Some residents remain skeptical about U.S. Steel Corp.'s proposed $1 billion upgrade of its Clairton coke plant, even as a host of city and business leaders lined up in favor of the plan to create cleaner air.

Though they support the project's aims -- to generate hundreds of construction jobs and secure steelmaking in the Mon Valley -- residents and environmentalists said they need more proof concerning its promises to reduce emissions and airborne particulates.

"I am asking that you please make sure that the final permit does everything possible to help Clairton's air meet federal standards," Clairton resident Lee Lasich said during a public hearing last night held by the Allegheny County Health Department.

Mrs. Lasich was one of about 25 people who spoke during the two-hour hearing on an installation permit for the first phase of U.S. Steel's planned overhaul..

"We understand there has been progress, but we still have unhealthy air, and the details of this final permit will determine how much more progress we're able to make," she said.

The first phase of the upgrade would allow the company to replace three of its 12 aging coke batteries with a single battery that would have fewer ovens but still provide the same amount of production.

According to U.S. Steel, when the new battery is completed in 2011 it will reduce all air pollution emissions by 39 percent and airborne particle emissions -- commonly termed soot -- by almost 58 percent.

Supporters of the upgrade pointed to the long-term benefits, saying it would modernize the coke plant, make the area more economically viable and strengthen steelmaking in Pittsburgh for generations to come.

"I'm ecstatic that I'm part of Clairton when this experiment is going on," resident Richard Lattanzi told the Health Department.

"U.S. Steel is going to make a difference for us."

The new battery will be the first in the United States to use a relatively new pressure-regulated oven technology developed in Europe and known as PROven, designed to draw in gases instead of letting them escape.

It also includes a new, low-emissions quench tower to capture pollutants released in the quenching process.

Environmental groups, however, said they want more assurance that the upgrade meets best available control technology, or the "BACT standard." They said the permit should be strengthened, not denied.

"Yes we want economic viability in the Mon Valley," Clairton resident Pat Jones said. "But we don't want to lose our health, either."

Some in the audience noted that air monitors in Liberty, about two miles north of Clairton, have repeatedly registered the highest levels of the tiniest soot particles, which are the most dangerous to human health.

An American Lung Association report released in May ranked Pittsburgh as the sootiest metropolitan area in the country.

Mrs. Lasich, whose husband, a maintenance worker at the coke works, died four years ago from cancer, said she feared debris associated with the project will further pollute the air.

"We must all work together to protect those jobs that we have, but the people who work those jobs won't be there if our air quality isn't vastly improved and monitored carefully," she said.

State Rep. David Levdansky, D-Forward, was among several public officials who voiced support for the project.

"It's going to guarantee that steel is going to be made in the Mon Valley not just in my lifetime but in my son's lifetime," he said.

About 200 Allegheny County residents submitted written comments about the project to the Health Department, said Kathy Lawson, of the environmental group Clean Water Action.

"We are not opposed to this project," Ms. Lawson said. "But there must be enough emission reductions to ensure healthy air. With a strong permit and clear guidelines, we are confident that U.S. Steel can play a major part in bringing the Liberty-Clairton area into federal compliance with the Clean Air Act."

Some looked at the project from a pragmatic approach.

"If U.S. Steel's going to put $1 billion into something that's going to clean the air up, why stop them?" resident Joseph Shedleski told the Health Department.

The Health Department must review and respond to the public comments before deciding whether to revise the permit in a process that could take more than two months.