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A Brief Report On The Association Of Drinking Water Fluoridation And The Incidence of Osteosarcoma Among Young Males.
by Perry D. Cohn.
New Jersey Department of Health,
November 8, 1992.
EXECUTIVE SUMMARY
It is well known that fluoride provides
important public health benefits by effectively preventing dental caries
in children. The Public Health Service (1991) endorses artificial fluoridation
of drinking water at a concentration of 0.7-1.2 milligrams of fluoride per
liter of water (or parts per million) as the optimally beneficial level
for preventing dental caries. The U.S. Environmental Protection Agency (USEPA)
allows up to 2 parts per million for artificial fluoridation and up to 4
parts per million for naturally occurring fluoride (National Primary Drinking
Water Regulations, 40 CFR 141.11 and 143.3). Other potential sources of
fluoride ingestion include food, vitamins, and swallowed toothpaste.
Recently, a national study of drinking water fluoridation at the county
level found a significant association with osteosarcoma incidence among
males under 20 years of age (Hoover et at 1991). However, the meaning of
the association was questioned by the authors because of the absence of
a linear trend of association with the duration of time for which the water
supplies were fluoridated. Furthermore, the simple study design used did
not have individual information on the average amount of water ingested
daily, use of dental fluoride supplements, long term residence, other potentially
confounding (or causal) exposures, or genetic involvement.
As a follow-up to the study by Hoover et at, a small study of similar design
was initiated by the New Jersey Department of Health to compare drinking
water fluoridation at the municipal level with the municipal residence of
osteosarcoma cases at the time of diagnosis. No interviews were conducted
and data on individual residential history, average amount of water ingested,
use of dental fluoride supplements, exposure to other carcinogens and familial
cancer history were not available. In addition, the total number of cases
was small. Therefore, observations should be interpreted cautiously because:
1) exposure misclassification could lead to under- or overestimation of
effects, 2) unmeasured confounding by other potential causes of osteosarcomas
could introduce bias leading to under- or overestimation of effects of exposure,
and 3) an observed association could be due to chance.
Osteosarcoma incidence between 1979 and 1987 was compared by ecologic epidemiology
methods to water supply fluoridation in seven counties in central New Jersey.
Twelve cases were diagnosed among males under age 20 in fluoridated municipalities
vs eight cases in non-fluoridated municipalities. The rate ratio of incidence
in fluoridated vs non-fluoridated municipalities was 3.4 with a 95% statistical
confidence interval (95%Cl) between 1.8 and 6.0. All twelve cases in fluoridated
municipalities resided in a three county area with the greatest prevalence
of fluoridation. The rate ratio of incidence in fluoridated vs non-fluoridated
municipalities in the three county area was 5.1 (95%CI 2.7-9.0). Among 10-19
year old males in those three counties, the rate ratio was 6.9 (95%Cl 3.3-13).
No other age/sex groups exhibited significant association with fluoridation.
Because of the limitations of the study design and the small numbers of
cases that occurred, this analysis does not imply a causal connection between
fluoridation and osteosarcoma. From the public health perspective, the findings
are not sufficient to recommend that fluoridation of water supplies be halted,
but do support the importance of investigating the possible link between
osteosarcoma and overall ingestion of fluoride, In addition, it is recommended
that dentists identify whether children reside in fluoridated communities
and appropriately advise on fluoride supplementation.
Reprints: State of New Jersey Department of Health, Trenton NJ 08625 0360,
USA.