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May 8, 1989
New Studies Cast Doubt on Fluoridation Benefits
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recently found -- but as yet unpublished -- by NIDR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 geographical 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 all the children aged five
to 17 were 2.0 teeth for both fluoridated and nonfluoridated areas. When
he omitted those children who had ever changed addresses, and thus confined
the study to children with an unchanging 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 differences were never greater than 0.5 teeth. He has submitted
his study for publication in the Danish journal Community Dentistry
& Oral Epidemiology.
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. are 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 says.
When analyzing the survey 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 than 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 very 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 ranged 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%.