Regression analysis of cancer incidence rates and water fluoride in the U.S.A. based on IACR/IARC (WHO) data (1978-1992). International Agency for Research on Cancer.

in Journal of epidemiology by K Takahashi, K Akiniwa, K Narita

TLDR

  • Researchers found that fluoride in drinking water is linked to an increased risk of some cancers, but a decreased risk of others, suggesting a complex mechanism of action.
  • The study highlights the need for further research to understand the impact of fluoridation on human health.

Abstract

Age-specific and age-standardized rates (ASR) of registered cancers for nine communities in the U.S.A. (21.8 million inhabitants, mainly white) were obtained from IARC data (1978-82, 1983-87, 1988-92). The percentage of people supplied with "optimally" fluoridated drinking water (FD) obtained from the Fluoridation Census 1985, U.S.A. were used for regression analysis of incidence rates of cancers at thirty six sites (ICD-WHO, 1957). About two-thirds of sites of the body (ICD) were associated positively with FD, but negative associations were noted for lip cancer, melanoma of the skin, and cancers of the prostate and thyroid gland. In digestive organs the stomach showed only limited and small intestine no significant link. However, cancers of the oral cavity and pharynx, colon and rectum, hepato-biliary and urinary organs were positively associated with FD. This was also the case for bone cancers in male, in line with results of rat experiments. Brain tumors and T-cell system Hodgkin's disease, Non-Hodgkin lymphoma, multiple myeloma, melanoma of the skin and monocytic leukaemia were also correlated with FD. Of the 36 sites, 23 were positively significant (63.9%), 9 not significant (25.0%) and 4 negatively significant (11.1%). This may indicate a complexity of mechanisms of action of fluoride in the body, especially in view of the coexising positive and negative correlations with the fluoridation index. The likelihood of fluoride acting as a genetic cause of cancer requires consideration.

Overview

  • The study analyzed the relationship between fluoride in drinking water and the incidence of 36 types of cancer in nine U.S. communities between 1978-1992.
  • The study found that two-thirds of the cancer sites were positively associated with fluoride levels in drinking water, but negative associations were found for lip cancer, melanoma, and some gastrointestinal cancers.
  • The study suggests that fluoride may have a complex mechanism of action in the body, with both positive and negative correlations with cancer incidence.

Comparative Analysis & Findings

  • The study found a positive association between fluoride levels in drinking water and the incidence of 23 types of cancer, including oral cavity and pharynx, colon and rectum, and urinary organ cancers.
  • Nine of the 36 cancer sites showed no significant association with fluoride levels, and four sites showed a negative association, including lip cancer and melanoma.
  • The study found a significant correlation between fluoride levels and incidence rates of brain tumors, T-cell system Hodgkin's disease, Non-Hodgkin lymphoma, multiple myeloma, melanoma of the skin, and monocytic leukaemia.

Implications and Future Directions

  • The study's findings suggest that fluoride may have a complex effect on cancer risk, and further research is needed to understand the mechanisms of action.
  • The study's results raise concerns about the potential health risks of widespread fluoridation, and further investigation is warranted.
  • Future research should explore the potential role of fluoride as a genetic cause of cancer and the impact of fluoridated drinking water on different populations.
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