accumulation, particularly during the growth spurts of childhood; 2) Fluoride is a mutagen when present at sufficient concentrations, and 3) Fluoride stimulates the proliferation of bone-forming cells (osteoblasts), which may “increase the risk for some of the dividing cells to become malignant.” (NRC 2006).
A number of studies have failed to detect an association between fluoride and osteosarcoma. None of these studies, however, have looked at the risk of fluoride during specific ages in life. This is important because, in 2001, an age-specific analysis of a national case-control study that previously reported no association between lifelong exposure to fluoridated water and osteosarcoma (Douglass 1995) found that boys consuming fluoridated water during their 6th, 7th, and 8th years of life (the mid childhood growth spurt) had a statistically significant, “remarkably robust,” risk of developing osteosarcoma during their teenage years. (Bassin 2001). Initially published as a PhD dissertation at Harvard, the study was later published in Cancer Causes & Control.
Although a study in 2011 purported to refute the findings that fluoride causes osteosarcoma (Kim 2011), the study’s methods — by the authors’ own admission — were incapable of assessing the age-specific risk during the critical window period (ages 6 to 8 ) that Bassin identified as the critical risk period from fluoride exposure.