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Chemical & Engineering News May 8, 1989:
New Studies Cast Doubt on Fluoridation Benefits
By Bette Hileman
AN ANALYSIS OF NATIONAL SURVEY DATA COLLECTED BY THE NATIONAL INSTITUTE OF
DENTAL RESEARCH (NIDR) CONCLUDES THAT CHILDREN WHO LIVE IN AREAS OF THE U.S.
WHERE THE WATER SUPPLIES ARE FLUORIDATED HAVE TOOTH DECAY RATES NEARLY
IDENTICAL WITH THOSE WHO LIVE IN NONFLUORIDATED AREAS.
The analysis was done by John A. Yiamouyiannis, a biochemist and expert on
the biological effects of fluoride, who has been an ardent opponent of
fluoridation for 20 years. His results are not widely different from those
recently found -- but as yet unpublished -- by NIDR in analyzing the same
data.
In the 1986-87 school year, NIDR examiners looked for dental caries in
39,207 schoolchildren aged five to 17 from 84 different geographic areas.
Yiamouyiannis obtained the survey data from NIDR under the Freedom of
Information Act.
Yiamouyiannis compared decay rates in terms of decayed, missing, and filled
permanent teeth. The average decay rates for children aged five to 17 were
2.0 teeth in both fluoridated and nonfluoridated areas. When he omitted
those chldren who had ever changed addresses, and thus confined the study
to children with an unchanged fluoridation status, the results were nearly
the same -- a decay rate of 2.0 for fluoridated areas and 2.1 for
nonfluoridated areas. Decay rates in the individual age groups were
sometimes lower in fluoridated areas, sometimes lower in nonfluoridated
areas. The differenecs were never greater than 0.5 teeth. He has submitted
his study for publication in the Danish journal _Community Dentistry & Oral
Epidemiology_.
[[ Chart omitted ]]
He also found that the percentages of decay-free children were virtually the
same in fluoridated and nonfluoridated areas and averaged about 34%. This
analysis included both permanent and deciduous (baby) teeth. NIDR's claim
that 50% of the children in the U.S. were decay-free, headlined in newspapers
across the country last summer, was based largely on the fact that NIDR
analyzed only permanent teeth in children aged five to 17, and a large
fraction of these children were not old enough to have many permanent teeth,
Yiamouyiannis saya.
When analyzing the surevey data, NIDR compared decay rates in two ways: In
terms of the number of decayed, missing, and filled permanent teeth; and in
terms of decayed, missing and filled surfaces of teeth. Both of these
methods are widely used today. NIDR found that children who have always
lived in fluoridated areas have 18% fewer decayed surfaces that those who
have never lived in fluoridated areas. But when NIDR analyzed the data in
terms of teeth, the differences were smaller. Janet A. Brunelle,
statistician in the epidemiology program at NIDR, tells C&EN the results for
teeth "are in a box somewhere" and she does not remember exactly what they
are.
Brunelle says NIDR is publishing only the results for surfaces because they
are more meaningful. Surface rates give a more complete picture of the
extent of decay, she adds, and the decay rate for teeth "is rather low so
that there is little difference in most anything." When asked to comment on
Yiamouyiannis' results, Brunelle said she didn't know whether they are valid.
In reaction to Yiamouyiannis' new study, the union of professional employees
at the Environmental Protection Agency has written a letter to EPA
Administrator William K. Reilly. The letter asks him to "immediately
suspend (not revoke) EPA's unqualified support for fluoridation" until the
agency conducts its own assessment of the risks and benefits of fluoride
exposure. The union, Local 2050 of the National Federation of Federal
Employees, has been concerned for some time that EPA evaluated fluoride
politically, rather than scientifically. The union also believes the safe
level of fluoride in drinking water should have been lowered rather than
raised in 1986, when EPA increased the maximum allowable contaminant level to
4 ppm from a range of 1.4 to 2.4 ppm.
Another analysis of decay rates is published in the current issue of the
_American Journal of Public Health_. Jayanth V. Kumar of the New York State
Department of Health examined decay rates in seven to 14 year olds in
Newburgh, N.Y., which has been fluoridated since 1945, and in nearby
Kingston, which has never been fluoridated. He found that the caries
prevalence in Newburgh -- 1.5 decayed, missing and filled permanent teeth --
is somewhat lower than it is in Kingston (2.0). However, since the 1954-55
school year, the decay rate has actually declined more in nonfluoridated
Kingston than in Newburgh.
When asked by C&EN, a spokesman for the American Dental Association said that
ADA believes that water fluoridation can reduce tooth decay 18 to 25%. But
as recently as 1988 the association claimed fluoridation reduces decay 40 to
60%.