The analysis, still being revised, considered more than 3,000 new health studies published since the agency proposed rules in 1997 intended to cut levels of soot and other smog ingredients produced mainly by power plants and vehicles. The proposed rules are still under review, and the final analysis could be a crucial factor in the Bush administration's decision about how tough the final rules should be.

From the start, businesses had strenuously fought the rules, saying the science was suspect and the costs would be enormous. But in the review of more recent research, one of the highlighted studies was in fact partly financed by industry.

Agency officials said that more changes in the report were inevitable and another draft was likely before the document was considered complete. But they said the review clearly eliminated almost any doubt that this kind of pollution posed a serious health threat.

"There is a veritable deluge of new research," said Dr. Lester D. Grant, the director of the agency's national center for environmental assessment, in Research Triangle Park, N.C., which is conducting the review.

"The bottom line is the studies very substantially confirm the original findings. That goes a long way toward laying to rest the sort of controversy that swirled around those studies."

So far, the Bush administration has not indicated whether it will change direction on the soot rule. In fact, President Bush's choice to head the environmental agency's air division, Jeffrey R. Holmstead, has not yet had his confirmation hearing.

But the administration did take a strong stand on a big source of this kind of pollution in February, when Christie Whitman, the E.P.A. administrator, strongly endorsed a rule drafted by the Clinton administration that would sharply curtail emissions of soot and other emissions from diesel engines.

The separate standard proposed for soot and air would limit concentrations of particles smaller than 2.5 microns to an average of 15 micrograms per cubic meter measured for three years in a row. Until now, the agency has only had limits on particles of 10 microns and smaller, but no specific limit on the smallest ones.

Levels of these particles have been slowly declining on average across the country for years, as stricter controls have been instituted on coal- fired power plants and as other plants have switched to cleaner- burning fuels, particularly natural gas. But many cities still see dozens of days each year when levels of the small soot particles far exceed the proposed federal standard.

For example, the study shows that in 1999, the latest year with comprehensive data, New York City, Los Angeles, Atlanta, Chicago, and several other cities had annual average levels of the 2.5-micron particles that would � if seen for three years in a row � violate the proposed rule.

Since the early 1980's, scientists' concerns about soot have focused increasingly on the smallest particles, which penetrate farthest into the lungs.

In 1987, regulations took effect that limited the concentration in air of particles less than 10 microns in diameter (a human hair is about 100 microns across). But the rule proposed in 1997 would sharply reduce allowable levels for particles less than 2.5 microns across.

These microscopic motes � composed of metals, carbon and other ingredients � are able to infiltrate the tiniest compartments in the lungs and pass readily into the bloodstream and have been most strongly tied to illness and early death, particularly in people who are already susceptible to respiratory problems.

One critical new research effort cited in the E.P.A. review was an analysis by an industry-financed research center, the Health Effects Institute, that supported the conclusions of two keystone studies from the early 1990's that drove the agency to write the new rule.

Those studies, by the Harvard School of Public Health and the American Cancer Society, found strong links between high levels of small particles and a rise in death rates. They were attacked by industry groups and some members of Congress as biased.

The Health Effects Institute, based in Boston, is financed by industry and the E.P.A. and was established in 1980 to serve as a referee on air pollution research. Its study, published last year, largely approved of the methods and data in the original studies and concurred that there was a link between soot and illness.

Many other new studies, Dr. Grant said, corroborate the link between the smallest particles, those under 2.5 microns, and the most serious health effects. Other studies cited in the new analysis strengthen the relationship between sooty conditions and a rise in hospital admissions of children with asthma attacks.

The 632-page research review, which was posted on the agency's Web site (www.epa.gov/ncea/) this month, has already been through one round of public comments and a critique by an agency panel that includes officials from industries that generate some of the pollution.

A second round of public comment will end in July, followed by another critique by the panel, the agency's Clean Air Science Advisory Committee. The agency is also beginning to draft a paper recommending how to translate the findings into the final language of a rule to cut fine soot.

Eventually, Mrs. Whitman, assessing the science and her staff's recommendations, would propose either to accept the Clinton administration standard or to modify it. Some supporters of strict controls decried the pace of the rule making, which has been delayed by court challenges, including one from the American Trucking Association and other industry groups that was rejected by the Supreme Court in February.

"We're already having another scientific review completed before step one has actually been taken to cut the pollution," said David G. Hawkins, a lawyer for the Natural Resources Defense Council, a private group. "In the meantime, there are about a quarter million Americans who have died prematurely as result of fine particle exposure."

Studies, including some cited in the new review and one by the natural resources group, have estimated that more than 50,000 people die prematurely each year from illnesses caused by exposure to fine soot.

More delays are expected, agency officials and environmental groups said, both because of other litigation and a law passed last year that could allow the Office of Management and Budget to review the quality of the data underlying the studies cited by the agency to justify its decision.

Despite the voluminous nature of the document, industry representatives said the E.P.A. analysis was basically a laundry list of existing work. With the regulation likely to cost industry billions of dollars a year, trade groups are demanding to see not only the studies, but also the raw data underlying the work.Agencies have generally not had to go to such lengths, which would require enormous amounts of paperwork.

"We're going to have to sit down and go over what the E.P.A. is basing its decision on and what other documents are out there," said William L. Kovacs, the vice president for environmental, technical, and regulatory affairs of the United States Chamber of Commerce, a lobbying group.

"If they really believe so strongly in the data, then why don't they release it? If it's that compelling, I'd be plastering it on the walls."