After years of smog, a shroud lifts

The Denver skyline has a different look these days: It's become more visible.

Denver hasn't exceeded a single federal health standard for air quality since 1999. Now the US Environmental Protection Agency (EPA) is set to declare Denver's air in full compliance with national standards. The official designation, expected soon, would mean that Denver's air passes federal muster for the first time in 30 years.

This is no small achievement. Before there was a Denver International Airport, a Colorado Rockies baseball team, or even the Denver Avalanche hockey team, the Mile High City was best known for smudged skies. Two decades ago, Denver was violating federal air-quality standards more than 200 days a year. Denver's notorious "brown cloud" regularly shrouded the city, obscuring snow-topped mountains that crown the horizon.

"Denver is the first city that has gone from the depths of air pollution, to a level where they are now attaining all [federal] standards," says Richard Long, EPA's air program director in Denver. "That's a remarkable accomplishment."

While metropolitan air quality throughout the United States has improved vastly in the last decade – thanks mostly to cleaner-burning automobiles and enforcement of the Clean Air Act's strict 1990 amendments – no other city has achieved a turnaround comparable to Denver's.

Beginning in the late 1970s, and continuing through the 1980s, Denver and Los Angeles shared the unwelcome distinction of having the worst air in the country. On any given day, both were in violation of five major federal standards: particulates, ozone, carbon monoxide, nitrogen oxide and lead. But while Los Angeles air remains among the nation's worst, Denver has distinguished itself by making unparalleled gains in cleaning its skies.

The EPA's proposal to remove Denver from its list of worst-air cities is subject to a 30-day public-comment period, after which the EPA will issue a final ruling.

"It eliminates the stigma from Denver," says Doug Benevento, environmental director for the Colorado Department of Public Health and Environment, echoing the feel-good sentiments of local officials. "You can't call Denver a 'bad-air city' anymore."

That's not to say that Denver is pollution-free. "We do still have a lingering pollution problem," says Mr. Long. "We meet all the health standards, and that's a tremendous accomplishment. But it's not a pristine area."

Even residents see as much brown as they do civic pride: The fact that Denver's air remains visible is a nagging concern. "The air still looks gross," says Christine Knight, a commuter and Denver native now living in suburban Adams County. "Especially after looking at it, I don't want to breathe it."

Denver's progress hasn't been an overnight sensation, but the product of aggressive efforts for 15 years. Beginning in the late 1980s, with the area economy lagging, Colorado leaders led the charge, intent on transforming Denver's historically boom-and-bust economy to one of sustained prosperity.

Recognizing that air that's bad for health is bad for business, the state established the Regional Air Quality Council, an agency that imposes strict air-quality regulations in a six-county area.

Some measures in the sweeping program were considered Draconian when initiated – such as a ban on wood-burning fireplaces in new homes. Colorado also implemented a stringent auto-emissions inspection program before any other state in the country. And the state was the first to require oxygenated gasoline during the winter months, to reduce carbon monoxide.

More recently, Denver was the first city to shift from sanding roads after snowfalls to using a liquid road de-icer, to help reduce particulate pollution. The region's power provider also agreed to switch power plants from coal to natural gas.

Perhaps what's most remarkable about Denver's dramatic air-quality improvement is that it occurred while the region emerged as one of the nation's fastest-growing areas.

Despite significant progress, no one is set to declare victory. Newspapers still publish a daily smog report. And city leaders acknowledge that vigilance will be required for Denver to remain in compliance as population continues to swell: The most recent 20-year projections add another 1 million people to the metro area's existing population of 2.4 million.

Ms. Knight, the Adams County resident, worries what will happen as sprawl continues. "The traffic is just getting worse.... To me, what they're doing [to improve the air] is not enough."

Nor, officials admit, has Denver eradicated the Brown Cloud: "We still exceed the state visibility standard 50 to 80 times a year," says Ken Lloyd, executive director of the Regional Air Quality Council, referring to an aesthetic standard set by the state in 1990. While the federal government does not regulate urban visibility now, it's possible that it will in the future, says Joe Paisie, an EPA air quality policy analyst in Research Triangle Park, N.C. If that were to happen, it could pose a problem for Denver, he says.

Indeed, some caution that this is no time for complacency: "It's absolutely critical that Denver build on its success, and not repeat past mistakes," says Vickie Patton, senior attorney for Environmental Defense, in Boulder, Colo. "It's not enough to just barely stay under the federal standard.... We can be visionary."

Mr. Benevento, of Colorado's health department, agrees without hesitation: "We can't say our work is done, and walk away." Looking out his office window, he observes that today, the mountain backdrop is veiled by a chocolate-tinged haze.

"That's a reminder that there's still work to be done," he says.