Sunshine on a cloudy day ... a new federal standard to reduce smog is making states clear the air sooner rather than later.

Taxes weren't the only thing due on April 15. On that day, the U.S. Environmental Protection Agency (EPA) charged all or parts of 474 counties in 31 states with violating its new ozone standard or contributing to another county's failure to comply. Although the number of counties in so-called "nonattainment" areas represents only 15 percent nationwide, they account for 159 million residents.

The new standard is designed to reduce ground-level ozone, or smog, that cauldron of pollutants that obstructs views and causes health problems. Ozone forms when volatile organic compounds and nitrogen oxides "cook" in the presence of sunlight. The primary sources are motor vehicles, power plants and industrial facilities. Ozone can aggravate asthma and damage lung tissue, making breathing more difficult, especially for children and the elderly.

So what does "nonattainment" actually mean?

Jeff Clark, with EPA's Office of Air Quality Planning and Standards, says there are several "myths" surrounding the designations. "It does not mean," he emphasizes, "that states will automatically lose highway funds," a contention that is often put forward since transportation sources account for much of the ozone problem. For those who think that nonattainment will prohibit growth, Clark points out "that some of the fastest growing areas in the country have been designated," citing Atlanta, Las Vegas and Phoenix as examples.

States will have to act, however. Nonattainment areas are subject to what's called "transportation conformity," which means local transportation and air quality officials must coordinate their planning efforts to ensure that transportation projects do not hinder an area's ability to reach its clean air goals. In addition, "new source review" (NSR) requirements will kick in. NSR is a permitting program for power plants and industrial facilities to ensure that new and modified sources of emissions are compatible with air quality standards.

Other actions may be necessary, and nonattainment areas must submit plans to EPA within three years detailing how they propose to comply with the new standard. Compliance deadlines range from 2007 to 2021, depending on how severe the ozone problem is.

Some states got a jump on meeting the standard through development of "early action compacts," which commit an area to reduce ozone sooner than required under the Clean Air Act. The benefit to states according to Howard Roitman, director of environmental programs in the Colorado Department of Public Health and Environment, is that "the compact defers the effective date of nonattainment designation so long as the terms and milestones contained in the plan are met."

To qualify, a state must submit a plan to EPA by the end of this year that lists control measures that will demonstrate compliance with the new standard by Dec. 31, 2007.

Colorado is one of eight states--the others are Maryland, North Carolina, South Carolina, Tennessee, Texas, Virginia and West Virginia--developing a compact. The Denver metro area recognized that it would have an ozone problem two years ago and prepared a plan in December 2002.

The department submitted its ozone control plan to the Colorado General Assembly in April. The legislature approved it unanimously. "That never happens," says Roitman.

Colorado Representative Shawn Mitchell, the bill's chief sponsor, chalks up its success to the early involvement of stakeholders. "We did the heavy lifting upfront," Mitchell notes, "well before it came to the legislature." And for Mitchell, the plan offers that "proverbial double-win scenario: We're on our way to improving air quality without the federal government micromanaging the process."

WHAT GOVERNMENTS CAN DO

* Design more efficient transportation systems.

* Develop traffic control measures.

* Adopt commuter programs.

* Make electricity available at truck stops so diesel engines can be turned off.

* Provide incentives for diesel bus retrofits.

* Establish clean fuel fleets.

* Use low sulfur fuels.

* Require gasoline vapor recovery.

* Encourage selected catalytic reduction controls on power plants.

* Administer vehicle inspection maintenance programs.

Larry Morandi heads NCSL's Energy, Environment and Transportation programs. Jennifer Smith tracks clean air issues for NCSL.