US study find no difference between cancer death rates in fluoridated and non-fluoridated areas (1991)

Analysis of data in the 35 years before and after fluoridation started shows no increase in risk of cancer

A study by Hoover et al for the US National Cancer Institute, published in 1991, examined as many as 2.3 million cancer deaths to try to establish whether the introduction of fluoridated water in US communities had affected mortality rates. (1)

Figures 1 and 2 show the pattern of cancer deaths in 1.2 million men and 1.1 million women for a period 35 years before and 35 years after fluoridation compared with cancer deaths in similar, but non-fluoridated, populations.

They show that 35 years of exposure to optimally fluoridated water did not increase the risk of death from cancer for either men or women compared with the risk before fluoridation, or compared with non-fluoridated populations.

The Hoover study singled out bone and joint cancers for detailed analysis and found no relationship with fluoridation.

Two further US reports conclude that there is no link with cancer

In 1993, the Sub Committee on Health Effects of Ingested Fluoride of the US National Research Council conducted an extensive literature review, including data from more than 50 human epidemiological studies and six animal studies, and concluded that there was no association between fluoridated water and cancer.

A 1999 report by the Centers for Disease Control and Prevention supported these findings, concluding that studies to date have produced “no credible evidence of association between fluoridated drinking water and an increased risk for cancer.”

1. Hoover RN, Devesa SS, Cantor KP, Lubin JH, Fraumeni JF (1991): Fluoridation of drinking water and subsequent cancer incidence and mortality, In Review of Fluoride Benefits and Risks (Appendix E). US Department of Health and Human Services, Public Health Service: Atlanta, Georgia.

Figure 1 NCI study, Hoover et al 1991
Mortality ratios, all cancers in men before and after fluoridation.  Mortality relative to non-fluoridated counties, adjusted for age, calendar-time, and geographic region. (1.2 m deaths) (Adapted from Hoover et al 1991)


Figure 2 NCI study, Hoover et al 1991
Mortality ratios, all cancers in women before and after fluoridation.  Mortality relative to non-fluoridated counties, adjusted for age, calendar-time, and geographic region. (1.1 m deaths) (Adapted from Hoover et al 1991)