Summation - Estimated "Threshold" Doses for Skeletal Fluorosis:

For over 40 years health authorities stated that in order to develop crippling skeletal fluorosis, one would need to ingest between 20 and 80 mg of fluoride per day for at least 10 or 20 years.

This belief, however, which played an instrumental role in shaping current fluoride policies, is now acknowledged by the National Academy of Sciences (NAS) and other US health authorities to be incorrect.

In 1993, the NAS revised its longstanding 20-80 mg/day estimate, by stating that crippling fluorosis could be caused by doses as low as 10 and 20 mg a day.

Left unaddressed, however, by the NAS and other US health authorities is the dose that could produce the earlier stages of fluorosis. Common sense would indicate that the dose which can produce the early stages of fluorosis, in which bone changes may not be detectable, would be less than the doses that can produce the crippling stages. Thus, we would expect the "threshold" dose for the early stages to be below 10 mg/day. Evidence from India (albeit limited) indicates that this is, in fact, the case.

Also left unaddressed by US health authorities is the extent to which the threshold dose varies based on the existence or absence of predisposing factors in an individual (e.g. kidney disease; genetic predisposition; and nutrient deficiencies).

Unfortunately, the longstanding assurances by health authorities that skeletal fluorosis could not be produced at doses below 20 mg/day, stunted scientific inquiry into the issue, and as a result, we know far less today about the range of doses that can produce fluorosis than might have otherwise been the case.

Excerpts from the Scientific Literature - Uncertainty Remains/Reigns: (back to top)

"There is no fixed toxic level of fluoride, since the development of fluorosis depends upon environmental factors."
SOURCE: Littleton J. (1999). Paleopathology of skeletal fluorosis. American Journal of Physical Anthropology 109: 465-483.

"The actual fluoride intake required to produce skeletal fluorosis is unknown."
SOURCE: Cook HA. (1972). Crippling fluorosis related to fluoride intake (case report). Fluoride 5: 209-213.

Excerpts from the Scientific Literature - Published Estimates of Doses Causing Fluorosis: (back to top)

"The levels of fluoride ingestion which can lead to long-term skeletal fluorosis (2-8 mg/day) appear to be exceeded in the diet of the average adult in a fluoridated community."
SOURCE: Groth, E. (1973). Two Issues of Science and Public Policy: Air Pollution Control in the San Francisco Bay Area, and Fluoridation of Community Water Supplies. Ph.D. Dissertation, Department of Biological Sciences, Stanford University, May 1973.

"In calcium-deficient children the toxic effects of fluoride mainfest even at marginally high (>2.5 mg/d) exposures to fluoride."
SOURCE: Teotia M, Teotia SP, Singh KP. (1998). Endemic chronic fluoride toxicity and dietary calcium deficiency interaction syndromes of metabolic bone disease and deformities in India: year 2000. Indian Journal of Pediatrics 65:371-81.

"In its final report, the Surgeon General’s panel said that radiologic changes have been found in bone when fluoride exposure has been about 5 mg per day."
SOURCE: Hileman B. (1988). Fluoridation of water.Questions about health risks and benefits remain after more than 40 years. Chemical and Engineering News August 1, 1988, 26-42.

"The histologic features of osteofluorosis were evident in the biopsy from the patient receiving the lowest amount of fluoride (6 mg. daily for 5 months)..."
SOURCE: Baylink DJ, Bernstein DS. (1967). The effects of fluoride therapy on metabolic bone disease. Clinical Orthopaedics and Related Research 55: 51-85.

"In areas of endemic fluorosis, levels of ingestion of fluoride from diet and water over 8 mg daily are common, although in certain regions in India, changes typical of skeletal fluorosis have been stated to occur at estimated lower dosages."
SOURCE: Singh A, Jolly SS. (1970). Chronic toxic effects on the skeletal system. In: Fluorides & Human Health. World Health Organization, Geneva. pp. 238-249.

"Singh and Jolly (1970) noted that a daily intake of 8 mg or more of fluoride is necessary to produce skeletal fluorosis. Those cases in which the disease could not be demonstrated radiologically were excluded."
SOURCE: Cook HA. (1972). Crippling fluorosis related to fluoride intake (case report). Fluoride 5: 209-213.

"According to our observations the prolific growth in periostitis deformans (skeletal fluorosis) continues as long as daily amounts greater than 8 to 10 mg of F are ingested no matter through what vehicle."
SOURCE: Soriano, M. (1968). Periostitis deformans due to wine fluorosis. Fluoride 1: 56-64.

"Only when relatively large amounts of fluoride (8-20 mg/day) are ingested for prolonged periods are generalized adverse effects encountered."
SOURCE: Fisher JR, et al. (1981). Skeletal fluorosis from eating soil. Arizona Medicine 38: 833-5.

"The present paper shows that daily intakes of 9-12 mg are associated with a very high prevalence of skeletal fluorosis. (The US Institute of Medicine's) upper safe limit may need to be revised/lowered on the basis of present data."
SOURCE: Cao J, et al. (2003). Brick tea fluoride as a main source of adult fluorosis. Food and Chemical Toxicology 41:535-42.

