The purpose of this report is the review of the present knowledge of the metabolism of fluorides, particularly in the human body, and the use of this knowledge in estimating the factors of safety in water fluoridation. In this discussion, many of the biological effects of fluorides (purported or well-established) will receive no mention. On the other hand, there are a few important biological effects of fluorides so well studied that there is an established relation between the effect and the intake of fluoride responsible, specifically, acute fluoride poisoning, crippling fluorosis, osteosclerosis and mottled enamel. The facts of fluoride metabolism give an insight into the nature and in some instances the mechanism of these effects. This report will include a discussion of the following: (1) blood fluoride levels; (2) the rates and mechanisms of urinary excretion of fluoride and (3) the magnitude and mechanisms of bone deposition. In each instance an attempt will be made to estimate the magnitude of the safety factors between these toxic fluoride effects and the fluoride exposure that will accompany the ingestion of fluoridated water. It is concluded from present information that the factors of safety are adequate to justify the practice of community water supply fluoridation.
Circulating human blood normally contains a trace of fluoride. When the drinking drinking water has only negligible levels of fluoride ( < 0.1 ppm), on the average, the blood level is about 1 microgram per hundred milliliters of blood.1 There is a considerable range of variation from individual to individual, and values as high as 10 micrograms per hundred milliliters of blood or higher have been obtained.
Presumably the blood level reflects in some measure the daily intake. Persons living in Rochester, N. Y., prior to water fluoridation ingested mostly by food 1 to 2 mg. of fluoride per day. The drinking water supply in Rochester, N. Y. prior to water fluoridation contained about 0.06 ppm of fluoride (F). When the daily fluoride intake is increased by fluoridating the water supply, the blood level of fluoride increases slightly. For example, in Newburgh, N. Y., where the water supply contains about 1.1 ppm of fluoride (F), the average blood level was 4 micrograms per hundred milliliters of blood. Thus, when Rochester and Newburgh are compared, it is seen that an increase of 20 times in the fluoride water concentration was accompanied by an in-
Presented as part of a symposium, ’’Newburgh-Kingston caries-fluorine study: final report,” at the New York Institute o f Clinical Oral Pathology, Inc., New York, December 12, 1955.
This paper is based on work performed under contract with the U. S. Atomic Energy Commission at the University o f Rochester Atomic Energy Proiect, Rochester, N. Y.
Division of pharmacology and toxicology, department of radiation biology, University o f Rochester School of Medicine and Dentistry.
I. Smith, F. A.; Gardner, D. E., and Hodge, H. C. Investigations on the metabolism of fluoride. II. Fluoride content of blood and urine as a function of the fluorine in drinking water. J. D. Res. 29:596 Oct. 1950.
*Original abstract online at https://www.sciencedirect.com/science/article/abs/pii/S0002817756230108