A report by the National Academy of Sciences (NAS), titled "Drinking Water and Health", expresses concern about a possible connection between water fluoridation and osteosarcoma in young males. To quote:

"There was an observation in the Kingston-Newburgh (Ast et al, 1956) study that was considered spurious and has never been followed up. There was a 13.5% incidence of cortical defects in bone in the fluoridated community but only 7.5% in the non-fluoridated community... Caffey (1955) noted that the age, sex, and anatomical distribution of these bone defects are `strikingly' similar to that of osteogenic sarcoma. While progression of cortical defects to malignancies has not been observed clinically, it would be important to have direct evidence that osteogenic sarcoma rates in males under 30 have not increased with fluoridation." (NAS 1977)

In December of 1989, the MEDICAL TRIBUNE reveals that a preliminary review of NTP's cancer bioassay indicates an increase in bone cancer among the fluoride-treated rats. According to John Sullivan, a representative for the American Water Works Association, "If fluoride turns out to be a carcinogen, it will be the environmental story of the century."

While controversy begins to surface about a "systematic downgrading" by NTP of non-bone tumors (liver, oral, and thyroid) found with increased incidence among the treated animals, the NTP upholds and confirms the dose-dependent increase in osteosarcoma among male rats.

However, the NTP rules that the statistically-significant, dose-dependent increase of cancer in the target organ (bone) for fluoride accumulation, only provides "equivocal evidence" - versus "some evidence" or "clear evidence" - that fluoride is a carcinogen. According to NTP, "Equivocal evidence of carcinogenic activity is demonstrated by studies that are interpreted as showing a marginal increase of neoplasms that may be chemically related."

The journal CHEMICAL & ENGINEERING NEWS reports:

"A number of other government officials who asked not to be identified also have told C&EN that they have concerns about the conclusions of the NTP study. They, too, believe that fluoride should have been placed in the "some evidence" category, in part because osteosarcoma is a very rare form of cancer in rodents."

Despite criticism, the NTP maintains their assessment of "equivocal evidence." In 1991, NTP scientists publish a paper on the study's findings. They state:

"The current findings are weakly supportive of an association between sodium fluoride administration and the occurrence of osteosarcomas in male rats, but are not conclusive... [I]n view of the widespread exposure of the population to fluorides from a variety of sources it would appear prudent to re-examine previous animal and human epidemiologic studies, and perform further studies as needed to evaluate more fully any possible association between exposure to fluorides and the occurrence of osteosarcomas of bone." (Bucher 1991).

In light of the concern raised by NTP's animal study, the National Cancer Institute (NCI) looks through its National Cancer Registry data to determine if osteosarcoma rates are higher in fluoridated communities. In a report released by the Public Health Service in 1991, the NCI reveals that the incidence of osteosarcoma throughout the U.S. has increased at a greater rate among young boys in fluoridated areas vs. unfluoridated areas. The NCI's analysis covers the years 1973-1987. (See study)

The NCI, however, dismisses this result because of an inability to demonstrate a linear-dose relationship between the duration of fluoridation and the increased osteosarcoma incidence in fluoridated areas. To quote:

"In summary, analysis of incidence data from the SEER program has revealed some age- and sex-specific increases over time for bone and joint cancers, and for osteosarcomas, which are more prominent in fluoridated than in non-fluoridated areas. However, on further analysis these increases are unrelated to the timing of fluoridation, and thus are not linked to the fluoridation of water supplies." (Hoover 1990)

In the spring of 1990, with the NTP's findings attracting media attention, Procter & Gamble, a manufacturer of fluoridated toothpaste, releases the findings of its own rat study of fluoride and cancer (which the company conducted between 1981-1983).

While Procter and Gamble's study finds several bone tumors in the fluoride-treated animals (versus none in the controls), the results do not achieve statistical significance and were thereby dismissed as random. According to Procter & Gamble's published report:

"All bone neoplasms were considered to be incidental and spontaneous and not related to fluoride treatment, because of their low incidence and random distribution" (Maurer 1990).

Later, in 1991, the FDA publishes an independent review of Procter & Gamble's rat study.

In their analysis, the FDA identify 2 additional osteosarcomas in the fluoride-treated rats which were not identified in Procter & Gamble's published report. According to the FDA:

"The adequacy of the gross examination at necropsy was questioned based upon the rat tumors that were not identified by the contract (Procter & Gamble) laboratory" (FDA 1991).

