This report is a comprehensive review and evaluation of the public health benefits and risks of fluoride from drinking water and other sources. Fluoride was first added to public drinking water in the 1940's to prevent tooth decay. While controversy has sometimes surrounded community water fluoridation, over half of the U.S. population is served by drinking water that is fluoridated naturally or adjusted. Additionally, since the 1950's, fluorides have been incorporated into toothpaste, other dental products, and dietary supplements.

The Assistant Secretary for Health, Dr. James O. Mason, requested an analysis of the benefits and risks of fluorides upon the receipt of the preliminary results of a study in which animals were given sodium fluoride in the drinking water. The study, conducted by the National Toxicology Program (NTP), a research and testing program within the U.S. Public Health Service (PHS), found a small number of malignant bone tumors (osteosarcomas) in male rats. The NTP study concluded that there was "equivocal" evidence of carcinogenic activity in male rats (HHS, 1990).

"Equivocal" evidence is one of five standard categories that are employed in NTP studies to describe the strength of the evidence of individual experiments. According to NTP's standard definition, "equivocal evidence of carcinogenicity is demonstrated by studies that are interpreted as showing a marginal increase of neoplasms that may be chemically related." The independent peer review panel which evaluated the NTP study requested the addition of a statement that further defined the term "equivocal evidence" of carcinogenicity as a category "for uncertain findings (emphasis added) demonstrated by studies that are interpreted as showing a marginal increase in neoplasms that may be chemically related" (HHS, 1990). The NTP study found no evidence of carcinogenic activity of sodium fluoride in female rats, or in mice of either sex.

Animal studies conducted at a range of dose levels, often at doses that are the maximum which can be tolerated without shortening the lifespan of the animal, are used to identify potential hazards to human health. The identification of a potential hazard from animal studies, which is one of the first steps in assessing a health risk to humans, does not necessarily mean that there is a risk to humans. Further steps are taken to determine potential human risks. Human epidemiological studies can help to determine if a hazard to humans exists. The results of epidemiological studies are then analyzed in combination with information from animal studies, dose-response relationships, and patterns of human exposure in order to characterize the magnitude of the risk to humans. This process of characterizing human riskthe likely harm to human healthis called risk assessment.

This report qualitatively assesses fluoride's health benefits as well as fluoride's health risks. It was prepared by the Ad Hoc Subcommittee on Fluoride of the PHS Committee to Coordinate Environmental Health and Related Programs (CCEHRP) and approved by CCEHRP. The data analyzed in the report include: the NTP study of sodium fluoride; human and animal studies published in the biomedical literature on both the benefits and the risks of fluoride; the U.S. Food and Drug Administration's (FDA) review of a chronic bioassay animal study sponsored by the Procter and Gamble Company; and new epidemiological studies performed by the National Cancer Institute (NCI). To ensure public input, an announcement was published in the Federal Register on March 1, 1990, soliciting peer-reviewed published articles on fluorides. A total of 24 individuals submitted over 100 articles which were considered by the Subcommittee.

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