Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: TUESDAY, March 13, 1990 TAG: 9003133285
SECTION: NATIONAL/INTERNATIONAL PAGE: A3 EDITION: METRO
SOURCE: The New York Times
DATELINE: LENGTH: Medium
The latest review was triggered by a congressionally mandated study that recently reported evidence that high doses of fluoride may cause cancer in rats.
The study was carried out by the National Toxicology Program, the federal government's top agency for evaluating chemical risks.
The findings, though preliminary, dismayed many health experts who have long felt, and still do, that the benefits of fluoridation were substantial and that the risks of ingesting the small amount of fluoride in water were slight.
The Department of Health and Human Services has scheduled a public meeting on April 26 in Research Triangle Park, N.C., at which a panel of outside experts will discuss and evaluate the fluoride study.
Dr. David G. Hoel, acting director of the department's National Institute of Environmental Health Sciences, said that "after 45 years of water fluoridation involving scores of human epidemiological studies both in the United States and in other countries there has not been any evidence that shows a relationship between fluoridation and cancer or other diseases in humans."
He added that the higher incidence of cancer in fluoride-dosed rats "could be the result of chance alone."
But worried representatives of the American Dental Association, the National Institute for Dental Research, the Centers for Disease Control and other medical groups conferred on the report at a special session of the International Association for Dental Research in Cincinnati last week.
Some of the discussion centered on the effect the report was likely to have on public confidence in fluoridation, and some participants predicted that it might be serious.
Speakers did not challenge the report's data, but most of them cautioned against interpreting the study as implying a hazard to health.
Meanwhile, the surgeon general's office announced the establishment of a panel to evaluate the report. It will be headed by Dr. Frank Young, former commissioner of the Food and Drug Administration.
Health officials are hastening to reassure the public that the results of the recent study do not imply a hazard to human beings from fluoridated drinking water.
They say that people consume far lower doses of fluoride than did the test rats and that a single animal test, no matter how well done, is not conclusive because the results could well be because of chance.
But opponents of fluoridation say the study proves that re-examination of the safety of fluoridation is warranted.
The National Toxicology Program is a branch of the National Institute of Environmental Health Sciences.
The study data showed that the incidence of bone cancer in male rats increased with increasing doses of sodium fluoride - the compound used in fluoridating public water supplies. Among 50 male rats who received a medium dose of fluoride, at 45 parts per million (ppm), one got bone cancer.
Among 80 male rats given the highest dose of fluoride, at 79 ppm, four developed bone cancers. Both doses were well above the levels found in drinking water. None of the female rats and none of the mice got the bone cancer.
Previous animal tests suggesting that water fluoridation might pose risks to humans have been widely discounted as technically flawed.
But the latest investigation was very careful to weed out sources of experimental or statistical error, many scientists say, and the results cannot be dismissed.
Dr. Edward Groth, a biologist serving as associate technical director of Consumers Union, said that many fluoride investigations have purported to show a risk associated with fluoridation, but that all had been challenged more or less successfully.
"The importance of this study by the National Toxicology Program is that it is the first fluoride bioassay giving positive results in which the latest state-of-the-art procedures have been rigorously applied," he said. "It has to be considered seriously."
Last month's report disclosed that besides a higher bone cancer rate in male rats, the effects of high fluoride doses also included an increased incidence of mouth cancer in male and female rats.
An almost identical study using mice in place of rats, however, produced no increase in these types of cancer, but according to at least one analyst, both mice and rats incurred a rare form of liver cancer more often at the higher doses.
by CNB