"Most epidemiological research has indicated that an intake of at least 10 mg/day for 10 or more years is needed to produce clinical signs of the milder forms of the condition.”
SOURCE: Institute of Medicine. (1997). Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride National Academy Press, Washington D.C. pp. 307

"Osteomalacia and osteoporosis may occur in older persons who ingest excessive fluorides (over 10-25 mg/d for 10-20 years)."
SOURCE: Ellenhorn MJ, Barceloux DG. (1988). Medical Toxicology: Diagnosis and Treatment of Human Poisoning. Elsevier; New York. pp. 534.

Excerpts from the Scientific Literature - U.S. Health Authorities Retract 20-80 mg/day Estimate for Crippling Fluorosis: (back to top)

"Crippling skeletal fluorosis might occur in people who have ingested 10-20 mg of fluoride per day for 10-20 years."
SOURCE: National Research Council. (1993). Health Effects of Ingested Fluoride. National Academy Press, Washington DC.

“Most estimates indicate that crippling skeletal fluorosis occurs when 10-20 mg of fluoride have been ingested on a daily basis for at least 10 years.”
SOURCE: Whitford G. (1996). The Metabolism and Toxicity of Fluoride. 2nd Revised Edition. Karger: Basel. pp. 138.

"It is generally stated that a dose of 10–20 mg/day for at least 10 years is necessary for the development of crippling skeletal fluorosis, but individual variation, variation in nutritional status, and the difficulty of determining water fluoride levels in such situations make it difficult to determine the critical dose."
SOURCE: Agency for Toxic Substances & Disease Registry [ATSDR]. (2003). Toxicological profile for Fluorides, Hydrogen Fluoride, and Fluorine. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service.

"Crippling fluorosis as an occupational disease follows exposures estimated at 10 to over 25 mg of fluoride daily during periods of 10-20 years."
SOURCE: Hodge HC. (1979). The Safety of Fluoride Tablets or Drops. In: Johansen E, Taves DR, Olsen TO, Eds. Continuing Evaluation of the Use of Fluorides. AAAS Selected Symposium. Westview Press, Boulder, Colorado. pp. 253-274.

"Skeletal changes are among the prominent chronic effects observed after long-continued exposures to large amounts of fluoride (20 to 80 mg per day or more). These abnormalities of the skeleton manifest themselves as osteosclerosis, osteoporosis, and exostoses of the long bones and of the vertebra, pelvis, jaw bone, and other flat bones; with somewhat smaller amounts, yet many times the 1 p.p.m. of water fluoridation, minor alterations in bone architecture, e.g., thickening of trabeculae, have been reported."
SOURCE: Food & Nutrition Board. (1953). The Problem of Providing Optimum Fluoride Intake for Prevention of Dental Caries. National Academy of Sciences. Publication #294.

"Crippling fluorosis occurs when men ingest or inhale 20 to 80 mg of fluoride or more daily for a period of 10 to 20 years. Since 5 gallons of fluoridated water (at 1 ppm) contain 20 mg, it is obvious that crippling fluorosis can never be produced by drinking fluoridated water."
SOURCE: Hodge HC. (1956). Fluoride metabolism: its significance in water fluoridation. Journal of the American Dental Association 52:307-314.

"Crippling fluorosis, a rarely described entity, may follow exposure of 10 to 20 years' duration when 20 to 80 mg. or more of fluoride are taken into the body daily."
SOURCE: Hodge HC. (1960). Notes on the effects of fluoride deposition on body tissues. Archives of Industrial Health 21: 350-352.

"This industrial disease identified by Roholm (1937) is described in his classic monograph Fluorine Intoxication. Danish workmen in the dusty cryolite industry became crippled and could no longer perform simple physical tasks. Exposures to 20 or 80 or more mg F/day for 10-20 years were responsible for the development of osteosclerosis, exostoses, and calcification of the ligaments. The consequent fixation of the spinal column, the 'poker back', was crippling."
SOURCE: Hodge HC. (1963). Safety factors in water fluoridation based on the toxicology of fluorides. Proceedings of the Nutrition Society 22: 111-117.

"Moller and Gudjonsson estimated that 20 to 80 (or more) mg F inhaled daily for 10 to 20 years will produce crippling fluorosis." (Note: Moller and Gudjonsson never produced such an estimate. Indeed, they provided no estimate at all of the dose that produced the skeletal fluorosis in the workers they studied.)
Hodge HC, Smith FA. (1970). Air quality criteria for the effects of fluorides on man. Journal of the Air Pollution Control Association 20:226-232.

"Crippling fluorosis as seen by Roholm is estimated to result from the daily ingestion of 20-80 mg for 10-20 years." SOURCE: NAS (1971). Fluorides. Committee on Biologic Effects of Atmospheric Pollutants, Division of Medical Sciences, National Academy of Sciences, Washington, D.C.

"The daily fluoride exposures to bring about the bony changes were roughly estimated by Moller and Gudjonsson (1932) to range from 20 to 80 mg F (or more) taken into the body daily for 10 to 20 years." (Note: Moller and Gudjonsson never produced such an estimate. Indeed, they provided no estimate at all of the dose that produced the skeletal fluorosis in the workers they studied.)
SOURCE: Hodge HC, Smith FA. (1977). Occupational fluoride exposure. Journal of Occupational Medicine 19: 12-39.

"It is estimated that the development of crippling skeletal fluorosis, requires the daily consumption of 20 mg or more of fluoride from all sources for 20 or more years."
SOURCE: Environmental Protection Agency. (1985). National primary drinking water regulations; fluoride. Federal Register May 14; 50(93): 20164-20175.

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