However, even with the newly identified osteosarcomas, the FDA notes that the incidence of bone tumors in the Procter & Gamble study still do not achieve statistical significance. The FDA thereby concurs with Procter & Gamble that the bone tumors are incidental.

In addition to reviewing Procter & Gamble's rat study (see above), the FDA also reviews Procter & Gamble's mouse study (Maurer 1993).

The FDA notes that, among both sexes of the fluoride-treated mice, there is a very significant, dose-dependent increase in benign bone tumors (osteomas), although no occurrence of osteosarcomas. While the occurrence of the osteomas is believed to be related to the presence of a virus in the mice, the FDA makes it clear that if the virus played a role, it did so in conjunction with the fluoride. To quote:

"Active virus was found in the osteomas but not in animals that did not have osteomas. It is clear, nonetheless, that if [the virus] had a role it was only in the presence of fluoride."

Nevertheless, the FDA rules that Procter & Gamble's mouse study - in light of the absence of malignant tumors - "do not add to the concerns raised by the NTP rat study."

Following NCI's analysis of national data, the New Jersey Department of Health conducts a study of osteosarcoma occurrence in Central New Jersey. The study finds a statistically significant relationship between fluoridation and osteosarcoma among males less than 20 years old (See study).

"Recently, a national study of drinking water fluoridation at the country level found a significant association with osteosarcoma incidence among males under 20 years of age (Hoover et al., 1991). However, the meaning of the association was questioned by the authors because of the absence of a linear trend of association with the duration of time for which the water supplies were fluoridated... As a follow-up to the study by Hoover et al., a small study of similar design was initiated by the New Jersey Department of Health to compare drinking water fluoridatiuon at the municipal level with the municpal residence of osteosarcoma cases at the time of diagnosis... The study observed an association between fluoridation of water and osteosarcomas among males under 20 years of age in seven Central New Jersey counties." (Cohn 1992)

Dr. John Yiamouyiannis, the biochemist whose research on fluoridation/cancer in the 1970s led to Congress' request for animal studies on fluoride/cancer, analyzes the National Cancer Institute's data in addition to two other databases containing fluoride exposure/osteosarcoma information. Like NCI's investigators (Hoover 1990), Yiamouyiannis finds osteosarcoma rates to be higher among young males under 20 in fluoridated versus unfluoridated areas. To quote:

"Recent studies showing substantial increases in the incidence of bone cancer and osteosarcoma in males (but not females) exposed to fluoride gave us the unique opportunity of using females as a control group to determine whether there is a link between fluoridation and bone cancer in males. Using three different data bases, we found that 1) the bone cancer incidence rate was as much as 0.95 cases a year per 100,000 population higher in males under age 20 living in fluoridated areas; 2) the osteosarcoma incidence rate was 0.85 new cases a year per 100,000 population higher in males under age 20 living in fluoridated areas; and 3) for males of all ages, the bone cancer death rate and bone cancer incidence rate was as much as 0.23 and 0.44 cases higher per 100,000 population, respectively, in fluoridated areas. These findings indicate that fluoridation is linked to an increase in bone cancer and deaths from bone cancer in human populations among males under age 20 and that this increase in bone cancer is probably all due to an increase in osteosarcoma caused by fluoride." (Yiamouyiannis 1993).

A team of Japanese researchers publish results showing that fluoride is genotoxic to rat bone. The authors note that the fluoride-induced genotoxicity in bone reinforce the biologic plausibility of a fluoride-osteosarcoma connectioin. (Many compounds that cause genotoxicity also cause cancer). The authors used the same type of rat (F344/N) used in NTP's cancer bioassay.

“Because the origin of osteosarcoma is considered to be osteoblastic/osteogenic cells, the ability of sodium fluoride to induce chromosome aberrations in these cells provides a mechanistic basis for the occurrence of osteosarcomas observed in sodium fluoride treated animals in the NTP study. Ingested fluoride is accumulated in bone, suggesting that osteoblastic/osteogenic cells in the bone microenvironment can be exposed to high levels of fluoride during bone formation. Our data and the NTP findings provide evidence that bone can be an organ for NaF carcinogenesis" (Mihashi 1996).