Ozone levels along the Front Range have remained flat and even increased in some years, despite a decade of major initiatives to cut emissions of the chemicals that create the pollutant.

The standoff against ozone is in stark contrast to success with other major airborne pollutants, including tiny particles and carbon monoxide, which have been driven down in the past two decades thanks to numerous local efforts and federal regulations.

The persistent ozone troubles are linked not only to chemical emissions but to clear, hot and stagnant summertime weather conditions that exacerbate the problem. The result: The region is on the wrong side of EPA health standards and under federal pressure to further cut pollutants behind ozone formation.

Regulators doing battle with ozone are frustrated, though not hopeless, as they point to some nuanced signs of progress, as well as computer simulations that show the pollutant falling slightly in some areas by 2010 due, in part, to increasingly cleaner cars and fuels.

"I don't think it's getting worse, it's just not getting better as we expected or hoped," said Ken Lloyd, who directs the Regional Air Quality Council, an agency that oversees pollution reduction in the metro area.

The optimists point out that ozone levels have essentially held steady since the early 1990s despite large increases in population, cars on the road, miles driven and an explosion in oil and gas drilling in the state.

"I call that success when we're at least keeping a lid on things and staying flat," said Mike Silverstein, a top air pollution regulator for the state's health department.

And while few are happy about skyrocketing fuel prices, the effects on ozone are almost certainly to be positive: fewer gas-guzzlers on the road, more use of mass transit, shorter commutes and a move toward higher efficiency autos could put a dent in fossil fuel combustion that leads to ozone formation.

77 million in U.S. affected

Denver is hardly alone in its struggle against ozone. EPA's recently released 2008 Report on the Environment showed ozone concentrations and ozone-forming emissions trending down nationally. Even so, the report said, in 2006, 77 million people - including residents of the Denver metro area - lived in counties where ozone levels failed to meet health standards.

"Despite reductions in ambient concentrations of ozone over the past quarter-century and decreases in (ozone-forming emissions) since 1990 . . . ozone remains one of the most persistent and ubiquitous air pollution issues in the U.S.," the EPA report said.

Inhaling ozone has been linked to numerous health effects, from causing pain when taking a deep breath to aggravating asthma or bronchitis. Evidence also suggests that adults older than 65 are at higher risk of hospitalization or death from elevated ozone levels.

Sanctions possible

The EPA - citing research on the hazards of the invisible gas - has tightened health standards twice, in 1997 and 2008.

In 1997, key monitors around the region showed higher-end ozone levels hovering between 65 and 75 parts per billion. A decade later, in 2007, the same monitors showed higher readings, between 75 and 85 ppb, even 90 ppb in one case.

It would be unfair to simply compare two years a decade apart, however, because between that time readings hovered in the midrange, with big spikes in the infamous ozone-choking summers of 1998, 2003 and, to a lesser extent, 2006, and slight drops in 2001 and 2004.

"When I eyeball the data, I see us taking the edge off the (highest readings), when I compare the first half of the 2000s and the second half," Silverstein said.

Silverstein also points to new modeling that predicts decreases in emissions of nitrogen oxides (8 percent drop) and volatile organic compounds (3 percent) - two key contributors to ozone formation - between 2006 and 2010.

But it's far from clear whether the region can drop ozone levels far enough - to consistently below 75 ppb - to measure up to new federal health standards.

Indeed, the region is still out of compliance with the old standard of 80 ppb. Failure to get levels down could eventually bring sanctions by the EPA such as a loss of highway funds and limits on new industry.

To avoid all that, officials are banking - at least in part - on further controls on oil and gas operations and the ongoing turnover of older, gas-guzzling and high-polluting cars as well as a slew of minor actions, such as paying drivers $1,000 to get rid of clunkers.

Since ozone-producing chemicals are also carried from other Western states, regulators hope improvements in those areas - such as emission controls in the oil and gas fields of Wyoming and New Mexico - also could improve Denver's situation.

Activist Jeremy Nichols of Rocky Mountain Clean Air Action, who has put relentless pressure on regulators to cut ozone, acknowledged progress, but warned that some regions are going backward, mostly due to emissions tied to the boom in natural gas drilling and production.

"We may be winning here in Denver, but losing in western Colorado and western Wyoming," where energy exploration is growing, Nichols said. "We have room for improvement for sure."

What you can do to prevent ozone formation

Drive less

Walk to lunch

Fill up your car at night

Don't top off your tank

Mow your lawn in the evening

Run errands after 5 p.m.

Ozone alert

* When: Until 4 p.m. today

* Where: Metro Denver area and along the Front Range

* Effects: Ozone pollution can trigger attacks and symptoms in people with asthma or other respiratory infections. It also can affect healthy people who work or exercise outdoors, causing breathing difficulties, eye irritation and reduced resistance to lung infections.

* Information: 24-hour air quality hotline at 303-758-4848

Efforts to cut pollutants

Along the Front Range, regulators have taken several steps to curb ozone:

* Mandated pollution controls on oil and gas drilling northeast of Denver

* Required refineries to produce lower-volatility gasoline

* Toughened auto emission tests; offered rebates to people who ditch older, high-polluting vehicles

BUT MORE PEOPLE, CARS, INDUSTRY

* Miles traveled by metro-area vehicles have gone from 40 million miles in 1990 to 68 million miles in 2005, according to the Denver Regional Council of Governments.

* The seven-county metro-area's population has increased by more than 250,000 since 2000, to nearly 2.7 million people in 2007, according to U.S. Census figures.

* An unprecedented energy rush has hit Colorado, where applications for permits to drill have tripled to beyond 6,000 a year since 2003, and could surpass 8,000 in 2008. Myriad elements of oil and gas drilling are significant sources of ozone-forming emissions.

hartmant@RockyMountainNews.com or 303-954-5048

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