Fluoride's effects depend not only on the total dosage and duration
of exposure, but also on other factors such as nutritional status,
kidney function, and interaction with other trace elements.
But what we really need to know is how much fluoride it takes before
it begins to cause us harm.
The bodge by Hodge
It is important when any new drug is marketed that the dose at which
it is toxic is determined. There is then a margin allowed for safety
(usually a factor of 100) and a maximum dose is published. In 1953
the National Academy of Sciences published their estimate of the
quantity of fluoride which produces the condition known as crippling
skeletal fluorosis. The calculation was done by a famous
toxicologist, Harold C. Hodge, Ph.D., who was chairman of the US
National Academy of Sciences (NAS) committee on toxicology.
To arrive at his figures, Hodge cited a classic study of the effects
of fluoride among cryolite workers by a European researcher, Kaj
Roholm, published in 1937[6]. Roholm's dosage figures were presented
in milligrams of fluoride per kilogram of body weight. In
his study, Roholm showed that at levels of 0.2 to 0.35mg/kg some
workers developed crippling skeletal fluorosis in a very short time.
The first stage of the disease appeared, in general, after 2 ½
years; Stage two was reached by 4 ½ years; and crippling
skeletal fluorosis appeared after 11 years.
Hodge wanted to apply Roholm's figures to a typical range of body
weights in order to set a maximum intake level in milligrams per
day. But Hodge was American and used to dealing in pounds rather
than kilograms. By using a range of body weights from 100 to 229
pounds, he multiplied the 0.2 mg figure by 100 pounds, giving a
figure of 20 mg/day; and 0.35 mg multiplied by 229 pounds yielded
80 mg/day. Thus the amounts of fluoride which would cause crippling
skeletal fluorosis, he said, were 20mg to 80mg per day. And rather
than quote Roholm's eleven year figure for crippling fluorosis,
he gave a range of 10 to 20 years. These
are the figures that appear in the American Dental Association's
pamphlet, Fluoridation Facts, and on which many other articles
are based, even today.
BUT
HODGE MADE A SIMPLE BUT SIGNIFICANT ERROR. Roholm's
figures were not calculated for pounds. They
were milligram per kilogram figures. Unfortunately, Hodge
was 'the expert' and no-one, apparently, checked his figures. This
error, which gave a false safety margin more
than double what it should have been, went unnoticed for
many years until anti-fluoride campaigner, Darlene
Sherrell tried to duplicate Hodge's arithmetic and couldn't
make it add up. She worked out that Hodge had made an error when
he neglected to convert pounds to kilograms.
Correcting for this error, Sherrell reduced the amount of fluoride
needed to cause crippling skeletal fluorosis to 10 to 25 milligrams
per day, for 10 to 20 years.
But fluorides accumulate throughout our lives so
a higher intake will have the same effect in a shorter time, and
smaller doses will have the same effect in a longer time.
If
we apply Roholm's dosage figures to a lifetime of 55 to 96 years,
just 1 mg per day (the amount in one litre of water) for each 55
pounds of body weight could be a crippling dosage.
The
National Academy of Science admits it was wrong
In 1989 Sherrell wrote to the NAS and asked on what they based their
20 to 80 mg/day figures. Two years passed
before the Academy told her that they had identified Hodge's interpretation
of Roholm as the data source.
Four years later the error was finally corrected
by the National Research Council's Board on Environmental Studies
and Toxicology in their 1993 publication, Health Effects of Ingested
Fluoride where they changed the figure from 20-80mg/day to 10-20mg/day[7].
As it happens, Hodge had written a chapter in a book released in
1979 entitled 'Continuing Evaluation of the Use of Fluorides'. In
it Hodge had corrected his previously published figures. But nobody
seemed to notice. In 1991, when the US Department of Health and
Human Services published their Review of Fluoride: Benefits and
Risks, they continued to use figures of 20-80 mg/day as the 'crippling
daily dose of fluoride'. As, indeed does the current RDA and Dietary
Reference Intakes published by the Institute of Medicine in 1997.
MYTHS ARE VERY HARD TO DISLODGE!
Myths are very hard to dislodg
We can get a good
idea of how much fluoride is safe by working with Roholm's figures.
You will remember that after the figures had been corrected, the
amount needed to cause crippling fluorosis in a 100 to 229 lb person
was reckoned to be 10 to 20 mg per day for 10 to 20 years. Since
fluorides accumulate in a linear fashion, the crippling dosage of
10 mg per day for 10 years is the same as 5 mg per day for 20 years,
and so on. If we extrapolate this to a normal lifetime with fluoridated
water this is the same as 2.5 to 5 mg per day for 40 to 80 years.
But we should note that, for persons with
kidney disease, the risk is greater because less fluoride will be
eliminated by their malfunctioning kidneys.
It is also important to note that these figures are for crippling
fluorosis, the last stage. It will take only four years at 10 mg/day,
or sixteen years at 2.5 mg per day before a 100 pound individual
can expect to experience phase 2, musculo-skeletal fluorosis, with
chronic joint pain and arthritic symptoms with or without osteoporosis.
That is the amount of fluoride found in just
2 ½ litres of water. And that's without counting the extra
that today is inevitably found in foods, toothpaste, et cetera.
From this
it is clear that the only safe limit for fluoride is NONE.
Also see
http://www.npwa.freeserve.co.uk/osteoporosis.htm
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References:
1. Waldbott GL, Burgstahler A, McKinney HL. Fluoridation: The Great
Dilemma. Coronado Press Inc, Kansas, 1978. pp81-4.
2. Albright JA. The effect of fluoride on the mechanical properties
of bone. Transactions of the Annual Meeting of the Orthopedics Research
Society. 1978; 240 (15): 1630-1.
3. Robin JC, et al. Studies on osteoporosis III. Effect of estrogens
and fluoride. J Med. 1980; II (1): 1-14.
4. Danielson C, et al. Hip fractures and fluoridation in Utah?s
elderly. JAMA 1992; 268: 746-8.
5. Trace Elements in Human and Animal Nutrition: Fifth Edition,
Edited by Walter Mertz, U.S. Dept. of Agriculture, Agricultural
Research Service, Beltsville Human Nutrition Research Center, Beltsville,
Maryland, 1987,
6. Roholm K. Fluorine Intoxication. A Clinical-Hygienic Study. Nyt
Nordisk, Copenhagen and H K Lewis, London 1937 pp 281-282.
7. Health Effects of Ingested Fluoride. National Academy of Sciences,
USA 1993: p 59.
