January 7, 2011
Kathleen M. Thiessen, Ph.D.
SENES Oak Ridge, Inc.,
Oak Ridge, TN
The Department of Health and Human Services (HHS) and the Environmental Protection Agency (EPA) have announced new recommendations regarding water fluoridation, the primary change being from a recommended range of 0.7-1.2 mg/L fluoride in drinking water (0.7-1.2 ppm) to 0.7 mg/L (0.7 ppm). (See press release.) The primary concern is the prevention of dental fluorosis, a condition ranging from mild spotting of the teeth to severe pitting and staining. Dental fluorosis is caused by excessive fluoride ingestion during the early years of childhood, before the permanent teeth erupt.
The former range of recommended fluoride concentrations was based on ambient temperature and the assumption that people’s water consumption varies with outdoor temperature. Thus the recommended fluoride levels varied from 0.7 mg/L in Florida and parts of Arizona and Texas to 1.2 mg/L in Alaska, Maine, Michigan, Minnesota, and North Dakota. The proposed change will therefore have a larger effect on the northern states than on the southern states, with some areas seeing no change in the recommended fluoride concentration. It is interesting to note that in 2009, Canada recommended a fluoride concentration of 0.7 mg/L for all parts of the country.
At a fluoride level of 0.7 mg/L, a 7-kg (15-lb) baby drinking 0.75 L per day of formula prepared with fluoridated water will ingest 0.075 mg of fluoride per kg body weight (0.75 L/day ´ 0.7 mg/L ¸ 7 kg = 0.075 mg/kg per day). Fluoride intakes above about 0.03 mg/kg per day have been associated with the occurrence of dental fluorosis, so the proposed change will still not be protective for infants drinking formula made from concentrate. Parents who happen to be aware of the need to avoid fluoride for their infants will still need to buy bottled water for preparation of infant formula, if they can afford to do so.
Several peer-reviewed studies in other countries have shown associations or correlations between the presence of dental fluorosis and a higher risk of adverse health effects, including effects on thyroid function, decreased IQ, and increased risk of bone fracture. These associations have not been studied in the U.S., or at least, there has been no report of such studies in the U.S. Besides indicating overexposure to fluoride during early childhood, the presence of dental fluorosis may indicate higher individual susceptibility to adverse effects from ingested fluoride. While considered by the dental profession to be merely a cosmetic problem, “objectionable” dental fluorosis can lead to a higher caries risk (due to the pitted tooth surfaces) and can be expensive to treat with respect to cosmetic appearance.
The best available studies in the U.S. show no benefit of water fluoridation on dental health. The only study to have looked at caries experience and individual fluoride intake (the Iowa study) reported no relationship between fluoride intake and caries experience, but a higher risk of dental fluorosis with increased fluoride intake. A population-wide study in the 1980s demonstrates essentially no difference in caries experience of children and water fluoride concentration, but a clear dose response for dental fluorosis and water fluoride concentration. The small differences in amount of caries per child between fluoridated and nonfluoridated areas are probably an artifact of the delay in tooth eruption caused by fluoride, another topic not addressed to date in the U.S.
The “benefits” of fluoride are due primarily to topical exposure (e.g., from toothpaste), not systemic ingestion of fluoride, according to the Centers for Disease Control and Prevention (CDC). Ingestion of fluoridated drinking water contributes essentially nothing to topical exposure of the teeth, as most of us do not “swish” our drinking water in our mouths before swallowing (our mothers refused to let us consider such things).
The CDC has made no mention of whether fluoride will be added to the long list of chemicals included in its periodic biomonitoring studies. This was recommended to them by the National Research Council (NRC) in 2006.
The NRC’s 2006 report provided the impetus for some of the recent studies by the EPA and HHS. Recent press releases from the EPA and from the American Dental Association state that the NRC report “did not question the safety” of water fluoridation. In fact, the NRC report did not address the question of the safety of water fluoridation, simply saying that the EPA’s drinking water standards for fluoride are not protective. There is considerable information in the NRC report which would support a conclusion that water fluoridation is not safe. In addition to effects on bones and teeth, fluoride is credibly associated with reduced thyroid function, other altered endocrine function, hypersensitivity, reduced IQ, genotoxicity, and carcinogenicity, among others. These effects, and the bone effects (bone and joint pain, increased brittleness and fracture risk) are inadequately studied in the U.S., although population information on prevalence of such things as hypothyroidism, diabetes, and bone and joint pain is consistent with widespread fluoride overexposure. The NRC report pointed out a number of areas where further research is justified. However, continuing to expose the American public while waiting for the research is not justified.
The NRC also discussed the issue of the most commonly used fluoridation chemicals, the silicofluorides. This issue is not mentioned in the proposed recommendations for a new fluoridation guideline. Use of silicofluorides in drinking water is associated with higher levels of blood lead in children, among other concerns. The use of both silicofluorides and chloramines (a disinfectant sometimes used instead of chlorine) has been demonstrated to increase the leaching of lead from plumbing fixtures. This was the probable explanation for high blood levels in children in Washington, D.C., a few years ago. The CDC’s attempt to cover up the situation was the topic of a Congressional hearing a year or so ago. The probable reason for the CDC wishing to avoid the issue was the potential threat to its longstanding fluoridation program.
Thus, while the proposed recommendation for a lower national fluoride level in drinking water is a step in the right direction, and a quiet admission that some people are ingesting too much fluoride, a number of concerns are not yet addressed. Infants fed reconstituted formula, people with high water consumption (e.g., athletes, laborers, persons with medical conditions such as diabetes insipidus), persons with impaired kidney function (and consequent reduced excretion of fluoride), and persons with a hypersensitivity to fluoride will continue to have fluoride intakes in excess of a safe level, even when the new recommendation is implemented. These people also deserve to be protected.