However, a senior author of the Harvard report said that top E.P.A. officials were made aware of its conclusions. “Many people have been presenting our study to E.P.A. They know about it,” said Francesca Dominici, a professor of biostatistics at Harvard who led the study.
“I’m disappointed but not surprised,” she said about the administration’s announcement. “But it is an unwise decision in light of the pandemic. There has been a constant tactic over the last few years by the administration to dismiss science in general.”
Mr. Lazarus, the Harvard lawyer, said that he expected that E.P.A. would be legally required to incorporate the findings of the Harvard study into the rationale for the rule before it is made final, likely later this year. “It will eventually be part of the legal record,” he said. “Historically, Harvard’s public health studies have been central to E.P.A. public health rules.”
The proposed rule, which will be open to public comment for 60 days before being reviewed by the White House and made final, retains a standard enacted in 2012. That rule limited the pollution of industrial fine soot particles — each about 1/30th the width of a human hair, but associated with heart attacks, strokes and premature deaths — to 12 micrograms per cubic meter. By law, the E.P.A. is required every five years to review the latest science and update that standard.
When E.P.A. scientists conducted that mandatory review, many concluded that if the federal government tightened that standard to about nine micrograms per cubic meter, more than 10,000 American lives could be saved a year.
In a draft 457-page scientific assessment of the risks associated with keeping or strengthening the fine soot pollution rule, career scientists at the E.P.A. estimated that the current standard is “associated with 45,000 deaths” annually. The scientists wrote that if the rule were tightened to nine micrograms per cubic meter, annual deaths would fall by about 27 percent, or 12,150 people a year.
“The E.P.A.’s own scientific report is overwhelmingly in support of a tougher standard. It over and over again shows that the evidence of harmful public health effects from PM 2.5 are much greater than were previously known,” Mr. Lazarus said.