CHICAGO, AUG. 20 -- Federal regulators have put millions of women at increased risk of toxic shock syndrome by failing to devise a uniform system for rating tampon absorbency, the head of a public health advocacy group said.

Scientists at the Centers for Disease Control in Atlanta said they have confirmed that higher-absorbency tampons increase the risk of toxic shock syndrome and that absorbency may be a greater factor than the materials used to make the tampons.

The study and criticisms by Dr. Sidney M. Wolfe of the Public Citizen Health Research Group in Washington, D.C., appear in Friday's Journal of the American Medical Association.

In an editorial, Wolfe wrote that the Food and Drug Administration received its first alert in 1981 that a population-based study had found a link between higher absorbency and higher risk.

Despite subsequent studies and the FDA's announced intention in 1984 to require standardized absorbency labeling, the agency has "gone on again, off again," he said.

"The failure of the {FDA} to warn women adequately based on evidence available more than six years ago, a failure prolonged by the tampon industry, has caused unnecessary risks to millions of American women who regularly use tampons," Wolfe wrote.

In a statement today, the FDA said, "The agency did hope that an industry agreement on standardization could produce useful information on the labeling quicker than by regulation."

But manufacturers could not agree, it said, and "the agency is completing work on a proposal now and hopes to publish it for public coment soon."

Dr. Claire V. Broome, one of the CDC researchers, said women must balance the convenience of high-absorbency tampons against "reducing the risk somewhat of a very rare disease.

"We're talking about only 2 cases per 100,000 menstruating women per year, which is a rare disease," she said today.

The CDC researchers reviewed 285 cases of tampon-associated toxic shock syndrome that occurred in 1983 and 1984 and found that increasing absorbency raised a woman's odds of getting the syndrome, regardless of the material the tampon is made of.

Wolfe's group is proposing that manufacturers be required to indicate on packages how a product compares to others in absorbency on a scale of 2 to 20.